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Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India
Journal of the Saudi Society of Agricultural Sciences xxx (xxxx) xxx
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Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India I. Rashmi a,⇑,1, A.K. Biswas b,2, K.S. Kartika c,3, S. Kala a,4 a
ICAR-IISWC, RC, Kota, India ICAR-IISS, Bhopal, India c ICAR-NBSSLUP, RC, Bangalore, India b
a r t i c l e
i n f o
Article history: Received 1 August 2018 Revised 2 November 2018 Accepted 14 November 2018 Available online xxxx Keywords: Reactive P Total P Soil types Phosphorus sorption Phosphorus leaching
a b s t r a c t Phosphorus leaching from soils is a major environmental concern leading to eutrophication of water bodies. Three different soil types namely black, red and alluvial soils from Nagpur, Raipur and Kanpur were taken for the study. Soil column leaching experiment was conducted during 2014–15 with different levels of P (0, 50, 100, 150, 300, 600 mg L1) application with the objective to evaluate P buildup and vertical distribution in different soil types. Soluble reactive P (RP) content in three soils increased slowly with P application rates and decreased with increase in number of leaching events. Total P in leachate followed the similar trend. Phosphorus leaching mainly occurred during the initial seven leaching events accounting to 50–60% of total P leached over whole period. Among the various soil types RP content in leachate followed the order alluvial (0.01–0.23 mg l1) followed by red (0.01–0.17 mg l1), and black (0–0.1 mg l1) soil. Soluble reactive P (RP) accounting for 75–80% leaching mainly during initial 10 leaching events with alluvial soil leached highest P followed by red and black soils. Vertical distribution and movement of Olsen and bray P content in all the soils were higher beneath 0–10 cm depth and increased with P application and decreased in untreated column section. Environmental test like water extractable P (WEP) and CaCl2 P content were higher in alluvial soil, suggesting the greater potential of P leaching loss under chemical P fertilization. The result of the study can further be extended at field level for efficient P management in various soil types and thus could quantify the contribution of P from different sources to P leaching in agricultural land. Ó 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction Phosphorus is the crucial constituent of genetic materials and other cell organelles. It is directly involved in DNA, RNA, ATP and photosynthetic system and catalyses a number of biochemical ⇑ Corresponding author at: ICAR-IISWC, RC, Kota, Rajasthan, India. E-mail address: [email protected] (I. Rashmi). Scientist, Soil Chemistry and Fertility, ICAR-Indian Institute of Soil and Water Conservation, Research Centre, Kota. 2 HOD, Principal scientist, Soil chemistry, ICAR-Indian Institute of Soil Science, Bhopal. 3 Scientist Soil Chemistry and Fertility, ICAR-NBSSLUP, Regional Centre, Bangalore. 4 Scientist, Forestry, ICAR-Indian Institute of Soil and Water Conservation, Research Centre, Kota. 1
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reactions from the beginning of seedling growth through to the formation of grain and maturity (Scholz et al., 2015; Balemi and Negisho, 2012). Soil P deficiency on one hand is a major constrain for crop production and on the other hand high P buildup in soil and its loss to water bodies often result in eutrophication. Eutrophication causes algal bloom in aquatic system affecting biological life and its quality. Based on (geographic information system) GIS soil fertility map of India, Muralidharudu et al. (2011) reported high fertilizer consumption in states of Punjab followed by Andhra Pradesh and Tamil Nadu. Application of high analysis and complex P fertilizers in excess of crop requirement can increase the P content in agricultural soil. Such instances were found in south India (Kerala state) where out of 1.5 lakh soil samples collected, 62% of samples showed high P content between 25 and 100 kg ha1 which corresponds to high soil P content (Dinesh et al., 2014). In India, high prices of P fertilizers are the major challenge but continuous supply of P through manures and fertilizers is indispensable for crop production sustenance. Multi locational fertility studies also show
https://doi.org/10.1016/j.jssas.2018.11.002 1658-077X/Ó 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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the influence of high accumulation and downward movement of P in soils. Aulakh et al. (2007) reported high P accumulation also results downward movement P to deeper layers in coarsetextured irrigated sandy loam soils of Punjab state pointing to the potential for extensive leaching under long-term P fertilizer applications. More information is thus to be elicited from subtropical soils of India where P fertilizers are fully imported and applied in excess of crop requirement. Several studies on P losses from soil are mostly concentrated to surface water runoff (Pote et al., 1996; Torbert et al., 2002). However, authors like Heckrath et al. (1995), Beaucheminet al. (1998), Li et al. (2013) highlighted the importance of P leaching as a main contributor to surface water eutrophication, mainly through field drainage, in many countries worldwide. Various studies illustrate increased P concentration in subsoil horizons attributed to the buildup of P as evidence of past P leaching and translocation of P from applied sources mostly organics (Eghball et al., 1996; Withers et al., 2005; Kim et al., 2011). Studies with inorganic P forms like those reported by Zhao et al. (2009) showed P leaching in light chernozem soil under different P fertiliser rates in soil column study where high clay content influenced vertical P distribution. In India, major input is soluble P fertilizers and P movement under inorganics has not been extensively studied. Djodjic et al. (2004) suggested both soil and sub soil properties along with P application rates affect P leaching in soil column experiment. In recent times, Garg and Aulakh (2010) experiment revealed P movement beyond 30 cm depth in coarse textured soils of Punjab followed by reports indicating deteriorating drinking water quality in Tamil Nadu (Rajmohan and Elango, 2005) point out a need to understand vertical movement of P and the soil potential for P loss. Current information of P movement is minimal for Indian subtropics. Therefore a soil column experiment was undertaken was undertaken for major cultivable soil types of India namely black (vertisol), alluvial (inceptisol) and red (alfisol) with the objective of the study was to investigate the different form of P in leachate, examine downward movement of soil P and comparing the P leaching characteristics of the soils. 