Hargopal Singh

Soil carbon pools under poplar-based agroforestry, rice-wheat, and maize-wheat cropping systems in semi-arid India

Labile fractions of soil organic C are considered important indicators of soil quality as these can respond rapidly to land-use changes and agricultural management. We studied the impact of three different land-use systems viz. poplar-based agroforestry involving wheat-legume rotation, rice-wheat and maize-wheat agroecosystems, on dynamics of total organic C (TOC), oxidisable soil organic C (SOC), very labile, labile, less labile, and recalcitrant C fractions, water extractable organic carbon (WEOC), hot water soluble C (HWC), microbial biomass C (MBC), and mineralizable C in the semi-arid subtropical India. The maize-wheat and agroforestry systems had 65–88% higher SOC stocks than the rice-wheat system and were characterized by predominantly labile C. About 56–60% of the total organic C in maize-wheat and agroforestry systems occurred as labile and very labile C compared to 37% under rice-wheat rotation. Contrarily, the majority of organic C (63%) in rice-wheat soils was stabilized in less labile and recalcitrant forms. The HWC and MBC were also higher in maize-wheat and agroforestry systems as opposed to the rice-wheat system. In the discriminant function analysis, a composite of indicators involving TOC, recalcitrant C and total N correctly distinguished the soils under the three systems. The results suggested that in agroforestry and maize-wheat systems the organic C in soils was less stable and thus could be lost following the land-use change.

Effect of sodic irrigation and gypsum on the reclamation of sodic soil and growth of rice and wheat plants

Abstract Effect of gypsum and sodic irrigation on the precipitation of Ca and removal of Na from a sodic soil reclaimed with different levels of gypsum (33, 67 and 100% of the total gypsum requirement of the soil) and growth of rice was investigated in a greenhouse experiment. Precipitation of Ca and carbonates and soil Na saturation increased with increase in sodicity of irrigation water. Application of gypsum for initial sodic soil reclamation or at each irrigation (Gei) during growth of rice and wheat increased the removal of Na from the soil and decreased exchangeable sodium percentage (ESP) and pH. Under sodic irrigation treatments, even the high levels of gypsum applied for initial sodic soil reclamation did not control the build-up of ESP to below the levels at which rice and wheat could produce normal growth. But under Gei treatments, soil pH and ESP values observed under sodic irrigation treatments were similar to those recorded under good water irrigation. When sodic irrigation water has to be used for reclamation of sodic soils, additional gypsum (more than was used for initial reclamation) should be applied to decrease SAR and alkalinity of water and control the build up of Na in soil and improve crop production.

Changes in Nitrogen, Phosphorus, and Potassium in a Long‐Term Continuous Maize–Wheat Cropping System in India

In a long‐term maize–wheat rotation at the Punjab Agricultural University, Ludhiana, India (subtropical climate), the effects of nitrogen (N), phosphorus (P), and potassium (K) addition on soil fertility and forms of inorganic P and K in the plow layer of an alkaline sandy loam soil were measured after 11 and 22 years of cropping. The treatments comprised four rates of N (0, 60, 120, and 180 kg N ha−1) as urea, three rates of P (0, 17.5, and 35 kg P ha−1) as single superphosphate, and two rates of K (0 and 33 kg K ha−1) as muriate of potash. The treatments selected for the present study were N0P0K0, N120P0K0, N120P17.5K0, N120P35K0, N120P17.5K33, and N120P35K33. A significant year × treatment interaction in decreasing available N [alkaline potassium permanganate (KMnO4)–oxidizable N) status of soils was found in all the treatments. Available P (Olsen P) in the control plot decreased over time whereas in plots with added P, available P increased significantly after years 11 and 22, with the greatest increase in the N120P17.5Ko treatment. Compared to the initial values, continuous P fertilization resulted in greater total P and chloride P concentrations after 11 and 22 years. Although sodium hydroxide (NaOH) P and sulfuric acid (H2SO4) P increased in P‐treated plots from the start of the trial to year 11, they decreased from year 11 to year 22. Among these inorganic P forms, chloride P was significantly positively correlated with P uptake (r = 0.811*). When only N and P were applied, available K [ammonium acetate (NH4OAc)–extractable K] significantly decreased over time. In plots without K addition, water‐soluble and exchangeable K decreased from their initial status. Compared to year 11, water‐soluble K increased, whereas exchangeable K decreased after year 22 in plots receiving no K fertilizer. Compared with NPK treatments, a significant decrease of total K in NP treatment plots suggests the release and uptake of nonexchangeable K. Water‐soluble K and exchangeable K were not correlated with K uptake. These results suggest that long‐term application of P fertilizers resulted in the accumulation of P in the soil, which could have resulted in saturation of P binding sites. Of the soil inorganic P fractions, only chloride P appears to be a good indicator of plant‐available P. The gradual loss in native soil K and release of nonexchangeable K indicates the need for adding K fertilizer to maintain soil fertility.

