A. K. Indoria

Long-Term Effects of Soil and Nutrient Management Practices on Soil Properties and Additive Soil Quality Indices in SAT Alfisols

A long term experiment was conducted for 11 years to study the effects of soil and nutrient management practices on soil fertility and additive soil quality indices in rainfed Alfisol, at Hyderabad, India. The treatments were comprised of conventional tillage (CT) and minimum tillage (MT) as main factors, sorghum stover (dry) @ 2 t/ha (SS), fresh gliricidia loppings @ 2 t/ha (GL) and no residue (NR) application on surface as sub-treatments and N levels @ 0, 30, 60 and 90 kg N/ha as sub- sub treatments in castor-sorghum yearly rotation. The results indicated that after 11 years, MT significantly improved organic carbon (OC), available N, available K, exchangeable Mg, available S, microbial biomass carbon (MBC), dehydrogenase activity (DHA), labile carbon (LC), bulk density (BD) and mean weight diameter (MWD) of soil aggregates. Application of sorghum residue and gliricidia loppings showed significant increase in OC by 6.28% and 3.7%, respectively over NR. Statistical regression functions indicated that soil parameters viz., MBC, LC, MWD, OC, S, Fe and DHA influenced by long term soil management practices significantly influenced the crop yield. The physical (PSQI), physico-chemical (PCSQI), chemical (CSQI), biological (BSQI) and additive SQIs (ASQI) were significantly influenced by management treatments. On an average, the percent contribution of these component soil quality indices towards ASQI was in the order of BSQI (32.1%) > CSQI (26.1%) > PSQI (25.7%) > PCSQI (16.2%). Crop yields were significantly correlated with these indices and thus emphasized their importance in increasing the productivity in these semi arid Alfisol soils.

Effect of Predominant Integrated Nutrient Management Practices on Soil Quality Indicators and Soil Quality Indices under Post Monsoon (Rabi) Sorghum (Sorghum Bicolor) in Rainfed Black Soils (Vertisols) of Western India

ABSTRACT A long-term study was conducted to study the impact of integrated nutrient management on soil quality in post-monsoon sorghum (Sorghum bicolor) at Solapur in Maharashtra State in Western India under All India Coordinated Research Project for Dryland Agriculture. The experiment was laid out with ten Integrated Nutrient Management Treatments in a randomized block design with three replications. The results of the study indicated that among all the integrated nutrient management treatments practiced, the application of 25 kg nitrogen (N) ha−1 through crop residue (CR) + 25 kg N ha−1 (urea) showed the highest soil quality index of 2.36, which was at par with other treatments receiving farmyard manure (FYM) and crop residues along with urea. The relative order of performance of the integrated nutrient management treatments in influencing soil quality was: T6: 25 kg N ha−1 (CR) + 25 kg N ha−1 (urea) (2.36) >T5: 25 kg N ha−1 (FYM) (2.31) > T7: 25 kg N ha−1 (FYM) +25 kg N ha−1 (urea) (2.30) = T8: 25 kg N ha−1 (CR) +25 kg N ha−1 (Leucaena loppings) (2.30) > T10: 25 kg N ha−1 (Leucaena loppings) +25 kg N ha−1 (urea) (2.17) > T4: 25 kg N ha−1 (CR:crop residues) (2.16) > T9: 25 kg N ha−1 (Leucaena loppings) (2.15) > T3: 50 kg N ha−1 (urea) (2.10) > T2: 25 kg N ha−1 (urea) (1.99) > T1: 0 kg N ha−1 (control) (1.77). The results of the study also indicated that average percent contribution of each soil key indicator towards soil quality indices was: pH (3.97%), EC (1.94%), organic carbon (18.6%), available P (2.80%), available K (6.57%), exchangeable Ca (7.02%), available S (3.45%), Available Zn (17.9%), dehydrogenase (DHA) (16.2%), microbial biomass carbon (MBC) (18.5%) and mean weight diameter (MWD) (3.14%). Thus, the results of the present study will be highly useful to the land managers in planning effective management of soil quality.