2. Materials and method 2.1. Soils Three soil types as per USDA soil classification system were black soil (Typic Chromousterts, Linga series, Clayey, Montmorillonitic, Hyperthermic) belonging to vertisol from Nagpur (21°80 N 79°50 E); alluvial soil (Typic Ustochrepts, Loamy, Hyperthermic) belonging to inceptisol from Kanpur (26°270 N, 80°140 E); and red soil (Typic Haplustalfs, Jhunvani series, Mixed, Hyperthermic) belonging to alfisol from Raipur (21°420 N 81°700 E) taken for the experiment. The soil samples were collected from 0 to 20 cm depth in all three soil types and processed passed through 2 mm sieve. The initial physico chemical properties of the soils were determined prior to soil column leaching experiment and shown in Table1. The P sorption was conducted in three soils using Langmuir equation to derive P sorption maxima (Psmax) of soils. 2.2. Soil column leaching experiment Soil column leaching experiment was conducted in all the three soil types by adding different P fertilizer rates at 0 (P1), 50 (P2), 100 (P3), 150 (P4), 300 (P5) and 600 (P6) mg kg1 (on oven dry basis) respectively. The inorganic source of P fertilizer as KH2PO4 was dissolved in distilled water and sprayed on to the soils and mixed in three replications. Prior to leaching experiment soils were incubated for six weeks by maintaining at field capacity by adding
Table 1 Initial physico chemical properties of the experimental soils. Soil parameters
Black soil
Alluvial soil
Red soil
pH Electrical conductivity (dS m1) Bulk density (g cm3) Organic carbon (g kg1) Clay (%) Sand (%) Silt (%) Amorphous Al (g kg1) Amorphous Fe (g kg1) P smax (mg kg1) Extractable P (mg kg1)
7.7 0.29 1.37 5.2 59.1 7.4 37.5 1.26 1.43 597.4 6.43
7.8 0.45 1.47 3.7 19.3 58.2 22.5 0.41 0.87 236.37 9.74
6.5 0.27 1.41 4.1 22.4 55.7 22.9 1.34 2.1 375.8 7.6
distill water and 40% moisture content in all the soil samples. Later, soils were subjected to alternate wetting and drying depending upon the moisture content to be maintained to get a representative/homogenized soil sample. The P incubated soil samples were kept in plastic bags at room temperature of 25–30 °C. After incubation, the soil samples were used for soil column experiment and are henceforth referred as P treated soil. A portion of the untreated soil was filled at the bottom of column section. One pore volume of the black, alluvial and red soil was 1204, 1027 and 1041 ml, respectively based upon porosity. The incubated soil was filled in column made of polyvinyl chloride (PVC) material to study phosphorus leaching fewer than twenty leaching events. The PVC columns of dimension 10.12 cm diameter and 60 cm length was coated with paraffin wax inside to seal between soil and column wall before filling the soil. The bottom of the column was packed with glasswool and acid washed gravel and 2 cm layer of acid washed sand was spread uniformly so as to get clear leachate. Then columns were first filled with P untreated soil from respective soil types and were slowly packed into the column to a depth of 20 cm. Then a thin layer of acid washed sand was spread on which P treated soil were filled slowly and pressed to its bulk density to a height of 30 cm, respectively for all the six treatments. A portion of P treated soil approximately weighing equivalent to 1.3–1.45 kg was filled to a depth of 30 cm and column was tapped uniformly on laboratory table resulting in average bulk density values of 1.32, 1.47 and 1.41 g cm3 for black, alluvial sand red soil, respectively similar to their field bulk densities (Table 1). After packing, 10 mm thickness of fine sand was spread on soil to avoid disturbance while applying deionised water. Each treatment was replicated three times in all the soil types. A total of 54 columns comprising of six treatments with three replications in three types of soil was stacked on wooden platform. After the soil was packed, the column was wetted from the bottom by allowing the water to rise by capillary action, until it was fully saturated. Uniform column leaching was done by applying 500 ml of double distilled water at interval of 5 days and thus 20 leaching events were carried out. After leaching study, the soil columns were allowed to dry at room temperature and were slowly loosen so as to cause minimum disturbance to the soil column. The soil from column was taken out carefully and sliced into different sections 0–10 cm (10 cm), 10–20 cm (20 cm), 20– 30 cm (30 cm) from treated column section and 30–40 cm (40 cm), 40–50 cm (50 cm) from untreated section. Leachate samples from each leaching events were collected and filtered through a Whatman 42 filter prior and analyzed for soluble reactive P (RP) and total P (TP) by blue color method (Murphy and Riley, 1962) and persulfate digestion method (Pote and Daniel, 2000). The soil samples taken from column sections were oven dried and sieved (2 mm) and analyzed for Olsen (Olsen et al., 1954), Bray P (Bray and Kurtz, 1945) and water extractable P (WEP) and 0.01 M CaCl2 P as described by Borling et al. (2004).
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
I. Rashmi et al. / Journal of the Saudi Society of Agricultural Sciences xxx (xxxx) xxx
The amount of P in leachate was calculated by multiplying volume of leachate and P content in leachate. The leachate data was analyzed for analysis of variance using SAS, 9.3 (2013) at 5% level of significance.
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treatments in all the soil types. The mean TP content in leachate of across various P treatments for black, alluvial and red soil ranged from 0.02 to 0.26, 0.04 to 0.5 and 0.03 to 0.46 mg l1 respectively. Higher TP content in leachate was observed in alluvial and red soil followed by black soils.
