Effects of Biochar and Biosolid on Adsorption of Nitrogen,Phosphorus, and Potassium in Two Soils

Increasing the retention of nutrients by agricultural soils is of great interest to minimize losses of nutrients by leaching and/or surface runoff. Soil amendments play a role in nutrient retention by increasing the surface area and/or other chemical processes. Biochar (BC) is high carbon-containing by-product of pyrolysis of carbon-rich feedstocks to produce bioenergy. Biosolid is a by-product of wastewater treatment plant. Use of these by-products as amendments to agricultural soils is beneficial to improve soil properties, soil quality, and nutrient retention and enhance carbon sequestration. In this study, the adsorption of NH₄-N, P, and K by a sandy soil (Quincy fine sand (QFS)) and a silty clay loam soil (Warden silty loam (WSL)) with BC (0, 22.4, and 44.8 mg ha^?1) and biosolid (0 and 22.4 mg ha^?1) amendments were investigated. Adsorption of NH₄-N by the QFS soil increased with BC application at lower NH₄-N concentrations in equilibrium solution. For the WSL soil, NH₄-N adsorption peaked at 22.4 mg ha^?1 BC rate. Biosolid application increased NH₄-N adsorption by the WSL soil while decreased that in the QFS soil. Adsorption of P was greater by the WSL soil as compared to that by the QFS soil. Biosolid amendment significantly increased P adsorption capacity in both soils, while BC amendment had no significant effects. BC and biosolid amendments decreased K adsorption capacity by the WSL soil but had no effects on that by the QFS soil. Ca release with increasing addition of K was greater by the WSL soil as compared to that by the QFS soil. In both the soils, Ca release was not influenced by BC amendment while it increased with addition of biosolid. The fit of adsorption data for NH₄-N, P, and K across all treatments and in two soils was better with the Freundlich model than that with the Langmuir model. The nutrients retained by BC or biosolid amended soils are easily released, therefore are readily available for the root uptake in cropped soils.     

Sodic Soil Reclamation Potential of Gypsum and Biocharadditions: Influence on Physicochemical Properties and Soil Respiration

Reclamation of sodic soils is proving increasingly vital as greater land area becomes salt-affected in the northern Great Plains of the United States. Flue gas desulfurization gypsum (FGDG) can be an agriculturally important resource for increasing land productivity through the amelioration of sodic soils. Biochar is also considered as an aid in reclaiming degraded soils. In this incubation study, two rates of FGDG (33.6 Mg ha^?1 and 66.2 Mg ha^?1), two rates of biochar made from sugar beet (Beta vulgaris L.) pulp (16.8 Mg ha^?1), and one rate of FGDG combined with one rate of biochar (33.6 Mg ha^?1 ea.) were applied to a sodic soil. Soil physicochemical properties, including cationic exchange, pH, electrical conductivity (EC_e), sodium adsorption ratio (SAR_e), total organic carbon (TOC), water retention, and soil respiration rate, were assessed during and at the end of the incubation period. Addition of FGDG to sodic soil increased EC_e from 3.5 to 8.4 dS m^?1 and decreased SAR_e from 16 to 9. Biochar addition to sodic soil increased TOC from 62.2 to 99.5 μg g^?1 and increased soil respiration rate (mg C kg^?1 soil day^?1) on every measurement period. When FGDG and biochar were both added to the sodic soil, TOC did not significantly improve; however, EC_e increased from 3.5 to 7.7 dS m^?1, SAR_e decreased from 16 to 9, and soil respiration rate increased for all measurements. The results confirm there is potential for FGDG and biochar to reclaim sodic soils alone, and applied in combination.     

