Dhyan Singh

Long-term continuous cropping, fertilisation, and manuring effects on physical properties and organic carbon content of a sandy loam soil

Effects of continuous cropping, fertilisation, and manuring on soil organic carbon content and physical properties such as particle size distribution, bulk density, aggregation, porosity, and water retention characteristics of a Typic Ustochrept were examined after 31 cycles of maize–wheat–cowpea (fodder) crop rotation. Five contrasting nutrient treatments from a long-term fertiliser experiment were chosen for this study: control (no fertiliser or manure); 100% (optimum dose) nitrogen (N) fertiliser; 100% nitrogen and phosphorus (NP); 100% nitrogen, phosphorus, and potassium (NPK); 100% NPK + farmyard manure (NPK+FYM). The NPK+FYM treatment significantly improved soil organic carbon (SOC) content in 0–0.15 m soil compared with the other 4 treatments; the NPK treatment resulted in significantly more SOC than the control and N treatments (P < 0.05). The SOC in NPK and NPK+FYM treatments was 38.6 and 63.6%, respectively, more than the initial level of SOC (4.4 g/kg) after 31 cycles of cropping. The control and N treatments maintained the SOC status of the soil at the initial value. NPK+FYM significantly improved soil aggregation, soil water retention, microporosity, and available water capacity and reduced bulk density of the soil at 0–0.30 m depth. Greater crop growth under the NPK treatment resulted in increased organic matter content of soil, which improved aggregate stability, water retention capacity, and microporosity compared with the control. The effects were more conspicuous with the NPK+FYM treatment and at the surface soil (0–0.15 m). Application of imbalanced inorganic fertiliser (N and NP treatments) did not have a deleterious effect on the physical properties of the soil compared with the control. SOC content showed a highly significant and positive correlation with mean weight diameter (0.60), % water-stable macro-aggregates (0.61), and soil water retention at –0.033 MPa (0.75) and –1.5 MPa (0.72), and negative correlation with bulk density (–0.70) for the surface 0–0.15 m soil. The study thus suggests that application of balanced mineral fertilisers in combination with organic manure sustains a better soil physical environment and higher crop productivity under intensive cultivation.

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.

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.

Distribution of fractions of zinc and their contribution towards availability and plant uptake of zinc under long-term maize (Zea mays L.)–wheat (Triticum aestivum L.) cropping on an Inceptisol

Intensive farming with high yielding cultivars, application of high analysis NPK fertilisers, and reduced use of organic manures caused a decrease in the availability of zinc (Zn) in Indian soils. We collected soil and plant samples from an ongoing long-term experiment at Indian Agricultural Research Institute, New Delhi, to study the distribution of different fractions of Zn in an Inceptisol and their contribution towards the Zn availability in soil and Zn uptake in maize-wheat crop rotation. The treatments used for the study were NPK, NPK + FYM, NPK + Zn, and control (no fertiliser or manure). The DTPA-Zn concentration in soil was higher where Zn had been applied and declined with an increase in soil depth. The distribution of different fractions of Zn under various treatments and depths was inconsistent, and varied in a cropping year. The average concentration of total Zn (mg/kg) was 183, 183, 171, and 211 in 0-0.15, 0.15-0.30, 0.30-0.45, and 0.45-0.60 m depth, respectively. Residual Zn was the dominant portion of total Zn at all soil depths. Grain and stover yield of maize ranged from 1.10 to 2.43 t/ha and 1.22 to 2.46 t/ha, respectively, under different treatments, whereas, the yield of wheat grain varied from 2.25 to 4.69 t/ha and that of wheat straw from 2.56 to 5.20 t/ha. Highest uptake of Zn by both the crops occurred in Zn-treated plots. Zinc associated with easily reducible manganese, carbonate and iron and aluminum oxides contributed directly towards DTPA-extractable Zn. Sorbed Zn (SORB-Zn) and Zn associated with organic matter (OM-Zn) contributed significantly towards Zn uptake by the 2 crops.

Balanced Fertilization along with Farmyard Manures Enhances Abundance of Microbial Groups and Their Resistance and Resilience against Heat Stress in a Semi-arid Inceptisol

The impact of long-term (36-year) application of balanced fertilizers and farmyard manures (FYM) on the abundance of microbial groups (bacteria, fungi, actinomycetes, Pseudomonas, Azotobacter, ammonia-oxidizing bacteria) and their resistance and resilience against heat stress was investigated in a semi-arid Inceptisol at New Delhi, India. Surface soils from selected treatments [control, nitrogen (N), N and phosphorus (P), NP and potassium (K), NPK + FYM] under a maize crop were assessed immediately after sampling (0-day) and at 1, 14, 28, and 56 day(s) after heat stress (48 °C for 24 h). The heat stress significantly reduced the microbial groups by 20 to 80%. Recovery after stress was 60 to 100% within 56 days. Resistance and resilience of fungi and actinomycetes were greater than other groups of organisms. Ammonia-oxidizing bacteria (AOB) were found to be most sensitive with the lowest resistance index. Application of NPK + FYM was most effective in enhancing the resistance and resilience of soil microorganisms against heat stress.

