Next Article in Journal
Fruit Yields Depend on Biomass and Nutrient Accumulations in New Shoots of Citrus Trees
Next Article in Special Issue
Micro-Water Harvesting and Soil Amendment Increase Grain Yields of Barley on a Heavy-Textured Alkaline Sodic Soil in a Rainfed Mediterranean Environment
Previous Article in Journal
Special Issue “Integrated Defense Responses in Crops against Soil-Borne Pathogens”
Previous Article in Special Issue
Soil Management Systems to Overcome Multiple Constraints for Dryland Crops on Deep Sands in a Water Limited Environment on the South Coast of Western Australia
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Agronomy
Volume 10
Issue 12
10.3390/agronomy10121987
agronomy-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Short- and Long-Term Effects of Lime and Gypsum Applications on Acid Soils in a Water-Limited Environment: 2. Soil Chemical Properties

by
Geoffrey C. Anderson
1,*,
Shahab Pathan
2,
James Easton
3,
David J. M. Hall
4 and
Rajesh Sharma
5
1
Department of Primary Industries and Regional Development, Northam 6401, Australia
2
Department of Primary Industries and Regional Development, South Perth 6151, Australia
3
CSBP Limited, Kwinana 6966, Australia
4
Department of Primary Industries and Regional Development, Esperance 6450, Australia
5
ChemCentre, Resources and Chemistry Precinct Level 2, Bentley 6102, Australia
*
Author to whom correspondence should be addressed.
Agronomy 2020, 10(12), 1987; https://doi.org/10.3390/agronomy10121987
Submission received: 5 November 2020 / Revised: 9 December 2020 / Accepted: 10 December 2020 / Published: 17 December 2020
(This article belongs to the Special Issue Management of Soil Constraints to Improve Crop Performance in Water-Limited Environments)
Browse Figures
Versions Notes

Abstract

:
Soil acidity or aluminum (Al) toxicity is a major limitation to crop production. In this paper, we examine the effects of surface-applied lime and gypsum on soil profile chemical properties that affect Al toxicity in short-term (1 year), medium-term (2 years and 8 months) and long-term (10 years) experiments. Sulfate applied to the soil surface as gypsum was leached rapidly to a depth of 40 cm in the short-term despite relatively low amounts (279 mm) of rainfall. In the medium and long-term experiments, 28–54% of the sulfate applied as gypsum was retained in the 0–50 cm soil layer due to adsorption and precipitation reactions. The combined application of lime and gypsum increased soil calcium, to a depth of 30 cm in the short-term and to a depth of 50 cm in the medium and long-terms. Increases in soil sulfate and calcium were associated with greater electrical conductivity to a depth of 50 cm for all sampling times. Application of lime alone had no impact on soil Al, pH, and calcium in the soil layers below 10 cm in the short and medium terms. In the long-term, increasing the rate of lime application from 2 to 8 t L ha−1 increased soil pH in the 10–20 cm soil layer while soil Al decreased to a depth of 30 cm. The combined use of lime and gypsum decreased soil Al in the 30–50 cm soil layer in the medium-term and the 20–30 cm soil layer in the long-term which was more than when only lime was applied. Hence, we recommend the use of lime plus gypsum for treating soils with subsoil Al toxicity. Additionally, soil Al measurements are a more sensitive measurement of the impact of surface application lime and lime plus gypsum than soil pH.

1. Introduction

Aluminum (Al) present in the soil solution as Al ( H 2 O ) 6 3 +   abbreviated, as Al3+, is toxic to root growth [1]. Soil pHCaCl2 and soil AlCaCl2 (Al and pH measured using 0.01 MCaCl2) are used to indicate the potential limitations imposed by soil acidity and Al toxicity, respectively [2]. When the subsoil or soil layers below 10 cm contain an AlCaCl2 content greater than 2.5 mg Al kg−1, there is a significant reduction in wheat (Triticum aestivum L.) grain yield. Lime (L, CaCO3) applied to Al toxic soils increases soil pHCaCl2 and decreases soil AlCaCl2 resulting in increased crop grain yields [2,3]. However, due to its comparatively low solubility, L broadcast onto the soil surface can be ineffective at treating subsoil Al toxicity in the short-term and medium-term [2]. Alternatively, gypsum (G, CaSO4.2H2O) has the potential to be more effective in treating subsoil Al toxicity due to its greater solubility (2.1 gm L−1 in water) compared to L which is sparingly soluble in water (0.013 gm L−1) [4,5]. The application of G increases the sulfate (SO4-S) and calcium (Ca) concentration of the soil solution leading to an increase in soil solution electrical conductivity (EC) [5]. Higher soil solution EC decreases the activity of Al3+ in the soil solution meaning plants can tolerate greater levels of Al3+ toxicity [4]. Additionally, the increase in soil SO4-S content results in the conversion of toxic Al3+ to Al sulfate (Al-SO4), which is not harmful to plant roots [6,7,8].
The application of G can either decrease, increase or have no effect on soil pHCaCl2 [9]. A decrease in soil pHCaCl2 arises when added Ca displaces A13+ and hydrogen ions (H+) from the cation exchange sites into the soil solution [10]. By contrast, an increase in pHCaCl2 happens due to SO4-S sorption resulting in the displacement of hydroxide ions (OH−) [11]. The net effect of these two reactions will determine the overall impact on pHCaCl2 [9]. For soils with high SO4-S sorption capacities, the net effect is to increase soil pHCaCl2 [12]. In contrast, for soils with low SO4-S sorption capacities, the net result is to decrease pHCaCl2. The SO4-S sorption capacity can be measured using the sulfur buffer index (SBI) [13]. Brazilian studies have shown that soils that have high SO4-S sorption capacity have a greater G requirement to overcome the Al toxicity limitations [14]. In contrast, G application did not affect the soil solution pH of soils of South Western Australia [6] because these soils generally have a low SBI [13].
Leaching of SO4-S from the 0–20 cm soil layer occurs in the medium rainfall zone of South Western Australia [15]. However, retention of this leached SO4-S takes place in the soil layers below 20 cm due to the greater SO4-S adsorption properties [15]. In general, soil layers below 10 cm have a greater capacity to adsorb SO4-S due to the lower carbon, phosphorus, pH, and greater clay content [13]. The rate of SO4-S leaching is related to the water holding capacity of the soil, the amount and frequency of rainfall events, and the SO4-S adsorption properties [15]. Hence, the rate of SO4-S leaching will be less in the low rainfall zone of South Western Australia compared to the rates observed in the medium rainfall zone [15]. Additionally, some soils within the region have net anion exchange capacity, which can reduce the rate of nitrate leaching [16]. The reduction in SO4-S leaching in soil with anion exchange capacity is expected to be greater than that which occurs for nitrate because soils adsorb SO4-S more strongly than nitrate. Calcium (Ca), when applied as G and L, can also be leached into the soil profile. The rate of leaching of G and L derived Ca varies according to the rates applied, reaction time and the soil type [17]. Calcium derived from G is leached at a faster rate than Ca derived from L because of the greater solubility of G compared to L and due to the presence of SO4-S as co–anions of G [17,18]. Additionally, L application increases soil pH and the effective cation exchange capacity (ECEC), which reduces the mobility of Ca due to the increased attraction by the pH-dependent negative charges of the soil particles [17].
In the first paper of this series, we concluded that the application of G is profitable in the low-rainfall, eastern wheat belt region of Western Australia despite the soils having a low capacity to adsorb SO4-S which results in rapid leaching of SO4-S and no self-liming effect [3]. In this paper, we examine the impact of surface application of G and L on soil chemical properties overtime to explain these crop grain yield responses. In this paper, we present changes in soil profile SO4-S, Ca, EC, Al, pH and ECEC over time. We hypothesize that measurement of soil Al, as opposed to pH, will provide a more sensitive measurement of the impact of surface-applied L on subsoil chemical properties. Additionally, the combined application of L and G will result in a greater reduction in soil Al than when L is applied alone.