Performance of Slag-Based Gypsum on Maize Yield and Available Soil Nutrients over Commercial Gypsum under Acidic and Neutral Soil

ABSTRACT

Effect of slag-based gypsum (SBG) and commercial gypsum (CG) on maize was investigated in acidic and neutral soils. A randomized complete block design (RCBD) with seven treatments consisting of three levels (150, 450, and 750 kg ha^?1) of SBG and CG with recommended dose of fertilizer (RDF) and one control was maintained. Application of SBG @750 kg ha^?1 recorded significantly higher (8.61 and 8.69 t ha^?1, respectively) cob yield of maize compared to CG and control treatments in both soil condition. Increased levels of SBG application increased soil pH and EC in both the soils, but decreased with the application of CG. Application of 750 kg SBG ha^?1 recorded significantly higher soil available nutrients like phosphorus in acidic soil and potassium in neutral soil. Higher exchangeable calcium and magnesium in acidic soil and exchangeable calcium in neutral soil were recorded with the application of CG @750 kg ha^?1. Available sulfur was significantly higher with CG @750 kg ha^?1 applied treatment in both soils. CaCl₂Si content in acidic soil varied significantly and recorded higher with application of SBG, while CaCl₂Si content in neutral soil and AASi in both soils had no significant effect by application of SBG. Significantly higher DTPA extractable micronutrients in acidic and neutral soil were noticed in SBG @750 kg ha^?1 applied treatment. However, application of SBG had no significant effect on iron and copper content in neutral soil. Higher uptake of nutrients was recorded with 750 kg SBG ha^?1 compared CG applied and other treatments.     

Soil phosphorous buffer coefficient as influenced by time and rate of P addition

Abstract

This study was conducted to investigate the effect of time and rate of phosphorus (P) addition on phosphorus availability and phosphorus buffer coefficient in some calcareous soils. Phosphorus was added to the samples at rates of 0, 50, 100, 200, 400, 600 and 800 mg P kg^?1 soil. The samples were incubated for 0.041, 1, 7, 14, 21, 30, 60 and 90 days at constant temperature and moisture. Extractable phosphorus was determined after the incubation. The results showed a sharp decrease in available P within 1 h after P addition. There was a linear relation between added P and extractable P in all soils. The buffer coefficients of soils were estimated by Olsen P for above incubation periods. Generally the buffer coefficient decreased with increasing time of incubation. The results indicated that inputs of between 23 – 59 mg kg^?1 are required to raise Olsen P by 10 mg kg^?1 in these calcareous soils, which assuming 2500 t soil ha^?1, gives a required input of 58 – 148 kg P ha^?1.     

Zinc Adsorption by Mineral Soils of Finland

Abstract

Zinc adsorption by 10 (pH 4.0–6.5) cultivated mineral soils from Finland was studied in batch experiments. Additions of Zn ranged up to 600 mg kg^?1 of soil and the corresponding equilibrium concentrations were 0.1–13 mg 1^?1. In each soil, Zn adsorption conformed to the Freundlich isotherm. Despite a relatively low initial Zn adsorption by the acidic soils, each of the soils proved to have a high potential to adsorb Zn, but the capacity was highly pH dependent. In addition to the conventional Freundlich adsorption isotherms, calculated separately for each soil, extended Freundlich-type isotherms that also incorporate soil pH and other soil characteristics were used to describe Zn adsorption of several soils simultaneously in one equation. The pH-dependent Freundlich adsorption isotherm proved to serve as a practical tool to assess Zn adsorption by soils varying in pH and other characteristics.     

Determination of Critical Soil Silicon Levels for Rice Production in Louisiana Using Different Extraction Procedures

While silicon (Si) fertilization is widely practiced in rice production, establishing critical soil Si levels has remained understudied. Field trials were established at 12 sites across Louisiana from 2013 to 2015 to determine critical soil Si for rice cultivation. Five silica slag (14% Si) rates at 0, 1, 2, 4, 6, and 8 Mg ha^?1 and two lime rates (2 and 4 Mg ha^?1) were arranged in randomized complete block design with four replications. Post harvest soil samples were analyzed for Si using seven extraction procedures. The critical soil Si levels established by the linear plateau model using 0.5 M acetic acid-1 hr (OAc-1) extraction procedure were 36, 41 and 50 mg kg^?1 for plant Si uptake, grain yield, and relative yield as response variables, respectively. Generally, soils having high initial Si and pH had minimal responses to Si fertilization, whereas Si content of soils with low initial Si was significantly increased.     