Evaluation of Pressmud Cake as Source of Phosphorus for Rice-Wheat Rotation

ABSTRACT Efficient utilization of P from pressmud cake (PMC) in rice-wheat rotation is critical in reducing the costs of fertilizer P and improving soil fertility. The objective of this study was to determine the effects of variable rates of PMC and fertilizer P on yield and soil fertility under rice-wheat rotation on a silt loam (Aquic Ustorthent) soil in the flood plains of Punjab, India. Phosphorus responses in rice were obtained at 13 kg P ha−1. Application of PMC at 51 ha−1 was as efficient as 13 kg P ha−1 in increasing grain yield of rice. Wheat responded to direct application of 26 kg P ha−1 when rice received zero or 13 kg P ha−1. In the presence of PMC at 5 t ha−1 applied to rice, grain yield responses were obtained up to 13 kg P ha−1, but no response to P was observed when 10 t PMC ha−1 was applied. Application of PMC helped to raise the yield potential of rice and wheat when compared with application of chemical P fertilizer. Application of PMC increased the organic carbon and available P contents in soil.

Intercropping studies in spring planted sugarcane under flood plain conditions

Results revealed that vegetables such as cabbage, onion, bell pepper, summer squash and tomato can be grown successfully to make the spring planted sugarcane more profitable. However, better results were achieved with cabbage and bell pepper, since these caused the lowest reduction in cane yield.

Chemical fractionation of heavy metals and nutrients in sludge and waste water generated by Coca-Cola soft drink industry

Coca-Cola soft drinks industry generates three sludge types, viz., water treatment sludge (WTS), effluent treatment plant sludge (ETPS) and filter cake sludge (FCS), and two waste waters, viz., effluent and influent. Total nitrogen (TN), phosphorus (TP), potassium (TK) and sulfur (TS) concentrations were significantly higher in ETPS than in WTS and FCS, indicating that Coca-Cola sludge is a good source of macronutrients. Among micronutrients, total iron (T-Fe) and copper (T-Cu) concentrations were significantly higher in ETPS, and total zinc (T-Zn) and manganese (T-Mn) concentrations were significantly higher in WTS compared with other sludge types. Among heavy metals, total cadmium (T-Cd) and arsenic (T-As) concentrations were significantly higher in ETPS, and total mercury (Hg) and nickel (T-Ni) concentrations were significantly higher in WTS than other sludge types. Speciation of micronutrients/heavy metals in sludge performed by using sequential extraction showed their predominance as crystalline and specifically adsorbed components. Only a small portion of each micronutrient/heavy metal was retrieved in readily exchangeable {water soluble (WS) + exchangeable (EXCH)} form. The existence of micronutrients/heavy metals in organic matter (OM) and oxide {manganese-oxide (MnOX) + amorphous iron and aluminum oxide (AMPOX) + crystalline iron and aluminum oxide (CRYOX)} bound fractions revealed very restricted release potential of sludge in soil solution.

Direct, Residual, and Cumulative Effects of Mixed Sludge Generated by Coca-cola Soft-Drink Industry on Crop Yield, Soil Fertility, and Heavy-Metal Uptake in Rice–Wheat Cropping Sequence

A field experiment was conducted to evaluate the effects of directly, residually, and cumulatively applied mixed sludge generated by the soft-drink industry on rice and wheat yields, soil fertility, grain heavy-metal uptake, depthwise distribution of micronutrients and heavy-metals after 3 years of application. Crop (rice/wheat) yield (grain/straw) increased significantly with direct sludge application at 10.0 t ha−1 year−1, either alone or jointly with fertilizers, over the absolute control. Interestingly, the effects of sludge application on crop (rice/wheat) yield either applied directly at 10.0 t ha−1 year−1, residually at 30.0 t ha−1 year−1, and/or cumulatively at 15.0 t ha−1 were nonsignificant. Direct sludge application at 5.0/10.0 t ha−1 year−1 resulted in significant increase in heavy-metal uptake over the absolute control. The micronutrient/heavy-metal contents in surface soil were significantly greater with sludge application than those in subsurface layers. The results thus show that sludge application results in significant improvement in yield and soil fertility.