Effect of soil application of nickel on growth,micronutrient concentration and uptake in barley (Hordeum vulgare L.) grown in Inceptisols of Varanasi

A pot experiment was conducted in a glass house on low nickel containing alluvial soil in the Department of Soil Science and Agricultural Chemistry, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi, during 2012–13 and 2013–14, to study the response of barley to soil application of nickel (Ni). There were ten treatments of Ni (0, 2.5, 5, 10, 15, 20, 30, 40, 50 and 60 mg kg^?1) studied with recommended dose of fertilizers nitrogen, phosphorus, potassium and sulfur (N:P:K:S :: 40:30:30:20 mg kg^?1).The results showed a significant increase in plant height, number of tillers, chlorophyll content, straw and grain yield, and 1,000 grains weight with application of 10 mg Ni kg^?1 soil during both years of study. The micronutrient concentration and uptake in straw and grain increased with application of <15 mg Ni kg^?1 soil and beyond that declined significantly. Diethylenetriaminepentaacetic acid-extractable micronutrient iron, manganese, copper, zinc and nickel (Fe, Mn, Cu, Zn and Ni) content in soil increased with increasing level of Ni. The maximum urease activity in post-harvest soil was noticed with application of 40 mg Ni kg^?1 soil. The microbial population viz. bacteria, fungi and actinomycetes were higher with 5, 30 and 10 mg Ni kg^?1 soil, respectively.     

Dunite in Agriculture: Physiological Changes,Nutritional Status and Soybean Yield

ABSTRACT

Brazil is an importer of fertilizers and the use of alternative sources is increasing in agriculture. The objective of this study was to evaluate the effect of Dunite rates on magnesium (Mg), silicium (Si), reducing sugars, sucrose and foliar starch, soil chemical attributes and soybean yield [Glycine max (L.) Merril] in two soil types. The treatments consisted in the five Dunite rates (0, 42, 208, 542, and 1542 mg kg^?1) in a clayey soil, and five Dunite rates (0, 150, 238, 411, and 933 mg kg^?1) in a sandy soil. In both crops and soils, the Mg and Si contents, reducing sugars and foliar glucose, as well as pH, Mg and Si of the soil, and yield components showed a positive response due to the increase of input rates. The Mg nutrition provides lower foliar starch levels, consequently, the best partition of metabolites to plant leads to better development, filling and yield of soybeans.     

Effect of Continuous Application of Fertilizers,Farmyard Manure and Lime on Soil Fertility and Productivity of the Maize-Wheat System in an Acid Alfisol

A study on the long-term effect of fertilizers and amendments on crop productivity and changes in soil fertility in maize-wheat cropping system in an acid Alfisol was carried out in randomized block design (RBD) with 11 treatments. Continuous application of chemical fertilizers along with farmyard manure (FYM) or lime significantly influenced the grain and straw/stover yield and the uptake of nutrients by wheat and maize crops significantly. The organic carbon content increased from 7.9 to 12.1 g kg^?1, cation exchange capacity (CEC) from 12.1 to 14.6 cmol (p⁺) kg^?1 and available phosphorus from 21.9 to 75.2 kg ha^?1 through the integrated use of organic and fertilizers for the last 42 years while the status of available nitrogen (N) and potassium (K) declined over the years in all the treatments. Continuous application of urea alone resulted in a drastic decline in soil pH at both depths. Imbalanced use of fertilizers led to a significant reduction in the productivity of both crops and depleted the soil fertility.     

Petiole N,P, K Concentrations and Yield of the Potato Cultivar Molli from Certified Organic Amendments and Fertilizer Formulations

This study evaluated the petiole uptake of nitrogen, phosphorus, potassium, and sulfur (N, P, K, and S) by the potato from two seed meals, mint compost, and five commercially available organic fertilizers under an irrigated certified organic production system. Available soil nitrate (NO₃-N) and ammonium (NH₄-N) from each amendment averaged 115 kg N ha^?1 at application and 25 kg N ha^?1 30 d after planting through harvest, with minor differences between fertilizers. Petiole N declined from an average of 25,000 mg N kg^?1, 4 wk after emergence to 3,000 mg N kg^?1 prior to harvest. Petiole P and K concentrations were maintained above 4,000 mg P kg^?1, 10,000 mg K kg^?1, and 2,000 mg S kg^?1 tissue, respectively, throughout the growing season in all treatments. Tuber yields were not different between fertilized treatments averaging 53 Mg ha^?1. This study provides organic potato growers baseline information on the performance of a diverse array of organic fertilizers and amendments.     

