S. Srivastava

Potassium supplying power of a Typic Ustochrept profile using quantity/intensity technique in a long-term fertilized plot

The effect of 27 years of continuous cropping, fertilization and manuring on potassium (K) supplying capacity of a Typic Ustochrept soil profile from Delhi, India under a maize–wheat–cowpea (fodder) cropping system was investigated by employing the quantity/intensity (Q/I) approach. The predominant mineral suite of the K E ), labile pools of K (K L ), immediately available K (ΔK 0 ), K available with difficulty (K X ) and water soluble+exchangeable K (1 M NH 4 OAc K) in different soil layers (0 to 105 cm) under different treatments were in the following order: 100% nitrogen, phosphorus and potassium (NPK)+farmyard manure (FYM) > 100% NPK > control (no fertilizer) > 100% N >100% NP. The AR K E value, a measure of availability or intensity of labile K in soil decreased with profile depth due to greater K fixation by specific sites in the lower layers. The quantity of specifically sorbed K (K X ) and the potential buffering capacity of soil (PBC K ) showed a increasing trend with soil depth. In soil without K fertilizer treatments (control, 100% N and 100% NP) about 100% of the total K uptake by crops was from non-exchangeable soil K reserve as compared to 49·5 and 32·2% when annually 84 kg K/ha and 84 kg K/ha+FYM at the rate of 15 t/ha were applied. The results showed the greatest depletion of non-exchangeable K reserves in the plots which did not receive K fertilization. To ensure sustained crop production under intensive cropping, application of recommended dose of NPK plus FYM is required.

Comparison of Modified Mitscherlich and Response Plateau Models for Calibrating Soil Test Based Nitrogen Recommendations for Rice on Typic Ustropept

Use of the right amount of nitrogenous fertilizer is fundamental for farm profitability and environmental protection. For efficient fertilizer use, it is necessary to have information on the optimum rates under different soil‐climatic conditions. Curve fitting techniques are often used to estimate optimal fertilizer rates, but a significant problem exists in selecting a proper model for a particular soil‐cropping situation. The objective of the work reported here was to compare and evaluate the linear and quadratic response models with yield plateau specifications and modified Mitscherlichs equation. The three models gave good fit to the data when evaluated by R2. Even though all three models predicted nearly the same maximum yields, the fertilization recommendations estimated by linear response plateau (LRP) and quadratic response plateau (QRP) models were considerably lower than that given by modified Mitscherlichs equation and also the systematic bias with Mitscherlichs model was higher. It is suggested that the yield plateau considerations should be given serious attention in response analysis to avoid the excess use of nitrogenous fertilizers than the actual need. Between the two plateau models, the QRP based recommendations were lower than those of LRP.

Effect of long‐term fertilization and manuring on potassium release properties in a Typic Ustochrept

A long-term fertilizer experiment, over 27 years, studied the effect of mineral fertilizers and organic manures on potassium (K) balances and K release properties in maize-wheat-cowpea (fodder) cropping system on a Typic Ustochrept. The treatments consisted of control, 100% nitrogen (100% N), 100% nitrogen and phosphorus (100% NP), 50% nitrogen, phosphorus, and potassium (50% NPK), 100% nitrogen, phosphorus, and potassium (100% NPK), 150% nitrogen, phosphorus, and potassium (150% NPK), and 100% NPK+farmyard manure (100% NPK+FYM). Nutrients N, P, and K in 100% NPK treatment were applied at N: 120 kg ha—1, P: 26 kg ha—1, and K: 33 kg ha—1 each to maize and wheat crops and N: 20 kg ha—1, P: 17 kg ha—1, and K: 17 kg ha—1 to cowpea (fodder). In all the fertilizer and manure treatments removal of K in the crop exceeded K additions and the total soil K balance was negative. The neutral 1 N ammonium acetate-extractable K in the surface soil (0—15 cm) ranged from 0.19 to 0.39 cmol kg—1 in various treatments after 27 crop cycles. The highest and lowest values were obtained in 100% NPK+FYM and 100% NP treatments, respectively. Non-exchangeable K was also depleted more in the treatments without K fertilization (control, 100% N, and 100% NP). Parabolic diffusion equation could describe the reaction rates in CaCl2 solutions. Release rate constants (b) of non-exchangeable K for different depth of soil profile showed the variations among the treatments indicating that long-term cropping with different rates of fertilizers and manures influenced the rate of K release from non-exchangeable fraction of soil. The b values were lowest in 100% NP and highest in 100% NPK+FYM treatment in the surface soil. In the sub-surface soil layers (15—30 and 30—45 cm) also the higher release rates were obtained in the treatments supplied with K than without K fertilization indicating that the sub-soils were also stressed for K in these treatments.