Changes in Fractions of Iron, Manganese, Copper, and Zinc in Soil under Continuous Cropping for More Than Three Decades

The effect of continuous cropping with maize and wheat on soil characteristics and various forms of micronutrient cations in an Incetisol over the years was studied in an ongoing long‐term experiment in New Delhi, India. The soil samples collected in the years of 1993, 1995, 1997, 1999, 2001, 2003, and 2004 were analyzed for different fractions of iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) by following a sequential extraction procedure. The pH, electrical conductivity (EC), and calcium carbonate (CaCO3) content of the soil varied from 8.28 to 8.53, 0.40 to 0.43 dSm−1, and 0.92 to 1.05%, respectively. Organic carbon content ranged from 0.38 in the control to 0.67% in 100% NPK + farmyard manure (FYM). Diethylenetriaminepentaacetic acid (DTPA)–extractable Fe and Mn (but not Zn and Cu) in soil declined from their respective initial (1971) values as a result of intensive cropping for more than three decades. It also resulted in a decrease in the concentrations of all the four metallic cations bound to organic matter, in addition to Fe and Zn, associated with carbonates in all the treatments in surface soil.

Fractions of Iron in Soil under a Long-Term Experiment and Their Contribution to Iron Availability and Uptake by Maize–Wheat Cropping Sequence

Soil and plant samples were collected from an ongoing long-term experiment (LTE) at the Indian Agricultural Research Institute farm, New Delhi, to study the distribution of various fractions of iron (Fe) and their contribution to availability and plant uptake in a maize–wheat sequence. The optimum dose-based treatments adopted for the study were nitrogen (N), nitrogen–phosphorus (NP), nitrogen–phosphorus–potassium (NPK), NPK + farmyard manure (FYM), NPK+ zinc (Zn), and control (no fertilizer or manure). Different fractions of Fe in the soil were sequentially extracted using different extractants. Diethylenetriaminepentaacetic acid (DTPA)–extractable Fe did not differ significantly among the treatments as a result of continuous cropping for more than three decades. The overall mean total iron (Fe) content varied from 2.36 to 2.61% under different treatments. Residual Fe constitutes a major portion of total Fe in all four layers of soil. The Fe associated with easily reducible Mn and organic matter contributed directly to DTPA-extractable Fe both in pre-maize and post-wheat soil. Residual Fe contributed directly to uptake Fe by maize and wheat crops.

Different Forms of Potassium and Their Contributions toward Potassium Uptake under Long-Term Maize (Zea mays L.)–Wheat (Triticum aestivum L.)–Cowpea (Vigna unguiculata L.) Rotation on an Inceptisol

In a long-term fertilizer experiment at the Indian Agricultural Research Institute, New Delhi, with maize, wheat, and cowpea, various forms of potassium (K) and their contribution toward K uptake were found to be affected by fertilizer use and intensive cropping. The treatments included for the study were a control, 100% nitrogen (N), 100% N–phosphorus (P), 50% NPK, 100% NPK, 100% NPK + farmyard manure (FYM at 15 t ha−1 to maize only), and 150% NPK. The concentration of nonexchangeable K was greatest, followed by exchangeable K and water-soluble K. The study revealed no significant change in water-soluble K concentration in surface soil compared to N, NP, and control, indicating existence of an equilibrium between different K forms. Application of 100% NPK significantly increased water-soluble K concentration in surface soil compared to N, NP, and control treatments after maize, wheat, and cowpea. Application of NPK + FYM and 150% NPK resulted in greater quantities of all the K forms as compared to other treatments. Among the three forms, water-soluble K contributed predominantly to K uptake by maize and wheat; however, nonexchangeable K contributed significantly to K uptake by cowpea.

Fractions of Copper in Soil under a Long-Term Experiment and Their Contribution to Copper Availability and Uptake by Maize―Wheat Cropping Sequence

ABSTRACT Soil and plant samples were collected from on-going long-term experiment at Indian Agricultural Research Institute, New Delhi farm to study the distribution of various forms of copper (Cu) and their contribution to availability and plant uptake in maize (Zea mays L.)—wheat (Triticum aestivum L.) sequence. The optimum dose-based treatments selected for the study were nitrogen-phosphorus-potassium (NPK), NPK + Farmyard manure (FYM), NPK+ zinc (Zn) and control (no fertilizer or manure). Uptake of Cu by maize and wheat varied from 17.0 to 37.5 and 60.8 to 149.3 g ha−1, respectively, under different treatments. Copper uptake by wheat was significantly higher under 100% NPK + FYM than that with 100% NPK. There was no significant difference among the treatments with respect to diethylenetriaminepentaacetic acid (DTPA)-extractable Cu in 0–15, 15–30, 30–45, and 45–60 cm soil layers. However, with increasing depth of soil, it showed declining trend under all the treatments. Mean value of total Cu was 28, 32, 25, and 21 mg kg−1 in 0–15, 15–30, 30–45, and 45–60 cm depths, respectively. Major part of the total Cu was present as residual form. Sorbed copper (SORB–Cu) contributed directly towards its availability both in pre-sowing maize and post-harvest wheat soil samples. SORB–Cu and organic matter bound Cu (OM–Cu) contributed directly towards the uptake by the component crops. Copper associated with easily reducible manganese, carbonate, and iron and aluminum oxides were most recalcitrant forms present in soil and their effects on availability and crop uptake were adverse.

An anaerobic incubation procedure for the major nutrients for cereal crops.

Abstract It is of utmost need to have a quick and suitable soil test method to analyse a large number of soil samples for various soils and crops. Ten procedures for N, three for P & K and three for N,P & K together were tried on surface ( 0–15 cm ) soil samples collected from control plots of field experiments conducted on three different soil series of Delhi, with wheat, bajra (Pennisetum typhoides) and rice crops. Out of the methods tried, anaerobic incubation procedure for the determination of available N which has been shown previously to be applicable to submerged rice crop, showed significant correlation with yields of aerable crops of bajra and wheat also. The same method was found to be superior to others for the simultaneous extraction of P & K.