Nitrogen availability,maturity and stability of bokashi-type fertilizers elaborated with different feedstocks of animal origin

Organic amendments, such as bokashi, are applied to the soil to increase the N. However, the available N provided by these fertilizers and the feedstocks with which they are produced have been poorly documented. In this work, the available N in bokashi was evaluated as well as their biological stability and chemical maturity. The treatments bokashi poultry (WVP); bokashi swine (WVS) and bokashi control (WVC) contained wheat straw and vegetable wastes; WVP and WVS also included poultry and swine manure, respectively. The temperature, mineral N, pH, EC, CO₂ production rate and germination index (IG) were measured. At the end of the trial, all of the treatments’ temperatures exceeded room temperature. The WVP presented a higher mineral N (1,054 mg kg^?1) than the WVS (844 mg kg^?1) and the WVC (907 mg kg^?1). In all treatments, the NH₄⁺ and NO₃^? decreased. EC reached phytotoxicity levels in all treatments (EC > 3 dS m^?1). None of the treatments showed biological stability or chemical maturity (IG of WVP, WVS and WVC: 10%, 29% and 19%, respectively). Therefore, it is concluded that applying these bokashi to soils could limit crop growth due to phytotoxic effects and immobilization of transient N.     

Calibration and Categorization of Plant Available Silicon in Rice Soils of South India

ABSTRACT

Calibration of field crop responses to nutrient availability acts as a basis for making fertilizer recommendations from soil and tissue analysis. The purpose of this study was to evaluate and summarize silicon (Si) fertilization of rice in different soils of south India. The experiment consists of four levels of calcium silicate as Si with three replications. Initially, soils were analyzed using eleven different extractants. The grain and straw yield were recorded and analyzed for Si content. The critical levels for plant available Si in the soil ranged from 14 mg kg^?1 (distilled water-1) to 207 mg kg^?1 [0.005 M sulfuric acid (H₂SO₄)]. There was a wide variation in low, medium, and high categories of plant available Si for different extractants calculated based on percent relative yield. The critical level of Si in straw and grain were 2.9 and 1.2%, respectively.     

Phosphorus,Potassium and Sulfur Interactions in Soybean Plants on a Typic Hapludox

Soybean (Glycine max (L.) Merril) has the largest acreage in Brazil where nutrients are provided to crops by formulated fertilizers, which is the most usual method. Under tropical and subtropical conditions, most of the nutrients required by soybean crops are phosphorus (P) and potassium (K), while sulfur (S) is applied in smaller amounts. The P, K, and S interactions under greenhouse conditions using completely randomized blocks in a factorial 3 × 3 × 3 arrangement were evaluated. The treatments were as follows: three P rates (0, 75, and 150 mg P kg^?1); three K rates (0, 150, and 300 mg K kg^?1); and three S rates (0, 50, and 100 mg S kg^?1). The P, K, and S application had a significant influence on the shoot dry weight (SDW) and number of pods per pot (NPP) in contrast with the increase in grain yield (GY) that had positive relationship with K and S rates. These results indicated that both nutrients were the most limiting to GY. In soil and leaves, only the P, K, and S concentrations were modified by the treatments (P, K, and S), but in the grains there was synergism of P rates with Mg concentration unlike K rates with Ca concentration. Physiological components as photosynthetic rate, intrinsic efficiency of water use, and chlorophyll had influence from P and K rates.     