2. Materials and Methods

2.1. Field Experimental Sites

The short-term (ST, 1 year), and medium-term (MT, 2 years and 8 months) experiments were located near the town of Burracoppin (−31°30′9′′ S latitude, 118°38′50′′ E longitude) and had a total of 2–4 t L ha−1 applied in the previous 15 years before the commencement of the experiment. The third was a long-term (LT, 10 years) experiment located near the town of Bonnie Rock (−30°37′3′′ S latitude, 118°14′9′′ E longitude) and had no history of L application. The experiments are located in the low rainfall region of the South Western Australian grain belt. Long term (1980–2018) average rainfall for the Bonnie Rock and Burracoppin sites are 309 mm (range 158–453 mm) and 364 mm (range 315–414 mm) respectively. While Bonnie Rock and Burracoppin are in the same rainfall zone, rainfall amount and distribution can differ, for example, annual rainfall at Bonnie Rock was 296 mm compared Burracoppin of 400 mm in 2015 [3]. Crop grain yield and nutrient concentration and measured soil chemical properties from the control treatment are presented by [3]. In summary, G application was profitable at the MT experiment where deep ripping had removed the subsoil compaction constraint. In contrast, the most profitable treatment at the LT experiment was where L and G were applied together. The soils at the experimental sites are classified as Tenosols [19]. At the LT site, the gravel content increased from 5% in 0–10 cm to 56% in 30–50 cm, which reduces the water holding capacity.
In the ST experiment, we top-dressed the G and L treatments on 31 March 2017. The treatments consisted of: a control (C), 2.5 t L ha−1 (L2.5), 2.5 t gypsum ha−1 (G2.5) and, 2.5 t L ha−1 plus 2.5 t gypsum ha−1 (L2.5 + G2.5). The MT experiment consisted of the same L and G treatments as the ST experiment, plus additional treatments comprising 5.0 t L ha−1 (L5.0) and 5.0 t L ha−1 plus 2.5 t G ha−1 (L5.0 + G2.5). In this experiment, we broadcasted the L and G treatments on 31 July 2015, which was followed by deep ripping and cultivation. The LT experiment treatments consisted of: a control (C) 2.0 t L ha−1 (L2), 4.0 t L ha−1 (L4), 8.0 t L ha−1 (L8), 2.0 t G ha−1 (G2), and 4.0 t L ha−1 plus 2.0 t G ha−1 (L4 + G2). We broadcasted half (1, 2, and 4 t L ha−1, and 1 t G ha−1) of the L and G rates in March of 2008 and in March of 2013. We used three treatments replication in all experiments. The distance of the experiment site for L sources was 370–380 km compared for the G source of 140–200 km. The L source consisted of 80–93% CaCO3 while the G source contained 175–178 g S kg−1 and 214–224 g Ca kg−1 [3].
Crops grown at the MT experiments were canola (Brassica napus L. cv Bonito) in 2016, wheat (cv Calingiri) in 2017, and barley (Hordeum vulgare cv Spartacus CL) in 2018. The same crops were grown at the ST experiment in 2017 and 2018. Wheat was grown at the LT experiment in 2008, 2010, 2011, 2013, 2014, 2015, and 2016. Seeding occurred with farmer equipment for the ST and MT experimental sites and plot cone seeder for the LT site in May. We used a small plot header to harvest the plots in November of each year.

2.2. Soil Measurements

We collected four 5 cm diameter soil cores in depth increments of 10 cm to 50 cm from each plot in March 2018 which was 1 year (ST), 2 years and 8 months (MT), and 10 years (LT) after the application of L and G treatments. The four cores were bulked to provide soil profile samples for each plot. In this paper, treatment effects on pHCaCl2 and AlCaCl2 were measured using a 1:5 soil to 0.01 M CaCl2 solution extraction and electrical conductivity (EC) using the same soil to solution ratio but with water [20]. The extractable sulfur content of the soil profile was measured using 0.25 M KCl heated for 3 h at 40 °C (SKCl40) [21]. Soil buffer index (SBI) was measured to assess the S-SO4 adsorption properties of the soil using the procedure of [13] in the control treatments [3]. Exchangeable cations, Al (AlEx), Ca (CaEx), potassium (KEx), magnesium (MgEx) and sodium (NaEx), were extracted using an unbuffered solution of 0.1 M ammonium chloride and barium chloride at 1:10 soil to solution ratio with cation concentration measured by ICP-AES [20]. The ECEC value is calculated as the sum of the cations, AlEx, CaEx, KEx, MgEx and NaEx [20]. The percentage of cation occupied by AlEx% and CaEx% is AlEx or CaEx divided by ECEC multiplied by 100. Other soil nutrient measurements included ammonium and nitrate, Colwell phosphorus and potassium, phosphorus buffering index, organic carbon, DTPA extractable copper, manganese, and zinc, and hot boron are summarized by [3].

2.3. Lime and Gypsum Recovery

Calculated SO4-S and Ca recovered from applied G is the difference between SKCl40 (mg S kg−1) and CaEx (mg Ca kg−1) content of each soil layer between the G and the C treatment. In the calculation, we used a bulk density of 1.7 gm cm3 multiplied by the sampling depth (10 cm) to convert mg kg−1 to kg ha−1. The difference for each soil layer is then summed to give the amount of G or L recovered in the 0–50 cm soil layer of the three experimental sites [3]. Percent L or G recovered in then the summed amount divided by the amount applied. In doing the calculation, we used the measured Ca and S content of the G and the CaCO3 content of the L sources. Gravel content for the LT experiment, reduced SKCl40 and CaEx content when expressed in the units of kg ha−1.

2.4. Statistical Analysis

For individual soil layers, analysis of variance was done using a treatment structure of treatments and a block structure of replicates to determine the significance of amendment treatment main effects at each soil depth using Genstat® [22]. Differences between treatments were then determined using the Duncan multiple range test. Throughout the paper, the least significant difference values, were determined at p ≤ 0.05. The exception where p ≤ 0.07 was used to denote significance because of the high variability in some measurements. These exceptions were, in the ST experiment for calculated SO4-S recovery from the applied G (Table 1), in the MT experiment for AlCaCl2, AlEx and the LT experiment for pHCaCl2. In retrospect, to account for the high variability, we should have collected more than four soil profile cores per plot. Regression equations for comparison between soil measurements were determined using the regression SigmaPlot® 12.5 analysis regression wizard [23].

