Evaluating Techniques For Reducing Ph Of Bauxite Processing Residue Sand At Depth Using Gypsum And Irrigation

ALCOA OF AUSTRALIA
No. 37
EVALUATING TECHNIQUES FOR
REDUCING pH OF BAUXITE PROCESSING
RESIDUE SAND AT DEPTH USING GYPSUM
AND IRRIGATION
I. R. Phillips
August 2010
ISSN 1320-4807
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SUMMARY
This report presents findings from a three year study that was established to identify the role of
irrigation in residue rehabilitation, and whether depth of gypsum placement affects rehabilitation
performance. Irrigation did not significantly improve rehabilitation performance nor did it
significantly affect the movement of gypsum throughout the residue sand profile. This was because
irrigation was not applied on a continuous basis, but when residue sand water storage decreased to a
value considered low enough to induce drought stress in the vegetation cover. Although some
movement of gypsum to depths below its zone of incorporation was detected, the rate of movement
was relatively slow, and incomplete removal of carbonate was still evident two years after
incorporation. It was suggested that restricted movement may be due to the low solubility of gypsum
coupled with the poor water retention properties of residue sand. Changes in Na, CO3 and HCO3
proved to be more reliable indicators of gypsum interaction with residue sand than pH, Ca and SO 4. If
shallow gypsum incorporation was to be recommended, additional studies would need to confirm that
its rate of movement throughout the residue sand profile was faster than the rate of plant root growth.
This would identify whether gypsum movement was a limiting factor to plant root growth, hence
water and nutrient uptake.
Irrigation was found to significantly increase above-ground biomass (as measured by cover) but had
no affect on species richness. Plant performance was found to be independent of gypsum incorporation
depth. This was because both the shallow and deep treatments resulted in gypsum being distributed
throughout much of the plant root zone. As such, neither the shallow or deep gypsum treatments
should have limited plant root distributions in terms of their accessibility to moisture and nutrients.
The higher bulk density, coupled with the hostile chemical characteristics, of residue sand below the
zone of gypsum incorporation was considered to pose the greater restriction to depth of root
penetration. Plant roots were also observed to be associated with high concentrations of gypsum,
particularly in the shallow treatments. It is possible that plant roots in shallow gypsum treatments may
preferentially remain closer to the surface, which may also render plants more susceptible to drought
stress during summer.
It is recommended that:
Irrigation be removed from the current prescription for residue rehabilitation because it (1) is
not a sustainable practice in terms of long term management of residue disposal areas, (2) is
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an inefficient use of a limited natural resource at a time when water management is essential,
and (3) may restrict root distribution to shallow depths in the residue sand profile.
Deep gypsum incorporation be retained as the preferred method due to its proven
effectiveness in rapidly altering the characteristics of residue sand such that it is more
conducive for plant growth, and it encourages deeper penetration of plant roots.
Maintain botanical monitoring of the trials to test whether any of the treatments causes a
reduction in rehabilitation performance in the longer term.
Use the parameters Na, CO3 and HCO3 in conjunction with Ca, SO4 and pH as a measure of
gypsum interaction with residue sand.
Prior to establishing any field trial, ensure that a complete history of past management is
obtained and assess whether any previous activity will affect the primary objectives (or
hypotheses to be tested) of the study.
INTRODUCTION
Developing and refining effective methods for improving the growth media for rehabilitating Alcoa of
Australia (Alcoa) bauxite-processing storage areas (RSA) represent a primary objective of residue
rehabilitation research. Maximising plant-root distribution throughout the residue sand profile is
considered critical to establishing and maintaining a sustainable vegetation cover across RSA
embankments. The incorporation of gypsum to reduce alkalinity and pH, and the use of irrigation to
increase plant-water availability throughout the profile and to leach soluble salts from the plant-root
zone, represent two key steps in residue rehabilitation to encourage root penetration to depth, and to
increase the volume of residue sand utilised by the plant rhizosphere.
In 2003, Alcoa’s Western Australian Operations (WAO) altered the depth and rate of gypsum
incorporation into residue sand from a shallow application of 50 t/ha (disced to a 300 mm depth) to
225 t/ha incorporated throughout a depth of 1500 mm. Gypsum incorporation to depth is expensive
(increased from $10,000/ha to $14,500/ha in 2006), and alternative methods of distributing gypsum
throughout the profile have been considered. These have included the use of a ripping tine (Phillips
2010b), and leaching surface-applied gypsum with irrigation and/or rainfall (Eastham and Mullins
2004b). The study by Eastham and Mullins (2004b) suggested that a shallow application of 225 t/ha
resulted in rapid leaching of gypsum through the residue sand profile with a corresponding reduction
in pH at depth (> 600 mm) 15 months after application.
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Up until 2008, irrigation had routinely been installed at all new rehabilitated residue sand
embankments to assist with plant establishment. It is impractical to maintain irrigation in the longterm; however, rehabilitation protocol currently does not include a strategy to gradually remove the
vegetation’s irrigation-dependency. Furthermore, there is concern that irrigated vegetation will not
achieve the required root structure to survive without artificial water additions, particularly over
summer, and the vegetation cover will be at a density which can only be sustained by continued
watering. Eastham and Morald (2004a) found that root density in 1 and 2 year old residue
rehabilitation tended to be highest in the surface 300 mm and decreased rapidly with depth.
Furthermore, total root biomass was observed to decrease significantly with increasing compaction of
residue sand. Recent work has found that the surface 300 mm of the residue sand profile dries out to
very low water contents (<0.03 m3/m3) during summer, and that compaction increases markedly below
the zone of gypsum incorporation (Dobrowolski et al. 2009). A better understanding of plant-water
relations is therefore required to determine if (1) a sustainable vegetation cover can be established
without irrigation, (2) the vegetation cover has a root structure and physiology capable of surviving
under extreme water-stress conditions, and (3) the resulting cover density is acceptable from a visual
amenity perspective.
To address the above concerns, a field trial was established at the Kwinana and Pinjarra RSAs in 2005
(Kiepert 2005) to (1) compare the performance of rehabilitation on residue sand embankments
receiving shallow and deep incorporation of 225 t/ha of gypsum, (2) determine if irrigation is
necessary for plant establishment and survival, (3) determine if irrigation assists in leaching of gypsum
to depth as a means of reducing residue profile pH and creating an environment encouraging root
growth to depth, (4) evaluate the effect of irrigation on the root architecture of selected plant species,
and (5) compare the visual perspective of non-irrigated and irrigated rehabilitated embankments due to
sustainable vegetation cover density. To date, chemical analysis of residue sand profiles and botanical
monitoring of the established vegetation have been undertaken on three occasions since
commencement of the trial. Additionally, root distribution and microbial “health status” of selected
rehabilitated areas of RSA were measured in 2007 (Dobrowolski et al. 2009).
The primary objectives of this study are to present data on (1) the effect of leaching on gypsum
distribution throughout the residue sand profile, and (2) the effect of irrigation on plant cover
performance. Results from root distribution, chemical distributions within a residue sand profile to a
depth of 3 m, and microbial “health status” at selected rehabilitated sites will also be provided to
support conclusions based on the above two objectives.
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MATERIALS AND METHODS
Field Trial Description
A detailed description of the trial can be found in Kiepert (2005) and Wilkinson (2005). A brief
summary of this information is presented below.
Trial establishment - Pinjarra
The trial was established on RSA4 and RSA5 in 2005. The southern batter of RSA5 was mechanically
placed in 1993 and 1996 where Block 1 treatments were created. Blocks 2 and 3 were created on the
SW corner of RSA4, and residue sand in this area had been mechanically placed in 1994 and 1995. All
three blocks were located on outer embankments that had previously received the standard shallow 50
t/ha of gypsum, fertiliser addition (poultry manure) and dust suppression crops. Thus, the effects of
shallow gypsum addition as a treatment may not be evident. Each block comprised of a randomised
plot design. Plots on RSA5 were 50 m wide by 60 m wide, and 50 m by 50 m on RSA4.
Trial establishment - Kwinana
Due to a lack of available space, the trial at Kwinana RSA was split across two areas. The irrigation
component of the trial was established on Area F3, and the depth of gypsum incorporation was
established on Areas F4 and F5. The irrigation trial (Area F3) was established on plots 70 m long by
17 m wide in an area that had been mechanically placed in 1996/1997, and had received fertilizers
(poultry manure) and multiple gypsum applications to establish dust suppression crops. The gypsum
trial (Area F4/5) comprised of a fully randomised treatment design incorporating plots 20 m long by
50 m wide. The trial was set-up on a residue sand outer embankment that had been hydraulically
placed in 2004 (i.e. 6 months old). Prior to commencement of the trial, this area had only received
surface bitumen and mulch for dust suppression. No gypsum or fertilizers had been applied prior to
trial establishment.
Gypsum Treatments
Pinjarra
Prior to shallow gypsum incorporation, all weeds were scrapped off to a depth of about 100 mm and
discarded. However, where deep incorporation of gypsum was studied, all weeds were buried at a
depth of about 1500 mm. For shallow gypsum incorporation treatments, 225 t/ha of gypsum were
spread on the residue sand surface and disc harrowed to a depth of 200 mm, after which the surface
was covered with bitumen for dust control. Each plot received a basal dressing of 2.571 t/ha of DAP5
based fertiliser (Appendix 1), which was incorporated by ripping to 600 mm. Since gypsum had been
applied prior to fertiliser incorporation, it is highly likely that ripping re-distributed the gypsum
throughout the 0 – 600 mm depth interval. This greater depth of incorporation will need to be
accounted for when assessing the depth of gypsum leaching. Unfortunately, the shallow gypsum
irrigated and non-irrigated plots received a higher rate of gypsum (300 t/ha) instead of 225 t/ha.
Each plot received 1.88 kg/ha of seed, followed by 60 mm of mulch (equivalent to a surface
application of 600 m3/ha), and planted out with about 3400 stems/ha. The seeded and planted species
and quantities used are provided in Appendix 2 (Wilkinson 2005). Each planted seedling received a 50
grams fertiliser tablet (Appendix 1), and was marked with a bamboo cane to assist with differentiating
between planted and seeded individuals. In each plot, 68 species were seeded and or planted; 18
species were planted only, 14 were seeded only and 36 were planted and seeded (Wilkinson 2005).
Kwinana
Trials were set-up as described above for Pinjarra, and all plots received the correct amount of gypsum
(i.e. 225 t/ha).
Irrigation Treatments
The method of irrigation was the same at both Kwinana and Pinjarra. Water was supplied along rows
of aluminium pipes (12 m apart) with riser sprinklers every 9 m of length. Each sprinkler had an
effective radius of about 9 m, resulting in some areas receiving 2 to 3 times more water than others.
The sprinkler system was constructed such that there was 20 m distance between the irrigated and nonirrigated areas.
Irrigation commenced on 21st December 2005, the day before the botanical monitoring was completed.
Thus, irrigation was not included as a treatment in data analysis for data collected before December
2005 as it would not have affected plant germination or growth, or gypsum leaching. Irrigation
scheduling was based on a water balance approach (G. Mullins, personal communication). During the
2005/2006 summer, irrigated plots received 20.4 mm per day for seven irrigation events. During the
2006/2007 summer the irrigated plots received 42.7 mm per day for three irrigation events.
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Sampling of Residue Sand Profiles
Pre-gypsum addition (April 2005)
Prior to gypsum incorporation, samples of residue sand at all plots (except the deep gypsum, no
irrigation treatment at Pinjarra) were collected at depths of 100, 300, 500, 700, 900, 1100, 1300 and
1500 mm for chemical analyses. Samples were obtained by hand-augering, stored in sealable plastic
bags, and transported to CSBP Ltd for chemical analysis. Prior to analysis, each sample was air-dried
and passed through a 2 mm sieve. The < 2 mm fraction was retained for analysis. Each sample was
analysed for available (2M KCl) nitrate (NO3) and ammonium (NH4), Colwell (0.5 M NaHCO3 pH
8.5) phosphorus (P), Colwell (0.5 M NaHCO3 pH 8.5) potassium (K), available (0.25 M KCl) sulphur
(S), organic carbon (Org C, Walkley Black), amorphous iron (am-Fe, ammonium oxalate), electrical
conductivity (EC, 1:5 residue sand to water ratio), pH (H2O and 0.01 M CaCl2, 1:5 residue sand to
solution ratio), exchangeable (0.1M BaCl2/0.1M NH4Cl) calcium (Ca), magnesium (Mg), sodium (Na)
and potassium (K) (Appendix 3 and 4).
Post-gypsum addition (November 2005)
Post-gypsum sampling of each plot was undertaken in November 2005. Each plot was sampled (n = 2)
at three random locations at depths of 0 – 100, 500 – 700 and 1300 – 1500 mm. Samples were
collected and analysed as outlined above. The non-consistent sampling depths between sampling
events limits the extent of statistical analysis that can be undertaken (Appendix 3 and 4).
6-month sampling (May 2006)
Additional sampling of residue sand profiles was undertaken 6-months after gypsum incorporation
(i.e. May 2006). Samples were collected only from those treatments receiving “a shallow application
of 225 t/ha and no irrigation” for the following reasons. Firstly, this treatment provided the highest
gypsum concentration in the smallest volume of residue sand, thereby providing the best opportunity
to detect gypsum leaching throughout the profile. Secondly, this treatment provided the opportunity to
monitor gypsum leaching via rainfall infiltration alone, which would reflect conditions should
irrigation be removed from standard rehabilitation operations.
Samples were collected from the 0 – 800 mm depth interval as follows. Sampling locations (n = 2) in
each plot were selected randomly; one from the upper section, the other from the lower section, of the
embankment. A PVC pipe (50 mm i.d.
900 mm long) was carefully hammered into the residue sand
to a depth of 800 mm. The pipe was then dug out and both ends sealed with a PVC end cap. Each
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sealed pipe was retained in a vertical position prior to extruding the residue sand core in 100 mm
increments. Each increment of residue sand was placed in a clearly identifiable, sealable plastic bag,
and transported to CSBP Ltd for chemical analysis.
