T. Satish Kumar

Effects of Soil Management Practices on Key Soil Quality Indicators and Indices in Pearl Millet (Pennisetum americanum (L.) Leeke)–Based System in Hot Semi-arid Inceptisols

Rainfed Inceptisol soils, despite their agricultural potential, pose serious problems, including soil erosion, low fertility, nutrient imbalance, and low soil organic matter, and ultimately lead to poor soil quality. To address these constraints, two long-term experiments were initiated to study conservation agricultural practices, comprising conventional and low tillage as well as conjunctive use of organic and inorganic sources of nutrients in Inceptisol soils of Agra center of the All-India Coordinated Research Project for Dryland Agriculture (AICRPDA). The first experiment included tillage and nutrient-management practices, whereas the second studied only conjunctive nutrient-management practices. Both used pearl millet (Pennisetum americanum (L.) Linn) as test crop. These experiments were adopted for soil quality assessment studies at 4 and 8 years after their completion, respectively, at the Central Research Institute for Dryland Agriculture (CRIDA), Hyderabad, India. Soil quality assessment was done by identifying the key indicators using principal component analysis (PCA), linear scoring technique (LST), soil quality indices (SQI), and relative soil quality indices (RSQI). Results revealed that most of the soil quality parameters were significantly influenced by the management treatments in both the experiments. In experiment 1, soil quality indices varied from 0.86 to 1.08 across the treatments. Tillage as well as the nutrient-management treatments played a significant role in influencing the SQI. Among the tillage practices, low tillage with one interculture + weedicide application resulted in a greater soil quality index (0.98) followed by conventional tillage + one interculture (0.94), which was at par with low tillage + one interculture (0.93). Among the nutrient-management treatments, application of 100% organic sources of nutrients gave the greatest SQI of 1.05, whereas the other two practices of 50% nitrogen (N) (organic) + 50% (inorganic source) (0.92) and 100% N (inorganic source) (0.88) were statistically at par with each other. The various parameters that emerged as key soil quality indicators along with their percentage contributions toward SQI were organic carbon (17%), exchangeable calcium (Ca) (10%), available zinc (Zn) (9%), available copper (Cu) (6%), dehydrogenase assay (6%), microbial biomass carbon (25%) and mean weight diameter of soil aggregates (27%). In experiment 2, SQI varied from 2.33 to 3.47, and 50% urea + 50% farmyard manure (FYM) showed the greatest SQI of 3.47, which was at par with 100% RDF + 25 kg zinc sulfate (ZnSO4) (3.20). Under this set of treatments, the key soil quality indicators and their contributions to SQI were organic carbon (19%), available N (20%), exchangeable Ca (3%), available Zn (4%) and Cu (17%), labile carbon (20%), and mean weight diameter of soil aggregates (17%). The quantitative relationship established in this study between mean pearl millet yields (Y) and RSQI irrespective of the management treatments for both the experiments together could be quite useful to predict the yield quantitatively with respect to a given change in soil quality for these rainfed Inceptisols. The methodology used in this study is not only useful to these Inceptisols but can also be used for varying soil types, climate, and associated conditions elsewhere in the world.

Effect of Organic Manure and Crop Residue Based Long-Term Nutrient Management Systems on Soil Quality Changes under Sole Finger Millet (Eleusine coracana (L.) Gaertn.) and Groundnut (Arachis hypogaea L.) – Finger Millet Rotation in Rainfed Alfisol

ABSTRACT A long-term experiment was conducted to evaluate the effect of integrated use of organic and inorganic sources of nutrients on soil quality and its relation to finger millet yield under two predominant crop rotations viz., groundnut–finger millet and finger millet monocropping in hot moist semiarid rainfed Alfisol soils in South India. Two experiments were laid out separately for each cropping system in a randomized complete block design with five treatments individually with FYM and maize residue-based combinations viz., Control (T1), FYM @ 10t ha −1 or Maize residue (MR) @ 5t ha −1 (T2), farm yard manure (FYM) @ 10t ha −1 or Maize residue (MR) @ 5t ha −1 + 50% RDF (Recommended Fertiliser Dose) N, P2O5 & K2O (T3), FYM @ 10t ha −1 or Maize residue (MR) @ 5t ha −1 + 100% RDF N,P2O5 & K2O (T4), Recommended N, P2O5 & K2O (T5). Thus, four sets of nutrient management systems were evaluated. The results showed that farm yard manure or maize residue application in combination with recommended dose of fertilizer significantly improved the soil physical, chemical, and biological properties compared to control and application of inorganic fertilizers alone. Based on evaluation of 19 soil quality parameters under each of the four nutrient management systems, the common key soil quality indicators emerged out were: organic C (OC), available nitrogen (N), available sulfur (S), and mean weight diameter (MWD) of soil aggregates. A significant correlation between the finger millet yield and the relative soil quality indices (RSQI) indicates the importance of soil quality in these semiarid Alfisol soils. The results and the methodology adopted in the present study could be of importance in improving the soil quality not only for the region of the study, but also in other identical soils and cropping systems across the world.

Combined effect of tillage and organic fertilization on soil quality key indicators and indices in alluvial soils of Indo-Gangetic Plains under rainfed maize–wheat system

Inceptisols in the submountainous region of Indo-Gangetic Plains in India are known as low productive areas due to several constraints like decline in soil organic matter and fertility, deterioration of soil physical and biological properties. The present study was conducted with tillage as main treatments and integrated nutrient management as subtreatments to improve soil quality and to identify the key indicators of soil quality after 5 years of experimentation in maize–wheat cropping system at Ballowal Saunkhri. Conventional tillage (CT) + interculture (IC) maintained significantly higher soil quality indices (SQI) of 1.12 which was at par with 50% CT + IC + chemical weed control (CWC) (1.08). Application of nitrogen (N) through 50% (organic) + 50% (inorganic) maintained higher soil quality with SQI of 1.10 followed by application of 100% N through organics (1.08). The results indicated that reduction in the intensity of tillage to 50% with interculture practices and combined use of organic and inorganic fertilizers maintained higher soil quality in these degraded Inceptisols. The methods of principal component analysis and computation of SQI adopted will be highly useful to future researchers, land managers, and students at locations across the world having similar climatic and edaphic conditions.

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.

Effects of Conjunctive Use of Organic and Inorganic Sources of Nutrients on Soil Quality Indicators and Soil Quality Index in Sole Maize, Maize + Soybean, and Sole Soybean Cropping Systems in Hot Semi-arid Tropical Vertisol

The soils in the hot semi-arid tropical (SAT) regions generally have low organic matter and nutrient reserves. Soil-management problems in these soils primarily occur because of poor physical conditions and inadequate drainage through excess runoff, finally resulting in poor crop growth. Hence, the present investigation was conducted to study the long-term impact of conjunctive nutrient use treatments on soil quality indicators and soil quality indices under three cropping systems: (i) sole soybean, (ii) soybean + maize, and (iii) sole maize cropping systems at the Indore Centre of the All-India Coordinated Research Project for Dryland Agriculture (AICRPDA) using Navjot and JS-335 as cultivars of maize and soybean, respectively. In 2005, the soil quality assessment study under this experiment was undertaken after 8 years of experimentation. Soil quality assessment was done by identifying the key indicators using principal component analysis (PCA) and linear scoring technique (LST). Soil quality indices (SQI) and relative soil quality indices (RSQI) were also computed. Results revealed that most of the soil quality parameters were significantly influenced by the conjunctive nutrient management treatments. The common key indicators that emerged in all the treatments were pH, organic carbon (OC), exchangeable magnesium (Mg), available zinc (Zn), copper (Cu), manganese (Mn), and boron (B). The soil quality indices across the management treatments under sole maize system varied from 1.70 to 2.40 and application of 20 kg nitrogen (N) (compost) + 20 kg N through urea as top dressing emerged as a one of the most superior treatments with SQI value of 2.40. The soil quality indices in maize + soybean system varied from 1.12 to 1.47 and application of 20 kg N (compost) + 20 kg N through urea + azotobacter at 2 kg ha−1 proved to be significant with the greatest SQI value of 1.47. In the case of the sole soybean system, the SQI varied from 1.21 to 1.61. After considering all the systems together, the average best performance SQI score (ABP-SQI score) was computed, which varied from 1.14 to 1.56. The greatest value was recorded in the treatment with 20 kg N (compost) + 20 kg N (gliricidia) + 10 kg N (urea). The quantitative relationship developed in this study between mean soybean and maize yields (Y) and RSQI values (X), irrespective of the management treatments, could be quite useful to predict the yield quantitatively with respect to a given change in key indicators for these rainfed Vertisols.

Preparation of Niobium Metal Powder by Two-Stage Magnesium Vapor Reduction of Niobium Pentoxide

Magnesium vapor reduction of niobium pentoxide was studied using a laboratory system. Niobium powder was prepared by the magnesium vapor reduction at 1123 K for 5 hours and it contained about 8 mass % oxygen. However, the oxygen concentration could be decreased to 0.65% when it was prepared by double-step reduction by magnesium vapor and a chemical treatment. Controlled and diluted supply of magnesium vapor to the reaction front has averted excess heat generation at the reaction front and thereby fine particles were produced. Effects of various factors on the vapor reduction process were studied and discussed.

EFFECT OF LONG-TERM USE OF TILLAGE, RESIDUES AND N LEVELS IN SORGHUM ( SORGHUM VULGARE (L)) – CASTOR ( RICINUS COMMUNIS ) CROPPING SYSTEM UNDER RAINFED CONDITIONS – CROP RESPONSES AND ECONOMIC PERFORMANCE – PART I

This experiment was conducted to study the long-term effect of soil management treatments on crop yields, sustainability yield indices (SYI) and soil fertility in rainfed semi-arid tropical Alfisol at Hayathnagar Research Farm, Hyderabad, India, during the period 1995 to 2009. The experiment was conducted in a split–split plot design with conventional tillage (CT) and minimum tillage (MT) as main factors, surface application of sorghum stover @ 2 t ha −1 (SS), fresh Gliricidia loppings @ 2 t ha −1 (GL) and ‘no’ residue (NR) as sub-factors and levels of N viz. 0 (N 0 ), 30 (N 30 ), 60 (N 60 ) and 90 (N 90 ) kg N ha −1 as sub–sub factors in a castor–sorghum two-year rotation. On an average, CT maintained 30.4 and 57.0% higher grain yields of sorghum and castor, respectively, over MT. Between two residues, GL performed well in both the crops. The highest yields of sorghum (1425 kg ha −1 ) and castor (876 kg ha −1 ) were recorded at 90 kg N ha −1 . CT maintained higher SYI of 0.44 compared to MT (0.38) and higher agronomic efficiency (AE) of 13.5 and 6.76 kg grain kg −1 N for sorghum and castor crop, respectively. Use of crop residue as mulch had an advantage in increasing the yield of both the crops with increase in rainfall under CT even without N application (control), probably by making the soil more receptive to water infiltration, better moisture storage and by reducing the evaporative losses. Using response functions, the optimum fertilizer N requirement was also computed for a given set of tillage and residue combinations. The revised optimum fertilizer N doses for sorghum and castor varied from 45 to 56 kg ha −1 and 46 to 74 kg ha −1 , respectively, under different tillage and residue combinations and could be recommended depending upon the soil management practices.

Soil Quality Assessment under Restorative Soil Management Practices in Soybean (Glycine Max) after Six Years in Semi-Arid Tropical Black Lands of Central India

ABSTRACT Vertisol soils of central India are heavy in texture, with high clay content and low organic matter. These soils are prone to degradation and the soil loss is due to poor management practices including excessive tillage. Based on a long-term study conducted for improving the quality of these soils, it was found that management practice such as low tillage (LT) + 4 t ha−1 compost + herbicide (Hb) recorded significantly higher organic carbon (OC) (6.22 g kg−1) and available N (188.5 kg ha−1) compared to conventional tillage (CT) + recommended fertilizer (RF) + off-season tillage (OT) + hand weeding (HW) (OC: 4.71 g kg−1, available nitrogen (N) (159.3 kg ha−1). Among the physical soil quality parameters, mean weight diameter (MWD) was significantly higher under LT + 4 t ha−1 straw + Hb (0.59 mm). The practice of LT + 4 t ha−1 straw + HW recorded significantly higher microbial biomass carbon (MBC) (388.8 μg g−1). The order of key indicators and their contribution towards soil quality was as follows: OC (29%) >, MBC (27%) > available zinc (Zn) (22%) > MWD (9%) > available boron (B) (8%), > dehydrogenase activity (DHA) (5%). The order of the best treatment which maintained soil quality index (SQI) values reasonably good (>1.5) was as follows: LT + 4t ha−1 compost + HW (1.65) > LT + 4 t ha−1 compost +Hb (1.60) > LT + 4t ha−1 straw + HW (1.50). Hence, these treatments could be recommended to the farmers for maintaining higher soil quality in Vertisols under soybean system. Correlation studies revealed stronger relationship between key indicators like OC (R2 = 0.627), MBC (R2 = 0.884), available Zn (R2 = 0.739) and DHA (R2 = 0.604) with Relative Soil Quality Index (RSQI). The results of the present study would be highly useful to the researchers, farmers and land managers.

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.