RESPONSE OF SOYBEAN TO SOIL APPLIED SULFUR AND BORON IN A CALCAREOUS SOIL

A greenhouse experiment with soybean grown on sulfur (S) and boron (B) deficient calcareous soil was conducted for two years in northwest India to study the influence of increasing sulfur and boron levels on yield and its attributing characters at different growth stages (55 days, maturity). The treatments included four levels each of soil applied sulfur viz. 0, 6.5, 13.4, 20.1 mg S kg^?1 and boron viz. 0, 0.22, 0.44, 0.88 mg B kg^?1 at the time of sowing. The highest dry matter yield at 55 days after sowing, DAS (19.3 g pot^?1) and maturity (straw yield ?25.2 g pot^?1 and grain yield ?7.3 g pot^?1) was recorded with B_0.44 S_13.4 treatment combination. The combined applications of sulfur and boron yielded highest oil content with B_0.44S_13.4 (21.7%) treatment level. Chlorophyll ‘a’ and ‘b’ increased significantly with successive levels of sulfur and boron addition at 55 DAS. The mean sulfur and boron uptake in straw and grains increased significantly with increasing levels of sulfur and boron up to 13.4 mg kg^?1 and 0.44 mg kg^?1 and decreased non-significantly thereafter. At both the growth stages, a synergistic interactive effect of combined application of sulfur and boron was observed with B_0.44 S_13.4 treatment level for sulfur and boron uptake in straw and grains.     

Phosphorus Nutrition of Upland Rice,Dry Bean,Soybean, and Corn Grown on an Oxisol

Rice, dry bean, corn, and soybean are important food crops. Phosphorus (P) deficiency is one of the most yield-limiting factors for these crops grown on highly weathered Brazilian Oxisols. Four greenhouse experiments were conducted to determine P requirements of these four crops. The P levels used were 0, 50, 100, 200, and 400 mg kg^?1. Growth, yield, and yield components evaluated of four crop species were significantly increased with the application of P fertilization. Most of the responses were quadratic in fashion when the P was applied in the range of 0 to 400 mg kg^?1. Maximum grain yield of upland rice was obtained with the application of 238 mg P kg^?1 of soil, maximum dry bean grain yield was obtained with the application of 227 mg P kg^?1 of soil, and maximum grain yield of soybean was obtained with the application of 224 mg P kg^?1 of soil. Maximum shoot growth of corn was obtained with the addition of 323 mg P kg^?1 of soil. Most of the growth and yield components had significant positive association with grain yield or shoot dry weight. Phosphorus concentration and uptake were greater in the grain compared to straw in upland rice and dry bean plants. Overall, P-use efficiencies decreased with increasing P rates.     

Effect of Graded Levels of Nitrogen and Sulfur and Their Interaction on Yields and Quality of Aromatic Rice

ABSTRACT

In a greenhouse experiment, involving factorial combinations of nitrogen (N) (0, 15, 30, 45, and 60 mg kg^{? 1} soil) and sulfur (S) (0, 7.5, 15.0, 22.5, 30.0 mg kg^{? 1}soil), application of all levels of N and S 15 mg kg^{? 1} and above increased the grain yield of aromatic rice (Basmati cv. ‘Taraori’) significantly. The highest grain yield of aromatic rice was recorded from the treatment combinations of 60 mg N + 15 mg S kg^{? 1} or 45 mg N + 30 mg S kg^{? 1}. The interaction of N and S influenced the N and S content in rice grain, N content in straw, N: S ratio both in grain and straw, milling (%), and other quality parameters significantly. Milling (%) and hulling (%), thousand grain weight, L: B ratio, cooked grain breadth, and aroma score were found to be significantly and positively correlated with the N: S ratio of rice grain while grain breadth had a significant inverse relationship with N: S ratio in grain.     