Effect of Graded Levels of Surface Crop Residue Application Under Minimum Tillage on Carbon Pools and Carbon Lability Index in Sorghum (Sorghum bicolor (L.) Moench)-Cowpea (Vigna unguiculata) System in Rainfed Alfisols

ABSTRACT A long term experiment (2005–2012) was conducted in rainfed semi-arid tropical Alfisol at Hayathnagar Research Farm of Central Research Institute for Dryland Agriculture, Hyderabad, India. The aim of this experiment was to study the long-term impacts of graded levels of surface crop residue application on carbon (C) pools, aggregate associated C, C lability index and their relationship with crop yield. The experiment was conducted in a randomized block design (RBD) with minimum tillage (MT). Experimental treatments comprised of four levels of surface application of sorghum crop residues (@ 0, 2, 4 and 6 t ha−1). The test crops, sorghum and cowpea, were grown in rotation yearly. Based on the pooled analysis of long term data (2005–2012), the study revealed that the surface application of sorghum residue @ 6 t ha−1 and 4 t ha−1 recorded 21% and 16% higher sorghum grain yields, respectively over control (no residue) whereas, the corresponding increase in the cowpea yield was 50% and 60%, respectively. Besides, the concentrations of soil organic carbon (SOC), inorganic carbon (IC), total carbon (TC), particulate organic carbon (POC) in the top surface soil (upper layer, 0–5cm depth) were found significantly higher than the sub-surface soil (lower layers, 5–15 cm depth) in all the treatments. Storage of soil C was assessed in soil aggregates fractions, and it was found that the smaller size aggregate fractions (0.053mm) contained significantly (p = 0.05) higher content of SOC compared to the large sized fractions (2 mm). The amount of very labile fraction of C extracted with 12 N H2SO4 was significantly higher (1.04 g kg−1) with the application of sorghum stover @ 6t ha-1 compared to other residue level treatments, in the 0-5 cm soil layer. The Lability Index (LI) increased with the increase in the amount of residues applied and was significantly higher in the surface soils compared to subsurface soil. The results of this study will be highly relevant and of significant value from the view point of managing SOC and its different pools in soil under abiotically stressed semiarid tropical Alfisols soils.

Effect of 13 Years Long Minimum Tillage Cum Conjunctive Nutrient Management Practices on Soil Fertility and Nitrogen Chemical Fractions under Sorghum (Sorghum bicolour (L.) Moench)–Mungbean (Vigna radiata (L.) Wilczek) System in Semi-Arid Tropical Alfisol (SAT) in Southern India

ABSTRACT A long-term experiment was conducted at the Central Research Institute for Dryland Agriculture for 13 years to evaluate the effect of low tillage cum cheaper conjunctive nutrient management practices in terms of productivity, soil fertility, and nitrogen chemical pools of soil under sorghum–mung bean system in Alfisol soils. The results of the study clearly revealed that sorghum and mung bean grain yield as influenced by low tillage and conjunctive nutrient management practices varied from 764 to 1792 and 603 to 1008 kg ha−1 with an average yield of 1458 and 805 kg ha−1 over a period of 13 years, respectively. Of the tillage practices, conventional tillage (CT) maintained 11.0% higher yields (1534 kg ha−1) over the minimum tillage (MT) (1382 kg ha−1) practice. Among the conjunctive nutrient management treatments, the application of 2 t Gliricidia loppings + 20 kg nitrogen (N) through urea to sorghum crop recorded significantly highest grain yield of 1712 kg ha−1 followed by application of 4 t compost + 20 kg N through urea (1650 kg ha−1) as well as 40 kg N through urea alone (1594 kg ha−1). Similar to sorghum, in case of mung bean also, CT exhibited a significant influence on mung bean grain yields (888 kg ha−1) which was 6.7% higher compared to MT (832 kg ha−1). Among all the conjunctive nutrient management treatments, 2 t compost + 10 kg N through urea and 2 t compost + 1 t Gliricidia loppings performed significantly well and recorded similar mung bean grain yields of 960 kg ha−1 followed by 1 t Gliricidia loppings + 10 kg N through urea (930 kg ha−1). The soil nitrogen chemical fractions (SNCFs) were also found to be significantly influenced by tillage and conjunctive nutrient management treatments. Further, a significant correlation of SNCF with total soil nitrogen was observed. In the correlation study, it was also observed that N fraction dynamically played an important role in enhancing the availability pool of N in soil and significantly influenced the yield of sorghum grain and mung bean.