Coal Fly Ash and Phospho‐gypsum Mixture as an Amendment to Improve Rice Paddy Soil Fertility

Abstract

Rice is a plant that requires high levels of silica (Si). As a silicate (SiO₂) source to rice, coal fly ash (hereafter, fly ash), which has an alkaline pH and high available silicate and boron (B) contents, was mixed with phosphor‐gypsum (hereafter, gypsum, 50%, wt wt^?1), a by‐product from the production of phosphate fertilizer, to improve the fly ash limitation. Field experiments were carried out to evaluate the effect of the mixture on soil properties and rice (Oryza sativa) productivity in silt loam (SiL) and loamy sand (LS) soils to which 0 (FG 0), 20 (FG 20), 40 (FG 40), and 60 (FG 60) Mg ha^?1 were added. The mixture increased the amount of available silicate and exchangeable calcium (Ca) contents in the soils and the uptake of silicate by rice plant. The mixture did not result in accumulation of heavy metals in soil and an excessive uptake of heavy metals by the rice grain. The available boron content in soil increased with the mixture application levels up to 1.42 mg kg^?1 following the application of 60 Mg ha^?1 but did not show toxicity. The mixture increased significantly rice yield and showed the highest yields following the addition of 30–40 Mg ha^?1 in two soils. It is concluded that the fly ash and gypsum mixture could be a good source of inorganic soil amendments to restore the soil nutrient balance in rice paddy soil.     

Increase of Available Phosphorus by Fly‐Ash Application in Paddy Soils

Abstract

Fly ash from the coal‐burning industry may be a potential inorganic soil amendment to increase rice productivity and to restore the soil nutrient balance in paddy soil. In this study, fly ash was applied at rates of 0, 40, 80, and 120 Mg ha^?1 in two paddy soils (silt loam in Yehari and loamy sand in Daegok). During rice cultivation, available phosphorus (P) increased significantly with fly ash application, as there was high content of P (786 mg kg^?1) in the applied fly ash. In addition, high content of silicon (Si) and high pH of fly ash contributed to increased available‐P content by ion competition between phosphate and silicate and by neutralization of soil acidity, respectively. With fly‐ash application, water‐soluble P (W‐P) content increased significantly together with increasing aluminum‐bound P (Al‐P) and calcium‐bound P (Ca‐P) fractions. By contrast, iron‐bound P (Fe‐P) decreased significantly because of reduction of iron under the flooded paddy soil during rice cultivation. The present experiment indicated that addition of fly ash had a positive benefit on increasing the P availability.     

Sulphate Adsorption in Soils of North and Northeast Iran

Abstract

Gypsum (CaSO₄ · 2H₂O) is used in agriculture both as a source of calcium (Ca) and sulphate (SO₄ ^2?) and as an amendment to improve soil structure. The effect of gypsum on the adsorption of SO₄ ^2? in irrigated and nonirrigated soils was examined. Almost all of the indigenous sulphate (SO₄) in a range of Golesthan and North Khorasan soils with moderate pH values (>6) was found to be present in the soil solution and, as a consequence, was highly susceptible to leaching. The adsorption of sulphate to the soils receiving no gypsum was greater with correlation coefficient of r=0.91 at 0 kg S ha^?1 as compared to the soils received 40 kg ha^?1 of gypsum as fertilizer with the value of r=0.88 in Golesthan Province. The same trend was observed in Khorasan Province with r=0.79 and r=0.75 with soils receiving 0 and 40 kg S ha^?1, respectively. The results were more pronounced in irrigated fields for both provinces. The amount of sulphate adsorption in Golesthan Province soils was comparatively greater than soils of Khorasan Province. The results raise questions regarding the efficiency of SO⁴‐containing fertilizers in correcting and preventing S deficiency in situations where leaching is a concern.     