The availability of potassium in Aeric Haplaquept and Typic Haplustert as affected by long-term cropping, fertilization and manuring

The effect of long-term cropping, fertilization and manuring after 21years of rice-rice cropping on an Aeric Haplaquept and after 27years of soybean-wheat system on Typic Haplustert on the availability ofpotassium (K) using a Quantity-Intensity (Q/I) relationship was investigated atBhubaneswar and Jabalpur, respectively in India. Q/I relationships of potassiumprovide general information on the nature of K equilibrium and serve as a goodindex of K supplying power of soil. The treatments selected for the study were:control (no fertilizer), nitrogen (N), nitrogen + phosphorus(NP), nitrogen + phosphorus + potassium(NPK) and NPK + farmyard manure (FYM). Nutrients N, P and Kwere applied at 200 kg N/ha, 52 kg P/ha and 100kg K/ha in Aeric Haplaquept to the rice-rice system and220 kg N/ha, 96 kg P/ha and 77 kg K/hainTypic Haplustert to the soybean-wheat system. Farmyard manure was applied everyyear only to Kharif (wet season) rice at 10t/ha (Aeric Haplaquept) and 15 t/ha to soybean crop(Typic Haplustert). In both soils the values of equilibrium activity ratio (AReK), the activity ratio of K in soil solution inequilibrium with the soil, non-specific or immediate available K and K onspecific sites or difficultly available K were observed in the following order:NPK + FYM > NPK > control > N > NP.The magnitude of AReK < 0.001 (moll−1)1/2 showed that the K adsorption at edgepositions was predominant in NP plots in the Typic Haplustert and in control, Nand NP plots in the Aeric Haplaquept. The ΔK0 became morenegative in the NPK and NPK + FYM treated plots, therebyindicating a greater K release into the soil solution. The potential bufferingcapacity, a measure of the ability of the soil to maintain the intensity of Kinthe soil solution was low in both the soils, irrespective of fertilizertreatments and indicated poor K release and low K supplying capacity of thesoils. Free energies of exchange (ΔG) for the replacement of calcium withpotassium ranged from −5348 to −3379 cal M−1 K−1 and were associatedwithpotassium deficiencies in plants in both the soils. The Aeric Haplaquept hadvery low values of exchangeable + water soluble K,AReK, KL and ΔG, thereby indicating a Kstress environment. The maximum and minimum contribution of non-exchangeable Kto plant uptake were found for NP and NPK + FYM plots,respectively. The results suggest that continuous cropping without K inputscaused a greater decline in K supplying power of the soil and emphasise theneedfor balanced and integrated use of organic and K inputs regularly to sustain asteady supply of K to successive crops.

Evaluation of Crop Responses to Applied Fertilizer Phosphorus and Derivation of Optimum Recommendations using the Mitscherlich–Bray Equation

Abstract In this article, the responses of three important crops (rice, wheat, and soybeans) to applied phosphorous (P) were examined and economically optimum P fertilizer recommendations using the Mitscherlich–Bray model were derived for the three crops at four locations in India. Crop‐yield responses were related to extractable P concentrations estimated by the Olsen method, employing a modification of Mitscherlichs equation. The parameters were considered reliable enough to use for the estimation of fertilizer recommendations at different fertilizer cost–price ratios (p) and marginal rate of return (R). The b parameter value explains how much soil P can substitute for fertilizer P. Thus, for each incremental unit of extractable P, fertilizer P could be reduced by 2.0, 2.9, 1.5, and 1.5 kg P/ha for rice (Periyar), rice (Bhubaneswar), wheat (Hisar), and soybean (Raipur), respectively. Optimum fertilizer rates for rice, wheat, and soybean were generated for different soil P fertility levels. There is also need for such information for other soils and crops.