Coffee‐husk biochar application increased AMF root colonization,P accumulation,N2 fixation,and yield of soybean grown in a tropical Nitisol,southwest Ethiopia

Low soil fertility and soil acidity are among the major bottlenecks that limit agricultural productivity in the humid tropics. Soil management systems that enhance soil fertility and biological cycling of nutrients are crucial to sustain soil productivity. This study was, therefore, conducted to determine the effects of coffee‐husk biochar (0, 2.7, 5.4, and 16.2 g biochar kg^?1 soil), rhizobium inoculation (with and without), and P fertilizer application (0 and 9 mg P kg^?1 soil) on arbuscular mycorrhyzal fungi (AMF) root colonization, yield, P accumulation, and N₂ fixation of soybean [Glycine max (L.) Merrill cv. Clark 63‐K] grown in a tropical Nitisol in Ethiopia. ANOVA showed that integrated application of biochar and P fertilizer significantly improved soil chemical properties, P accumulation, and seed yield. Compared to the seed yield of the control (without inoculation, P, and biochar), inoculation, together with 9 and 16.2 g biochar kg^?1 soil gave more than two‐fold increment of seed yield and the highest total P accumulation (4.5 g plant^?1). However, the highest AMF root colonization (80%) was obtained at 16.2 g biochar kg^?1 soil without P and declined with application of 9 mg P kg^?1 soil. The highest total N content (4.2 g plant^?1) and N₂ fixed (4.6 g plant^?1) were obtained with inoculation, 9 mg P kg^?1, and 16.2 g biochar kg^?1 soil. However, the highest %N derived from the atmosphere (%Ndfa) (> 98%) did not significantly change between 5.4 and 16.2 g kg^?1 soil biochar treatments at each level of inoculation and P addition. The improved soil chemical properties, seed yield, P accumulation and N₂ fixation through combined use of biochar and P fertilizer suggest the importance of integrated use of biochar with P fertilizer to ensure that soybean crops are adequately supplied with P for nodulation and N₂‐fixation in tropical acid soils for sustainable soybean production in the long term.     

CALIBRATION OF SOIL AND PLANT SILICON ANALYSIS FOR RICE PRODUCTION*

Calibration of field crop response to nutrient availability is the bases for making a fertilizer recommendation from soil and tissue analyses. The purpose of this study was to evaluate and summarize results from a series of experiments on silicon (Si) fertilization of rice in the Everglades Agriculture Area. Twenty-eight rice field experiments were conducted from 1992 through 1996. The experiments consisted of 2 to 5 rates of calcium silicate applied to soils (Histosols) of varying Si soil-test values. Soil samples were taken before planting and analyzed for acetic acid (0.5 mol L^?1) extractable Si. Straw samples were collected at harvest and analyzed for total Si. Grain yield was determined. The “critical” levels for Si in the soil (point below which response to Si fertilizer is expected) calculated by the Cate & Nelson procedure was 19 mg Si L^?1 soil. The amount of silicon to correct Si deficiency in the soil and to obtain optimum rice yield was 1500, 1120 and 0 kg ha^?1 for low (<6 mg L^?1), medium (6 to 24 mg L^?1), and high (>24 mg L^?1) level of soil Si, respectively. Silicon in the straw was classified as high when Si concentration was >34 g kg^?1, medium when in between 17 and 34, and low when <17 g kg^?1 (3.4 and 1.7%, respectively).

     

Improvement in Reproductive Development,Seed Yield,and Quality in Wheat by Zinc Application to a Soil Deficient in Zinc

A pot experiment was done to study the effect of zinc (Zn) application on the reproductive development and quality of wheat (Triticum aestivum L. cv. SP 343) seeds. The soil was low in diethylenetriaminepentaacetate (DTPA)–extractable Zn and was fortified with a mixture of nitrogen, phosphorus, and potassium (NPK) as basal fertilizers. Four treatments included a control (no Zn), 5 mg Zn, 10 mg Zn, and 10 mg Zn kg^?1 soil with urea instead of ammonium nitrate. Zinc addition improved the pollen-producing capacity of anthers, pollen viability, and seed yield with an increase in seed Zn, phytate, and starch contents but decreased the phytate/zinc molar ratio at 5 mg Zn kg^?1 and increased it at 10 mg Zn kg^?1. Application of urea increased the seed protein content at 10 mg Zn kg^?1 but was ineffective in lowering the phytate/Zn ratio, which was still less than the alarming level.     