Use of Two-Surface Langmuir-Type Equations for Assessment of Phosphorus Requirements of Lentil on Differently Textured Alluvial Soils

If soil solution phosphorus (P) optimum levels for plant growth (external P) are known, P adsorption isotherms or their equations could further be used to assess how much fertilizer P may be needed for optimum plants yield (QFPN) by adjusting this known external solution P requirement in the soil (ESPR). Surface soil samples were collected from a farmer's field area and research area. An adsorption study was conducted on Ustic Endoaquerts (S₁ soil), Typic Calciargids (S₂ soil), and Typic Torripsamments (S₃ soil) to develop the two-surface Langmuir-type equations. Phosphorus adsorption data were obtained by equilibrating 10-g soil samples in 100 mL of 0.01 M calcium chloride (CaCl₂) containing various amounts of monopotassium phosphate (KH₂PO₄). Thereafter, 11 P fertilizer rates were calculated by two-surface Langmuir-type equations to adjust different estimated soil solution P levels (EPAS) that were designated as treatments (0.05 to 0.90 mg L^?1). Then field experiments on lentil (cv. Niab Masoor 2002) were conducted according to a randomized complete block design (RCBD) on these soils to determine internal (plant tissue), external (soil solution), and fertilizer P requirements. Maximum lentil seed yield (Mg ha^?1) was 0.87 with T₄ (0.17 mg P L^?1) in S₁ soil, 1.8 with T₃ (0.20 mg P L^?1) in S₂ soil, and 0.73 with T₇ (0.28 mg P L^?1) in S₃ soil, obtained by applying 170 kg P₂O₅ ha^?1 in S₁ soil, 110 kg P₂O₅ ha^?1 in S₂ soil, and 78 kg P₂O₅ ha^?1 in S₃ soil. Internal P concentrations (%) of the whole plant associated with 95% of maximum lentil seed yield at flowering stage were 0.245, 0.210, and 0.315 in S₁, S₂, and S₃ soils, respectively. Internal P requirements of lentil seed were 0.290 in S₁, 0.245% in S₂, and 0.380% in S₃ soil. The ESPRs for 95% of maximum yield of lentil were 0.16 mg L^?1, in S₁ soil, 0.23 mg L^?1 in S₂ soil, and 0.27 mg L^?1 in S₃ soil. The QFPN estimated from graphs corresponding to these ESPR values were 160 kg P₂O₅ ha^?1 in S₁ soil, 125 kg P₂O₅ ha^?1 in S₂ soil, and 74 kg P₂O₅ ha^?1 in S₃ soil. The QFPNs estimated from corresponding two-surface Langmuir-type equation by using respective ESPR values were 164, 127, and 75 kg P₂O₅ ha^?1 in S₁, S₂, and S₃ soil, respectively. Field-applied P₂O₅ amounts to adjust soil solution P levels (mg L^?1) at 0.166 (T₄), 0.229 (T₄), and 0.281 (T₇) were 170, 126, and 78 kg ha^?1 in S₁, S₂, and S₃ soil, respectively. Based on the results of these studies, we propose that QFPNs estimated by graphs against identified ESPR values or calculated by the use of corresponding two-surface Langmuir-type equations are in close proximity to the field-applied P to adjust desired EPAS value. Therefore, either of the two techniques may be used to estimate QFPN for optimum lentil yield. Close     

Plant and Soil Responses to the Combined Application of Organic Amendments and Inorganic Fertilizers in Degraded Sodic Soils of Indo-Gangetic Plains