3. Result 3.2. Soil test P extractants and P leaching dynamics 3.1. Phosphorus leaching pattern in soil Soluble RP content of black, alluvial and red soils varied significantly with (p = 0.05) different P treatments. In black, red and alluvial soils, no P leaching was observed in the P1 treatment, with further increase in P levels, P leaching was observed in other treatments. Soluble RP content was greatest during initial leaching events and thereafter gradually decreased almost after 10th leaching events (Figs. 1 and 2). Soluble RP content varied significantly (p < 0.05) during first 9 leaching events; in case of after 2nd leaching events, greater concentration of RP was observed in P6 treatment and among soil followed the order alluvial soil (0.19– 0.41 mg ml1), red soil (0.08–0.36 mg l1) and black soil (0.1– 0.25 mg l1) as shown in Fig. 1. Similar, trend in TP content of leachate was observed in alluvial soil (0.33–0.81 mg l1), red soil (0.26–0.77 mg l1) and black soil (0.21–0.77 mg l1). Significant amount of soluble RP was lost in P4, P5 and P6 treatments in black soils. The amount of soluble RP on average varied from 0 to 0.10 mg l1 across the treatment and leaching events. The mean soluble RP increased significantly (p < 0.05) from 2nd to 8th leaching events ranging from 0.017 to 0.12 mg l1 across treatments. The soluble RP in leachate of black soil constituted 38% of total P in P6 treatment. In alluvial soil, the average soluble RP varied from 0.01 to 0.23 mg l1 in P1 to P6 treatment from 20 leaching events. Significant amount of soluble RP was leached in P5 and P6 treatment during 1st batch of leaching events as compared to black and red soils. A sharp increase in soluble RP in leachate was observed from 2nd batch of leaching to 8th batch of leaching ranging from 0.24 to 0.41 mg l1, although the amount of soluble RP leached after 5thbatch of leaching was significantly higher compared to other treatments (Fig. 1). The amount of soluble RP and TP content in P6 treatment were 0.41 mg l1 and 0.79 mg l1, respectively during 7th leaching event which was 2 times more than control treatment (P1). The soluble RP content in leachate constituted 46% of TP in P6 treatment. The mean soluble RP content in red soil ranging from 0.01 to 0.17 mg l1 when subjected to 20 leaching events as shown in Fig. 1. The soluble RP and TP content varied from 0.08 to 0.36 mg l1 and 0.26 to 0.77 mg l1 during the first 6 leaching events and sharply decreased in later events. Inorganic soluble RP constituted 36% of total P in P6 treatment. The amount of soluble RP leached decreased sharply after 14th leaching events in all the treatments. The result of the study also indicated that there is significant amount of soluble RP leached from alluvial, red and vertisol at P5 and P6 treatments. Soluble RP content in leachate observed for longer time in alluvial soil (0.02 mg l1) throughout leaching events compared to red and black soils. There was a significant and sharp increase in soluble RP content of leachate was observed during the initial 10 leaching events which was decreased to negligible amount in later stages of leaching events during the experiment. Mean soluble RP content initial 10 leaching events for black, alluvial and soils were 0.073, 0.12 and 0.094 mg l1 and reduced during the later stages of leaching events as 0.010, 0.032 and 0.024 mg l1 respectively. The results clearly illustrated greater and significant amount of inorganic RP content was leached from alluvial soil followed by red and black soils. Similarly, total P (TP) content varied among treatments significantly (p < 0.05) among P
The soil available P contents of the soils and the other chemical properties of soil is detailed in Table 1. Among the various soil types, Olsen P varied depth wise in columns of black and alluvial soil and significantly increased with P additions. The Olsen P content in the upper soil layers (0–30 cm) of column study showed significant P distribution in alluvial soil (96–145.04 mg kg1) compared to black soil (74.3–111 mg kg1) in P6 treatment. It was also revealed that the higher Olsen P distribution content was observed in three sections of P treated soils (0–10, 10–20 cm and 20–30 cm) of black and alluvial soils. The significant P movement observed in all the treatments and highest P movement and accumulation was observed in P2 to P6 treatments. The Olsen P content in the soil remained similar in treated and untreated soil column layer as depicted in Fig. 2. On comparing both the soil types it was observed that alluvial soil lead to higher P accumulation in both layers of column section compared to black soils. The Fig. 2(a) and (b) clearly illustrates that in P1 to P4 treatment there was no significant difference between Olsen P content, however much difference was observed in P5 and P6 treatments of black soil. In alluvial soil significant difference in Olsen P was observed in P4 to P6 treatments. In red soils, Bray extractant was used for determining available P content after column leaching experiment. At the lower P treatments i.e. P1 and P2 treatment does not show any significant difference in upper soil layers. The Bray P content varied with P levels and increased with increasing P doses as depicted in Fig. 2 (c). In the highest P levels (P5 and P6 treatment) the Bray content varied from 46.45 to 100.36 mg kg1 and 73.05 to 121.45 mg kg1 respectively. Significant P movement from treated to untreated column section was observed in P4 to P6 treatments. Environmental STP like WEP and 0.01 M CaCl2-P was determined column depth wise for all soil types. The values for WEP and CaCl2 P content in black, red and alluvial soil types were comparatively less than routine STP like Olsen and Bray extractant. Effect of various P treatments on WEP and CaCl2 P content is shown in Figs. 3 and 4 for all soil types. The WEP and CaCl2P extractable P content for P1 treatment in all soil types were negligible. Highest P accumulation was recorded at 10–20 cm depth which increased with increasing soil depth (20–40 cm) in P6 and P5 treatments of the treated column section layers. In black soils, WEP content did not significantly vary among column depth in all treatments except for P6 treatment. Similar trends were observed in red and alluvial soil where only difference was observed in P5 and P6 treatments. In CaCl2-P content there was not significant for most of the treatments except for P6. In alluvial soil, potential release of P into soil solution (CaCl2-P and WEP) was higher from 0 to 30 cm depth resulting in higher amount of leachate P. It was also observed that higher accumulation of P forms in alluvial soil indicate higher potential of these soil to release P into water. Higher P accumulation was observed at the depth of 10–20 cm which increased with increasing depth at 20– 30 cm depth (Figs. 3 and 4). In red soils no significant difference was observed in P2 and P3 treatment depth wise, but significant difference was from P4 to P6 treatments. Both WEP and CaCl2-P content increased with higher P additions and accumulated more at 30 cm depth and thereafter it decreased sharply in P untreated soil column section (Figs. 3 and 4).