Each sample was analysed for the parameters listed above, with the addition of amorphous Al (am-Al,
ammonium oxalate) and exchangeable Al (1M KCl). Amorphous Al represents a significant
adsorption surface for P, and contributes significantly to the surface charge characteristics of residue
sand (Phillips and Chen 2010). Exchangeable Al (which includes soluble and weakly-sorbed forms of
Al) is known to vary with pH, and so may represent a major cation balancing the surface electrical
charge carried by residue sand.
12-month sampling (December 2006)
Sampling of the “non-irrigated plots with a shallow gypsum incorporation of 225t/ha of gypsum” was
repeated after winter to determine if infiltrating rainwater has caused leaching of gypsum to depths
below the zone of incorporation (i.e. > 600 mm). Cores of residue sand to a depth of 800 mm were
collected as outlined above. Previous sampling events highlighted the difficulty in detecting
statistically significant differences between specific samples based on solid phase concentrations.
Changes in solution phase concentrations are known to be more reliable measures of treatment effects
on soil chemistry (Phillips and Bond 1989). Consequently, the water-soluble and solid phase
concentrations of a range of parameters were measured for each sample as follows. A saturated paste
was prepared by mixing a known mass of residue sand with Mill-Q deionised water until saturation
characteristics were attained (θsat ≈ 0.3). The paste was left overnight to equilibrate, and a sample of
the pore-water removed under vacuum. The pore-water was analysed for Ca, Mg, K, Na, Al, pH, EC,
P, Cl, SO4, NH4, NO3, HCO3 and CO3 using standard techniques (Rayment and Higginson 1992). The
remaining solids were sub-sampled and analysed for the parameters listed above, and for EDTAextractable copper (Cu), zinc (Zn), manganese (Mn) and Fe, exchangeable Fe, phosphorus buffering
index (PBI), Total Fe and Total Al. All analyses were performed by CSBP Ltd.
Botanical Monitoring
Botanical monitoring has been undertaken on three occasions since trial establishment; December
2005 (Wilkinson 2005), July 2006 (Narducci 2006) and August 2007 (LeRoy 2007) as follows. Three
botanical monitoring plots were set-up within each treatment plot (Figure 1); (a) two 36 m2 (6
for density and cover of seeded and planted species, and (b) one 400 m2 (20
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20 m or 10
6 m)
40 m) for
density and survival of planted seedlings. At both RSAs, one of the 36 m2 plots was placed on the
upper slope and one was placed on the lower slope, thereby allowing position on the slope to be
included in data analyses. For the KW irrigation trial, the treatment plots were not wide enough for
upper and lower plots to be meaningful so the two monitoring plots were treated as replicates (pseudo
replicates). An aluminium tag marked with a permanent plot number and a fence dropper was used to
mark the north-west corner of each monitoring plot and wooden stakes were used to mark the
remaining plot corners (Figure 1). A more detailed description of individual plot locations can be
found in Wilkinson (2005).
Germination success
A quadrat (2
2 m) was laid within the 36 m² monitoring plots, and the number and percent cover (of
the 4 m² area) of each species recorded. Planted seedlings were recorded separately from germinated
seed. This process was repeated until the entire 36 m² plot had been monitored (i.e. 9 quadrats per 36
m² plot). A single plant within a 36 m² plot is equivalent to 278 plants/ha (10,000 m²
36 m²),
assuming even distribution of the plants. Therefore, the density of a species required in the field to
ensure that it occurs within the monitoring plot is at least 278 plants/ha. However, given the way seed
is applied during rehabilitation (hand-seeding with preferential segregation of seeds of different mass),
an even distribution of seed is highly unlikely. In fact, groups of plants of the same species can often
be observed in the field.
Planted success
The number of each planted species was recorded in a 400 m² area. As the density of many planted
species was low, large monitoring plots were used to increase the reliability of the data. Each plant
was identified, the bamboo cane moved as close as possible to the base of the plant, and fluorescent
paint sprayed on the top of the cane to indicate it had been counted. If the plant was dead, the death
was recorded and the cane was removed. For the Kwinana Irrigation Trial there were three monitoring
plots (RD117, RD123 and RD129) which contained large pipes close to, or exposed at, the soil
surface. As these areas may not have received gypsum and the pipe may affect plant growth, they were
not included in the calculations for the plots. The approximate area affected by the pipes was measured
and subtracted from the plot area, the bamboo stakes were removed and the reduced area was taken
into account for species density calculations. A single plant within a 400 m² area is equivalent to 25
plants/ha (10,000 m²
400 m²), assuming even distribution of the plants. Therefore, the density of a
species required to ensure that it is monitored in our plots is at least 25 plants/ha.
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Data Analyses
Residue sand
Statistical differences between residue sand characteristics were analysed at discrete depths using
ANOVAs and LSD All-Pairwise Comparisons Tests. Data for the two sites was analysed separately
due to the difference in past history of gypsum and fertiliser at Pinjarra but not at Kwinana (depth of
gypsum incorporation site).
Botanical monitoring
Summary data for each site was determined by averaging the density and cover data for all monitoring
plots regardless of treatment. Irrigation trial plots were analysed separately from gypsum trial plots.
Density, cover and number of species (species richness) were summed across species for each 36 m²
monitoring plot, and this number was used to compare treatments. Data was analysed using Statistix
8.0 using ANOVAs and LSD All-Pairwise Comparisons Tests. Data for the two sites, Kwinana and
Pinjarra, was analysed separately to determine site differences.
RESULTS AND DISCUSSION – RESIDUE SAND
Effect of Time on Gypsum Leaching In Residue Sand Profiles
Water Inputs Over The Period Of Study
The amounts of rainfall ± irrigation added over the four sampling events are presented in Figure 2.
Irrigated treatments received significantly more water (p <0.05) than unirrigated treatments, and this
was most obvious over the December 2005 to June 2006 period (Event 2). Both the non-irrigated and
irrigated treatments received the same amount of water over events 1 and 3 since irrigation was not
applied over the winter period. Over the monitoring period (August 2005 to December 2007),
Kwinana received significantly more water (p <0.05) than Pinjarra (i.e. 1869 mm versus 1808 mm).
2005 Sampling: Pre- and Post- Gypsum Incorporation - Pinjarra
Gypsum addition, either via shallow or deep incorporation, generally increased exchangeable Ca,
available-S, and EC, and decreased pH, relative to residue sand characteristics prior to gypsum
addition (Figure 3). The magnitude of these changes was more pronounced in the shallow gypsum
treatments. Changes in exchangeable Na, bicarbonate-K and bicarbonate-P concentrations were less
obvious, which may be due to previous fertiliser and gypsum additions as part of RSA5’s
rehabilitation management history. Generally, nutrient concentrations, pH and EC for irrigated
treatments were found to be similar in magnitude to those for non-irrigated treatments. However, this
finding was not consistent throughout the trial.
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A primary objective of this trial was to determine if shallow incorporation (0 – 300 mm) of high rates
of gypsum and subsequent leaching, could improve subsoil characteristics that promote root growth to
depth. The parameters initially considered to demonstrate this effect best are pH, EC, exchangeable
Ca, exchangeable Na and available-S (Figure 3). Prior to gypsum incorporation, (Figure 3), values of
pH, EC, exchangeable Ca, exchangeable Na and available-S in the 0 – 100, 500 – 700 and 1300 –
1500 mm depth intervals was 7.8, 9.0 and 9.2; 57, 7 and 9 mS/m; 5.5, 4.3 and 4.1 cmol/kg; 0.1, 0.1
and 0.6 cmol/kg; and 602, 10 and 9 mg/kg, respectively. For post-gypsum incorporation, values of pH,
EC, exchangeable Ca, exchangeable Na and available-S in the 0 – 100, 500 – 700 and 1300 – 1500
mm depth intervals was 7.4, 8.3 and 8.4; 138, 26 and 32 mS/m; 10.5, 4.6 and 4.4 cmol/kg; 0.1, 0.3 and
0.8 cmol/kg; and 3043, 200 and 233 mg/kg, respectively. These data suggest that in the shallow
gypsum incorporation treatment, much of the gypsum still remains in the surface layer (0 - 100 mm),
although some penetration to depth (up to 1500 mm) may have occurred.
2005 Sampling: Pre- and Post- Gypsum Incorporation - Kwinana
Gypsum addition, either via shallow or deep incorporation, generally increased exchangeable Ca,
available-S, and EC, and decreased pH and exchangeable Na, relative to residue sand characteristics
prior to gypsum addition (Figure 4). The magnitudes of these changes were more pronounced in the
shallow gypsum treatments. Changes in bicarbonate-K and bicarbonate-P were less obvious,
particularly in the deep gypsum treatments.
Prior to gypsum incorporation (Figure 4), values of pH, EC, exchangeable Ca, exchangeable Na and
available-S in the 0 – 100, 500 – 700 and 1300 – 1500 mm depth intervals were 9.8, 10.1 and 10.1; 48,
94 and 104 mS/m; 3.0, 2.6 and 2.4 cmol/kg; 3.7, 5.9 and 5.7 cmol/kg; and 10, 21 and 25 mg/kg,
respectively. Following gypsum incorporation, values of pH, EC, exchangeable Ca, exchangeable Na
and available-S in the 0 – 100, 500 – 700 and 1300 – 1500 mm depth intervals were 8.0, 9.0 and 9.0;
163, 50 and 103 mS/m; 9.9, 4.0 and 5.6 cmol/kg; 0.6, 2.4 and 3.5; and 2965, 357 and 594 mg/kg,
respectively. These data are consistent with that from the Pinjarra trial, and suggest that following
shallow gypsum incorporation, the majority of gypsum still remains in the surface layer (0 - 100 mm),
although some penetration to depth (up to 1500 mm) may have occurred.
2006 Sampling: 6-Month and 12-Month - Pinjarra
Additional sampling at times of 6-months and 12-months following gypsum incorporation were
undertaken to better understand if gypsum leaching to depth within the residue sand profile has
11
occurred. Sampling was restricted to only those shallow gypsum plots receiving no irrigation for
reasons outlined earlier. For clarity, only the data for those ions (i.e. Ca, Na and SO4) and parameters
(i.e. pH and EC) indicative of the presence of gypsum will be discussed in this report. Data for all
other analyses undertaken are provided in Appendix 5.
The distribution of pH within the residue sand profile tended towards lower values with increasing
time (Figure 5). For example, the pH of the 0 – 100 mm depth for the pre-gypsum, post-gypsum, 6month and 12 month samplings was 7.8, 7.4, 7.1 and 6.9 respectively, while the pH of the 600 – 700
mm depth for the pre-, post- gypsum, 6-month and 12 month samplings was 9.0, 8.3, 8.7 and 6.8
respectively. After 12 months, the pH remained relatively constant at pH 7 over the 0 – 800 mm
interval. A similar trend was observed for the EC. Exchangeable Ca and Na tended to demonstrate
relatively small non-significant changes throughout the profile. Available SO4 did not display any
significant variation throughout the profile with time.
Distributions of water-soluble Ca, Na, SO4, CO3 and HCO3 are presented in Figure 6. Very little Ca
and SO4 were found in the soil solution below a gypsum incorporation depth of 600 mm. There
appeared to be a good relationship between the distribution of soluble and exchangeable Na with depth
and pH at the 12-month sampling event. This relationship suggests that Na and its accompanying
anion may be largely responsible for controlling the pH of residue sand.
2006 Sampling: 6-Month and 12-Month - Kwinana
The pH of residue sand over the 0 – 800 mm depth decreased with time, although the changes over the
12-month period were small relative to values immediately following gypsum incorporation (Figure
5). For example, the pH of the 0 – 100 mm depth for the pre-gypsum, post-gypsum, 6-month and 12
month samplings was 9.8, 8.0, 8.3 and 7.6 respectively, while the pH of the 600 – 700 mm depth for
the pre-gypsum, post-gypsum, 6-month and 12 month samplings was 10.1, 9.0, 9.8 and 8.7
respectively. In contrast to Pinjarra, however, the pH was observed to increase steadily over the 0 –
800 mm depth, and mimicked values observed immediately post-gypsum incorporation. The EC
decreased significantly (p < 0.05) between the 6-month and 12-month sampling events in the 0 – 300
mm zone, and remained relatively constant at 10 mS/m below this depth. Exchangeable Ca and
available SO4 tended to demonstrate relatively small non-significant changes throughout the profile. In
contrast, exchangeable Na concentrations tended to decrease with increasing time within the 0 – 800
mm depth.
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Water-soluble Ca and SO4 concentrations within the 0 – 800 mm depth were typically low relative to
that in the adsorbed phase (Figure 6). The distribution of water-soluble Na concentrations displayed a
similar pattern to that observed for pH.
General Discussion
Of the two sites at which the study was conducted, Kwinana provided the best opportunity to assess
the effects of gypsum incorporation depth and subsequent leaching. This is because the depth of
gypsum incorporation study was established at the only area which had not received previous gypsum
and/or fertiliser additions. Although data interpretation for both sites was complicated by the absence
of sampling immediately following gypsum and fertiliser addition (which may have highlighted the
effect of gypsum on various chemical properties), previous fertiliser additions at the Pinjarra study
area appear to have already resulted in a build-up of plant nutrients in the residue sand profiles.
Therefore, gypsum and/or fertiliser from past additions could not be separated from that applied at the
commencement of the trial, which limited an assessment of whether the non-irrigated and irrigated
treatments have had a positive or otherwise impact on gypsum and nutrient availability and movement
in residue sand profiles.