ABSTRACT

Soil degradation due to salinization and sodication is the paramount threat in Indo-Gangetic plains. The studies on reclamation and management of such soils can provide a pragmatic solution for improving fertility and productivity of these soils. Lack of organic matter and poor availability of nutrients are the major factors for low productivity of sodic soils. Rice-wheat is a major cropping system in Indo-Gangetic alluvial plain region even in reclaimed sodic soils and farmers used inorganic fertilizers only to get higher yields. In this study, we used different organic sources of amendments in conjunction with different nitrogen (N) doses supplied through inorganic fertilizers to investigate the combined effect of organic and inorganic amendments on soil fertility and the productivity of rice- wheat system in sodic soils. Salt tolerant varieties of rice and wheat were grown in sodic soil (pH: 9.30, EC: 1.12 dSm^?1 and exchangeable sodium percentage, ESP: 52) during 2014–15 to 2016–17 in a field experiment with 13 treatment combinations of organic and inorganic amendments (T₁- (control) 100% of recommended dose of N (RDN), T₂-municipal solid waste compost (MSWC) @10 t ha^?1 + 50%RDN, T₃- MSWC @10 t ha^?1 + 75% RDN,T₄- MSWC @10 t ha^?1 + 100%RDN, T₅-Vermicompost (VC) @10 t ha^?1 + 50% RDN, T₆- VC @10 t ha^?1 + 75% RDN, T₇-VC@10 t ha^?1 + 100% RDN, T₈- Farm yard manure (FYM) @ 10 t ha^?1 + 50% RDN,T₉- FYM@10 t ha^?1 + 75%RDN, T₁₀- FYM@10 t ha^?1 + 100% RDN, T₁₁-Pressmud (PM) @10 t ha^?1 + 50% RDN, T₁₂-PM@10 t ha^?1 + 75%RDN, and T₁₃- PM @ 10 t ha^?1 + 100% RDN). Use of organic amendments supplemented with reduced dose of N through inorganic fertilizer has significantly improved soil bio-physical and chemical properties. Application of VC@10 t ha^?1 + 100% RDN (T₇) decreased soil bulk density, pH, EC, ESP and Na content to 2.0, 4.2, 26.5, 42.8, and 56.6% respectively and increased soil organic carbon by 34.6% over control (T₁). Soil fertility in terms of available N, P, K, Ca, and Mg increased by 20.5, 33.0, 36.4, and 44%, respectively, over control (T₁). Soil microbial biomass carbon, nitrogen, and phosphorus also improved significantly due to combined use of organic amendments and inorganic fertilizers over the only use of inorganic fertilizers. Decreasing in soil sodicity and increasing soil fertility showed significant increase (P < 0.05) in crop growth, growth indices, and grain yields of rice and wheat. The study revealed that combined use of VC or MSW compost @10 t ha^?1 in conjunction with 75% RDN through inorganic fertilizers in sodic soils proved sustainable technology for restoration of degraded sodic soils and improving crop productivity.     

CALIBRATION OF SUGARCANE RESPONSE TO CALCIUM SILICATE ON FLORIDA HISTOSOLS

Silicon is considered a beneficial nutrient for sugarcane (Saccharum spp.) and yield responses to Si applications on Florida organic soils have been well documented. Growers need calibrated Si recommendations to be able to make cost-effective decisions regarding Si applications. The objective of this study was to develop a soil-test Si calibration based on yield responses to Ca silicate on Everglades Histosols. Twelve paired commercial field comparisons and three small-plot tests of Ca silicate application were conducted. Strong responses in t cane ha^?1 and t sucrose ha^?1 were determined with acetic acid-extractable soil Si <15 g m^?3, with some response to approximately 25 g m^?3. Recommendations were developed over this range with a maximum Ca silicate rate of 6.7 t ha^?1. Optimum leaf Si concentration was determined to be ≥ 6.0 g kg^?1, with 0.95 and 0.80 relative yield at 5.0 and 2.5 g kg^?1, respectively.     

Bioavailability of Silicon from Different Sources and Its Effect on the Yield of Rice in Acidic,Neutral, and Alkaline soils of Karnataka,South India

Several silicon (Si) sources have been reported to be effective in terms of their effectiveness on rice growth and yield. Apart from that, it is crucial to understand the bioavailability of silicon from different silicon sources for adequate plant uptake and its performances in varying types of soils. In this point of view, a pot experiment was conducted to assess the bioavailability of silicon from three Si sources and its effect on yield of rice crop in three contrasting soils. Acidic (pH 5.86), neutral (pH 7.10), and alkaline (pH 9.38) soils collected from different locations in Karnataka were amended with calcium silicate, diatomite, and rice husk biochar (RHB) as Si sources. Silica was applied at 0, 250, and 500 kg Si ha^?1, and the pots were maintained under submerged condition. There was a significant increase in the yield parameters such as panicle number pot^?1, panicle length pot^?1, straw dry weight pot^?1, and grain weight pot^?1 in acidic and neutral soils with the application of Si over no Si treatment, whereas only straw dry weight pot^?1 increased significantly with the application of Si sources over control in alkaline soil. Higher Si content and uptake was noticed in neutral soil followed by acidic and alkaline soils. The bioavailability of Si increased with the application of Si sources but varied based on the types of soil. Application of calcium silicate followed by diatomite performed better in acidic and neutral soils whereas RHB was a better source of Si in alkaline soil. A significant difference in plant-available silicon status of the soil was noticed with the application of Si sources over control in all three studied soils.     