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 1. Dynamics of soluble RP and total P content in (a & d) black soil (b & e) alluvial soil (c & f) red soil with different P rates. Vertical bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
On comparing the three soil types, it was observed that the soluble P in leachate was not significantly differed at low level of P treatments. However, a positive effect of soluble P leachate was observed at higher P level treatments. It was observed that alluvial soils resulted in higher P movement and accumulation various column section layers and present the scope of P leaching from soil. 4. Discussion The concentration of soluble RP during initial leaching events (1–10) were higher than subsequent leaching events in all soil
types. The greatest RP content was lost from alluvial (20–46%), followed by that of red (18–37%) and black soil (16–38%) across various P treatments. Soil texture and applied P rates are the major factors which influenced loss and accumulation of P under different batches of leaching events. The alluvial soils were sandy loam in texture and therefore contributed for higher P leaching. Similar reports of higher P leaching from coarse texture soil have been reported by many authors (Zhao et al., 2009; Kim et al., 2011; Rashmi et al., 2017). Easy water movement through coarse textured soil provide less time for P sorption resulting in high amount of P leaching (Zhang, 2008). On contrary black and red soil have
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 2. Vertical distribution of Olsen P in (a) black soil (b) alluvial soil and by Bray P in (c) red soil treated with different P rates. Horizontal bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
clayey and clay loam texture resulting in lower P leaching rates compared to those of alluvial soil. Effect of high clay content on low P leaching from the soils was also reported by Djodjic et al. (2004). High P sorption of black soil due to higher clay content resulted in slower P movement as shown in Table 1. It was observed that during the initial three leaching events soluble RP content was <0.01 mg l1, but subsequently from fourth to tenth leaching there was significant increase in RP content. Phos-
phorus content in leachate increased with increasing P levels but decreased with increasing leaching events reaching a stable level almost after 11th leaching event (Fig. 1). Similar results were also obtained by who reported higher inorganic P leaching was observed during the initial days of leaching and decreased with time. During the early phase of leaching events RP content increased was associated with travel time of dissolved P in soil solution and desorption of P as extractable form during leaching.
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 3. Vertical distribution of WEP in (a) black soil (b) alluvial soil and by Bray P in (c) red soil treated with different P rates. Horizontal bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
In present study soluble RP content in all soil types showed a skewed distribution during leaching under different rate of P application. According to Li et al. (2013) the loss of P during initial leaching was gradual and logarithmic in nature. This logarithmic decreased in soluble RP content in the leachate with increasing number of leaching events might be due to complete soil surface saturation with the applied P and the excess P could rapidly be release to soil solution.
Higher STP values of range in treated column section (0–30 cm) was observed in alluvial (82–122.5 mg kg1), followed by red (61.7–100.4 mg kg1) and black soils (52.5–94.8 mg kg1) shown in Fig. 2(a)–(c). In all soil types significant P accumulation was observed beneath 20 cm of column section in P5 and P6 treatment, but at lower depth the Olsen P decreased (Fig. 2). Both Olsen and Bray method estimated P accumulation and distribution in column sections indication the potential of higher P release from alluvial
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 4. Vertical distribution of 0.01 M CaCl2 in (a) black soil (b) alluvial soil and by Bray P in (c) red soil treated with different P rates. Horizontal bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
soil which is supported by higher RP in leaching events of alluvial soil than those of red and black soils. Besides using regular STP, environmental STP like 0.01 M CaCl2-P and WEP provides insight for P movement and threat of soil to enrich water bodies with P via runoff or leaching (Borling et al., 2004). In the present study alluvial soil reported higher values for environmental STP like 0.01 M CaCl2-P and WEP content due to higher P accumulation resulting in higher P leaching compared to other soils. Both red and black soil observed no significant differences in environmental STP values upto P3 treatments, however higher and significant val-
ues (p < 0.05) values were obtained for alluvial soil from P2 treatment. On comparing both P forms, it was observed that CaCl2-P values were lower than that of WEP values in all the soil types. In black and red soil significant difference in the environmental soil test was observed with P5 and P6 treatment in both treated and untreated soil column layers. Alluvial soils showed higher environmental P values in almost all the treatments except for P1 treatment. Use of CaCl2-P is easy available option for soil testing laboratories as it work similar to that of soil solution at field capacity (Wiklander and Andersson, 1974) and can simulate the release
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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of P to soil solution. Similarly P estimation by distilled water (WEP) represents the rapidly soluble P form that can be transported though the soil profile following heavy rainfall or preferential flow (Yli-Halla et al., 1995; Jensen et al., 1998). In the present experiment the role of soil texture and P loading rates determined the significance of P movement. Soil properties like P sorption capacity, clay content, Al and Fe oxides and Ca content influence P sorption desorption mechanism and governs P retention and release form soils. In black soil the Olsen P content was less compared to alluvial because of higher clay content which influenced P sorption capacity and sorbed more P (Table 1). In red soils, the oxalate extractable Al and Fe content played an important role in P sorption in untreated column section (Table 1). Sometimes percentage of P loss does not dependent upon the rate of P application but on P retention capacity of soil (Lewis et al., 1981; Kim et al., 2011). The present study also illustrated that high P sorption capacity of black soil lower P leaching compared to those of red and alluvial soil. Phosphorus loss from intact column study cannot predict extent of P loss for long term from continuously fertilized soils. However, routine STP like Osen and Bray can be used to monitor the buildup of P in alluvial and red soils with low P sorption capacity. Utilization of easy environmental STP like WEP and 0.01 M CaCl2-P can also be included in soil testing programmes at field levels in areas with high soil P values especially in alluvial and red soils of India. Soil texture can be considered as one of the major factor that effect low retention and leaching of soluble P as explained by Glasner et al. (2011). Movement and distribution of P in various column treated and untreated section resulted in higher P levels where the rate of water flow surpassed the P sorption capacity resulting in more soluble RP content in leachate. 5. Conclusion Soil column leaching experiment revealed that alluvial soil leached more soluble RP compared to red and black soil. Significant amount of soluble RP in leachate was observed with application P5 (300 mg kg1) and P6 (600 mg kg1) treatment in alluvial, red and black soils. During leaching experiment period, soluble RP and TP content in leachate was higher during initial ten leaching events and thereafter it started to decrease releasing less amount of P. Soluble RP leached from alluvial soil accounted for 20–46%, followed by that of red and black soil which was 18–37% and 16–38%, respectively. Among the three soil types, alluvial soil have a greater potential of P leaching loss under chemical P fertilization. The study also suggests that beside the routine STP, environmental STP like WEP and 0.01 M CaCl2-P can be used for P testing in soils with high STP. The outcome of present soil column study needs further verification on more number of soils with varying physico - chemical properties so that it can used to predict the leaching threshold values for different soil orders of India. Such studies will establish threshold P levels for soil and water in combination with site vulnerability of soil P loss and identify appropriate best management practices (BMPs) for mitigating P loss from soils. Conflict of interest Authors declare no conflict of interest. Acknowledgement Authors would like to thank ICAR and Director ICAR-IISS Bhopal for providing all the technical and financial support for the project work.