The effects of gypsum on plant nutrient (N, P, K, Mg, Ca and S) concentrations and pH observed at
Kwinana were not unexpected based on the known behaviour of gypsum in residue sand (Phillips
2010a). In general, these can be summarised as follows. The movement of gypsum throughout the
residue sand profile will primarily be governed by its rate of dissolution, hence solubility in the porewater. The dissolution of gypsum is described as:
CaSO4.2H2O ↔ Ca2+ + SO42- + 2H2O
(CaSO4 log Ksp = - 4.58)
(1)
The solubility product (Ksp) of gypsum used in residue rehabilitation is about 0.22 g/100 mL (Phillips
2010a). This implies that when the concentration of gypsum in the pore-water is less than 0.22 g/100
mL, Eqn (1) will proceed to the right and dissolution of gypsum should occur. Whereas if pore-water
gypsum concentrations exceed 0.22 g/100 mL, then Eqn (1) proceeds to the left and gypsum
precipitation would occur. Due to the high application rates (particularly in the shallow incorporation
treatment) and low solubility of gypsum, coupled with poor water retention properties of residue sand,
considerable amounts of applied gypsum could persist in the residue sand for extended periods of
time. In fact, excavations in the shallow incorporation trial found exceedingly high amounts of
undissolved gypsum within the 0 – 200 mm depth, with some locations exhibiting nearly 100%
13
gypsum (i.e. no residue sand) in the 0 – 150 mm zone (Figure 7). The impacts of this dominance of
gypsum on plant establishment and nutrient availability are currently unknown, although preliminary
root distribution studies (see below) suggest this may in fact restrict root penetration depths. The
ability of gypsum to alter the chemical properties of residue sand below the zone of gypsum
incorporation must be considered limited, at least in the short term.
Prior to gypsum amendment, residue sand typically contains very high concentrations of carbonate
(about 18000 mg CO3 /L), with lower concentrations of bicarbonate (about 600 mg HCO3 /L), anions
(Appendix 6). Following gypsum amendment, the concentration of these anions are considerably
reduced (through formation of CaCO3 and conversion of CO3 to HCO3 as a function of pH (Stumm
and Morgan 1981), with HCO3 becoming the dominant inorganic carbon-based ion (about 590 mg
HCO3 /L; Appendix 6).The reduction in pH following gypsum addition arises from the reaction of
Ca2+ with carbonate (CO32-) to form weakly-soluble CaCO3 (Barrow 1982):
CaSO4 + Na2CO3 ↔ CaCO3 + Na2SO4
(CaCO3 log Ksp = - 8.48; Na2SO4 log Ksp = 0.7)
(2)
The smaller Ksp for CaCO3 compared to Na2SO4 results in CaCO3 being precipitated within the residue
sand, with the more soluble Na2SO4 being leached from the material with drainage water. However, as
soluble Ca moves with the leaching water, the opportunity for Na:Ca cation exchange reactions can
also occur. Residue sand has a cation exchange capacity (CEC) of about 5 cmol/kg, and this is initially
dominated by exchangeable Na. The dissolution of gypsum (Eqn 1) provides Ca in the water phase
which can subsequently displace Na from the exchange sites according to:
2X-Na+ + Sol-Ca2+ ↔ X-Ca + 2Sol-Na2+
(3)
where X refers to exchangeable cation and Sol refers to solution cation.
As solution Ca concentrations decrease due to precipitation (Eqn 2) and cation exchange (Eqn 3), this
would stimulate further dissolution of gypsum until the saturation index became zero, after which the
Ca, SO4, Na, pH and EC of the solution phase would remain relatively constant.
Over the period August to November 2005, the cumulative rainfall plus irrigation was ≈ 300 mm for
both sites (Figure 2). If it is assumed that field capacity of residue sand is 0.2 cm3/cm3, then the depth
of water movement can be conservatively estimated to be about 300÷0.2 = 1500 mm. Since the depth
of shallow gypsum incorporation was up to 600 mm, sufficient water appears to have been applied to
14
the treatment plots to cause movement of gypsum to depths of up to 1500 mm. In fact, the depth of
penetration of the wetting front from an individual irrigation event of 20 mm can potentially exceed
1200 mm (Figure 8). Changes in exchangeable Ca, exchangeable Na, available-S, EC and pH profiles
were consistent with gypsum interaction with residue sand. For example, exchangeable Na
concentrations in the 0 – 100, 500 – 700 and 1300 – 1500 mm depth intervals pre- and post- gypsum
incorporation were 3.7, 5.9 and 5.7, and 0.6, 2.4 and 3.5, respectively. These changes may be a result
of Ca:Na exchange as soluble Ca moves through the residue sand profile with drainage water
(particularly in the surface layer) and leaching of readily-soluble Na. This suggests that shallow
gypsum incorporation may be capable of altering the chemical composition of residue sand profiles,
albeit at a much slower rate relative to deep incorporation.
Based on the chemical composition of gypsum (CaSO4), the presence of Ca and/or SO4 below the zone
of gypsum incorporation should be a good indicator of gypsum leaching. Typically, the sorption
characteristics of these two ions in the presence of hydrous Fe and Al oxides can limit their availability
and mobility (Theng 1980; Cichota et al. 2007). Consequently, the combined effects of low gypsum
solubility and strong sorption of the dissolution products (coupled with the formation of low solubility
CaCO3), may be a major cause for only small (and possibly non-significant) changes in the
concentration of Ca and/or SO4 in both the soluble and adsorbed phases.
As mentioned above, non-gypsum amended residue sand is dominated by Na2CO3 and NaHCO3
(Appendix 6), whereas after gypsum amendment, the concentration of these anions are considerably
reduced through formation of CaCO3 and conversion of CO3 to HCO3 as a function of pH. Thus, the
relative proportion of water-soluble CO3 to HCO3 may provide a more reliable indicator of gypsum
interaction with residue sand and mobility. For the Pinjarra study, no CO3 was present within the 0 –
800 mm depth, although HCO3 was present at a relatively constant concentration of 300 – 400 mg/L
(Figure 6). Although this suggests gypsum leaching has occurred below the depth of incorporation
(about 600 mm), there is a strong possibility this movement may be a consequence of previous
gypsum additions (i.e. prior to trial establishment). In contrast, the Kwinana study demonstrated watersoluble CO3 concentrations about 1% of that found in unamended residue sand (about 200 mg/L) were
present at depths below 400 mm (Figure 6). Since the Kwinana trial was established on an
embankment which had not previously received gypsum and fertilizer additions, this finding suggests
some gypsum leaching below the depth of incorporation (about 600 mm) may have occurred.
Unfortunately, the limited sampling depth of 0 – 800 mm does not provide information on how the
CO3 to HCO3 ratio varies at greater depths which may have indicated the depth of gypsum penetration
15
since trial commencement. Alternately, CO3 concentrations may have decreased naturally over time
due to leaching and/or carbonation by infiltrating water (Phillips 2010a).
In 2008, samples of residue sand were collected from a 4-year old rehabilitated residue sand
embankment to a depth of 3 m, and were analysed for a range of chemical and physical parameters
(Phillips, unpublished data). Parameters relevant to gypsum leaching are provided in Appendix 6b.
Gypsum was incorporated to a depth of up to 1.5 m, and key indicators such as pH, Ca, Na (in both the
solid and soluble fractions), and soluble SO4, CO3 and HCO3, indicate that the effects of gypsum were
primarily confined to its depth of incorporation (1 – 1.5 m). These data provide strong evidence that
little movement below the zone of incorporation has occurred within a 4 year period. Thus, leaching of
surface-applied gypsum would not appear to be suitable for ameliorating the pH of residue sand at
depth.
Previous studies (Phillips 2010a) suggested that Ca preferentially reacts with CO3 (Eqn 1) prior to
undergoing cation exchange. Calcium sorption involves both adsorption and precipitation reactions but
the relative importance of these two mechanisms in removing solution Ca was not studied in this
experiment. Wong and Ho (1995) reported that Na was preferentially adsorbed by residue mud relative
to Ca at solution cation fractions > 10%, and that Ca rarely exceeded 20% of the exchange phase. This
cation exchange behaviour can be attributed to the presence of zeolitic-type minerals grouped as
desilication product (DSP; Wong and Ho 1995). Desilication product (DSP) is formed by the reaction
of soda and alumina with reactive silica during the Bayer process. Residue mud contains about 11%
DSP, whereas residue sand contains about 1% DSP. Phillips (2010a) estimated that DSP may account
for up to 3 cmol/kg of charge, or ≈ 40% of the overall CEC. This implies that a significant proportion
of the CEC of residue sand may exhibit a relatively low affinity for Ca (particularly at high solution
Ca fractions) and this would encourage Ca to remain in solution and be preferentially lost via
precipitation as CaCO3.
Additional Information
Plant root distribution
Field studies on root distribution for three plant species, Hardenbergia comptoniana, Acacia
cochlearis and Eucalyptus gomphocephala were selected to represent examples of ground cover, shrub
and tree species, respectively (Dobrowolski et al. 2009). It was generally found that irrespective of
plant species, the roots were primarily confined to the zone of gypsum incorporation. Also,
compaction within the residue sand profile increased dramatically below the zone of gypsum
16
incorporation. This appeared to restrict root penetration below the gypsum zone, which was
particularly evident for the shallow gypsum treatment. This restriction would severely limit the
volume of residue sand available to the plant for extracting water and nutrients, which may markedly
affect the long term sustainability of the plant cover system. The apparent dependency of depth of root
penetration on depth of gypsum incorporation provides strong support for not recommending shallow
gypsum incorporation for residue rehabilitation.
Health criteria
The soil microbial biomass is mainly composed of fungi and bacteria, and provides an indication of
short-term changes in soil fertility. The fungi and bacteria present in residue sand would be largely
responsible for the decomposition of plant residues, and they can release plant nutrients via
mineralisation, or can accumulate nutrients through immobilisation within the microbial biomass. To
assess the fertility status of the residue sand at the Pinjarra site, residue sand from the 300 (within root
zone), 1000 (below root zone) and 1800 (compaction zone) mm depths were analysed for microbial
biomass. All samples recorded negligible microbial biomass and would be regarded as exhibiting low
fertility (Dobrowolski et al. 2009). Although these findings are not directly related to the objectives of
this study, they do highlight the need to improve the fertility status and nutrient-supplying capacity of
the overall residue sand profile as a means of encouraging greater plant root distribution. Without this
ability to supply nutrients, plant roots may be restricted to zones of artificial nutrient sources such as
that created by gypsum incorporation and/or fertiliser addition.
Conclusions and Recommendations
Shallow and deep gypsum incorporation improved the chemical characteristics of residue sand for
plant growth, although these effects were less obvious in profiles which had a previous history of
gypsum and/or fertiliser additions. Gypsum addition typically reduced pH and Na concentrations, and
increased Ca and SO4 concentrations within the zone of incorporation. Some gypsum leaching below
the zone of incorporation was evident, but shallow incorporation may limit amelioration of
unfavourable chemical conditions at depth due to the limited solubility of gypsum in residue sand. The
extent of leaching was however better described using water-soluble CO3 to HCO3 ratios.
Shallow gypsum incorporation represents a significant cost-saving in operational residue
rehabilitation. However, based on (1) issues associated with solubility and in-situ movement within
the residue sand profile, and (2) possible limitations on plant root distribution, this method of
17
incorporation is not recommended as part of the operational prescription of residue rehabilitation. It is
recommended that the current method of deep incorporation be maintained.
RESULTS AND DISCUSSION – BOTANICAL MONITORING
A detailed description of the botanical monitoring component of this study was prepared by LeRoy
(2007). A summary of those findings are provided in this report.
Irrigation Trial - Pinjarra
Irrigation did not affect cover or species richness of natives and exotics (p >0.05). However, density
was significantly greater in non-irrigated plots than irrigated plots (p <0.05), which was largely due to
the contribution from exotics (Figures 9, 10 and 11). Native species contributed to a significantly
greater amount of cover and species richness relative to the exotic species (p <0.001) despite exotics
having a significantly greater density measurement than natives (p<0.001).
Over the 2005 – 2007 monitoring period, the proportion of cover increased significantly with each
consecutive year (p<0.001). Plant density in 2006 and 2007 was significantly greater than in 2005 (p
<0.001), whereas species richness was significantly greater in 2005 and 2006 than in 2007 (p <0.05).
Visually, rehabilitation in Block 1 appeared to be out-performing that in Blocks 2 and 3. Block 1
contained less exotic species and therefore looked healthier (Figures 12 and 13). Analyses of results
showed Block 1 had significantly less density than Blocks 2 and 3 (p <0.05), as well as significantly
less species richness (p <0.05). This may be due to the exotic plants in Blocks 2 and 3 contributing to
the higher density and species richness.
Vegetation on the upper slope appeared to be less healthy than vegetation at the bottom of the slope.
Although the upper slope of the plots exhibited a higher cover, density and species richness than the
lower slope, these differences were not statistically significant (p >0.05). The history of RSA5
embankment construction revealed that the upper section was hydraulically poured whilst the lower
section was mechanically constructed. It is possible that this difference in embankment construction
may have contributed to differences in plant performance (mechanically constructed tend to be
compacted); however, any compaction should have been relieved during trial establishment and
gypsum incorporation. Moisture profiles within the plant root zone (<2 m) did not exhibit major
differences in between upper slope and lower slope locations, particularly during the late-summer
period (Phillips unpublished data). However, plant water use (based on plant transpiration data over
2009; Phillips unpublished data) appeared to be greater on the lower than upper slopes. Other factors
18
contributing to the performance of vegetation located on the upper part of the embankment may also
involve operational activities at the adjacent mudlake (e.g. exposed to alkaline spray from mud/sand
pipe discharge and/or alkaline dust).
Irrigation Trial - Kwinana
Irrigated plots displayed a significantly greater cover by natives and exotics (p <0.05) yet significantly
less density than non-irrigated plots (p <0.05). Species richness was not significantly affected by
irrigation (p >0.05) (Figure 14, 15 and 16). There was no significant difference in proportion of cover
between native and exotic species (p >0.05). The density of exotic species was significantly greater (p
<0.001) than that of natives, irrespective of irrigation treatment. In contrast, exotic plants exhibited
significantly less species richness compared with native species (p <0.001). Over the three monitoring
periods, species richness of natives numbered 21 compared to 7 for exotic species.