3. Results

3.1. Sulphur

Soil SKCl40 in the ST experiment for the C treatment increased from 14–22 mg S kg−1 in the 0–10 cm to 28–61 mg S kg−1 in the 40–50 cm soil layer (Figure 1a). In the ST experiment, G application increased soil SKCl40, from 22 to 537–676 mg S kg−1 in the 0–10 cm soil layer which was equivalent to more than the amount of SO4-S applied (Table 1). In contrast, the application of L had no effect on soil SKCl40 in the ST. In the MT, the L5.0 + G2.5 treatment increased soil SKCl40 by 526–551% in the 0–20 cm soil layer and by 53–157% in the 20–50 cm soil layer compared to the C treatment (Figure 1b). In the MT, these increases accounted for 28–54% of the applied SO4-S (Table 1). In the LT, G alone increased SKCl40 by 415% in the 0–10 cm soil layer (Figure 1c), while SKCl40 was 56–144% greater for the G treatments compared to the C treatment in the 10–50 cm soil layers. In the LT, these increases in SKCl40 only accounted for 26–27% of applied SO4-S (Table 1).

3.2. Calcium

Soil CaEx decreased from 1.96–3.23 cmol kg−1 in the 0–10 cm to 0.23–0.35 cmol kg−1 in the 40–50 cm soil layer for the ST and MT experiments (Figure 1d,e). Soil CaEx was lower for the LT experiment, but the content also decreased with increasing soil depth from 0.81 cmol kg−1 in the 0–10 cm to 0.49 cmol kg−1 in the 40–50 cm soil layer (Figure 1f).
In the ST, the L2.5 + G2.5 treatment increased soil CaEx relative to the C treatment by 96–122% in the 0–20 cm soil layer and by 77–99% in the 20–40 cm soil layer (Figure 1d). In comparison, the G and L alone treatments increased CaEx by 49–72% compared to the C treatment in the 0–10 cm soil layer. In the MT, soil CaEx for the L5.0 + G2.5 treatment was greater than the C by 46–141% in the 0–50 cm soil layer, (Figure 1e). In contrast, the G and L alone treatments had no significant effect on CaEx. In the LT, the L4, L8, and L4 + G2 treatments increased CaEx by 131–249% in the 0–20 cm soil layer and for the L4 + G2 treatment by 94% in the 20–50 cm soil layer compared to the C treatment (Figure 1f). At the same time, soil CaEx content for the L2 treatment was greater by 139% in the 0–10 cm soil layer and by 77% in the 10–20 cm soil layer than the C treatment (Figure 1e). For the G2 treatment in the LT experiment, CaEx content was not significantly greater than the C treatment in the 0–20 cm soil layer.
Calcium recovery, as indicated by the increase in CaEx was low (−2–31%) for all L treatments across the 3 three experiments (Table 2). In contrast, Ca recovery for the G treatments was high (82–92%) in the ST and MT but relatively low (48%) in the LT while Ca recovery was low (23–37%) for the L + G treatments for the three experiments.

3.3. Electrical Conductivity

The application of L did not affect soil EC in the three experiments (Figure 1g–i). In contrast, the use of G resulted in a substantial increase in EC in the surface soil layers in the ST, and to lesser extents in the MT and LT. In the ST, the highest increase for the G treatments compared to the C and L2.5 treatments was in the 0–10 cm soil layer (636–490%) declining to a 67–98% increase in the 30–40 cm soil layer (Figure 1g). There was also an increase of 28% for the L5.0 + G2.5 compared to the C treatment in the 40–50 cm soil layer. In the MT, EC values of the L5.0 + G2.5 treatment were 64–154% greater than the C in the 0–50 cm soil layer (Figure 1h). In the LT, soil EC value for the L4 + G2 treatment was 178% greater than the C treatment in the 0–10 cm soil layer while for the G2 and L4 + G2 treatments EC was 41–93% greater than the C in the 10–50 cm soil layer (Figure 1i).

3.4. Aluminum and pH

For the C treatment, soil AlCaCl2 in the ST and MT experiments increased from 0.1–0.2 mg Al kg−1 in the 0–10 cm to 15.4–22.2 mg Al kg−1 in the 40–50 cm (Figure 2a,b). In the LT experiment, the highest soil AlCaCl2 for the C treatment was 11.1–11.2 mg Al kg−1 in the 10–30 cm (Figure 2c).
The L treatments decreased AlCaCl2, while G alone treatment had no impact on AlCaCl2. The extent and depth to which L application reduced on AlCaCl2 varied with time, L rate, and G application. In both the ST and MT experiment L, AlCaCl2 is near zero in the 0–10 cm soil layers and hence was not lowered further by L application. In the ST, L G, and L + G application decreased AlCaCl2 compared to the C treatment by 48–69% in the 10–20 cm soil layer (Figure 2a).
In the MT, AlCaCl2 was again near-zero and not lowered further by L application in 0–30 cm soil layer (Figure 2b). In contrast, AlCaCl2 was 74–91% lower for the L5.0 + G2.5 treatment compared to the C treatment in the 30–50 cm soil layer with the difference significant at p = 0.054 for the 30–40 cm soil layer. In the LT, soil AlCaCl2 content for the L treatments was lower than the C treatment by 91–92% in the 0–10 cm (Figure 2c). In the 10–20 cm soil layer, AlCaCl2 content was 55% lower for the L4 treatment, and 77–95% lower for the L4, L4 + G2, and L8 treatments than the C treatment. In the 20–30 cm soil layer, the L4 + G2 treatment had a 70% lower AlCaCl2 than the C treatment.
Soil AlEx in the ST and MT experiments, for the C treatment, increased with increasing soil depth from 0.09–0.10 cmol kg−1 in the 0–10 cm to 0.53–0.81 cmol kg−1 in the 40–50 cm soil layer (Figure 2d,e). In the LT experiment, the highest soil AlEx for the C treatment of 0.36–0.45 cmol kg−1 occurred in the 10–30 cm soil layer (Figure 2f).
In the ST, the L and G treatments decrease AlEx by 29–49% in the 10–20 cm soil layer (Figure 2d). In the MT, soil AlEx was 48–62% lower for the G5.0 + L5.0 treatment than the C treatment in the 30–50 cm soil layer, with the difference significant at p = 0.062 in the 40–50 cm soil layer (Figure 2e). In the LT, soil AlEx for the L and L + G treatments was 72–86% lower in the 0–10 cm soil layer than the C treatment (Figure 2f). In the 10–20 cm soil layer, the L4, L4 + G2, and L8 treatments decreased AlEx content by 53–72% compared to the C treatment. For the L4 + G2 treatment, AlEx content was 46–47% lower in the 20–30 cm soil layer compared to the C treatment. Application of G2 did not affect AlEx in the 0–50 cm soil layer.
Soil pHCaCl2 in the ST and MT experiments, for the C treatment, decreased with increasing soil depth from 5.5–6.6 in the 0–10 cm to 4.2–4.7 in the 40–50 cm soil layer (Figure 2g,h). In the LT experiment, soil profile pHCaCl2 ranged between 4.5–4.7 (Figure 2i). In the ST and MT, neither L nor G application altered pHCaCl2 in any soil layers (Figure 2g,h). In the LT, soil pHCaCl2 ranged between 6.0–6.4 for the L4, L8, and L4 + G2 treatments compared to 4.6 for the C treatment in the 0–10 cm soil layer (Figure 2i). Additionally, pHCaCl2 for the L8 treatment was greater at 5.1 compared to 4.5 for the C treatment in the 10–20 cm soil layer at p = 0.066.
The relationships between pHCaCl2 and AlCaCl2 were similar for the three experimental sites (Figure 3). In the LT experiment, the L treatments decreased AlCaCl2 from 11.3 to 2.8 mg Al kg−1 with the associated change in pHCaCl2, ranging from 4.4 to 4.6. The lowest pHCaCl2 and greatest AlCaCl2 occurred in the 20–50 cm soil layer for the ST experiment, in the 30–50 cm soil layer for the MT experiment, and in the 10–30 cm soil layer for the LT experiment (Figure 2). Soil pHCaCl2 and AlCaCl2 were both related to AlEx (Figure 4). The relationships and equations used to convert AlCaCl2 to AlEx are presented in Figure 4.