Zinc,Copper, Boron and Iron Requirement of Upland Rice Grown on a Brazilian Oxisol

Deficiency of micronutrients increasing in field crops, including upland rice in recent years. The objective of this study was to determine requirement of zinc (Zn), copper (Cu) boron (B) and iron (Fe) for upland rice grown on a Brazilian Oxisol. The levels used were: Zn (0, 10, 20, 40, and 80 mg kg^?1), Cu (0, 5, 10, 20 and 40 mg kg^?1), B (0, 5, 10, 20 and 40 mg kg^?1) and Fe (0, 250, 500, 1000, and 2000 mg kg^?1). Plant height, straw yield, grain yield, panicle number and grain harvest index (GHI) were significantly improved with the addition of these micronutrients. Root growth was also improved with the application of micronutrients, except with the addition of B. Maximum grain yield was obtained with the addition of 51 mg Zn, 24 mg Cu, 5 mg B kg^?1, and 283 mg Fe kg^?1 soil. Similarly, maximum straw yield was obtained with the addition of 38 mg Zn, 17 mg Cu, 6 mg B kg^?1, and 1500 mg Fe kg^?1 soil. Maximum plant height was obtained with the addition of 54 mg Zn, 10 mg B kg^?1, and 1197 mg Fe kg^?1 soil. Copper did not affect plant height significantly. Maximum panicle number was obtained with the addition of 22 mg Cu kg^?1, 3 mg B kg^?1, and 1100 mg Fe kg^?1 soil. Zinc did not affect panicle number significantly. Maximum GHI was obtained with the addition of 61 mg Zn kg^?1, and 8 mg B kg^?1. Zinc was had a linear increase in GHI in the range of 0 to 80 mg kg^?1, and Fe showed a negative relationship with GHI.     

Effect of Silicon on Growth, Physiology, and Cadmium Translocation of Tobacco (Nicotiana tabacum L.) in Cadmium-Contaminated Soil

Silicon(Si) offers beneficial effect on plants under cadmium(Cd) stress such as promoting plant growth and increasing resistance to heavy metal toxicity. In this study, a pot experiment was performed to study the role of Si in alleviating Cd toxicity in tobacco(Nicotiana tabacum L.) plants on a yellow soil taken from Guiyang, China. Nine treatments consisting of three concentrations of Cd(0, 1, and 5 mg kg~(-1)) together with three Si levels(0, 1, and 4 g kg~(-1)) were established. Plant growth parameters, Cd concentration,and the malondialdehyde(MDA), chlorophyll, and carotenoid contents were determined 100 d after transplanting of tobacco seedlings.Application of exogenous Si enhanced the growth of tobacco plants under Cd stress. When 5 mg kg~(-1) Cd was added, Si addition at 1 and 4 g kg~(-1) increased root, stem, and leaf biomass by 26.1%–43.3%, 33.7%–43.8%, and 50.8%–69.9%, respectively, compared to Si addition at 0 g kg~(-1). With Si application, the transfer factor of Cd in tobacco from root to shoot under both 1 and 5 mg kg~(-1) Cd treatments decreased by 21%. The MDA contents in the Si-treated tobacco plants declined by 5.5%–17.1% compared to those in the non-Si-treated plants, indicating a higher Cd tolerance. Silicon application also increased the chlorophyll and carotenoid contents by 33.9%–41% and 25.8%–47.3% compared to the Cd only treatments. Therefore, it could be concluded that Si application can alleviate Cd toxicity to tobacco by decreasing Cd partitioning in the shoots and MDA levels and by increasing chlorophyll and carotenoid contents, thereby contributing to lowering the potential health risks of Cd contamination.     