Water Absorption and Release Characteristics of a Polymer and its Effect on Available Water Content, Tomato (Lycopersicon esculentum) Productivity and Water Use Efficiency in a Semi-arid Sandy Loam Soil

The problem of inefficient use of rain and irrigation water by crops is most important on light textured soils of semi-arid and arid regions. Application of super absorbent polymers into the soil could be one of the effective ways to increase water use efficiency in crops. Therefore, laboratory and field investigations have been conducted to study water retention and release characteristics of a cross linked polymer of polyacrylamide and potassium acrylate (PAM) and to evaluate its effect on yield and water productivity in tomato grown on sandy loam soil under field conditions. In laboratory studies, irrespective of source of water, polymer showed rapid initial hydration followed by no more water absorption towards the point of equilibrium. Overall, the amount of water absorbed by one gram of polymer ranged from 247–369 g in distilled water, 141–175 g in 50% Hoagland solution, 120–155 g in irrigation water, 116–141 g in 100% Hoagland solution, 96–115 g in 0.01 M CaCl2 and 86–111 g in 200% Hoagland solution over 5–240 min saturation period. The amount of water absorbed by polymer decreased from 360 to 110 g g−1 with increasing electrical conductivity (EC) of the source of water from 0.03 to 2.23 dS m−1. Application of polymer at graded rates (0.25–1.0% of soil, w/w) to sandy loam and sandy clay loam soils increased the available water content by 101–192 per cent as compared to untreated soils. In field experiment, at every week irrigation, application of polymer @ 25 or 50 kg ha−1 had no significant effect on tomato plant height and fruit yield. Similarly, application of polymer had no significant effect on plant height and fruit yield when tomato was irrigated every third week. But application of polymer at 25 kg ha−1 with alternate week irrigation not only produced the higher tomato yield but also increased the water productivity to 290.6 kg ha-mm−1 and thereby saved 180 ha-mm irrigation waters during a crop growth season.

Effects of Conjunctive Nutrient Management on Soil Fertility and Overall Soil Quality Index in Submountainous Inceptisol Soils under Rainfed Maize (Zea mays L.)–Wheat (Triticum aestivum) System

The present long-term study was initiated to quantify the long-term effects of conjunctive nutrient management on soil quality, identify key indicators, and assess soil quality indices under a rainfed maize–wheat system in marginal Inceptisol soils in India. Results of the study revealed that soil organic carbon was significantly influenced by the conjunctive nutrient-management treatments. Among the nine treatments, the application of 100% recommended dose of nitrogen (RDN) (80 kg N ha−1), 15 kg N (compost) + 20 kg N ha−1 (inorganic), 25 kg N (compost), and 15 kg N (compost) + 10 kg N ha−1 (green leaf) resulted in greater organic carbon contents of 5.57, 5.32, 5.27, and 5.26 g kg−1, which were greater by 29.5%, 24%, 23%, and 22%, respectively, over the control. The greatest soil quality index (1.61) was observed with application of 25 kg nitrogen (N; compost) as well as with application of 15 kg N (compost) + 10 kg N ha−1 (green leaf). The order of percentage contribution of key indicators toward soil quality indices was available potassium (K) (34%) > available phosphorus (P) (32%) > available N (13%) > microbial biomass carbon (12%) > exchangeable calcium (Ca) (9%). The linear regression equation revealed the principal role of soil quality indicators in maize crop yield. The methodology and the results of the study could be of great relevance in improving and assessing soil quality not only for the study locations but also for other climatically and edaphically identical regions across the world.