Over the three-year monitoring period, cover increased significantly with each consecutive year (p
<0.001) (Figure 14). The density of plants was significantly greater in 2007 than in 2005 and 2006 (p
<0.001). Species richness was greatest in 2005, but this number decreased significantly in 2006 and
2007 (Figure 16).
Gypsum Trial - Pinjarra
There were no significant differences (p >0.05) in cover, density and species richness for natives and
exotics growing in shallow and deep gypsum treatments (Figures 17, 18, 19). Also, there were no
significant differences (p >0.05) in vegetation cover and density between position on the embankment
(i.e. upper or lower). However, species richness was significantly greater on the upper slope than the
lower slope (p <0.001).
Block 1 exhibited significantly less cover than Blocks 2 and 3 (p <0.05) and significantly less density
than Block 3 (p <0.05). Blocks 1, 2 and 3 were all significantly different from each other with respect
to species richness, with Block 1 having the least number of species and Block 3 the most (p <0.001).
Native plants displayed significantly greater species richness than exotic plants (p <0.001), but
significantly less density (p <0.001). There was no significant difference between the proportion of
cover for exotic and native species (p >0.05) (Figure 17, 18 and 19).
19
Over the three-year monitoring period, cover was found to significantly increase on an annual basis (p
<0.001). Plant density increased significantly from 2005 to 2006, but species richness declined
significantly in 2007 relative to that in 2006 (p <0.001).
Gypsum Trial - Kwinana
There was no significant difference between shallow and deep gypsum treatments with respect to
vegetation density, cover and species richness of natives and exotics (p >0.05). There was however a
significant difference between the density, cover and species richness of native and exotic species.
Native species displayed significantly greater cover and species richness (p <0.001), yet significantly
less density (p <0.05) than exotic species (Figures 20, 21 and 22).
Vegetation cover and density significantly increased over the 2006 – 2007 period relative to that
observed in 2005 (p <0.001 and p <0.05 respectively). In contrast, species richness significantly
declined in 2007 compared to that in 2005 and 2006 (p <0.001). Position of vegetation on the
embankment (upper or lower slope) had no significant effect on cover, density or species richness of
native and exotic species (p >0.05).
Discussion and Conclusions
Irrigation trial
Plant density was found to be significantly lower in irrigated plots compared with non-irrigated plots.
This was associated with a lower density of exotic species in irrigated plots than non-irrigated plots. It
is possible that the additional water provided by irrigation may have accelerated growth of the native
vegetation, thereby crowding out exotic species. This is supported from the finding that exotics have
proliferated in non-irrigated plots. Furthermore, irrigation did not improve species richness at either
site.
From the monitoring data, amounts of irrigation based on soil-water deficits have not been found to
provide any significant benefit to residue rehabilitation. To achieve any significant benefits, much
greater and more frequent irrigation applications may be required. However, this is not practical from
a water resource perspective, and if a sustainable vegetation cover is to be achieved.
During the summer of 2006/2007 many species became stressed and some senesced (LeRoy 2007).
Despite this, many species recovered after early winter rain periods, with many plants producing new
growth. This provides additional support for removing irrigation from operational residue
20
rehabilitation prescription; however, continued monitoring of species performance will be undertaken
to ensure that rehabilitation failure will not occur in future years.
An additional finding from this study has been identification of those species that cannot survive under
non-irrigated conditions (LeRoy 2007). These data are being used to refine the current rehabilitation
seed mix.
Gypsum trial
Depth of gypsum incorporation in residue rehabilitation did not affect the measurement indices cover,
species richness or density. Based on plant performance alone, it could be concluded that plant
performance is independent of gypsum incorporation depth. But it must be remembered that the
majority of plant roots resided in the surface 0 – 300 mm which was well within the depth of gypsum
incorporation for both gypsum treatments.
CONCLUSIONS AND RECOMMENDATIONS
Conclusions
This report presents findings from a three year study to identify the role of irrigation in residue
rehabilitation, and whether depth of gypsum placement affects rehabilitation performance. The
chemical analysis of residue sand profiles at varying times after gypsum incorporation suggested some
movement of gypsum to depths below its zone of incorporation, and that the rate of movement was
relatively slow. This rate of movement may be related to the low solubility of gypsum and the poor
water retention properties of residue sand. Importantly, changes in Na, CO3 and HCO3 proved to be
more reliable indicators of gypsum interaction with residue sand than pH, Ca and SO4. This was
because the strong sorption (adsorption and/or precipitation) of Ca and SO4 tended to reduce their
concentrations in solution to very low concentrations. If shallow gypsum incorporation were to be
recommended, studies would need to confirm that its rate of movement throughout the residue sand
profile was faster than the rate of plant root growth. This study would need to ensure that gypsum
movement was not a limiting factor to plant root growth, hence water and nutrient uptake.
Irrigation did not significantly improve rehabilitation performance. These findings are not unexpected
because irrigation was not applied on a continuous basis, rather when plant-stress from water-deficit in
residue sand storage was estimated. Although irrigated plots received significantly more water than
non-irrigated plots, the additional water probably was of little benefit to the plant cover due to the
rapid hydraulic conductivity of residue sand (≈ 20 m/d).
21
Botanical monitoring found that a major response to irrigation was higher above-ground biomass (as
measured by cover) but no difference in species richness. Plant performance was also found to be
independent of gypsum incorporation depth. The combined effect of this would be that operational
prescription for residue rehabilitation would involve the removal of irrigation and inclusion of shallow
incorporation of gypsum. Although the removal of irrigation would not be expected to significantly
hinder plant performance, shallow gypsum incorporation is not recommended for the following
reasons.
Firstly, shallow incorporation should have been restricted to a depth of 0 – 300 mm; however, the
actual depth was most likely 0 – 600 mm. Secondly, independent root distribution studies showed that
a very high proportion of roots reside in the 0 – 300 mm with only a few roots penetrating to greater
depths (Dobrowolski et al. 2009). Therefore, both the shallow and deep gypsum treatments resulted in
gypsum being distributed throughout the root zone. As such, neither the shallow or deep gypsum
treatments would have hindered plant root distributions and their accessibility to moisture and
nutrients due to hostile chemical characteristics of the residue sand. Also, plant roots were observed to
be associated with high concentrations of gypsum, particularly in the shallow treatments. Gypsum may
provide a less-hostile environment for plant roots due to its lower pH, high nutritional value and
potentially higher water content by virtue of its finer texture, compared to residue sand. It is possible
therefore that plant roots in shallow gypsum treatments may preferentially remain closer to the surface
with gypsum. Unfortunately this may also render plants more susceptible to drought stress during
summer.
Recommendations
Although this study has provided good information on the reaction of gypsum with residue sand,
factors such as past gypsum and fertiliser additions, incorporation of gypsum throughout the root zone
irrespective of gypsum treatment, and irrigation applications which did not markedly affect plant
available water, may not have truly tested the effect of gypsum placement and irrigation on plant
performance. Despite this, it is recommended that:
Irrigation be removed from the current prescription for residue rehabilitation because (1) it is
not a sustainable practice in terms of long term management of residue disposal areas, (2) is
an inefficient use of a limited natural resource at a time when water management is essential,
and (3) may restrict root distribution to shallow depths in the residue sand profile.
22
Deep gypsum incorporation be retained as the preferred method because (1) its proven
effectiveness in rapidly altering the characteristics of residue sand such that it is more
conducive for plant growth, and (2) it encourages deeper penetration of plant roots.
Maintain botanical monitoring of the trials to test whether any of the treatments causes a
reduction in rehabilitation performance in the longer term.
Use the parameters Na, CO3 and HCO3 in conjunction with Ca, SO4 and pH as a measure of
gypsum interaction with residue sand.
Prior to establishing any field trial, ensure that a complete history of past management is
obtained and assess whether any previous activity will affect the primary objectives (or
hypotheses to be tested) of the study.
REFERENCES
Barrow NJ (1982) Possibility of using caustic residue from bauxite for improving the chemical and
physical properties of sandy soils. Australian Journal of Agricultural Research 33, 275-285
Cichota R, Vogeler I, Bolan N, Clothier B (2007) Simultaneous adsorption of calcium and sulfate and
its effect on their movement. Soil Science Society of America Journal 71, 703 – 710
Dobrowolski MP, Mullins RG, Phillips IR (2009) Factors affecting plant root distribution in sand
embankments of bauxite residue disposal areas. (Environmental Department Research Note No.
29 Alcoa of Australia: Perth)
Eastham J, Morald T (2004a) Improving root penetration and vegetation growth on bauxite residue
embankments. (Unpublished Report Alcoa Western Australia Engineering Operations Alcoa of
Australia: Perth)
Eastham J, Mullins G (2004b) Evaluating techniques for reducing pH of bauxite residue at depth using
gypsum. (Unpublished Report Alcoa Western Australia Engineering Operations Alcoa of
Australia: Perth)
Keipert N (2005) Chemical properties of residue prior to application of gypsum and irrigation
treatments. (Unpublished Report Environmental Department Alcoa of Australia: Perth)
LeRoy M (2007) The effect of gypsum depth and irrigation on plant growth in residue sand.
(Unpublished Report Environmental Department Alcoa of Australia: Perth)
Narducci M (2006) Effect of irrigation on survival and growth of rehabilitation on residue
embankments. (Unpublished Report Environmental Department Alcoa of Australia: Perth)
Phillips IR (2010a) Characteristics of gypsum and fertiliser used in residue rehabilitation.
(Environmental Department Research Note No. 35 Alcoa of Australia: Perth)
23
Phillips IR (2010b) Comparing techniques for incorporating gypsum into residue sand embankments
at Alcoa’s residue disposal areas. (Environmental Department Research Note No. 32 Alcoa of
Australia: Perth)
Phillips IR, Bond WJ (1989) An extraction procedure for determining solution and exchangeable ions
on the same soil sample. Soil Science Society of America Journal 53, 1294 – 1297
Phillips IR, Chen C (2010) Surface charge properties and sorption properties of bauxite-processing
residue sand. Australian Journal of Soil Research 48, 77-87
Rayment GE, Higginson FR (1992) “Australian laboratory handbook of soil and water chemical
methods”. (Inkata Press: Melbourne)
Stumm W, Morgan JJ (1981) “Aquatic chemistry. 2nd edition”. (John Wiley & Sons: Brisbane)
Theng BKG (1980) “Soils with variable charge”. (New Zealand Society of Soil Science: Lower Hutt
New Zealand)
Wilkinson C (2005) Botanical monitoring of gypsum/irrigation trials on bauxite residue – December
2005. (Unpublished Report Environmental Department Alcoa of Australia: Perth)
Wong JWC, Ho GE (1995) Cation exchange behaviour of bauxite refining residues from Western
Australia. Journal of Environmental Quality 24, 461- 466
24
Figure 1. A diagram (not to scale) of the botanical monitoring plots set up within each treatment plot.
Distances for the different plots and compass bearings are shown. The dark square (■) is the Northwest corner of the plot and is marked in the field by a fence dropper and a permanent plot number
Treatment plot area
20 m, 90º
N
36 m²
20 m,
180º
28.28 m,
135º
Down slope
400 m²
6m
6m
8.48 m
36 m²
25
Figure 2. Rainfall ± irrigation received over each residue sand sampling event (1 = August 2005 to
November 2005; 2 = December 2005 to June 2006; 3 = July 2006 to December 2006; 4 = January
2007 to December 2007)
1000
KW -I
PJ -I
KW +I
PJ +I
Water Input Per Sampling Event (mm)
800
600
400
200
0
1
2
Sampling Event
3
26
4
pH (1:5 soil:water)
6
(a)
8
10
12
0
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
pH (1:5 soil:water)
6
(b)
8
10
0
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
400
Depth (mm)
12
800
1200
1600
27
EC (mS/m 1:5 soil:water)
0
(a)
40
80
120
160
200
0
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
EC (mS/m 1:5 soil:water)
0
(b)
40
80
120
160
0
Depth (mm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
28
200
Exch Ca (cmol/kg)
0
(a)
4
8
12
0
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
Exch Ca (cmol/kg)
0
(b)
4
8
12
0
Depth (cm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
29
Exch Na (cmol/kg)
0.0
(a)
0.2
0.4
0.6
0.8
1.0
0
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
Exch Na (cmol/kg)
0.0
(b)
0.2
0.4
0.6
0.8
1.0
0
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
30
Avail S (mg/kg)
0
(a)
1000
2000
3000
4000
0
Depth (mm)
400
800
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
Avail S (mg/kg)
0
(b)
1000
2000
3000
4000
0
Depth (mm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
31
Bicarb K (mg/kg)
0
(a)
20
40
60
80
100
120
0
Depth (mm)
400
800
Deep Gypsum
1200
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1600
Bicarb K (mg/kg)
0
(b)
40
80
120
0
Depth (mm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
32
Bicarb P (mg/kg)
0
(a)
40
80
120
160
200
0
Depth (mm)
400
800
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
Bicarb P (mg/kg)
0
(b)
40
80
120
160
200
0
Depth (mm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
Figure 3. Pinjarra gypsum irrigation trial – effects of (a) deep or (b) shallow gypsum incorporation on
the vertical distribution of pH, EC, exchangeable Ca, exchangeable Na, available S, available K and
available P. Values presented are for pre- and post- gypsum incorporation, and minus and plus
irrigation
33
pH (1:5 soil:water)
6
(a)
8
10
12
0
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
pH (1:5 soil:water)
6
(b)
8
10
0
Depth (mm)
400
800
Shallow Gypsum
1200
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1600
34
12
EC (mS/m 1:5 soil:water)
0
(a)
40
80
120
160
200
0
Depth (mm)
400
800
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
EC (mS/m 1:5 soil:water)
0
(b)
40
80
120
200
0
400
Depth (mm)
160
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
800
1200
1600
35
Exch Ca (cmol/kg)
0
(a)
4
8
12
0
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
Exch Ca (cmol/kg)
0
(b)
4
8
12
0
Depth (cm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
36
Exch Na (cmol/kg)
0
(a)
2
4
6
8
0
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
Depth (mm)
400
800
1200
1600
Exch Na (cmol/kg)
0
(b)
2
4
0
Depth (mm)
400
800
1200
1600
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
37
6
8
Avail S (mg/kg)
0
(a)
1000
2000
3000
4000
0
Depth (mm)
400
800
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
Avail S (mg/kg)
0
(b)
1000
2000
3000
4000
0
Depth (mm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
38
Bicarb K (mg/kg)
0
(a)
20
40
60
80
100
0
Depth (mm)
400
800
Deep Gypsum
1200
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1600
Bicarb K (mg/kg)
0
(b)
40
80
120
0
Depth (mm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
39
Bicarb P (mg/kg)
0
(a)
40
80
120
160
200
0
Depth (mm)
400
800
Deep Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
Bicarb P (mg/kg)
0
(b)
40
80
120
160
200
0
Depth (mm)
400
800
Shallow Gypsum
Pre -Irr
Pre +Irr
Post -Irr
Post +Irr
1200
1600
Figure 4. Kwinana gypsum irrigation trial – effects of (a) deep or (b) shallow gypsum incorporation
on the vertical distribution of pH, EC, exchangeable Ca, exchangeable Na, available S, available K
and available P. Values presented are for pre- and post- gypsum incorporation, and minus and plus
irrigation.