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Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India I. Rashmi a,⇑,1, A.K. Biswas b,2, K.S. Kartika c,3, S. Kala a,4 a
ICAR-IISWC, RC, Kota, India ICAR-IISS, Bhopal, India c ICAR-NBSSLUP, RC, Bangalore, India b
a r t i c l e
i n f o
Article history: Received 1 August 2018 Revised 2 November 2018 Accepted 14 November 2018 Available online xxxx Keywords: Reactive P Total P Soil types Phosphorus sorption Phosphorus leaching
a b s t r a c t Phosphorus leaching from soils is a major environmental concern leading to eutrophication of water bodies. Three different soil types namely black, red and alluvial soils from Nagpur, Raipur and Kanpur were taken for the study. Soil column leaching experiment was conducted during 2014–15 with different levels of P (0, 50, 100, 150, 300, 600 mg L1) application with the objective to evaluate P buildup and vertical distribution in different soil types. Soluble reactive P (RP) content in three soils increased slowly with P application rates and decreased with increase in number of leaching events. Total P in leachate followed the similar trend. Phosphorus leaching mainly occurred during the initial seven leaching events accounting to 50–60% of total P leached over whole period. Among the various soil types RP content in leachate followed the order alluvial (0.01–0.23 mg l1) followed by red (0.01–0.17 mg l1), and black (0–0.1 mg l1) soil. Soluble reactive P (RP) accounting for 75–80% leaching mainly during initial 10 leaching events with alluvial soil leached highest P followed by red and black soils. Vertical distribution and movement of Olsen and bray P content in all the soils were higher beneath 0–10 cm depth and increased with P application and decreased in untreated column section. Environmental test like water extractable P (WEP) and CaCl2 P content were higher in alluvial soil, suggesting the greater potential of P leaching loss under chemical P fertilization. The result of the study can further be extended at field level for efficient P management in various soil types and thus could quantify the contribution of P from different sources to P leaching in agricultural land. Ó 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
1. Introduction Phosphorus is the crucial constituent of genetic materials and other cell organelles. It is directly involved in DNA, RNA, ATP and photosynthetic system and catalyses a number of biochemical ⇑ Corresponding author at: ICAR-IISWC, RC, Kota, Rajasthan, India. E-mail address: [email protected] (I. Rashmi). Scientist, Soil Chemistry and Fertility, ICAR-Indian Institute of Soil and Water Conservation, Research Centre, Kota. 2 HOD, Principal scientist, Soil chemistry, ICAR-Indian Institute of Soil Science, Bhopal. 3 Scientist Soil Chemistry and Fertility, ICAR-NBSSLUP, Regional Centre, Bangalore. 4 Scientist, Forestry, ICAR-Indian Institute of Soil and Water Conservation, Research Centre, Kota. 1
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reactions from the beginning of seedling growth through to the formation of grain and maturity (Scholz et al., 2015; Balemi and Negisho, 2012). Soil P deficiency on one hand is a major constrain for crop production and on the other hand high P buildup in soil and its loss to water bodies often result in eutrophication. Eutrophication causes algal bloom in aquatic system affecting biological life and its quality. Based on (geographic information system) GIS soil fertility map of India, Muralidharudu et al. (2011) reported high fertilizer consumption in states of Punjab followed by Andhra Pradesh and Tamil Nadu. Application of high analysis and complex P fertilizers in excess of crop requirement can increase the P content in agricultural soil. Such instances were found in south India (Kerala state) where out of 1.5 lakh soil samples collected, 62% of samples showed high P content between 25 and 100 kg ha1 which corresponds to high soil P content (Dinesh et al., 2014). In India, high prices of P fertilizers are the major challenge but continuous supply of P through manures and fertilizers is indispensable for crop production sustenance. Multi locational fertility studies also show
https://doi.org/10.1016/j.jssas.2018.11.002 1658-077X/Ó 2018 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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the influence of high accumulation and downward movement of P in soils. Aulakh et al. (2007) reported high P accumulation also results downward movement P to deeper layers in coarsetextured irrigated sandy loam soils of Punjab state pointing to the potential for extensive leaching under long-term P fertilizer applications. More information is thus to be elicited from subtropical soils of India where P fertilizers are fully imported and applied in excess of crop requirement. Several studies on P losses from soil are mostly concentrated to surface water runoff (Pote et al., 1996; Torbert et al., 2002). However, authors like Heckrath et al. (1995), Beaucheminet al. (1998), Li et al. (2013) highlighted the importance of P leaching as a main contributor to surface water eutrophication, mainly through field drainage, in many countries worldwide. Various studies illustrate increased P concentration in subsoil horizons attributed to the buildup of P as evidence of past P leaching and translocation of P from applied sources mostly organics (Eghball et al., 1996; Withers et al., 2005; Kim et al., 2011). Studies with inorganic P forms like those reported by Zhao et al. (2009) showed P leaching in light chernozem soil under different P fertiliser rates in soil column study where high clay content influenced vertical P distribution. In India, major input is soluble P fertilizers and P movement under inorganics has not been extensively studied. Djodjic et al. (2004) suggested both soil and sub soil properties along with P application rates affect P leaching in soil column experiment. In recent times, Garg and Aulakh (2010) experiment revealed P movement beyond 30 cm depth in coarse textured soils of Punjab followed by reports indicating deteriorating drinking water quality in Tamil Nadu (Rajmohan and Elango, 2005) point out a need to understand vertical movement of P and the soil potential for P loss. Current information of P movement is minimal for Indian subtropics. Therefore a soil column experiment was undertaken was undertaken for major cultivable soil types of India namely black (vertisol), alluvial (inceptisol) and red (alfisol) with the objective of the study was to investigate the different form of P in leachate, examine downward movement of soil P and comparing the P leaching characteristics of the soils. 