3.5. Effective Cation Exchange Capacity

Soil ECEC of the soil profile, in the three experiments, decreased with increasing soil depth from 1.51–2.40 cmol kg−1 in the 0–10 cm to 1.07–1.15 cmol kg−1 in the 40–50 cm soil layer (Figure 5). In the ST, soil ECEC for the L and G treatments was 44–87% greater than the C treatment in the 0–10 cm soil layer while ECEC was 16–50% greater for the L2.5 + G2.5 treatment was than the C in the 10–30 cm soil layer. In the MT, ECEC of the L5.0 + G2.5 treatment was greater than the C, L2.5, and L5.0 treatments by 27–96% in the 0–50 cm soil layer (Figure 5b). In the LT, ECEC for the L2 treatment was 56–65% greater in the 0–20 cm soil layer compared to the C treatment (Figure 5c). For the L4, L8, and L4 + G2 treatments ECEC was 90–148% greater in the 0–20 cm soil layer compared to the C treatment. Soil ECEC for the G2 treatment was the same as the C treatment.

4. Discussion

4.1. Sulfate

Leaching of soil SO4-S occurs in light texture soils of South Western Australia due to the low water holding capacity of the soil profile, high June and July rainfall and limited adsorption of SO4-S [15]. The soil profile for the LT experiment had SBI of 10–14, indicating the soil has a low capacity to adsorb SO4-S [13]. The soil profiles at the other two experimental sites had a greater ability to adsorb SO4-S, especially in the soil layers below 10 cm with SBI of 9–36. Due to this combination of rainfall, water holding capacity of the soil, and SO4-S adsorbing capacity, SO4-S derived from G was readily leached into and through the soil profile. In the ST experiment, SO4-S was leached rapidly into the soil profile, as measured by the increase SKCl40 content, even after a relatively low rainfall (279 mm) growing season (Figure 1a). The increase in SKCl40 was associated with increased EC (Figure 1g) and Al-SO4 [24], leading to an increasing canola grain yield in the first year after application [3]. In retrospect, in the ST, to cope with the variation observed following a recent application of G, we should have collected more soil cores to define the G effect on SKCl40 measurement accurately. In the MT and LT, the effectiveness of G declines [3] because SO4-S is leached below the 50 cm sampling depth as indicated by the low recovery of the applied SO4-S (28–54%) (Table 1).
The leaching of SO4-S can also occur within 3.5 years, even for soils with high SO4-S adsorption capacities [12]. In the LT, G application increased SKCl40 content resulting in the retention of 26–27% of the applied SO4-S within 0–50 cm soil layer (Table 1). Retention of SO4-S was also observed in the subsoil 13 years after the G application due to the high SO4-S adsorption capacity [12]. Soils retain SO4-S by the processes of adsorption and precipitation [25]. The precipitation of Al-SO4 is more critical in soils with high Al content which occurs in soil with pHCaCl2 less than 4.5 [26]. Soil with greater pHCaCl2 has a lower ability to adsorb SO4-S due to decreases in anion exchange capacity on variable charge surfaces [27]. Hence, L application which increases soil pH results in lower retention of SO4-S or lower SKCl40 content in the 0–20 cm for the LT experiment (Figure 1c). We have confirmed the retention of SO4-S as Al-SO4 for these experiments using soil solution and modelling approach [24]. However, in the LT, the lower wheat grain yield response to the G treatment occurs over time is attributed to the leaching of SO4-S below the Al3+ toxic layer (10–40 cm) [3].

4.2. Calcium

In general, the effect of the application of L and G is to increase CaEx (Figure 1d–f), and decrease AlEx (Figure 2d–f) with the net result an increase in ECEC (Figure 5a–c) [28]. Leaching of Ca derived from G and L varies according to application rates, time of contact with the soil and soil properties [17]. In these experiments, we applied Ca at different rates of L and G, and it was not possible to directly compare the leaching rates of the two Ca sources. Nevertheless, in the LT experiment, the application of L and G together resulted in an increase in soil CaEx to a depth of 30 cm compared to only 20 cm when only L8 or G was applied (Figure 1f). Similarly, the combined application of L and G increased CaEx to a greater depth than the use of only L or G on soils in southern Brazil [17].

4.3. Electrical Conductivity

The EC of Tenosols of South Western Australia is generally less than 0.11 dS m−1 due to the highly weathered and leached nature of the soil [29]. EC is an important measurement when examining subsoil Al toxicity limitations because soils with greater EC decreases Al3+ activity and increases ion paring, which together makes the solution Al3+ less toxic [30]. For example, soils with greater EC have a lower critical AlEx% value [31]. In the three present experiments, EC was less than 0.07 dS m−1 in the soil profile (Figure 1g–i). The critical range for tolerant wheat cultivars to achieve 90% of maximum grain yield is between 21–32 AlEx%, which is equivalent to AlCaCl2 of 3.9–7.0 mg Al kg−1 (Figure 4b). For the three experimental sites, AlEx% for the sampling depth 10–30 cm ranged between 10–59% indicating Al toxicity at levels that would reduce wheat grain yield. In these experiments, the application of G increased soil EC to ≥ 0.07 dS m−1 in the 0–30 cm soil layer in the ST (Figure 1g). This increase in EC reduced the critical range 13–21 AlEx%, which is equivalent to AlCaCl2 of 2.0–3.9 mg kg−1 and is more consistent with the critical range observed by [2]. The increase in EC due to G application is, therefore, likely to have contributed to reducing the adverse effects of subsoil Al3+ toxicity and increased grain yield [3].