Phosphorus accumulation and leaching risk of greenhouse vegetable soils in Southeast China

Over-fertilization has caused significant phosphorus(P) accumulation in Chinese greenhouse vegetable production(GVP) soils. This study, for the first time, quantified profile P accumulation directly from soil P measurements, as well as subsoil P immobilization, in three alkaline coarse-textured GVP soil profiles with 5(S5), 15(S15), and 30(S30) years of cultivation in Tongshan, Southeast China. For each profile, soil samples were collected at depths of 0–10(topsoil), 10–20, 20–40, 40–60, 60–80, and 80–100 cm. Phosphorus accumulation was estimated from the difference in P contents between topsoil and parent material(60–100 cm subsoil). Phosphorus mobility was assessed from measurements of water-soluble P concentration(PSol). Finally, P sorption isotherms were produced using a batch sorption experiment and fitted using a modified Langmuir model. High total P contents of 1 980(S5), 3 190(S15), and 2 330(S30) mg kg~(-1) were measured in the topsoils versus lower total P content of approximately 600 mg kg~(-1) in the 80–100 cm subsoils. Likewise, topsoil PSol values were very high, varying from 6.4 to 17.0 mg L~(-1). The estimated annual P accumulations in the topsoils were 397(S5), 212(S15), and 78(S30) kg ha~(-1) year~(-1). Sorption isotherms demonstrated the dominance of P desorption in highly P-saturated topsoils, whereas the amount of adsorbed P increased in the 80–100 cm subsoils with slightly larger P adsorption capacity. The total P adsorption capacity of the 80–100 cm subsoils at a solution P concentration of0.5 mg L~(-1) was 15.7(S5), 8.7(S15), and 6.5(S30) kg ha~(-1), demonstrating that subsoils were unable to secure P concentrations in leaching water below 0.5 mg L~(-1) because of their insufficient P-binding capacity.     

Effect of long-term intensive rice cultivation on the available silica content of sawah soils: Java Island,Indonesia

Abstract

The dramatic increases in rice productivity and cultivation intensity through the implementation of green revolution (GR) technology using high yielding varieties (HYVs) of rice and chemical fertilizers were not long lasting in Indonesia. The stagnancy of rice productivity in recent years without any scientific reasons presents a challenge for agronomists and soil scientists in Indonesia. This study describes the effects of long-term intensive rice cultivation on the change in available silica (Si) in sawah soil. The term sawah refers to a leveled and bounded rice field with an inlet and an outlet for irrigation and drainage. Soil samples collected by Kawaguchi and Kyuma in 1970 and new samples taken in 2003 from the same sites or sites close to the 1970 sites were analyzed and compared. From 1970 to 2003, the average content of available Si decreased from 1,512 ± 634 kg SiO₂ ha^?1 to 1,230 ± 556 kg SiO₂ ha^?1 and from 6,676 ± 3,569 kg SiO₂ ha^?1 to 5,894 ± 3,372 kg SiO₂ ha^?1 in the 0–20 cm and 0–100 cm soil layers, respectively. Cultivation intensity differences between seedfarms planted with rice three times a year and non-seedfarms rotating rice and upland crops appeared to affect the changing rates of available Si within the study period. In the 0–20 cm soil layer, the average content of available Si decreased from 1,646 ± 581 kg SiO₂ ha^?1 to 1,283 ± 533 kg SiO₂ ha^?1 (?22%) and from 1,440 ± 645 kg SiO₂ ha^?1 to 1,202 ± 563 kg SiO₂ ha^?1 (?17%) in seedfarms and non-seedfarms, respectively. Differences in topographical position also influenced the decreasing rate of available Si in this study. Using similar management practices and cultivation intensity, upland sampling sites lost more Si compared with lowland sites. Planted rice under a rain fed system with no Si addition from rain water in an upland position may be a reason for the higher loss of Si, particularly in non-seedfarms. The Si supply from irrigation water might have contributed to the slowdown in the decreasing rate of available Si in Java sawah soils.     