40
Exchangeable Na (cmol/kg)
Exchangeable Ca (cmol/kg)
0
(a)
20
40
0
60
(b)
0
4
6
0
40
80
Depth (cm)
40
Depth (cm)
2
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
80
120
160
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
Exchangeable Na (cmol/kg)
Exchangeable Ca (cmol/kg)
0
20
40
0
60
(d)
(c) 0
2
4
6
0
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
40
Depth (cm)
Depth (cm)
40
80
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
80
120
160
160
41
pH (water)
6
(a)
7
8
9
EC (mS/m)
10
0
11
(b)
0
Depth (cm)
80
120
160
200
0
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
EC (mS/m)
pH (water)
6
7
8
9
10
0
11
(d)
(c) 0
40
80
120
160
200
0
40
Depth (cm)
40
Depth (cm)
120
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
80
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
120
160
80
40
40
Depth (cm)
40
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
42
Available SO4 (mg/kg)
0
(a)
2000
4000
6000
0
Depth (cm)
40
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
160
Available SO4 (mg/kg)
0
(b)
2000
4000
6000
0
Depth (cm)
40
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
160
Figure 5. Effect of time (pre- and post- (0, 6 and 12 months) after gypsum incorporation, on fertilizer
and gypsum transport, and selected chemical properties. Values presented are for pre- and postshallow gypsum incorporation, and minus irrigation. For each set of 4 graphs, (a) and (b) refer to data
for the Kwinana trial, and (c) and (d) refer to data for the Pinjarra trial. For available S, (a) refers to
data
for
the
Kwinana
trial,
and
(b)
refers
43
to
data
for
the
Pinjarra
trial.
Ca (cmol/kg)
0
(a)
5
10
15
20
25
0
Depth (cm)
20
40
Available
Soluble
60
80
Ca (cmol/kg)
0
(b)
5
10
15
0
Depth (cm)
20
40
Available
Soluble
60
80
44
20
25
Na (cmol/kg)
0
(a)
0.4
0.8
1.2
2
0
20
Depth (cm)
1.6
Available
Soluble
40
60
80
Na (cmol/kg)
0
(b)
0.4
0.8
1.6
0
20
Depth (cm)
1.2
Available
Soluble
40
60
80
45
2
SO4-S (mg/kg)
0
(a)
2000
4000
6000
0
Depth (cm)
20
40
Available
Soluble
60
80
SO4-S (mg/kg)
0
(b)
2000
4000
0
Depth (cm)
20
40
Available
Soluble
60
80
46
6000
CO3 and HCO3 (mg/L)
0
(a)
1000
2000
3000
0
HCO3
CO3
CO3 + HCO3
Depth (mm)
200
400
600
800
CO3 and HCO3 (mg/L)
0
(b)
100
200
300
400
500
0
HCO3
CO3
Depth (mm)
200
CO3 + HCO3
400
600
800
Figure 6. Vertical distribution of Ca, Na and SO4 in the water-soluble and solid (available phase)
fractions, and soluble alkalinity, for residue sand 12 months after shallow gypsum incorporation. For
each set of 2 graphs, (a) refers to data for the Kwinana trial, and (b) refers to data for the Pinjarra trial
47
(a)
(b)
Figure 7. (a) Large pieces of gypsum present within the residue sand profile, and (b) high
concentrations of gypsum in the 0 – 200 mm depth interval at the shallow gypsum incorporation trial.
48
(b)
0.3
0.25
0.2
0.15
0.1
0.05
0
5 mm
100 mm
300 mm
600 mm
Control
0
50
100
150
Time (hours)
200
250
Drainage Below 600 mm (% of applied)
Volumetric Water Content (mm3/mm3)
(a)
6
4
2
0
0
50
100
150
Time (hours)
200
250
Volumetric Water Content (mm3/mm3)
(c)
0.3
0.25
10 mm
100 mm
300 mm
600 mm
1200 mm
1500 mm
0.2
0.15
0.1
0.05
0
0
50
100
150
Time (hours)
200
250
Figure 8. Simulated (HYDRUS-1D) water content at specific depths within the (a) 600 and (c) 1500 mm depth interval, and the amount of
drainage following a single irrigation event
49
120
Cover (%)
100
80
2005
60
2006
2007
40
20
0
Natives +irr
Exotics +irr
Natives -irr
Exotics -irr
Figure 9. Comparison of cover of natives and exotics in irrigated and non-irrigated plots over 3
monitoring years at Pinjarra.
35
Density (plants/m2)
30
25
2005
20
2006
15
2007
10
5
0
Natives +irr
Exotics +irr
Natives -irr
Exotics -irr
Figure 10. Comparison of density of natives and exotics in irrigated and non-irrigated plots over 3
monitoring years at Pinjarra
35
Species Richness
30
25
2005
20
2006
15
2007
10
5
0
Natives +irr
Exotics +irr
Natives -irr
Exotics -irr
Figure 11. Comparison of species richness of natives and exotics in irrigated and non-irrigated plots
over 3 monitoring years at Pinjarra
50
Figure 12. Rehabilitation in Block 1 at Pinjarra with few exotics
Figure 13. Rehabilitation in Block 3 at Pinjarra showing a groundcover of exotic species including
Medicago polymorpha and Lupinus cosentinii
51
60
50
Cover (%)
40
2005
30
2006
2007
20
10
0
Natives +irr
Exotics +irr
Natives -irr
Exotics -irr
Figure 14. Comparison of cover of natives and exotics in irrigated and non-irrigated plots over 3
monitoring years at Kwinana
25
Density (plants/m2)
20
15
2005
2006
2007
10
5
0
Natives +irr
Exotics +irr
Natives -irr
Exotics -irr
Figure 15. Comparison of density of natives and exotics in irrigated and non-irrigated plots over 3
monitoring years at Kwinana
30
Number of species
25
20
2005
15
2006
2007
10
5
0
Natives + irr
Exotics + irr
Natives - irr
Exotics - irr
Figure 16. Comparison of species richness of natives and exotics in irrigated and non-irrigated plots
over 3 monitoring years at Kwinana
52
45
40
Density (plants/m2)
35
30
2005
25
2006
20
2007
15
10
5
0
Natives deep
Exotics deep
Natives surface Exotics surface
Figure 17. Comparison of density of natives and exotics in surface and deep gypsum plots over 3
monitoring years at Pinjarra
80
70
Cover (%)
60
50
2005
40
2006
2007
30
20
10
0
Natives deep
Exotics deep
Natives surface Exotics surface
Figure 18. Comparison of cover of natives and exotics in surface and deep gypsum plots over 3
monitoring years at Pinjarra
35
Number of Species
30
25
2005
20
2006
15
2007
10
5
0
Natives deep
Exotics deep
Natives surface Exotics surface
Figure 19. Comparison of species richness of natives and exotics in surface and deep gypsum plots
over 3 monitoring years at Pinjarra
53
14
Density (plants/m2)
12
10
2005
8
2006
6
2007
4
2
0
Natives deep
Exotics deep
Natives surface Exotics surface
Figure 20. Comparison of density of natives and exotics in surface and deep gypsum plots over 3
monitoring years at Kwinana
40
35
Cover (%)
30
25
2005
20
2006
2007
15
10
5
0
Natives deep
Exotics deep
Natives surface Exotics surface
Figure 23. Comparison of cover of natives and exotics in surface and deep gypsum plots over 3
monitoring years at Kwinana
45
40
Number of species
35
30
2005
25
2006
20
2007
15
10
5
0
Natives deep
Exotics deep
Natives surface Exotics surface
Figure 24. Comparison of species richness of natives and exotics in surface and deep gypsum plots
over 3 monitoring years at Kwinana
54
Appendix 1. Chemical composition of di-ammonium phosphate (DAP) fertiliser and tablets
Chemical Composition of DAP Fertiliser
Component
Rate
Active Element Rate
DAP
1500kg/ha
P = 300kg/ha N = 265kg/ha
K2S04 (granulated)
K= 300kg/ha
CuS04
Cu = 10kg/ha
ZnS04 (Granulated)
Zn = 16kg/ha
MgS04
Mg = 30kg/ha
MnS04 (granulated)
Mn = 15kg/ha
NaMo
Mo = 0.25kg/ha
Boron (Granulated)
B = 1.5kg/ha
Chemical Composition of DAP Tablet (50 g)
Total Nitrogen (N)
Total Phosphorous (P)
Total Potassium (K)
Sulphur (S)
Calcium (Ca)
Chloride (Cl)
Iron (Fe)
Manganese (Mn)
Copper (Cu)
Zinc (Zn)
Concentration
14.4%
16.0%
6.3%
1.1%
0.01%
5.7%
0.01%
1.3%
0.64%
0.34%
55
Appendix 2a. Summary of species used, whether they were planted and/or seeded and the quantity of seeds or planted seedlings used
Species
Spp code
Planted/seeded
Seeds used (g/ha)
Pinjarra block 1
Acacia cochlearis
Acacia Cyclops
Acacia huegelii
Acacia lasiocarpa
Acacia pulchella
Acacia rostellifera
Acacia saligna
Acacia truncate
Agonis flexuosa
Allocasuarina fraseriana
Allocasuarina humilis
Brachyscome iberidifolia
Callitris preissii
Calothamnus quadrifidus
Carpobrotus virescens
Conospermum triplinervum
Conostylis aculeate
Conostylis candicans
Daviesia divaricata
Daviesia nudiflora
Dianella revolute
Dichopogon capillipes
Diplolaena dampiera
Dodonaea aptera
Dodonaea hackettiana
Dryandra lindleyana
Dryandra sessilis
Eremophila glabra
Eucalyptus decipiens
Eucalyptus foecunda
Eucalyptus gomphocephala
Gompholobium tomentosum
Grevillea crithmifolia
Grevillea thelmanniana
Guichenotia ledifolia
Hakea lissocarpha
ACACOC
ACACYC
ACAHUE
ACALAS
ACAPUL
ACAROS
ACASAL
ACATRU
AGOFLE
ALLFRA
ALLHUM
BRAIBE
CALPRE
CALQUA
CARVIR
CONTRI
CONACU
CONCAN
DAVDIV
DAVNUD
DIAREV
DICCAP
DIPDAM
DODAPT
DODHAC
DRYLIN
DRYSES
EREGLA
EUCDEC
EUCFOE
EUCGOM
GOMTOM
GRECRI
GRETHE
GUILED
HAKLIS
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
P
S
S
S
S
7.6
35.3
5.0
28.4
S
S
S
S
15.1
1.0
46.0
1.7
S
S
S
14.8
51.0
17.7
S
S
S
S
17.7
11.7
127.1
2.5
S
S
S
S
45.4
5.0
3.1
10.1
S
S
S
S
10.1
11.4
20.2
37.3
S
19.8
14
39
48
236
18
18
18
76
80
65
21
56
Planted (/ha)
Pinjarra block
Kwinana
2&3
Gypsum
14
14
39
39
48
48
237
236
18
18
18
18
19
18
77
76
80
80
66
65
21
21
Kwinana
Irrigation
14
39
42
236
18
18
18
76
80
65
21
8
99
81
24
148
80
26
0
100
56
24
149
80
26
8
99
81
24
148
80
26
8
99
81
24
148
80
26
153
15
15
16
35
154
15
15
16
35
153
15
15
16
35
153
15
15
16
35
22
93
31
29
106
28
118
45
52
85
22
94
31
29
107
28
118
45
52
85
22
93
31
29
106
28
118
45
52
85
22
93
31
29
106
28
118
45
52
85
Species
Spp code
Planted/seeded
Seeds used (g/ha)
Pinjarra block 1
Planted (/ha)
Pinjarra block
Kwinana
2&3
Gypsum
19
19
113
112
Hakea prostrata
HAKPRO
P
S
30.3
19
Hakea trifurcata
HAKTRI
P
S
6.2
112
Hardenbergia comptoniana
HARCOM
S
201.9
Hovea pungens
HOVPUN
S
105.9
Isolepis nodosa
ISONOD
P
S
20.2
181
182
Jacksonia furcellata
JACFUR
P
S
22.7
24
25
Jacksonia sternbergiana
JACSTE
S
7.6
Kennedia prostrata
KENPRO
P
S
201.6
13
0
Leucophyta brownii
LEUBRO
P
119
119
Macrozamia riedlei
MACREI
S
7600, 1250, 9660¹
Melaleuca acerosa
MELACE
P
S
31.1
100
100
Melaleuca huegelii
MELHUE
S
12.6
Melaleuca lanceolata
MELLAN
P
S
0.9
67
67
Melaleuca nesophila
MELNES
P
48
48
Melaleuca viminea
MELVIM
P
73
73
Myoporum insulare
MYOINS
P
60
60
Nemcia capitatum
NEMCAP
P
43
43
Olearia axillaris
OLEAXI
P
S
25.2
74
74
Olearia rudis
OLERUD
P
S
15.5
29
25
Petrophile serruriae
PETSER
S
12.6
Phyllanthus calycinus
PHYCAL
P
S
151.4
56
57
Pimelea ferruginea
PIMFER
P
77
78
Podotheca gnaphalioides
PODGNA
S
20.2
Rhagodia baccata
RHABAC
P
S
35.3
92
92
Scaevola crassifolia
SCACRA
P
S
76.1
64
64
Sollya heterophylla
SOLHET
P
S
151.4
57
57
Spyridium globulosum
SPYGLO
P
S
7.7
49
49
Templetonia retusa
TEMRET
P
S
15.1
18
18
Trachymene coerulea
TRACOE
S
50.5
Trymalium ledifolium
TRYLED
S
9.0
Viminaria juncea
VIMJUN
P
S
7.6
19
19
Xanthorrhoea preissii
XANPRE
P
S
116.0
145
145
¹ A different quantity of Macrozamia riedlei seeds were planted at Pinjarra, Kwinana gypsum trial and Kwinana irrigation trial respectively.