2. Materials and method 2.1. Soils Three soil types as per USDA soil classification system were black soil (Typic Chromousterts, Linga series, Clayey, Montmorillonitic, Hyperthermic) belonging to vertisol from Nagpur (21°80 N 79°50 E); alluvial soil (Typic Ustochrepts, Loamy, Hyperthermic) belonging to inceptisol from Kanpur (26°270 N, 80°140 E); and red soil (Typic Haplustalfs, Jhunvani series, Mixed, Hyperthermic) belonging to alfisol from Raipur (21°420 N 81°700 E) taken for the experiment. The soil samples were collected from 0 to 20 cm depth in all three soil types and processed passed through 2 mm sieve. The initial physico chemical properties of the soils were determined prior to soil column leaching experiment and shown in Table1. The P sorption was conducted in three soils using Langmuir equation to derive P sorption maxima (Psmax) of soils. 2.2. Soil column leaching experiment Soil column leaching experiment was conducted in all the three soil types by adding different P fertilizer rates at 0 (P1), 50 (P2), 100 (P3), 150 (P4), 300 (P5) and 600 (P6) mg kg1 (on oven dry basis) respectively. The inorganic source of P fertilizer as KH2PO4 was dissolved in distilled water and sprayed on to the soils and mixed in three replications. Prior to leaching experiment soils were incubated for six weeks by maintaining at field capacity by adding
Table 1 Initial physico chemical properties of the experimental soils. Soil parameters
Black soil
Alluvial soil
Red soil
pH Electrical conductivity (dS m1) Bulk density (g cm3) Organic carbon (g kg1) Clay (%) Sand (%) Silt (%) Amorphous Al (g kg1) Amorphous Fe (g kg1) P smax (mg kg1) Extractable P (mg kg1)
7.7 0.29 1.37 5.2 59.1 7.4 37.5 1.26 1.43 597.4 6.43
7.8 0.45 1.47 3.7 19.3 58.2 22.5 0.41 0.87 236.37 9.74
6.5 0.27 1.41 4.1 22.4 55.7 22.9 1.34 2.1 375.8 7.6
distill water and 40% moisture content in all the soil samples. Later, soils were subjected to alternate wetting and drying depending upon the moisture content to be maintained to get a representative/homogenized soil sample. The P incubated soil samples were kept in plastic bags at room temperature of 25–30 °C. After incubation, the soil samples were used for soil column experiment and are henceforth referred as P treated soil. A portion of the untreated soil was filled at the bottom of column section. One pore volume of the black, alluvial and red soil was 1204, 1027 and 1041 ml, respectively based upon porosity. The incubated soil was filled in column made of polyvinyl chloride (PVC) material to study phosphorus leaching fewer than twenty leaching events. The PVC columns of dimension 10.12 cm diameter and 60 cm length was coated with paraffin wax inside to seal between soil and column wall before filling the soil. The bottom of the column was packed with glasswool and acid washed gravel and 2 cm layer of acid washed sand was spread uniformly so as to get clear leachate. Then columns were first filled with P untreated soil from respective soil types and were slowly packed into the column to a depth of 20 cm. Then a thin layer of acid washed sand was spread on which P treated soil were filled slowly and pressed to its bulk density to a height of 30 cm, respectively for all the six treatments. A portion of P treated soil approximately weighing equivalent to 1.3–1.45 kg was filled to a depth of 30 cm and column was tapped uniformly on laboratory table resulting in average bulk density values of 1.32, 1.47 and 1.41 g cm3 for black, alluvial sand red soil, respectively similar to their field bulk densities (Table 1). After packing, 10 mm thickness of fine sand was spread on soil to avoid disturbance while applying deionised water. Each treatment was replicated three times in all the soil types. A total of 54 columns comprising of six treatments with three replications in three types of soil was stacked on wooden platform. After the soil was packed, the column was wetted from the bottom by allowing the water to rise by capillary action, until it was fully saturated. Uniform column leaching was done by applying 500 ml of double distilled water at interval of 5 days and thus 20 leaching events were carried out. After leaching study, the soil columns were allowed to dry at room temperature and were slowly loosen so as to cause minimum disturbance to the soil column. The soil from column was taken out carefully and sliced into different sections 0–10 cm (10 cm), 10–20 cm (20 cm), 20– 30 cm (30 cm) from treated column section and 30–40 cm (40 cm), 40–50 cm (50 cm) from untreated section. Leachate samples from each leaching events were collected and filtered through a Whatman 42 filter prior and analyzed for soluble reactive P (RP) and total P (TP) by blue color method (Murphy and Riley, 1962) and persulfate digestion method (Pote and Daniel, 2000). The soil samples taken from column sections were oven dried and sieved (2 mm) and analyzed for Olsen (Olsen et al., 1954), Bray P (Bray and Kurtz, 1945) and water extractable P (WEP) and 0.01 M CaCl2 P as described by Borling et al. (2004).
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
I. Rashmi et al. / Journal of the Saudi Society of Agricultural Sciences xxx (xxxx) xxx
The amount of P in leachate was calculated by multiplying volume of leachate and P content in leachate. The leachate data was analyzed for analysis of variance using SAS, 9.3 (2013) at 5% level of significance.
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treatments in all the soil types. The mean TP content in leachate of across various P treatments for black, alluvial and red soil ranged from 0.02 to 0.26, 0.04 to 0.5 and 0.03 to 0.46 mg l1 respectively. Higher TP content in leachate was observed in alluvial and red soil followed by black soils.