Phosphorus Management of Lucerne Grown on Calcareous Soil in Turkey

ABSTRACT

Lucerne or alfalfa (Medicago sativa L.) is grown as a forage crop on many livestock farms. In calcareous soils in eastern Turkey, lucerne production requires phosphorus (P) additions as the soils are naturally P deficient. Phosphorus sorption isotherms were used to estimate P fertilizer needs for lucerne grown for two years in a 3-cut system on a calcareous P deficient Aridisol in eastern Anatolia, Erzurum province, Turkey. Annual P applications ranged from 0–1200 kg P ha^?1. The Langmuir two-surface adsorption equation was used to derive the maximum P sorption capacity of unamended soil and to determine soil solution P, maximum buffer capacity (MBC), equilibrium buffer capacity (EBC), and P saturation at the optimum economic P rate (OEPR) for dry matter (DM) production. Soils were tested for Olson P at the onset of the study and after two years of P applications. In both years, tissue was analyzed for P content at flowering prior to first cutting. The OEPR (2-year average) was 754 kg P ha^?1 yr^?1 corresponding with a soil solution P concentration of 0.30 mg L^?1, a DM yield of 8725 kg DM ha^?1, and $528 ha^?1 annual profit. The P content of leaves at flowering increased linearly with P application beyond 100 kg P ha^?1 and was 3.2 g kg^?1 P at the OEPR. The unfertilized soil had an EBC, MBC, P saturation, and X_max of 3304 mL g^?1, 3401 mL g^?1, 6%, and 1086 mL g^?1, respectively, whereas two years of fertilization to the OEPR decreased EBC and MBC to 358 mL g^?1 and 540 mL g^?1, and increased P saturation and Olsen P to 56% and 32 mg kg^?1, respectively. These results suggest a P saturation >50% or Olsen P >30 mg kg^?1 are needed to maintain an optimum soil solution concentration of 0.30 mg L^?1 in this calcareous Aridisol. Similar studies with different soils and initial soil test P levels are needed to conclude if these critical soil test values can be applied across the region.     

Influence of Sulfur Fertility on Wheat Yield Performance on Alluvial and Upland Soils

Abstract: In recent years, sulfur (S) deficiencies in winter wheat (Triticum aestivum L.) have become more common, particularly on coarse‐textured soils. In Study I, field experiments were conducted in 2001/2002 through 2003/2004 on Mississippi River alluvial soils (Experiment I) and an upland, loessial silt loam (Experiment II) to evaluate the influence of spring S rates of 0, 5.6, 11.2, and 22.4 kg ha^?1 and a fall rate of 22.4 kg sulfate (SO₄)‐S ha^?1 on grain yield of three varieties. In Study II, field experiments were conducted in 2001/2002 and 2004/2005 on alluvial soils to evaluate the influence of spring S rates of 0, 5.6, 11.2, and 22.4 kg SO₄‐S ha^?1 in fields where S‐deficiency symptoms were present. Grain yield response to applied S occurred only on alluvial, coarse‐textured, very fine sandy loam soils (Study II) that had soil SO₄‐S levels less than the critical level of 8 mg kg^?1 and organic‐matter contents less than 1 g kg^?1 in the 0‐ to 15‐, 15‐ to 30‐, and 30‐ to 45‐cm depths. Soil pH increased with soil depth. Optimum S rate was 11.2 kg SO₄‐S ha^?1 in 2001/2002 and 5.6 kg SO₄‐S ha^?1 in 2004/2005. On the upland, loessial silt loam soil, soil SO₄‐S levels accumulated with depth, whereas organic‐matter content and pH decreased. In the loessial soils, average soil SO₄‐S levels in the 15‐ to 30‐ and 30‐ to 45‐cm soil depths were 370% greater than SO₄‐S in the surface horizon (0 to 15 cm).     