57
Kwinana
Irrigation
19
112
181
24
181
24
13
119
0
119
100
100
67
48
73
60
43
74
29
67
48
73
60
43
74
29
56
77
56
77
92
64
57
49
18
92
64
57
49
18
19
145
19
145
Appendix 2b. Location and treatments applied to each botanical monitoring plot
Site
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Pinjarra
Kwinana
Kwinana
Kwinana
Kwinana
Permanent
plot number
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
Location
Block
RSA5
RSA5
RSA5
RSA5
RSA5
RSA5
RSA5
RSA5
RSA5
RSA5
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSA4
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
na
na
na
na
Treatment
Gypsum
Irrigation
shallow
shallow
deep
deep
deep
deep
deep
shallow
shallow
shallow
deep
deep
shallow
shallow
shallow
deep
deep
deep
shallow
shallow
shallow
deep
deep
deep
deep
deep
shallow
shallow
shallow
shallow
shallow
deep
deep
deep
deep
no
no
yes
yes
yes
no
no
yes
yes
yes
no
no
yes
yes
yes
yes
yes
yes
no
no
no
no
no
no
yes
yes
yes
yes
yes
no
no
no
no
no
no
58
Slope
Easting
Northing
upper
lower
upper
lower
397948
397951
398001
398006
397996
398054
398051
398110
398108
398101
397716
397706
397736
397743
397724
397756
397743
397748
397828
397821
397814
397886
397874
397872
397927
397933
397987
397981
397973
398144
398158
389486
389498
389506
389497
6388588
6388558
6388587
6388552
6388580
6388581
6388559
6388584
6388566
6388583
6387350
6387342
6387295
6387292
6387315
6387257
6387255
6387257
6387181
6387170
6387184
6387167
6387146
6387154
6387137
6387133
6387156
6387138
6387153
6387154
6387141
6435783
6435765
6435758
6435794
upper
lower
upper
lower
upper
lower
upper
lower
upper
lower
upper
lower
upper
lower
upper
lower
upper
lower
upper
lower
upper
lower
upper
Peg
position
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
NW
A
NW
Plot
6x6 and 20x20m
6x6m
6x6m
6x6m
20x20m
6x6 and 20x20m
6x6m
6x6m
6x6m
20x20m
6x6m
6x6 and 20x20m
6x6m
6x6m
20x20m
6x6m
6x6m
20x20m
6x6m
6x6m
20x20m
6x6m
6x6m
20x20m
6x6 and 20x20m
6x6m
6x6m
6x6m
20x20m
6x6 and 20x20m
6x6m
6x6m
6x6m
10x40m
6x6m
Site
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Kwinana
Permanent
plot number
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
Location
Block
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF4/5
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
RSAF3
na
na
na
na
na
na
na
na
na
na
na
na
na
na
1
1
1
1
1
1
2
2
2
2
2
2
3
3
3
3
3
3
Treatment
Gypsum
Irrigation
deep
deep
shallow
shallow
shallow
shallow
shallow
shallow
shallow
shallow
shallow
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
deep
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
no
yes
yes
yes
yes
yes
yes
yes
no
no
no
yes
yes
yes
no
no
no
59
Slope
Easting
Northing
lower
389510
389516
389510
389517
389527
389519
389532
389545
389529
389546
389550
389546
389554
389564
390035
390050
390015
390081
390091
390076
390119
390132
390106
390161
390180
390148
390205
390213
390189
390247
390247
390228
6435783
6435773
6435826
6435799
6435802
6435825
6435816
6435798
6435840
6435831
6435818
6435858
6435849
6435837
6436313
6436345
6436323
6436381
6436403
6436377
6436435
6436452
6436422
6436489
6436511
6436481
6436547
6436554
6436527
6436599
6436615
6436592
upper
lower
upper
lower
upper
lower
upper
lower
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
na
Peg
position
NW
A
NW
NW
A
NW
NW
A
NW
NW
A
NW
NW
A
NW
NW
B
NW
NW
B
NW
NW
B
NW
NW
B
NW
NW
B
NW
NW
B
Plot
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
6x6m
6x6m
10x40m
Appendix 3. Chemical properties of residue sand pre- and post- gypsum incorporation for the Pinjarra site
Pre-Gypsum Incorporation
Treatment
No irrig +
Deep gyp
No irrig +
Deep gyp
No irrig +
Deep gyp
No irrig +
Deep gyp
No irrig +
Deep gyp
No irrig +
Deep gyp
No irrig +
Deep gyp
No irrig +
Deep gyp
Plus irrig +
Deep gyp
Plus irrig +
Deep gyp
Plus irrig +
Deep gyp
Plus irrig +
Deep gyp
Plus irrig +
Deep gyp
Plus irrig +
Deep gyp
Plus irrig +
Deep gyp
Plus irrig +
Deep gyp
No irrig +
Shallow gyp
Dept
h
(mm)
NO3
NH4
BicarbP
(mg/kg)
BicarbK
(mg/kg)
Avail-S
(mg/kg
)
(mg/kg
)
Ox-Fe
EC
pH
pH
Ex Ca
Ex Mg
Ex Na
Ex K
ECEC
(mg/kg
)
(mS/m
)
(CaCl2
)
(H2O
)
(cmol/kg
)
(cmol/kg
)
(cmol/kg
)
(cmol/kg
)
(cmol/kg
)
100
4.67
1.00
92.00
110.33
2.00
1.00
10.00
57.33
169.4
3
9.97
0.44
2574
26
7.63
8.23
4.87
0.16
0.17
0.21
5.41
3
300
0.15
3813
7
8.07
8.93
4.53
0.07
0.14
0.12
4.86
3
500
1.33
1.00
3.33
44.67
5.97
0.12
3373
7
8.10
9.07
4.32
0.05
0.24
0.09
4.70
5
700
1.33
1.00
3.67
33.67
6.50
0.11
3723
7
8.27
9.23
4.17
0.06
0.36
0.08
4.67
7
900
1.33
1.00
4.33
25.00
9.73
0.13
3354
8
8.30
9.30
4.17
0.06
0.51
0.05
4.78
10
110
0
130
0
150
0
100
1.33
1.00
4.00
16.67
13.27
0.17
3484
9
8.33
9.27
4.02
0.07
0.64
0.04
4.76
13
1.33
1.00
5.00
15.00
13.63
0.12
3948
10
8.30
9.23
3.74
0.07
0.62
0.03
4.46
13
2.00
1.00
4.67
22.67
10.10
0.21
3913
12
8.33
9.23
4.97
0.27
0.74
0.03
6.01
13
7.00
1.00
138.50
103.00
31.75
0.67
2211
10
7.50
8.10
5.05
0.49
0.15
0.20
5.88
3
300
1.50
1.00
31.50
102.00
4.30
0.14
3740
7
8.15
8.85
3.73
0.11
0.07
0.19
4.09
2
500
1.50
1.00
9.00
110.50
4.15
0.11
4325
7
8.10
9.00
4.32
0.07
0.12
0.20
4.71
2
700
1.50
1.00
9.00
87.50
2.80
0.10
3618
6
8.20
9.10
3.97
0.06
0.17
0.17
4.36
4
900
1.50
1.00
6.50
85.00
4.15
0.09
3372
8
8.25
9.20
3.84
0.07
0.38
0.13
4.42
8
110
0
130
0
150
0
100
1.50
1.00
8.50
36.00
3.65
0.13
3086
8
8.25
9.15
3.87
0.08
0.58
0.08
4.61
12
1.50
1.00
5.00
15.00
4.20
0.09
2594
8
8.30
9.25
3.91
0.11
0.61
0.02
4.65
13
1.50
1.00
6.50
15.00
3.80
0.12
3048
8
8.30
9.35
3.78
0.10
0.60
0.03
4.50
13
6.33
1.00
111.00
98.33
601.8
0
0.62
2277
57
7.30
7.77
5.52
0.20
0.10
0.17
5.99
2
(mg/kg
)
Org
C
(%)
60
ES
P
(%)
No irrig +
Shallow gyp
No irrig +
Shallow gyp
No irrig +
Shallow gyp
No irrig +
Shallow gyp
No irrig +
Shallow gyp
No irrig +
Shallow gyp
No irrig +
Shallow gyp
Plus irrig +
Shallow gyp
Plus irrig +
Shallow gyp
Plus irrig +
Shallow gyp
Plus irrig +
Shallow gyp
Plus irrig +
Shallow gyp
Plus irrig +
Shallow gyp
Plus irrig +
Shallow gyp
Plus irrig +
Shallow gyp
300
1.33
1.00
8.33
46.67
35.53
0.13
2998
12
8.03
8.87
4.65
0.06
0.21
0.11
5.02
4
500
1.33
1.00
7.00
85.33
12.40
0.13
3337
8
8.00
8.97
4.71
0.07
0.11
0.15
5.04
2
700
1.33
1.00
10.67
70.67
9.57
0.17
3482
7
8.10
9.03
4.26
0.08
0.09
0.13
4.57
2
900
1.33
1.00
5.33
31.67
10.13
0.12
3728
8
8.23
9.20
4.05
0.06
0.38
0.07
4.56
8
110
0
130
0
150
0
100
1.33
1.00
4.67
20.67
8.63
0.12
4227
9
8.27
9.20
4.12
0.07
0.51
0.04
4.74
10
1.33
1.00
6.33
15.00
34.70
0.16
4203
11
8.30
9.20
4.10
0.08
0.58
0.03
4.78
11
1.33
1.00
6.33
15.00
9.07
0.12
4310
9
8.30
9.23
4.10
0.11
0.61
0.02
4.85
12
6.33
1.00
93.00
91.33
63.97
0.57
3045
17
7.63
8.23
4.95
0.18
0.10
0.19
5.42
2
300
1.33
1.00
13.67
60.33
15.93
0.16
3850
8
8.03
8.97
4.70
0.07
0.07
0.11
4.95
1
500
1.33
1.00
4.00
68.00
15.97
0.11
3530
7
8.10
9.07
4.25
0.05
0.12
0.13
4.55
3
700
1.33
1.00
4.33
36.67
8.23
0.12
2759
6
8.30
9.27
4.22
0.06
0.26
0.08
4.62
6
900
1.33
1.00
4.67
26.33
5.23
0.12
3789
7
8.33
9.30
4.14
0.06
0.45
0.05
4.69
9
110
0
130
0
150
0
1.33
1.00
4.33
23.33
9.67
0.13
3599
8
8.43
9.50
4.13
0.06
0.58
0.04
4.82
12
1.67
1.00
4.00