Potential of Mauritius Hemp (Furcraea gigantea Vent.) for the Remediation of Chromium Contaminated Soils

The present study was conducted to evaluate the ability of a high biomass producing, drought tolerant succulent plant Mauritius hemp (Furcraea gigantea Vent.) for its tolerance to different levels of Cr (0, 25, 50, 100 and 200 mg Cr kg soil−1) and its potential for phytoremediation purposes. Based on the data on inhibition of the growth of plants with Cr, tolerance index and grade of growth inhibition, it was observed that the plant could tolerate up to 50 mg Cr kg −1 soil. Absorption of Cr from soil to plant and its translocation into plant tissues were discussed in terms of bio concentration factor (BCF), transfer factor (TF), and translocation efficiency (TE%). Cr was mainly accumulated in the roots and exclusion of Cr was found to be the principal physiological tolerance mechanism followed by a marked increase in proline, ascorbic acid, total free amino acids in the leaf tissue and malic acid in the rhizosphere samples to counter Cr stress. Based on the tissue concentration of Cr (< 300 μg g−1 in the leaves and TF<1), it was concluded that, Furcraea gigantea could not be considered a hyperaccumulator and therefore unsuitable for phytoextraction of Cr. Nevertheless, Furcraea gigantea could be a suitable candidate for phytostablization of Cr contaminated soils.

Crop Residue Retention and Nutrient Management Practices on Stratification of Phosphorus and Soil Organic Carbon in the Soybean–Wheat System in Vertisols of Central India

ABSTRACT The long-term crop residue retention coupled with external nutrient inputs are crucial for maintaining soil phosphorus (P) and soil organic carbon (SOC) in Vertisols of Central India. A study was conducted to evaluate the long-term effect of three wheat residue management practices (residue burning, incorporation, and surface retention) in combination with three supplementary nutrient inputs (SNI) [control, fertilizer, and farmyard manure (FYM)] on stratification of P and SOC in the soybean–wheat system in Vertisol. The wheat residue either incorporated or retained on the soil surface increased the availability of P and SOC content as compared to the common practices of residue burning. Residue retention or incorporation increased stratification of P and soil organic carbon over the residue burning. Irrespective of the nutrient treatments, greater stratification ratio of SOC and P were registered under wheat residue incorporation or retention compared to residue burning. It is evident from the study that wheat residue incorporation or retention plus addition of FYM could be an effective strategy for increasing the soil fertility in a soybean–wheat system of Vertisols of Central India.

Long-Term Wheat Residue Management and Supplementary Nutrient Input Effects on Phosphorus Fractions and Adsorption Behavior in a Vertisol

The management of crop residues coupled with external nutrient inputs is important for improving and conserving soil fertility and productivity. We assessed the long-term effects of three wheat residue management options (RMO) (residue burning, incorporation, and surface retention) in combination with three supplementary nutrient inputs (SNI) [control, fertilizer, and farmyard manure (FYM)] on phosphorus (P) fractions and adsorption behavior of a Vertisol under soybean–wheat system. Wheat residue incorporation and retention improved the labile inorganic P [sodium bicarbonate (NaHCO3-Pi)] by 3.2 and 5.0 mg kg−1 and the labile organic P (NaHCO3-Po) by 2.4 and 4.2 mg kg−1, respectively, as compared to residue burning. The soils under residue incorporation and retention had 38 and 26% more moderately labile organic P [sodium hydroxide (NaOH-Po)], respectively, than the soil under residue burning. The SNI either as fertilizer or FYM further enhanced NaHCO3-Pi, NaHCO3-Po, and NaOH-Po. In contrast, less labile P fractions [hydrochloric acid (HCl)-P and residual-P] remained unaffected by RMO and SNI treatments. Residue retention or incorporation decreased P adsorption over the residue burning for all the three nutrient inputs. The P-adsorption data fitted well to the Langmuir equation (R2 ranged from 0.970 to 0.994). The P-adsorption maximum (b), bonding energy constant (k), differential P-buffering capacity (DPBC), and standard P requirement (SPR) were lower with residue incorporation or surface retention than with residue burning. The SPR followed the order residue burning > incorporation > retention for RMOs and control > fertilizer > FYM for SNI treatments. The NaHCO3-Pi, NaHCO3-P0, and NaOH-Po had negative correlation with P-adsorption parameters and showed positive correlation with soybean P uptake. Wheat residue incorporation or retention plus FYM could be an effective strategy for enhancing the P fertility of Vertisols under a soybean–wheat system.

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.