4.4. Aluminum and pH

Leaching of alkalinity derived from dissolved L occurs when pHCaCl2 of the 0–10 cm soil layer is greater than 5.5 [32]. When L is applied, both Ca, and Mg cations are leached, suggesting the ions are moving as Ca and Mg bicarbonate [12]. Once pHCaCl2 of the 0–10 cm soil layer has achieved a pHCaCl2 of 7.1, L will stop dissolving [33,34]. Due to this restriction on L dissolution, the pool of alkalinity available to be leached into the subsoil is insufficient for the L application to have an impact on subsoil pH [2,32,35,36]. In the ST and MT experiments, pHCaCl2 in the 0–10 cm soil layer was greater than 5.5, and the application of additional L resulted in no impact on subsoil pHCaCl2 over the sampling period of two years and eight months. In the LT, a high rate of L application (4–8 t ha−1) increased pHCaCl2 in the 10–20 cm soil layer while 2 t L ha−1 did not affect subsoil pHCaCl2 (Figure 2i). This observation is consistent with other studies that have shown L application can be slow or in some cases, ineffective in increasing subsoil pHCaCl2 [2,35,36].
There are a diverse array of chemical reactions that can arise when G is applied, resulting in a change in soil pH [37]. In soils with a high capacity for SO4-S sorption, the net effect is an increase in soil pHCaCl2 [12]. In contrast, the LT experiment soil profile has an SBI of 10–14, indicating a low ability to sorb SO4-S, [3]. Hence, the net effect of G application on the low SBI was no significant impact on soil pHCaCl2 in the 10–30 cm soil layer (Figure 2i). Nevertheless, small changes in the pHCaCl2 within the range of 4.3–4.5 can result in significant changes in AlCaCl2 (Figure 4). However, in this case, G application did not affect AlCaCl2 compared to the C treatment in the 10–20 cm soil layer (Figure 2c).
Application of L to the soil surface resulted in a more significant decline in soil Al values (AlCaCl2 and AlEx) than the increase in pHCaCl2 in the soil layers below 10 cm because there is an exponential relationship between pHCaCl2 and these soil Al measurements (Figure 3 and Figure 4a). Hence, for small changes in pHCaCl2 below 4.5, there is a greater change in AlCaCl2 and AlEx. Therefore, both AlCaCl2 and AlEx are a more sensitive measurement of the impact of L application on soil properties than pHCaCl2. For example in the LT experiment, L8 resulted in a 50–92% decrease in the AlCaCl2 content to a depth of 40 cm (Figure 2c) compared to pHCaCl2 which only increased from 4.6 to 5.1 in the 10–20 cm soil layer (Figure 2i). Furthermore, in the MT experiment, the L2.5 + G2.5 treatment resulted in a 54–84% reduction in soil AlCaCl2 in the soil layers 20–50 cm (Figure 2e) and no effect subsoil pHCaCl2 (Figure 2h). These observations are consistent with other experiments that observed the application of L decreased AlEx to a greater depth than the decrease in pHCaCl2 [38,39,40]. For example, in an experiment monitored over time, application of 6 t L ha−1 increased pHCaCl2 in the 10–20 cm soil layer by 0.2–0.4 pH units after 2.5 years with the effect remaining constant over time while AlEx decrease by 55% after 2.5 years and to 68% after ten years [41]. However, reductions in AlCaCl2 and AlEx observed for the L8 treatment did not increase crop grain yield compared to the L2 treatment [3].
An effective LT strategy is to apply sufficient L to maintain the soil pHCaCl2 of the 0–10 cm greater than 5.5 because it will maximize the impact that a surface L application will have on the subsoil Al toxicity content [32]. In the LT experiment, 4–8 t L ha−1 resulted in a pHCaCl2 of greater than 6.1 in the 0–10 cm soil layer measured in March 2018, but the treatments did not affect pHCaCl2 in the 20–30 cm soil layer (Figure 2c). In contrast, L and G have a synergistic effect on soil Al toxicity by increasing alkalinity leaching as indicated by a more significant decline in AlCaCl2 and AlEx in the MT (Figure 2b,e). In retrospect, to account for the high variability, we should have collected more soil cores than 4 to define this effect better. In the LT experiment, the L4 + G2 treatment resulted in a greater and deeper decline in AlCaCl2 and AlEx compared to the L4 treatment (Figure 2c,f). Other researchers have also hypothesized the combined application of L and G could have a synergistic effect in improving soil chemical properties and crop grain yields as observed by for highly acidic subsoil [6,42,43]. However, the response was not consistent between sampling years at another experiment conducted located near the ST experimental site [6]. Additionally, in high rainfall subtropical region, the combined use of L and G had no synergistic effect in improving soil chemical properties and crop grain yields [44]. In that agricultural system and soil, surface application of L was effective in increasing pHmeasured using water as the extracting solution to a depth of 60 cm within the first year. In contrast, in the South Western Australia agricultural region L application can be ineffective in increasing subsoil pHCaCl2 [2]. Hence, the synergistic L and G effect in improving soil chemical properties and crop grain yields could play a significant role in South Western Australia. However, further research is required to examine the combination of soil and growing environments where this effect occurs.

5. Conclusions

The combined application of lime and gypsum is more effective than applying lime alone in managing subsoil Al constraints for crop production in the short-term (1 year) due to the increased soil sulfate, calcium and electrical conductivity of the subsoil with the application of gypsum even following relatively dry year (279 mm). Use of lime and gypsum together in the medium-term (two years and eight months) and long-term (ten years) lead to a decrease in soil Al, to a greater depth than the application of lime only. The impact of broadcast lime plus gypsum and lime alone resulted in changes in subsoil Al measurements to a greater depth than changes in soil pH, indicating soil Al measurements are more sensitive than soil pH measurements.

Author Contributions

Conceptualization, G.C.A., S.P., D.J.M.H. and J.E.; Data curation, S.P. and J.E.; Formal analysis, G.C.A., S.P. and J.E.; Funding acquisition, D.J.M.H. and J.E.; Investigation, G.C.A., S.P., D.J.M.H., J.E., and R.S.; Methodology, G.C.A., S.P., D.J.M.H. and J.E.; Project administration, D.J.M.H. and J.E.; Resources, D.J.M.H.; Supervision, D.J.M.H. and J.E.; Writing–original draft, G.C.A.; Writing–review & editing, G.C.A., S.P., D.J.M.H., R.S., and J.E. All authors read and approved the final manuscript.

Funding

This research was funded by Grain Research and Development Corporation project number DAW00242, Department of Primary Industries and Regional Development and CSBP.