15.67
9.27
0.12
3873
10
8.33
9.37
3.99
0.08
0.71
0.03
4.81
15
1.33
1.00
6.33
15.00
6.30
0.20
3242
10
8.37
9.47
3.93
0.18
0.80
0.02
4.93
16
61
Post-Gypsum Incorporation
Treatment
No irrig + Deep
gyp
No irrig + Deep
gyp
No irrig + Deep
gyp
Plus irrig + Deep
gyp
Plus irrig + Deep
gyp
Plus irrig + Deep
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
Plus
irrig
+
Shallow gyp
Plus
irrig
+
Shallow gyp
Plus
irrig
+
Shallow gyp
Dept
h
(cm)
NO3
NH4
BicarbK
(mg/kg)
Avail-S
(mg/kg)
BicarbP
(mg/kg)
Ox-Fe
EC
pH
pH
Ex Ca
Ex Mg
Ex Na
Ex K
E
(mg/kg)
Org
C
(%)
(mg/kg)
(mg/kg)
(mS/m)
(H2O)
(cmol/kg)
(cmol/kg)
(cmol/kg)
(cmol/kg)
(
77.17
444.7
0.19
911
49
(CaCl2
)
7.57
5
1.00
1.00
85.67
7.95
4.80
0.19
0.12
0.15
5
60
1.67
1.00
19.00
51.17
929.2
0.20
945
82
7.63
7.98
5.61
0.19
0.18
0.10
6
140
4.50
1.00
25.33
39.17
1007.5
0.23
887
93
7.75
8.20
5.99
0.23
0.64
0.09
6
5
1.33
1.00
53.83
66.67
244.5
0.18
1020
28
7.55
8.03
4.54
0.18
0.12
0.16
4
60
1.50
1.00
8.17
47.17
411.8
0.14
1061
43
7.72
8.13
4.63
0.14
0.20
0.10
5
140
4.17
1.00
14.33
38.00
459.3
0.14
1111
51
7.85
8.28
5.03
0.14
0.44
0.09
5
5
1.00
1.00
172.50
67.17
3042.7
0.28
760
138
7.25
7.38
10.49
0.28
0.08
0.14
1
60
1.17
1.00
6.67
64.00
199.6
0.11
1161
26
7.63
8.28
4.63
0.10
0.30
0.13
5
140
1.83
1.00
11.67
26.17
233.0
0.11
1173
32
7.87
8.38
4.43
0.11
0.82
0.06
5
5
1.17
1.00
79.17
71.33
2892.8
0.32
736
150
7.47
7.68
9.04
0.32
0.10
0.14
9
60
1.00
1.00
3.17
85.33
160.0
0.10
1134
24
7.55
8.25
4.83
0.09
0.12
0.15
5
140
1.83
1.00
7.58
28.17
474.1
0.10
1328
49
7.90
8.35
4.74
0.10
0.65
0.06
5
62
Appendix 4. Chemical properties of residue sand pre- and post- gypsum incorporation for the Kwinana site
Pre-Gypsum Incorporation
Treatment
No irrig + Deep gyp
No irrig + Deep gyp
No irrig + Deep gyp
No irrig + Deep gyp
No irrig + Deep gyp
No irrig + Deep gyp
No irrig + Deep gyp
No irrig + Deep gyp
Plus irrig + Deep gyp
Plus irrig + Deep gyp
Plus irrig + Deep gyp
Plus irrig + Deep gyp
Plus irrig + Deep gyp
Plus irrig + Deep gyp
Plus irrig + Deep gyp
Plus irrig + Deep gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
Dept
h
(cm)
NO3
NH4
BicarbP
(mg/kg)
BicarbK
(mg/kg)
AvailS
(mg/kg
)
Org
C
(%)
Ox-Fe
EC
pH
pH
Ex Ca
Ex Mg
Ex Na
Ex K
ECEC
(mg/kg
)
(mg/kg
)
10
30
50
70
90
110
130
150
10
30
50
70
90
110
130
150
10
2.00
2.00
2.00
2.33
2.00
2.00
2.00
2.00
3.67
2.00
2.00
2.00
2.00
2.33
2.00
2.33
1.00
30
(mg/kg
)
(mS/m
)
(CaCl2
)
(H2O)
(cmol/kg
)
(cmol/kg
)
(cmol/kg
)
(cmol/kg
)
(cmol/kg
)
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.00
56.33
8.33
3.00
3.33
4.67
4.00
6.67
7.67
69.33
12.33
6.00
3.33
5.33
4.33
5.33
5.00
2.17
42.33
34.33
21.67
18.67
17.67
15.00
15.00
15.00
87.67
56.67
37.67
24.33
25.67
20.00
17.67
15.00
32.67
826
207
51
54
107
25
106
69
930
69
52
42
121
44
84
148
8
0.41
0.14
0.09
0.10
0.14
0.11
0.16
0.10
0.63
0.20
0.15
0.11
0.11
0.13
0.10
0.10
0.23
2007
2132
2642
3370
3453
3456
3519
2925
1784
2662
2787
3259
3308
3603
3413
2871
4004
79
37
12
15
14
14
23
25
87
22
15
14
17
16
19
26
41
7.80
7.87
7.97
8.03
8.30
8.27
8.27
8.23
7.63
8.07
8.00
8.07
8.23
8.23
8.27
8.20
8.07
8.27
8.60
8.90
9.00
9.23
9.40
9.20
9.40
8.03
8.90
8.97
8.97
9.20
9.30
9.27
9.27
9.82
7.92
6.68
5.89
6.09
5.35
4.96
5.29
5.09
8.44
6.91
7.56
6.20
5.81
5.49
5.62
5.05
2.79
0.11
0.08
0.11
0.10
0.12
0.09
0.08
0.09
0.20
0.17
0.17
0.11
0.09
0.09
0.08
0.08
0.09
0.17
0.14
0.20
0.35
0.69
1.02
1.39
1.54
0.22
0.71
0.44
0.84
0.86
1.06
1.19
1.66
3.37
0.08
0.08
0.05
0.03
0.03
0.01
0.02
0.02
0.14
0.11
0.08
0.03
0.04
0.03
0.03
0.02
0.10
8.29
6.98
6.24
6.58
6.19
6.09
6.78
6.74
9.00
7.90
8.25
7.18
6.80
6.67
6.92
6.82
6.35
2
2
3
5
11
17
20
23
3
8
5
11
12
15
17
24
51
1.00
1.00
2.50
15.50
8
0.21
3933
68
8.13
2.43
0.06
4.70
0.04
7.22
64
50
1.00
1.00
2.17
15.00
14
0.20
4440
94
8.18
2.06
0.06
6.06
0.04
8.22
74
70
1.00
1.00
3.00
15.17
19
0.19
4069
99
8.23
2.56
0.08
6.25
0.03
8.92
70
90
1.00
1.00
2.67
15.00
22
0.19
4236
102
8.18
2.17
0.06
6.30
0.03
8.56
73
110
1.00
1.00
3.33
15.00
25
0.17
4098
105
8.30
2.38
0.07
6.39
0.03
8.88
72
130
1.00
1.00
3.17
15.00
24
0.16
4002
103
8.23
2.27
0.06
6.18
0.03
8.54
72
150
1.00
1.00
2.50
15.00
24
0.19
3917
106
8.28
10.0
2
10.1
2
10.1
2
10.1
0
10.1
0
10.1
0
10.1
5
2.28
0.08
6.01
0.03
8.41
71
63
ES
P
(%)
Plus
gyp
Plus
gyp
Plus
gyp
Plus
gyp
Plus
gyp
Plus
gyp
Plus
gyp
Plus
gyp
irrig + Shallow
10
1.00
1.00
2.17
32.67
8
0.23
4004
41
8.07
9.82
2.79
0.09
3.37
0.10
6.35
51
irrig + Shallow
30
1.00
1.00
2.50
15.50
8
0.21
3933
68
8.13
2.43
0.06
4.70
0.04
7.22
64
irrig + Shallow
50
1.00
1.00
2.17
15.00
14
0.20
4440
94
8.18
2.06
0.06
6.06
0.04
8.22
74
irrig + Shallow
70
1.00
1.00
3.00
15.17
19
0.19
4069
99
8.23
2.56
0.08
6.25
0.03
8.92
70
irrig + Shallow
90
1.00
1.00
2.67
15.00
22
0.19
4236
102
8.18
2.17
0.06
6.30
0.03
8.56
73
irrig + Shallow
110
1.00
1.00
3.33
15.00
25
0.17
4098
105
8.30
2.38
0.07
6.39
0.03
8.88
72
irrig + Shallow
130
1.00
1.00
3.17
15.00
24
0.16
4002
103
8.23
2.27
0.06
6.18
0.03
8.54
72
irrig + Shallow
150
1.00
1.00
2.50
15.00
24
0.19
3917
106
8.28
10.0
2
10.1
2
10.1
2
10.1
0
10.1
0
10.1
0
10.1
5
2.28
0.08
6.01
0.03
8.41
71
Total
N
(%)
Total
P
(mg/k
g)
0.02
8
0.02
3
0.02
8
0.02
3
0.02
0
0.02
2
0.02
8
0.02
7
0.03
0
167
Post-Gypsum Incorporation
Treatment
No irrig + Deep
gyp
No irrig + Deep
gyp
No irrig + Deep
gyp
Plus irrig + Deep
gyp
Plus irrig + Deep
gyp
Plus irrig + Deep
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
No irrig + Shallow
gyp
Dept
h
(cm)
NO3
NH4
BicarbK
(mg/kg
)
AvailS
(mg/k
g)
Org
C
(%)
Ox-Fe
EC
pH
pH
Ex Ca
Ex Mg
Ex Na
Ex K
ECEC
(mg/k
g)
Bicarb
-P
(mg/kg
)
(mg/k
g)
(mS/
m)
(CaCl
2)
(H2
O)
(cmol/k
g)
(cmol/k
g)
(cmol/k
g)
(cmol/k
g)
(cmol/k
g)
ES
P
(%
)
(mg/k
g)
5
2.33
1.17
69.92
72.50
726
2241
77
7.83
0.21
0.44
0.14
7.74
6
7.25
1.00
9.83
23.42
1490
2417
107
8.03
8.20
0.19
0.94
0.05
9.39
12
140
1.17
1.00
13.42
18.08
593
2354
85
8.22
6.20
0.16
1.76
0.04
8.17
22
5
1.83
1.00
60.67
82.83
2594
2103
166
7.57
10.65
0.18
0.24
0.13
11.21
2
60
1.00
13.17
32.17
1821
1875
142
7.77
9.28
0.20
0.45
0.06
10.00
5
140
10.1
7
1.33
1.00
15.00
33.33
1571
2183
145
8.02
8.44
0.16
1.09
0.07
9.76
11
5
2.00
1.67
84.67
89.33
2965
2965
163
7.75
9.90
0.24
0.61
0.18
10.94
6
60
5.33
1.00
4.83
33.33
357
2965
50
8.10
3.99
0.14
2.35
0.08
6.56
36
140
1.17
1.00
15.50
19.17
594
2975
103
8.32
8.2
1
8.4
0
8.7
3
7.9
2
8.0
5
8.2
3
7.9
5
8.9
5
9.0
2
6.95
60
0.2
2
0.1
4
0.1
0
0.2
7
0.1
6
0.1
1
0.3
7
0.1
0
0.1
1
5.58
0.14
3.53
0.04
9.31
40
64
60
51
191
70
54
198
40
48
Plus
irrig
Shallow gyp
Plus
irrig
Shallow gyp
Plus
irrig
Shallow gyp
+
5
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
+
60
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
+
140
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
M
65
Appendix 5. Effect of time (pre- and post- (0, 6 and 12 months) after gypsum incorporation, on
fertilizer and gypsum transport, and selected chemical properties. Values presented are for pre- and
post- shallow gypsum incorporation, and minus irrigation. For each set of 4 graphs, (a) and (b) refer to
data for the Kwinana trial, and (c) and (d) refer to data for the Pinjarra trial.