Effect of liming central European loess soils on soil extractable phosphorus and potassium as determined by electro-ultrafiltration

The benefits of liming acidic or calcium (Ca)-deficient soils for soil structure and fertility are well documented. However, little is known about the effect of liming nearly neutral loess soils – lacking Ca – on interactions between soil nutrients. Over a 2-year period, 62 field trials were conducted in Germany and Austria with three treatments (0, 3 and 12 t CaO ha^?1) on slightly acidic loess soils. Soil samples from the top soil layer were taken 4, 8, 16 and 24 weeks after liming. In addition to the pH_CaCl2, the phosphorus (P), potassium (K) and Ca contents were analysed using electro-ultrafiltration (EUF). The application of lime increased the pH in average from 6.6 up to 7.0 and 7.2, but did not decrease EUF extractable P and K below the level of untreated control. Contrary to our expectations, EUF extractable P increased 4 weeks after liming in the treatment with 3 t CaO ha^?1. At the end of incubation period, 24 weeks after liming, the EUF extractable K in treatment 12 t CaO ha^?1 remained still 1.3 mg K 100 g^?1 soil above the untreated control.     

Estimating soil ammonium adsorption using pedotransfer functions in an irrigation district of the North China Plain

Extensive use of chemical fertilizers in agriculture can induce high concentration of ammonium nitrogen(NH4⁺_-N) in soil. Desorption and leaching of NH4⁺_-N has led to pollution of natural waters. The adsorption of NH4⁺_-N in soil plays an important role in the fate of the NH4⁺_-N. Understanding the adsorption characteristics of NH4⁺_-N is necessary to ascertain and predict its fate in the soil-water environment, and pedotransfer functions(PTFs) could be a convenient method for quantification of the adsorption parameters. Ammonium nitrogen adsorption capacity, isotherms, and their influencing factors were investigated for various soils in an irrigation district of the North China Plain. Fourteen agricultural soils with three types of texture(silt, silty loam, and sandy loam) were collected from topsoil to perform batch experiments. Silt and silty loam soils had higher NH4⁺_-N adsorption capacity than sandy loam soils.Clay and silt contents significantly affected the adsorption capacity of NH4⁺_-N in the different soils. The adsorption isotherms of NH4⁺_-N in the 14 soils fit well using the Freundlich, Langmuir, and Temkin models. The models’ adsorption parameters were significantly related to soil properties including clay,silt, and organic carbon contents and Fe²⁺ and Fe³⁺ ion concentrations in the groundwater. The PTFs that relate soil and groundwater properties to soil NH4⁺_-N adsorption isotherms were derived using multiple regressions where the coefficients were predicted using the Bayesian method. The PTFs of the three adsorption isotherm models were successfully verified and could be useful tools to help predict NH4⁺_-N adsorption at a regional scale in irrigation districts.     

A Comparative Study of Different Amendments on Amelioration of Saline-Sodic Soils Irrigated with Water Having Different EC: SAR Ratios

Soil degradation affects soil properties such as structure, water retention, porosity, electrical conductivity (EC), sodium adsorption ratio (SAR), and soil flora and fauna. This study was conducted to evaluate the response of contrasting textured soils irrigated with water having different EC:SAR ratios along with amendments: gypsum (G), farm manure (FM), and mulch (M). Water of different qualities viz. EC 0.6 + SAR 6, EC 1.0 + SAR 12, EC 2.0 + SAR 18, and EC 4.0 + SAR 30 was used in different textured soils with G at 100% soil gypsum requirement, FM at 10 Mg ha^?1, and M as wheat straw was added on surface soil at 10 Mg ha^?1. Results revealed that the applied amendments in soils significantly decreased pH_s and electrical conductivity (EC_e) of saturated paste and SAR. Four pore volumes of applied water with leaching fraction 0.75, 0.77, and 0.78 removed salts 3008, 4965, and 5048 kg ha^?1 in loamy sand, silty clay loam, and sandy clay loam soils, respectively. First four irrigations with LF of 0.82, 0.79, 0.75, and 0.71, removed 5682, 5000, 3967, and 2941 kg ha^?1 salts, respectively. The decreasing order for salt removal with amendments was FM > G > M > C with LF = 0.85, 0.84, 0.71, and 0.68, respectively. This study highlights a potential role of soil textures to initiate any mega program for reclamation of saline-sodic soils in the perspective of national development strategies.