Acknowledgments

Warakarri Cropping managed the ST and MT experiments.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Ritchie, G.S.P. Soluble aluminium in acidic soils: Principles and practicalities. In Plant Soil Interactions at Low pH; Date, R.A., Grundon, N.J., Rayment, G.E., Probert, M.E., Eds.; Kluwer Academic Publishers: Dordrecht, The Netherlands, 1995; pp. 23–33. [Google Scholar]
  2. Anderson, G.C.; Bell, R.W. Wheat grain-yield response to lime application: Relationships with soil pH and aluminium in Western Australia. Crop. Pasture Sci. 2019, 70, 295–305. [Google Scholar] [CrossRef]
  3. Anderson, G.C.; Pathan, S.; Hall, D.J.M.; Sharma, R.; Easton, J. Short and long term effects of lime and gypsum application on acid soils in a water-limited environment 1. Grain yield response and nutrient concentration. Agronomy 2020, 10, 1213. [Google Scholar] [CrossRef]
  4. Lebedev, A.; Kosorukov, V.L. Gypsum solubility in water at 25 °C. Geochem. Int. 2017, 55, 205–210. [Google Scholar] [CrossRef]
  5. Aylward, G.H.; Findlay, T.J.V. SI Chemical Data Book, 6th ed.; John Wiley and Sons: Chichester, UK, 2008; ISBN 978-0-730-30246-9. [Google Scholar]
  6. McLay, C.D.A.; Ritchie, G.S.P.; Porter, W.M.; Cruse, A. Amelioration of subsurface acidity in sandy soils in low rainfall regions. 2. Changes to soil solution composition following the surface application of gypsum and lime. Aust. J. Soil Res. 1994, 32, 847–865. [Google Scholar] [CrossRef] [Green Version]
  7. Zoca, S.M.; Penn, C. An important tool with no instruction manual: A review of gypsum use in agriculture. Adv. Agron. 2017, 144, 1–44. [Google Scholar] [CrossRef]
  8. Sumner, M.E. Gypsum as an Ameliorant for the Subsoil Acidity Syndrome; Publication No 01-024-090; Florida Institute of Phosphate Research: Bartow, FL, USA, 1990. [Google Scholar]
  9. Smith, C.J.; Peop1es, M.B.; Keerthisinghe, T.R.; James, T.R.; Garden, D.L.; Tuomi, S.S. Effect of surface applications of lime, gypsum and phosphogypsum on the alleviating of surface and subsurface acidity in a soil under pasture. Aust. J. Soil Res. 1994, 32, 995–1008. [Google Scholar] [CrossRef]
  10. Alva, A.K.; Sumner, E.M.; Noble, A.D. Alleviation of aluminium toxicity by phospho-gypsum. Commun. Soil Sci. Plant Anal. 1988, 19, 385–403. [Google Scholar] [CrossRef]
  11. Curtin, D.; Syers, J.K. Mechanism of sulphate adsorption by two tropical Soils. J. Soil Sci. 1990, 41, 295–304. [Google Scholar] [CrossRef]
  12. Blum, S.C.; Caires, E.F.; Alleoni, L.R.F. Lime and phosphogypsum application and sulfate retention in subtropical soils under no-till system. J. Soil Sci. Plant Nutr. 2013, 13, 279–300. [Google Scholar] [CrossRef] [Green Version]
  13. Anderson, G.C. Sulfate sorption as measured by a buffering index over a range of soil properties from south Western Australia. Soil Res. 2020, 58, 651–661. [Google Scholar] [CrossRef]
  14. Tiecher, T.; Pias, O.H.C.; Bayer, C.; Martins, A.P.; Denardin, L.G.O.; Anghinoni, I. Crop response to gypsum application to subtropical soils under no-till in Brazil: A systematic review. Rev. Bras. Cienc. Solo. 2018, 42, e0170025. [Google Scholar] [CrossRef]
  15. Anderson, G.C.; Fillery, I.R.P.; Ripper, F.H.; Leach, B.J. Sulfur mineralization in a coarse-textured soil after different sulfate fertilization histories and yield responses of wheat and lupin. Aust. J. Soil Res. 2006, 44, 165–174. [Google Scholar] [CrossRef]
  16. Wong, M.T.F.; Wittwer, K. Positive charge discovered across Western Australian wheatbelt soils challenges key soil and nitrogen management assumptions. Aust. J. Soil Res. 2009, 47, 127–135. [Google Scholar] [CrossRef]
  17. Caires, E.F.; Joris, H.A.W.; Churka, S. Long-term effects of lime and gypsum additions on no-till corn and soybean yield and soil chemical properties in southern Brazil. Soil Use Manag. 2011, 27, 45–53. [Google Scholar] [CrossRef]
  18. Zambrosi, F.C.B.; Alleoni, L.R.F.; Caires, E.F. Nutrient concentration in soil water extracts and soybean nutrition in response to lime and gypsum applications to an acid Oxisol under no-till system. Nutr. Cycl. Agroecosyst. 2007, 79, 169–179. [Google Scholar] [CrossRef]
  19. Isbell, R.F.; National Committee on Soil and Terrain. The Australian Soil Classification, 2nd ed.; CSIRO Publishing: Collingwood, VIC, Australia, 2016. [Google Scholar]
  20. Rayment, G.E.; Lyons, D.J. Soil Chemical Methods-Australasia; Aust. Soil and Land Survey Handbooks Series; CSIRO Publishing: Melbourne, Australia, 2010; ISBN 9780643101364. [Google Scholar]
  21. Blair, G.J.; Chinoim, N.; Lefroy, R.D.B.; Anderson, G.C.; Crocker, G.J. A soil sulfur test for pasture and crops. Aust. J. Soil Res. 1991, 29, 619–629. [Google Scholar] [CrossRef]
  22. VSN International Genstat for Windows, 18th ed.; VSN International: Hemel Hempstead, UK, 2015; Available online: genstat.co.uk (accessed on 1 December 2020).
  23. SYSTAT Sigmaplot 12.5; SYSTAT: San Jose, CA, USA, 2013; Available online: systatsoftware.com (accessed on 16 December 2020).
  24. Anderson, G.C.; Pathan, S.; Hall, D.J.M.; Sharma, R.; Easton, J. Short and long term effects of lime and gypsum application on acid soils in a water-limited environment 3. Soil solution properties. 2020; unpublished; manuscript in preparation. [Google Scholar]
  25. Johnson, D.W.; Mitchell, M.J. Responses of forest ecosystems to changing sulfur inputs. In Sulfur in the Environment; Maynard, D.G., Ed.; Marcel Dekker: New York, NY, USA, 1998; pp. 219–262. [Google Scholar]
  26. Khanna, P.K.; Prenzel, J.; Meiwes, K.J.; Ulrich, B.; Matzner, E. Dynamics of sulfate retention by acid forest soils in an acidic deposition environment. Soil Sci. Soc. Am. J. 1987, 51, 446–452. [Google Scholar] [CrossRef]