Exchangeable Na (cmol/kg)
Exchangeable Ca (cmol/kg)
0
(a)
20
40
0
60
(b)
0
4
6
0
40
80
Depth (cm)
40
Depth (cm)
2
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
80
120
160
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
Exchangeable Na (cmol/kg)
Exchangeable Ca (cmol/kg)
0
20
40
0
60
(d)
(c) 0
2
4
6
0
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
40
Depth (cm)
Depth (cm)
40
80
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
80
120
160
160
66
2M KCl NO3 (mg/kg)
2M KCl NH4 (mg/kg)
0
(a)
0.4
0.8
1.2
1.6
0
2
(b)
0
Depth (cm)
Depth (cm)
80
120
6
8
0
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
160
2M KCl NO3 (mg/kg)
2M KCl NH4 (mg/kg)
0
0.4
0.8
1.2
1.6
0
2
(d)
(c) 0
2
4
6
8
0
40
Depth (cm)
40
Depth (cm)
4
40
40
80
120
2
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
160
67
1M KCl SO4 (mg/kg)
Organic Carbon (%)
0
(a)
0.2
0.4
0.6
0
0.8
(b)
0
Depth (cm)
Depth (cm)
80
120
6000
0
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
160
1M KCl SO4 (mg/kg)
Organic Carbon (%)
0
0.2
0.4
0.6
0
0.8
(d)
(c) 0
2000
4000
6000
0
40
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
Depth (cm)
40
Depth (cm)
4000
40
40
80
2000
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
120
160
160
68
Oxalate Al (mg/kg)
Oxalate Fe (mg/kg)
0
(a)
2000
4000
6000
0
8000 10000
(b)
0
Depth (cm)
Depth (cm)
2000
3000
4000
0
20
40
80
40
60
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
80
160
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
100
Oxalate Al (mg/kg)
Oxalate Fe (mg/kg)
0
2000
4000
6000
0
8000 10000
(d)
(c) 0
1000
2000
3000
0
20
Depth (cm)
40
Depth (cm)
1000
80
40
60
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
80
160
69
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
4000
Bicarbonate K (mg/kg)
Bicarbonate P (mg/kg)
0
(a)
40
80
120
160
0
200
(b)
0
Depth (cm)
Depth (cm)
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
120
0
80
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
120
160
160
Bicarbonate K (mg/kg)
Bicarbonate P (mg/kg)
0
40
80
120
160
0
200
(d)
(c) 0
40
80
120
0
40
Depth (cm)
40
Depth (cm)
80
40
40
80
120
40
80
120
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
160
160
70
Pre-gypsum
Post-gypsum
6mo Post-gypsum
12mo Post-gypsum
K (mg/kg)
0
(a)
20
40
60
80
100
80
100
0
Depth (cm)
20
40
Available
Soluble
60
80
K (mg/kg)
0
(b)
20
40
0
Depth (cm)
20
40
Available
Soluble
60
80
71
60
NH4-N (mg/kg)
0
(a)
0.2
0.4
0.6
0.8
1
0.8
1
0
Depth (cm)
20
40
Available
Soluble
60
80
NH4-N (mg/kg)
0
(b)
0.2
0.4
0.6
0
Depth (cm)
20
40
60
Available
Soluble
80
100
72
NO3-N (mg/kg)
0
(a)
0.5
1
1.5
2
0
20
Depth (cm)
2.5
Available
Soluble
40
60
80
NO3-N (mg/kg)
0
(b)
0.5
1
1.5
2
2.5
0
Depth (cm)
20
40
Available
Soluble
60
80
100
73
P (mg/kg)
0
(a)
40
80
120
160
200
160
200
0
Depth (cm)
20
40
Available
Soluble
60
80
P (mg/kg)
0
(b)
40
80
120
0
Depth (cm)
20
40
Available
Soluble
60
80
74
Appendix 6a. Chemical Characteristics of Natural Topsoil, and Residue Sand Before (unamended)
and After (1% gypsum amended) Gypsum Addition
Topsoil
Water-Soluble Fraction (Saturated paste analysis)
Na
(mg/L)
34.04
Mg
(mg/L)
6.52
Al
(mg/L)
50.15
PO4-P
(mg/L)
0.47
SO4-S
(mg/L)
8.65
Cl
(mg/L)
58.10
K
(mg/L)
4.96
Ca
(mg/L)
18.45
Fe
(mg/L)
20.45
NH4-N
(mg/L)
4.06
NO3-N
(mg/L)
<0.01
EC
(mS/m)
4.1
pH
6.12
θg
(kg/kg)
0.32
HCO3
(mg/L)
373.20
CO3
(mg/L)
<0.01
Unamended
Gypsum-amended (1% gypsum)
2708
0.39
29.59
10.29
110
17.5
13.1
<0.01
8.0
0.2
0.6
11630
9.82
0.30
589
18380
2677
3.11
0.42
0.09
1804
7.9
40.6
111.9
0.3
2.6
0.7
13730
8.45
0.32
378
<0.01
Exchangeable or Available Fraction (after water-extraction)
2M KCl NO3-N
(mg/kg)
5.3
3.0
2M KCl NH4-N
(mg/kg)
<0.01
1.0
Bicarbonate P
(mg/kg)
2.1
4.0
Bicarbonate K
(mg/kg)
37
24
Available S
(mg/kg)
4.67
24
Organic C
(%)
1.21
0.10
Amorphous-Fe
(mg/kg)
96
2350
Amorphous-Al
(mg/kg)
33
871
Exchangeable Ca
(cmol/kg)
3.35
3.63
Exchangeable Mg
(cmol/kg)
0.48
0.08
Exchangeable Na
(cmol/kg)
0.11
5.53
Exchangeable K
(cmol/kg)
0.04
0.06
Exchangeable Al
(cmol/kg)
0.01
0.02
Exchangeable Fe
(cmol/kg)
1.94
10.71
Total N
(%)
0.02
0.02
Total P
(mg/kg)
28.39
27
ECEC
(cmol/kg)
3.98
9.32
3.0
1.0
7.0
36
634
0.19
2662
1007
5.76
0.08
4.18
0.09
0.03
6.59
0.02
60
10.14
75
Appendix 6b. Chemical Characteristics of a 4-year old Rehabilitated Residue Sand Profile (Watersoluble and exchangeable parameters)
Exchangeable
and
Available Ions
1:5
1M KCl (BRS:Water)
SO4-S
EC
(cm)
(mg/kg)
(dS/m)
1:5
1M
(BRS:Water)
NH4Cl/BaCl2
Exch
pH
Ca
Exch Na
(cmol/k
g)
(cmol/kg)
0-5
5 - 20
20 - 40
40 - 60
60 - 80
80
100
100 120
120 140
140 160
160 180
180 200
200 220
220 240
240 260
260 280
280 300
86
201
327
841
388
0.19
0.22
0.36
0.76
0.48
8.35
8.60
8.45
8.20
8.35
8.18
6.30
5.97
7.67
5.95
0.22
0.17
0.17
0.26
0.30
142
0.27
8.70
4.31
0.60
42
0.21
9.45
2.46
2.03
40
0.23
9.40
2.74
2.32
27
0.31
9.10
2.36
3.28
42
0.35
8.70
2.91
3.90
33
0.36
8.85
3.19
3.91
32
0.37
8.85
2.63
3.70
30
0.40
8.95
2.41
4.12
33
0.49
8.95
2.72
4.43
39
0.48
9.00
2.71
4.46
51
0.46
9.00
3.25
4.44
Depth
Water Soluble Ions
Depth
Sol Ca
Sol Na
Sol
SO4-S
Sol
CO32-
Sol
HCO3-
(mg/L)
(mg/L)
(mg/L)
(mg/L)
(mg/L)
Sol
Al
(mg/
L)
7.54
7.54
7.34
7.37
7.31
203
372
491
687
589
57
58
67
101
115
480
294
379
551
468
0
0
0
0
0
51
37
26
28
27
0.84
<0.01
<0.01
<0.01
<0.01
1.80
7.62
316
281
373
0
43
0.02
1.79
2.15
9.26
9.35
5
3
412
544
115
112
0
0
322
409
2.93
2.56
θg
EC
(cm)
(g/g)
(dS/m)
0-5
5 - 20
20 - 40
40 - 60
60 - 80
80
100
100 120
120 -
0.42
0.34
0.35
0.37
0.37
1.08
1.38
1.74
2.19
1.95
0.34
0.36
0.35
pH
76
140
140
160
160
180
180
200
200
220
220
240
240
260
260
280
280
300
0.35
2.77
9.94
3
714
54
0
627
5.77
0.38
3.26
9.99
2
897
77
399
0
5.96
0.36
3.45
10.02
2
958
69
401
0
6.38
0.36
3.48
10.05
1
966
75
298
0
6.48
0.36
3.74
10.08
1
1065
69
425
0
7.21
0.35
4.00
10.14
1
1163
80
473
0
5.92
0.35
4.34
10.14
1
1299
113
383
0
8.89
0.36
4.62
10.18
1
1398
136
375
0
10.20
-
77
Appendix 7. Summary of botanical monitoring undertaken from 2005 to 2007 at Kwinana and
Pinjarra irrigation trials and associated ANOVA
Site
Treatment
Block #
Year
Pinjarra
Irrigated
(deep
gypsum)
1
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2
3
Average
NonIrrigated
(deep
gypsum)
1
2
3
Average
Kwinana
Irrigated
(deep
gypsum)
1
2
3
Average
NonIrrigated
(deep
gypsum)
1
2
3
Average
Density
/m2
Natives
(Exotics)
1.8 (1.6)
1.3 (4.7)
1.6 (8.0)
4.1 (0.7)
2.8 (11.9)
1.7 (11.9)
2.7 (0.5)
3.0 (8.6)
2.1 (27.6)
2.9 (0.9)
2.4 (8.4)
1.8 (15.8)
1.8 (0.8)
1.4 (5.4)
2.3 (16.4)
2.4 (1.5)
2.2 (38.3)
1.0 (32.2)
4.8 (1.5)
6.6 (15.2)
1.5 (38.3)
3.0 (0.9)
3.4 (19.6)
1.6 (29.0)
3.1 (3.1)
1.6 (1.8)
1.4 (4.8)
1.4 (4.7)
0.8 (2.8)
0.7 (2.9)
1.5 (9.3)
1.1 (3.3)
1.0 (17.9)
2.0 (5.7)
1.2 (2.5)
1.0 (8.5)
0.8 (4.8)
1.0 (4.0)
0.5 (21.2)
2.7 (6.4)
2.6 (2.2)
1.5 (23.0)
2.9 (5.3)
1.6 (4.4)
1.5 (24.0)
2.1 (5.2)
1.7 (3.5)
1.2 (22.7)
78
Cover
Natives
(Exotics)
2.2 (4.5)
83.5 (4.3)
93.9 (21.2)
1.7 (2.5)
112.9 (9.8)
146.0 (8.7)
2.3 (4.0)
76.9 (13.6)
93.1 (42.0)
2.1 (3.7)
91.1 (9.2)
111.0 (24.0)
2.4 (1.9)
44.1 (1.9)
76.2 (21.6)
1.7 (4.1)
42.7 (17.8)
54.2 (108.7)
3.1 (5.2)
53.0 (16.7)
81.0 (89.6)
2.4 (3.7)
46.6 (12.1)
70.5 (73.3)
2.6 (12.0)
37.1 (33.2)
56.9 (41.9)
1.7 (22.1)
29.9 (43.6)
39.4 (57.1)
0.7 (42.7)
30.6 (16.0)
49.3 (7.8)
1.7 (25.6)
32.5 (30.9)
48.5 (35.6)
1.1 (13.9)
20.8 (11.0)
47.0 (35.8)
1.5 (23.3)
20.2 (15.9)
47.6 (37.6)
0.8 (23.0)
9.7 (3.8)
40.0 (11.7)
1.1 (20.1)
16.9 (10.2)
44.9 (28.3)
%
Species
Richness
Natives
(Exotics)
27 (4.5)
26 (5.5)
22.5 (6)
32.5 (10)
30 (9.5)
22 (7.5)
27 (7)
28 (8.5)
20 (7.5)
28.8 (7.2)
28 (7.8)
21.5 (7)
22 (5.5)
18.5 (7)
18.5 (7)
31.5 (8.5)
27.5 (10)
19.5 (5.5)
35.5 (8.5)
34.5 (8)
25.5 (8)
29.7 (7.5)
26.8 (6)
21.2 (6.8)
28.5 (7)
24.5 (5)
21.5 (8)
27.5 (9)
13.5 (6.5)
15.5 (6.5)
24.5 (9)
18 (6)
19 (7.5)
26.8 (8.3)
18.7 (5.8)
18.7 (7.3)
17.5 (9.5)
11.5 (5)
12 (6)
32 (9)
23.5 (7.5)
22 (8.5)
30.5 (7)
19.5 (4.5)
19.5 (10)
26.7 (8.5)
18.2 (5.7)
17.8 (8.2)
Summary of ANOVA for cover, density and species richness across variables of block, rep, irrigation prescription,
site, species and age of rehab. Significance levels **p<0.001, *p<0.05.
Independent Variable
Block (1, 2 &3)
Irrigation (irrigated & non-irrigated)
Rep (1 & 2)
Site (KW & PJ)
Species (Natives & Exotics)
Year (2005, 2006, 2007)
Cover
Density
*
*
Species Richness
*
*
**
**
*
**
**
*
**
**
79
Appendix 8. Summary of botanical monitoring undertaken from 2005 to 2007 at Kwinana and
Pinjarra gypsum trials and associated ANOVA
Site
Treatment
Block #
Year
Pinjarra
Surface
Gypsum (not
irrigated)
1
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2005
2006
2007
2
3
Average
Deep Gypsum
(not irrigated)
1
2
3
Average
Kwinana
Surface
Gypsum (not
irrigated)
1
2
3
Average
Deep Gypsum
(not irrigated)
1
2
3
Average
Density
/m2
Natives
(Exotics)
1.9 (1.0)
4.0 (8.8)
1.9 (36.4)
2.0 (2.6)
2.0 (28.8)
0.9 (33.8)
3.2 (5.4)
5.1 (45.6)
1.1 (47.1)
2.4 (3.0)
3.9 (27.7)
1.3 (39.1)
1.8 (0.8)
1.4 (5.3)
2.2 (16.4)
2.4 (1.5)
2.3 (38.2)
1.0 (32.2)
4.8 (1.5)
6.7 (15.2)
1.5 (38.3)
3.0 (1.3)
3.5 (19.6)
1.6 (29.0)
7.6 (0.2)
4.4 (9.6)
2.1 (11.7)
5.0 (0.2)
7.3 (8.2)
3.2 (17.5)
4.7 (0.5)
2.6 (11.4)
1.9 (8.4)
5.8 (0.3)
4.8 (9.7)
2.4 (12.5)
6.4 (0.2)
4.2 (4.8)
2.1 (18.9)
2.2 (0.1)
1.4 (6.2)
1.2 (4.1)
1.8 (0.7)
1.8 (17.1)
1.0 (10.7)
3.5 (0.3)
2.5 (9.4)
1.4 (11.2)
80
Cover
Natives
(Exotics)
1.6 (3.3)
32.3 (4.0)
44.3 (24.1)
1.7 (9.3)
29.4 (32.0)
43.3 (100.3)
1.8 (13.8)
16.8 (31.5)
27.3 (94.9)
1.7 (8.8)
26.2 (22.5)
38.3 (73.1)
2.5 (1.9)
44.1 (1.9)
76.2 (21.6)
1.7 (4.1)
42.7 (17.8)
54.2 (108.7)
3.2 (5.2)
53.0 (16.7)
81.0 (89.6)
2.5 (3.7)
46.6 (12.1)
70.5 (73.3)
5.0 (0.9)
37.5 (2.7)
41.0 (6.2)
3.7 (2.4)
30.4 (5.4)
29.7 (19.9)
3.7 (3.7)
37.4 (3.6)
34.4 (2.6)
4.1 (2.3)
35.1 (3.9)
35.0 (9.6)
3.5 (2.5)
23.4 (2.6)
41.4 (4.9)
2.3 (1.6)
19.4 (1.7)
35.3 (0.6)
1.6 (3.0)
27.4 (18.4)
23.8 (3.6)
2.5 (2.4)
23.4 (7.6)
33.5 (3.0)
%
Species
Richness
Natives
(Exotics)
23.0 (8.0)
20.0 (9.5)
18.5 (10.5)
26.0 (12.5)
26.0 (9.5)
17.5 (7.5)
32.0 (16.5)
29.5 (12.5)
19.0 (7.5)
27.0 (12.3)
25.2 (10.5)
18.3 (8.5)
22.0 (5.5)
19.0 (6.5)
18.5 (7.0)
31.0 (9.0)
27.5 (10.0)
18.5 (6.5)
35.5 (8.5)
35.0 (7.5)
25.0 (8.5)
29.5 (7.7)
27.2 (8.0)
20.7 (7.3)
40.0 (3.5)
34.5 (6.5)
21.0 (7.5)
42.0 (1.5)
27.0 (5.0)
19.5 (5.5)
39.0 (1.0)
29.5 (3.5)
19.5 (4.5)
40.3 (2.0)
30.3 (5.0)
20.0 (5.8)
37.0 (3.5)
30.0 (7.0)
24.0 (6.5)
30.5 (3.0)
28.0 (5.5)
22.5 (5.5)
32.0 (3.0)
22.0 (4.5)
15.0 (4.5)
33.2 (3.2)
26.7 (5.7)
20.5 (5.5)
Summary of ANOVA for cover, density and species richness across variables of block, rep, irrigation prescription,
site, species and age of rehab. Significance levels **p<0.001, *p<0.05.
Independent Variable
Block (1, 2 &3)
Gypsum Depth (surface & deep)
Rep (1 upper slope, 2 lower slope)
Site (KW & PJ)
Species (Natives & Exotics)
Year (2005, 2006, 2007)
Cover
Density
**
*
**
**
**
**
Species Richness
*
81
**
**