3. Result 3.2. Soil test P extractants and P leaching dynamics 3.1. Phosphorus leaching pattern in soil Soluble RP content of black, alluvial and red soils varied significantly with (p = 0.05) different P treatments. In black, red and alluvial soils, no P leaching was observed in the P1 treatment, with further increase in P levels, P leaching was observed in other treatments. Soluble RP content was greatest during initial leaching events and thereafter gradually decreased almost after 10th leaching events (Figs. 1 and 2). Soluble RP content varied significantly (p < 0.05) during first 9 leaching events; in case of after 2nd leaching events, greater concentration of RP was observed in P6 treatment and among soil followed the order alluvial soil (0.19– 0.41 mg ml1), red soil (0.08–0.36 mg l1) and black soil (0.1– 0.25 mg l1) as shown in Fig. 1. Similar, trend in TP content of leachate was observed in alluvial soil (0.33–0.81 mg l1), red soil (0.26–0.77 mg l1) and black soil (0.21–0.77 mg l1). Significant amount of soluble RP was lost in P4, P5 and P6 treatments in black soils. The amount of soluble RP on average varied from 0 to 0.10 mg l1 across the treatment and leaching events. The mean soluble RP increased significantly (p < 0.05) from 2nd to 8th leaching events ranging from 0.017 to 0.12 mg l1 across treatments. The soluble RP in leachate of black soil constituted 38% of total P in P6 treatment. In alluvial soil, the average soluble RP varied from 0.01 to 0.23 mg l1 in P1 to P6 treatment from 20 leaching events. Significant amount of soluble RP was leached in P5 and P6 treatment during 1st batch of leaching events as compared to black and red soils. A sharp increase in soluble RP in leachate was observed from 2nd batch of leaching to 8th batch of leaching ranging from 0.24 to 0.41 mg l1, although the amount of soluble RP leached after 5thbatch of leaching was significantly higher compared to other treatments (Fig. 1). The amount of soluble RP and TP content in P6 treatment were 0.41 mg l1 and 0.79 mg l1, respectively during 7th leaching event which was 2 times more than control treatment (P1). The soluble RP content in leachate constituted 46% of TP in P6 treatment. The mean soluble RP content in red soil ranging from 0.01 to 0.17 mg l1 when subjected to 20 leaching events as shown in Fig. 1. The soluble RP and TP content varied from 0.08 to 0.36 mg l1 and 0.26 to 0.77 mg l1 during the first 6 leaching events and sharply decreased in later events. Inorganic soluble RP constituted 36% of total P in P6 treatment. The amount of soluble RP leached decreased sharply after 14th leaching events in all the treatments. The result of the study also indicated that there is significant amount of soluble RP leached from alluvial, red and vertisol at P5 and P6 treatments. Soluble RP content in leachate observed for longer time in alluvial soil (0.02 mg l1) throughout leaching events compared to red and black soils. There was a significant and sharp increase in soluble RP content of leachate was observed during the initial 10 leaching events which was decreased to negligible amount in later stages of leaching events during the experiment. Mean soluble RP content initial 10 leaching events for black, alluvial and soils were 0.073, 0.12 and 0.094 mg l1 and reduced during the later stages of leaching events as 0.010, 0.032 and 0.024 mg l1 respectively. The results clearly illustrated greater and significant amount of inorganic RP content was leached from alluvial soil followed by red and black soils. Similarly, total P (TP) content varied among treatments significantly (p < 0.05) among P
The soil available P contents of the soils and the other chemical properties of soil is detailed in Table 1. Among the various soil types, Olsen P varied depth wise in columns of black and alluvial soil and significantly increased with P additions. The Olsen P content in the upper soil layers (0–30 cm) of column study showed significant P distribution in alluvial soil (96–145.04 mg kg1) compared to black soil (74.3–111 mg kg1) in P6 treatment. It was also revealed that the higher Olsen P distribution content was observed in three sections of P treated soils (0–10, 10–20 cm and 20–30 cm) of black and alluvial soils. The significant P movement observed in all the treatments and highest P movement and accumulation was observed in P2 to P6 treatments. The Olsen P content in the soil remained similar in treated and untreated soil column layer as depicted in Fig. 2. On comparing both the soil types it was observed that alluvial soil lead to higher P accumulation in both layers of column section compared to black soils. The Fig. 2(a) and (b) clearly illustrates that in P1 to P4 treatment there was no significant difference between Olsen P content, however much difference was observed in P5 and P6 treatments of black soil. In alluvial soil significant difference in Olsen P was observed in P4 to P6 treatments. In red soils, Bray extractant was used for determining available P content after column leaching experiment. At the lower P treatments i.e. P1 and P2 treatment does not show any significant difference in upper soil layers. The Bray P content varied with P levels and increased with increasing P doses as depicted in Fig. 2 (c). In the highest P levels (P5 and P6 treatment) the Bray content varied from 46.45 to 100.36 mg kg1 and 73.05 to 121.45 mg kg1 respectively. Significant P movement from treated to untreated column section was observed in P4 to P6 treatments. Environmental STP like WEP and 0.01 M CaCl2-P was determined column depth wise for all soil types. The values for WEP and CaCl2 P content in black, red and alluvial soil types were comparatively less than routine STP like Olsen and Bray extractant. Effect of various P treatments on WEP and CaCl2 P content is shown in Figs. 3 and 4 for all soil types. The WEP and CaCl2P extractable P content for P1 treatment in all soil types were negligible. Highest P accumulation was recorded at 10–20 cm depth which increased with increasing soil depth (20–40 cm) in P6 and P5 treatments of the treated column section layers. In black soils, WEP content did not significantly vary among column depth in all treatments except for P6 treatment. Similar trends were observed in red and alluvial soil where only difference was observed in P5 and P6 treatments. In CaCl2-P content there was not significant for most of the treatments except for P6. In alluvial soil, potential release of P into soil solution (CaCl2-P and WEP) was higher from 0 to 30 cm depth resulting in higher amount of leachate P. It was also observed that higher accumulation of P forms in alluvial soil indicate higher potential of these soil to release P into water. Higher P accumulation was observed at the depth of 10–20 cm which increased with increasing depth at 20– 30 cm depth (Figs. 3 and 4). In red soils no significant difference was observed in P2 and P3 treatment depth wise, but significant difference was from P4 to P6 treatments. Both WEP and CaCl2-P content increased with higher P additions and accumulated more at 30 cm depth and thereafter it decreased sharply in P untreated soil column section (Figs. 3 and 4).
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 1. Dynamics of soluble RP and total P content in (a & d) black soil (b & e) alluvial soil (c & f) red soil with different P rates. Vertical bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
On comparing the three soil types, it was observed that the soluble P in leachate was not significantly differed at low level of P treatments. However, a positive effect of soluble P leachate was observed at higher P level treatments. It was observed that alluvial soils resulted in higher P movement and accumulation various column section layers and present the scope of P leaching from soil. 4. Discussion The concentration of soluble RP during initial leaching events (1–10) were higher than subsequent leaching events in all soil
types. The greatest RP content was lost from alluvial (20–46%), followed by that of red (18–37%) and black soil (16–38%) across various P treatments. Soil texture and applied P rates are the major factors which influenced loss and accumulation of P under different batches of leaching events. The alluvial soils were sandy loam in texture and therefore contributed for higher P leaching. Similar reports of higher P leaching from coarse texture soil have been reported by many authors (Zhao et al., 2009; Kim et al., 2011; Rashmi et al., 2017). Easy water movement through coarse textured soil provide less time for P sorption resulting in high amount of P leaching (Zhang, 2008). On contrary black and red soil have
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 2. Vertical distribution of Olsen P in (a) black soil (b) alluvial soil and by Bray P in (c) red soil treated with different P rates. Horizontal bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
clayey and clay loam texture resulting in lower P leaching rates compared to those of alluvial soil. Effect of high clay content on low P leaching from the soils was also reported by Djodjic et al. (2004). High P sorption of black soil due to higher clay content resulted in slower P movement as shown in Table 1. It was observed that during the initial three leaching events soluble RP content was <0.01 mg l1, but subsequently from fourth to tenth leaching there was significant increase in RP content. Phos-
phorus content in leachate increased with increasing P levels but decreased with increasing leaching events reaching a stable level almost after 11th leaching event (Fig. 1). Similar results were also obtained by who reported higher inorganic P leaching was observed during the initial days of leaching and decreased with time. During the early phase of leaching events RP content increased was associated with travel time of dissolved P in soil solution and desorption of P as extractable form during leaching.