  27. Bolan, N.S.; Adriano, D.C.; Curtin, D. Soil acidification and liming interactions with nutrient and heavy metal transformation and bioavailability. Adv. Agron. 2003, 78, 215–272. [Google Scholar]
  28. Aitken, R.L.; Dickson, T.; Moody, P.W. Field amelioration of acidic soils in south-east Queensland. II. Effect of amendments on the yield and leaf nutrient composition of maize. Aust. J. Agric. Res. 1998, 49, 639–647. [Google Scholar] [CrossRef]
  29. Dolling, P.J.; Ritchie, G.S.P. Estimates of soil solution ionic strength and the determination of pH in West Australian soils. Aust. J. Soil Res. 1985, 23, 309–314. [Google Scholar] [CrossRef] [Green Version]
  30. McLay, C.D.A.; Ritchie, G.S.P.; Porter, W.M.; Cruse, A. Amelioration of subsurface acidity in sandy soils in low rainfall regions. 1. Responses of wheat and lupins to surface-applied gypsum and lime. Aust. J. Soil Res. 1994, 32, 835–846. [Google Scholar] [CrossRef]
  31. Upjohn, B.; Fenton, G.; Conyers, M. Soil Acidity and Liming. Agfact AC. 19, 3rd ed.; NSW Department of Primary Industries: Orange, NSW, Australia, 2005. [Google Scholar]
  32. Li, G.D.; Conyers, M.K.; Helyar, K.R.; Lisle, C.J.; Poile, G.J.; Cullis, B.R. Long-term surface application of lime ameliorates subsurface soil acidity in the mixed farming zone of south-eastern Australia. Geoderma 2019, 338, 236–246. [Google Scholar] [CrossRef]
  33. Stumm, W.; Morgan, J.J. Aquatic Chemistry: Chemical Equilibria and Rates in Natural Waters; John Wiley and Sons: New York, NY, USA, 1996; ISBN 978-0-471-51185-4. [Google Scholar]
  34. Nye, P.H.; Ameloko, A.Y. Predicting the rate of dissolution of lime in soils. J. Soil Sci. 1987, 38, 641–644. [Google Scholar] [CrossRef]
  35. Whitten, M.G.; Wong, M.T.F.; Rate, A.W. Amelioration of subsurface acidity in the south-west of Western Australia: Downward movement and mass balance of surface-incorporated lime after 2–15 years. Aust. J. Soil Res. 2000, 38, 711–728. [Google Scholar] [CrossRef]
  36. Azam, G.; Gazey, C. Slow movement of alkali from surface-applied lime warrants the introduction of strategic tillage for rapid amelioration of subsurface acidity in south-western Australia. Soil Res. 2020. [Google Scholar] [CrossRef]
  37. Menzies, N.W.; Bell, L.C.; Edwards, D.G. Exchange and solution phase chemistry of acid, highly weathered soils. I. Characteristics of soils and the effects of lime and gypsum amendments. Aust. J. Soil Res. 1994, 32, 251–267. [Google Scholar] [CrossRef]
  38. Scanlan, C.A.; Brennan, R.F.; D’Antuono, M.F.; Sarre, G.A. The interaction between soil pH and phosphorus for wheat yield and the impact of lime-induced changes to soil aluminium and potassium. Soil Res. 2017, 55, 341–353. [Google Scholar] [CrossRef]
  39. De Vargas, J.P.R.; Santos, D.R.; Bastos, M.C.; Schaefer, G.; Parisi, P.B. Application forms and types of soil acidity corrective: Changes in depth chemical attributes in long term period experiment. Soil Tillage Res. 2019, 185, 47–60. [Google Scholar] [CrossRef]
  40. Costa, C.H.M.; Carmeis Filho, A.C.A.; Crusciol, C.A.C.; Soratto, R.P.; Guimarães, T.M. Intensive annual crop production and root development in a tropical acid soil under long-term no-till and soil-amendment management. Crop Pasture Sci. 2018, 69, 488–505. [Google Scholar] [CrossRef]
  41. Caires, E.F.; Alleoni, L.R.F.; Cambri, M.A.; Barth, G. Surface application of lime for crop grain production under a no-till system. Agron. J. 2005, 97, 791–798. [Google Scholar] [CrossRef]
  42. Costa, C.H.M.; Crusciol, C.A.C. Long-term effects of lime and phosphogypsum application on tropical no-till soybean-oat-sorghum rotation and soil chemical properties. Eur. J. Agron. 2016, 74, 119–132. [Google Scholar] [CrossRef] [Green Version]
  43. Crusciol, C.A.C.; Artigiani, A.C.C.A.; Arf, O.; Carmeis Filho, A.C.A.; Soratto, R.P.; Nascente, A.S.; Alvarez, R.C.F. Soil fertility, plant nutrition, and grain yield of upland rice affected by surface application of lime, silicate, and phosphogypsum in a tropical no-till system. Catena 2016, 137, 87–99. [Google Scholar] [CrossRef] [Green Version]
  44. Fontoura, S.M.V.; de Castro Pias, O.H.; Tiecher, T.; Cherubin, M.R.; de Moraes, R.P.; Bayer, C. Effect of gypsum rates and lime with different reactivity on soil acidity and crop grain yields in a subtropical Oxisol under no-tillage. Soil Tillage Res. 2019, 193, 27–41. [Google Scholar] [CrossRef]
Agronomy 10 01987 g001a 550Agronomy 10 01987 g001b 550
Figure 1. (a–c) Soil SKCl40, (d–f), CaEx, and (g–i) EC (a,d,g) in the ST for C, L2.5, G2.5, L2.5 + G2.5 treatments (b,e,h), in the MT for C, L2.5, G2.5, L2.5 + G2.5, L5.0, and L5.0 + G2.5 treatments and; (c,f,i) in the LT for C, L4, G2, L4 + G2, L2, and L8 treatments. Error bars represent least significant difference values at p = 0.05, n = 3 for each depth with ns denoting p > 0.05.
Figure 1. (a–c) Soil SKCl40, (d–f), CaEx, and (g–i) EC (a,d,g) in the ST for C, L2.5, G2.5, L2.5 + G2.5 treatments (b,e,h), in the MT for C, L2.5, G2.5, L2.5 + G2.5, L5.0, and L5.0 + G2.5 treatments and; (c,f,i) in the LT for C, L4, G2, L4 + G2, L2, and L8 treatments. Error bars represent least significant difference values at p = 0.05, n = 3 for each depth with ns denoting p > 0.05.
Agronomy 10 01987 g001aAgronomy 10 01987 g001b
Agronomy 10 01987 g002a 550Agronomy 10 01987 g002b 550
Figure 2. (a–c) Soil AlCaCl2, (d–f) AlEx, and (g–i) pHCaCl2 (a,d,g) in the ST for C, L2.5, G2.5, L2.5 + G2.5 treatements (b,e,h), in the MT for C, L2.5, G2.5, L2.5 + G2.5, L5.0, and L5.0 + G2.5 treatments; and (c,f,i) and in the LT for C, L4, G2, L4 + G2, L2, and L8 treatments. Error bars represent least significant difference values at p = 0.05, n = 3 for each depth with ns denoting p > 0.05. The exceptions were in (e) for the 40–50 cm where p = 0.062 and (i) for the 10–20 cm where p = 0.066.