Efficiency of Sulfur Application on Soybean in Two Types of Oxisols in Southern Brazil

Modern agricultural techniques have been increasing the yield of soybean (Glycine max (L.) Merr.) while also causing increasing removal of sulfur (S) from the soil. Besides this, the use of concentrated fertilizers with this element and inadequate soil management, with consequent formation of organic matter with low S concentrations, has been causing frequent symptoms of deficiency in the plants. To assess the effect of S on soybean yield and to establish critical levels of sulfur sulfate (S-SO₄^2-) available in the soil, two experiments were conducted over a 2-year period in the Paraná State, Brazil, in fields containing Typic Haplorthox and Typic Eutrorthox soils, located in the Ponta Grossa and Londrina Counties, respectively. The experimental design was randomized blocks with five S rates (0, 25, 50, 75, and 100 kg ha^?1) and four replicates. The source used was elementary S with 98 percent purity. The maximum estimated yields on average for the 2 years were obtained with application of 49.9 and 63.0 kg ha^?1 in the Typic Haplorthox and Typic Eutrorthox soils, for an overall average of 56.4 kg ha^?1, with concentrations of available S-SO₄^2- in the 0- to 20-cm depth of 16.9, 19.3m and 17.1 mg kg^?1, respectively, values greater than the 10 mg kg^?1 indicated as the adequate concentration for soybean plant. In turn, at the 21- to 40-cm depth, the S concentrations were 49.5, 74.2, and 56.4 kg ha^?1. The efficiency of the fertilization diminished with increasing S rates, in both soil types, while the greatest yield efficiency was obtained in the plants grown in the Typic Haplorthox soil.     

Response of Maize (Zea Mays L.) to Phosphorus Fertilizers in Two Alfisols with Contrasting Phosphorus Availabilities and Sorption Capacities

Increase in phosphorus (P) availability with fertilizer addition is influenced by soil properties such as P sorption capacity. We investigated P availability changes and response of maize (Zea mays L) to four P fertilizers rates (0, 20, 30 and 40 kg ha^?1) in a two-site field experiment, having soils of contrastingly different available P (2.9 and 22.1 mg kg^?1) and P sorption capacities (171.9 and 54.2 mg kg^?1). Increase in available P was significantly greater in the soil with higher available P but lower P sorption capacity, than in the other; however, yield responses were similar in the two soils. Fertilizer P rates of 30 and 40 kg ha^?1 gave significantly greater maize yields than the unfertilized treatment in both soils. Results suggest the need to account for the P sorption capacity when deciding rates of P fertilizers to increase available P in soils.     

Effectiveness of crop straws,and swine manure in ameliorating acidic red soils: a laboratory study

Purpose

Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.

Materials and methods

Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg^?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH₄⁺) and nitrate plus nitrite (NO₃^??+?NO₂^?).

Results and discussion

All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg^?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol₍₊₎ kg^?1 compared to 2.82 and 4.19 cmol₍₊₎ kg^?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol₍₊₎ kg^?1 per pH unit increase for both straws compared to 6.25 cmol₍₊₎ kg^?1 per pH unit from the manure. The NO₃^??+?NO₂^? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.

Conclusions

While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.

     

Potassium Release in an Aeric Haplaquept as Influenced by Long-Term Rice–Rice Cropping with Different Rates of Fertilizers and Manuring

Different fractions of potassium (K) and the kinetics of K release as influenced by 21 cycles of rice–rice cropping with different rates of fertilizers and manuring were investigated on an Aeric Haplaquept (kaolinitic Inceptisol) soil profile from Bhubaneswar, India. The neutral 1 N ammonium acetate–extractable K in the surface soil layer (0–15 cm) increased from its initial value of 11.2 mg K kg^?1 to 14.8, 14.2, and 17.5 mg K kg^?1 soil in different treatments. However, the nonexchangeable K content in the surface soil layer dropped considerably to a level of 4.8–20.0 mg K kg^?1 soil. Cumulative nonexchangeable K release after 121 h of extraction with 0.01 M calcium chloride (CaCl₂) was <14 mg K kg^?1. The first-order kinetic model best described the nonexchangeable K release. The decrease in pH and increase in iron (Fe) content indicated the possibilities of K supply to plants through the dissolution of soil minerals.     

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.