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 3. Vertical distribution of WEP in (a) black soil (b) alluvial soil and by Bray P in (c) red soil treated with different P rates. Horizontal bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
In present study soluble RP content in all soil types showed a skewed distribution during leaching under different rate of P application. According to Li et al. (2013) the loss of P during initial leaching was gradual and logarithmic in nature. This logarithmic decreased in soluble RP content in the leachate with increasing number of leaching events might be due to complete soil surface saturation with the applied P and the excess P could rapidly be release to soil solution.
Higher STP values of range in treated column section (0–30 cm) was observed in alluvial (82–122.5 mg kg1), followed by red (61.7–100.4 mg kg1) and black soils (52.5–94.8 mg kg1) shown in Fig. 2(a)–(c). In all soil types significant P accumulation was observed beneath 20 cm of column section in P5 and P6 treatment, but at lower depth the Olsen P decreased (Fig. 2). Both Olsen and Bray method estimated P accumulation and distribution in column sections indication the potential of higher P release from alluvial
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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Fig. 4. Vertical distribution of 0.01 M CaCl2 in (a) black soil (b) alluvial soil and by Bray P in (c) red soil treated with different P rates. Horizontal bars are the standard errors of the mean. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)
soil which is supported by higher RP in leaching events of alluvial soil than those of red and black soils. Besides using regular STP, environmental STP like 0.01 M CaCl2-P and WEP provides insight for P movement and threat of soil to enrich water bodies with P via runoff or leaching (Borling et al., 2004). In the present study alluvial soil reported higher values for environmental STP like 0.01 M CaCl2-P and WEP content due to higher P accumulation resulting in higher P leaching compared to other soils. Both red and black soil observed no significant differences in environmental STP values upto P3 treatments, however higher and significant val-
ues (p < 0.05) values were obtained for alluvial soil from P2 treatment. On comparing both P forms, it was observed that CaCl2-P values were lower than that of WEP values in all the soil types. In black and red soil significant difference in the environmental soil test was observed with P5 and P6 treatment in both treated and untreated soil column layers. Alluvial soils showed higher environmental P values in almost all the treatments except for P1 treatment. Use of CaCl2-P is easy available option for soil testing laboratories as it work similar to that of soil solution at field capacity (Wiklander and Andersson, 1974) and can simulate the release
Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002
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of P to soil solution. Similarly P estimation by distilled water (WEP) represents the rapidly soluble P form that can be transported though the soil profile following heavy rainfall or preferential flow (Yli-Halla et al., 1995; Jensen et al., 1998). In the present experiment the role of soil texture and P loading rates determined the significance of P movement. Soil properties like P sorption capacity, clay content, Al and Fe oxides and Ca content influence P sorption desorption mechanism and governs P retention and release form soils. In black soil the Olsen P content was less compared to alluvial because of higher clay content which influenced P sorption capacity and sorbed more P (Table 1). In red soils, the oxalate extractable Al and Fe content played an important role in P sorption in untreated column section (Table 1). Sometimes percentage of P loss does not dependent upon the rate of P application but on P retention capacity of soil (Lewis et al., 1981; Kim et al., 2011). The present study also illustrated that high P sorption capacity of black soil lower P leaching compared to those of red and alluvial soil. Phosphorus loss from intact column study cannot predict extent of P loss for long term from continuously fertilized soils. However, routine STP like Osen and Bray can be used to monitor the buildup of P in alluvial and red soils with low P sorption capacity. Utilization of easy environmental STP like WEP and 0.01 M CaCl2-P can also be included in soil testing programmes at field levels in areas with high soil P values especially in alluvial and red soils of India. Soil texture can be considered as one of the major factor that effect low retention and leaching of soluble P as explained by Glasner et al. (2011). Movement and distribution of P in various column treated and untreated section resulted in higher P levels where the rate of water flow surpassed the P sorption capacity resulting in more soluble RP content in leachate. 5. Conclusion Soil column leaching experiment revealed that alluvial soil leached more soluble RP compared to red and black soil. Significant amount of soluble RP in leachate was observed with application P5 (300 mg kg1) and P6 (600 mg kg1) treatment in alluvial, red and black soils. During leaching experiment period, soluble RP and TP content in leachate was higher during initial ten leaching events and thereafter it started to decrease releasing less amount of P. Soluble RP leached from alluvial soil accounted for 20–46%, followed by that of red and black soil which was 18–37% and 16–38%, respectively. Among the three soil types, alluvial soil have a greater potential of P leaching loss under chemical P fertilization. The study also suggests that beside the routine STP, environmental STP like WEP and 0.01 M CaCl2-P can be used for P testing in soils with high STP. The outcome of present soil column study needs further verification on more number of soils with varying physico - chemical properties so that it can used to predict the leaching threshold values for different soil orders of India. Such studies will establish threshold P levels for soil and water in combination with site vulnerability of soil P loss and identify appropriate best management practices (BMPs) for mitigating P loss from soils. Conflict of interest Authors declare no conflict of interest. Acknowledgement Authors would like to thank ICAR and Director ICAR-IISS Bhopal for providing all the technical and financial support for the project work.
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Please cite this article as: I. Rashmi, A. K. Biswas, K. S. Kartika et al., Phosphorus leaching through column study to evaluate P movement and vertical distribution in black, red and alluvial soils of India, Journal of the Saudi Society of Agricultural Sciences, https://doi.org/10.1016/j.jssas.2018.11.002