Figure 2. (a–c) Soil AlCaCl2, (d–f) AlEx, and (g–i) pHCaCl2 (a,d,g) in the ST for C, L2.5, G2.5, L2.5 + G2.5 treatements (b,e,h), in the MT for C, L2.5, G2.5, L2.5 + G2.5, L5.0, and L5.0 + G2.5 treatments; and (c,f,i) and in the LT for C, L4, G2, L4 + G2, L2, and L8 treatments. Error bars represent least significant difference values at p = 0.05, n = 3 for each depth with ns denoting p > 0.05. The exceptions were in (e) for the 40–50 cm where p = 0.062 and (i) for the 10–20 cm where p = 0.066.
Agronomy 10 01987 g002aAgronomy 10 01987 g002b
Agronomy 10 01987 g003 550
Figure 3. (a) Relationship between pHCaCl2 and AlCaCl2 (mg Al kg−1) across sampling depths for the ST (AlCaCl2 = (85,221,378 × exp(−3.67 × pHCaCl2), r2 = 0.94; (b) MT (AlCaCl2 = 0.09 + (47,860,313 × exp(−3.56 × pHCaCl2), r2 = 0.78); and (c) LT (AlCaCl2 = 0.001 + (292,525 × exp(−2.41 × pHCaCl2), r2 = 0.60 experiments for the various L and G treatments measured in March 2018. The ST, MT, and LT; L and G treatments are C (●), L2.5 (▼), G2.5 (▲), and L2.5+G2.5 (◆). The additional treatments in the MT are; L5.0 (■) and L5.0+G2.5 (■); and in the LT are L2 (■) and L8 (■).
Figure 3. (a) Relationship between pHCaCl2 and AlCaCl2 (mg Al kg−1) across sampling depths for the ST (AlCaCl2 = (85,221,378 × exp(−3.67 × pHCaCl2), r2 = 0.94; (b) MT (AlCaCl2 = 0.09 + (47,860,313 × exp(−3.56 × pHCaCl2), r2 = 0.78); and (c) LT (AlCaCl2 = 0.001 + (292,525 × exp(−2.41 × pHCaCl2), r2 = 0.60 experiments for the various L and G treatments measured in March 2018. The ST, MT, and LT; L and G treatments are C (●), L2.5 (▼), G2.5 (▲), and L2.5+G2.5 (◆). The additional treatments in the MT are; L5.0 (■) and L5.0+G2.5 (■); and in the LT are L2 (■) and L8 (■).
Agronomy 10 01987 g003
Agronomy 10 01987 g004 550
Figure 4. (a) Relationship between pHCaCl2 and AlEx: AlEx = 0.04 + (13,648 × exp(−2.40 × pHCaCl2), r2 = 0.82; and (b) AlCaCl2 and AlEx, AlEx = 0.05 + (0.093 × (AlCaCl20.668), r2 = 0.93.
Figure 4. (a) Relationship between pHCaCl2 and AlEx: AlEx = 0.04 + (13,648 × exp(−2.40 × pHCaCl2), r2 = 0.82; and (b) AlCaCl2 and AlEx, AlEx = 0.05 + (0.093 × (AlCaCl20.668), r2 = 0.93.
Agronomy 10 01987 g004
Agronomy 10 01987 g005 550
Figure 5. (a) Soil ECEC in the ST for C, L2.5, G2.5, L2.5 + G2.5 treatments, (b) in the MT for C, L2.5, G2.5, L2.5 + G2.5, L5.0, and L5.0 + G2.5 treatments; and (c) in the LT for C, L4, G2, L4 + G2, L2, and L8 treatments. Error bars represent least significant difference values at p = 0.05, n = 3 for each depth with ns denoting p > 0.05.
Figure 5. (a) Soil ECEC in the ST for C, L2.5, G2.5, L2.5 + G2.5 treatments, (b) in the MT for C, L2.5, G2.5, L2.5 + G2.5, L5.0, and L5.0 + G2.5 treatments; and (c) in the LT for C, L4, G2, L4 + G2, L2, and L8 treatments. Error bars represent least significant difference values at p = 0.05, n = 3 for each depth with ns denoting p > 0.05.
Agronomy 10 01987 g005
Table
Table 1. Recovery (%) of the applied SO4-S as calculated by the difference in SKCl40 between the G and C treatments for the short-term (ST), medium-term (MT) and long-term (LT) experiments using soil samples collected in March 2018.
Table 1. Recovery (%) of the applied SO4-S as calculated by the difference in SKCl40 between the G and C treatments for the short-term (ST), medium-term (MT) and long-term (LT) experiments using soil samples collected in March 2018.
ST MT LT
Depth (cm)G2.5L2.5 + G2.5G2.5L2.5 + G2.5L5.0 + G2.5G2.0L4 + G2
0–10NANA101329306
10–2034419102396
20–301718461178
30–4079271267
40–501238835
TotalNANA2831542627
L is the lime treatments. NA Recoveries are greater than 100% due to the insufficient number of soil cores collected to account for site variation.
Table
Table 2. Recovery (%) of the applied Ca from the L and G application as calculated by the difference in CaEx between the L and G treatments compared to the C treatment for the ST, MT, and LT experiments using soil samples collected in March 2018.
Table 2. Recovery (%) of the applied Ca from the L and G application as calculated by the difference in CaEx between the L and G treatments compared to the C treatment for the ST, MT, and LT experiments using soil samples collected in March 2018.
ST MT LT
Depth (cm)L2.5G2.5L2.5 + G2.5L2.5L5G2.5L2.5 + G2.5L5.0 + G2.5L2L4L8G2.0L4 + G2
0–10194319−1−21569201592015
10–10720100333511655149
20–1031550194411164
30–10283−10125401132
40–1016111134400041
Total319237−238223312822154830
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Anderson, G.C.; Pathan, S.; Easton, J.; Hall, D.J.M.; Sharma, R. Short- and Long-Term Effects of Lime and Gypsum Applications on Acid Soils in a Water-Limited Environment: 2. Soil Chemical Properties. Agronomy 2020, 10, 1987. https://doi.org/10.3390/agronomy10121987

AMA Style

Anderson GC, Pathan S, Easton J, Hall DJM, Sharma R. Short- and Long-Term Effects of Lime and Gypsum Applications on Acid Soils in a Water-Limited Environment: 2. Soil Chemical Properties. Agronomy. 2020; 10(12):1987. https://doi.org/10.3390/agronomy10121987

Chicago/Turabian Style

Anderson, Geoffrey C., Shahab Pathan, James Easton, David J. M. Hall, and Rajesh Sharma. 2020. "Short- and Long-Term Effects of Lime and Gypsum Applications on Acid Soils in a Water-Limited Environment: 2. Soil Chemical Properties" Agronomy 10, no. 12: 1987. https://doi.org/10.3390/agronomy10121987

APA Style

Anderson, G. C., Pathan, S., Easton, J., Hall, D. J. M., & Sharma, R. (2020). Short- and Long-Term Effects of Lime and Gypsum Applications on Acid Soils in a Water-Limited Environment: 2. Soil Chemical Properties. Agronomy, 10(12), 1987. https://doi.org/10.3390/agronomy10121987

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop