K. L. Sharma

Green manuring: its effect on soil properties and crop growth under rice–wheat cropping system

Abstract A field experiment was conducted on rice ( Oryza sativa L.) and wheat ( Triticum aestivum L.) during rainy and winter seasons of 1994–95 in a clay loam soil (Typic Ustochrept) at the experimental farm of Indian Agricultural Research Institute, New Delhi, India. The objectives were to study the influence of different green manuring ( Sesbania rostrata, Sesbania aculeata , green gram ( Vigna radiata ) residues) and in combination with different levels of nitrogen (0, 60, and 120 kgxa0Nxa0ha −1 ) on physical properties, organic matter and total nitrogen contents of soil and on root growth and spectral response of rice and wheat crop. The organic matter and total soil nitrogen concentrations were found to be higher under green manuring treated plots than summer fallow. The magnitude of reduction in bulk density due to green manuring over fallow was 0.03–0.07 Mgxa0m −3 in 0–15 cm soil layer and 0.05–0.09 Mgxa0m −3 in 15–30 cm soil layer during the growth of rice and wheat. Green manuring improved the soil physical environments as was evident from higher values of mean weight diameter and saturated hydraulic conductivity than fallow. The better physical and chemical environment in Sesbania ( S ) and green gram residue incorporated plots influenced higher Normalized Difference Vegetation Index (NDVI) than under fallow. The NDVI attained peak values at 62 days after transplanting of rice and 90 days after sowing of wheat. The root length density (RLD) and yields were higher in green manure plots than in fallow both in rice as well as in succeeding wheat crop. In all cases, in both rice and wheat the application of 120 kgxa0Nxa0ha −1 treatment resulted in higher RLD than 60 kgxa0Nxa0ha −1 and no nitrogen treatments. Poor soil conditions were mainly responsible for restricted root growth and its distribution in surface soil layer in summer fallow plots.

Assessing Soil Quality Under Long‐Term Rice‐Based Cropping System

Abstract Productivity of the rice‐based cropping system is low, and it continues to decline in India because of worsening soil‐related constraints. Keeping in view the importance of soil quality in rice‐based intensive cropping system, the present investigation was undertaken with the objective of identifying several biological, chemical, and physical indicators of soil quality using data collected from a long‐term experiment being conducted since 1972 on rice‐wheat‐jute cropping system in Indo Gangetic alluvial soils of India. The experiment was laid out in a randomized block design with five treatments, under long‐term fertilizer experiment [i.e., control (no fertilizer and manure); 100% of the recommended dose of nitrogen (100% N); 100% of the recommended dose of N and phosphorus (100% NP); 100% of the recommended dose of N, P, and potassium (100% NPK); and 100% of the recommended dose of N, P, K, and farm yard manure (100% NPK+FYM]. Soil samples were collected after the harvest of rice during the 2002 experiment and were analyzed for physical, chemical, and biological parameters. On the basis of the long‐term yield data, sustainable yield index was calculated. Multivariate statistical techniques were used to determine the smallest set of chemical, physical, and biological indicators that account for at least 95% of the variability in the total data set. The total soil N, available P, dehydrogenase activity, and mean weight diameter of the aggregates were the most important indicators in this case study. A multiple regression was run to evaluate the efficacy of minimum data set (MDS) taking sustainable yield index as goal (r2=0.69). Each MDS was transformed into score. The soil quality index (SQI) was calculated by using weighing factors derived from principal component analysis for each scored MDS variable. The highest SQI was found in 100% NPK+FYM treatment followed by 100% NPK, 100% NP, 100% N, and control treatment, respectively. To compare the soil aggradation or degradation, an undisturbed fallow soil was taken as reference, and it has been observed that 100% NPK+FYM and 100% NPK showed positive change in soil quality that is aggradation of soil quality, but the other three treatments, 100% N, 100% NP, and control, showed negative change of soil quality and indicates degradation of the system.

Evaluation of long-term soil management practices using key indicators and soil quality indices in a semi-arid tropical Alfisol

Alfisol soils of rainfed semi-arid tropics (SAT) are degrading due to several physical, chemical, and biological constraints. Appropriate soil-nutrient management practices may help to check further soil degradation. A long-term experiment comprising tillage and conjunctive nutrient use treatments under a sorghum (Sorghum bicolor (L.) Moench)–mung bean (Vigna radiata (L.) Wilkzec) system was conducted during 1998–05 on SAT Alfisols (Typic Haplustalf) at the Central Research Institute for Dryland Agriculture, Hyderabad. The study evaluated soil and nutrient management treatments for their long-term influence on soil quality using key indicators and soil quality indices (SQI). Of the 21 soil quality parameters considered for study, easily oxidisable N (KMnO4 oxidisable-N), DTPA extractable Zn and Cu, microbial biomass carbon (MBC), mean weight diameter (MWD) of soil aggregates, and hydraulic conductivity (HC) played a major role in influencing the soil quality and were designated as the key indicators of ‘soil quality’ for this system. The SQI obtained by the integration of key indicators varied from 0.66 (unamended control) to 0.83 (4u2009Mg compostu2009+u200920u2009kg N as urea) under conventional tillage (CT), and from 0.66 (control) to 0.89 (4u2009Mg compostu2009+u20092u2009Mg gliricidia loppings) under reduced tillage (RT). Tillage did not influence the SQI, whereas the conjunctive nutrient-use treatments had a significant effect. On an average, under both CT and RT, the sole organic treatment improved the soil quality by 31.8% over the control. The conjunctive nutrient-use treatments improved soil quality by 24.2–27.2%, and the sole inorganic treatment by 18.2% over the control. Statistically, the treatments improved soil quality in the following order: 4u2009Mg compostu2009+u20092u2009Mg gliricidia loppings > 2u2009Mg Gliricidia loppingsu2009+u200920u2009kg N as ureau2009=u20094u2009Mg compostu2009+u200920u2009kg N as urea > 40u2009kg N as urea. The percentage contribution of the key indicators towards the SQI was: MBC (28.5%), available N (28.6%), DTPA-Zn (25.3%), DTPA-Cu (8.6%), HC (6.1%), and MWD (2.9%). The functions predicting the changes in yield and sustainability yield index with a given change in SQI were also determined.

Influence of Soil and Fertilizer Nutrients on Sustainability of Rainfed Finger Millet Yield and Soil Fertility in Semi-arid Alfisols

Productivity of rainfed finger millet in semiarid tropical Alfisols is predominantly constrained by erratic rainfall, limited soil moisture, low soil fertility, and less fertilizer use by the poor farmers. In order to identify the efficient nutrient use treatment for ensuring higher yield, higher sustainability, and improved soil fertility, long term field experiments were conducted during 1984 to 2008 in a permanent site under rainfed semi-arid tropical Alfisol at Bangalore in Southern India. The experiment had two blocks—Farm Yard Manure (FYM) and Maize Residue (MR) with 5 fertilizer treatments, namely: control, FYM at 10 t ha−1, FYM at 10 t ha−1 + 50% NPK [nitrogen (N), phosphorus (P), potassium (K)], FYM at 10 t ha−1 + 100% NPK (50 kg N + 50 kg P + 25 kg K ha−1) and 100% NPK in FYM block; and control, MR at 5 t ha−1, MR at 5 t ha−1 + 50% NPK, MR at 5 t ha−1 + 100% NPK and 100% NPK in MR block. The treatments differed significantly from each other at p < 0.01 level of probability in influencing finger millet grain yield, soil N, P, and K in different years. Application of FYM at 10 t ha−1 + 100% NPK gave a significantly higher yield ranging from 1821 to 4552 kg ha−1 with a mean of 3167 kg ha−1 and variation of 22.7%, while application of maize residue at 5 t ha−1 + 100% NPK gave a yield of 593 to 4591 kg ha−1 with a mean of 2518 kg ha−1 and variation of 39.3% over years. In FYM block, FYM at 10 t ha−1 + 100% NPK gave a significantly higher organic carbon (0.45%), available N (204 kg ha−1), available P (68.6 kg ha−1), and available K (107 kg ha−1) over years. In maize residue block, application of MR at 5 t ha−1 + 100% NPK gave a significantly higher organic carbon (0.39%), available soil N (190 kg ha−1), available soil P (47.5 kg ha−1), and available soil K (86 kg ha−1). The regression model (1) of yield as a function of seasonal rainfall, organic carbon, and soil P and K nutrients gave a predictability in the range of 0.19 under FYM at 10 t ha−1 to 0.51 under 100% NPK in FYM block compared to 0.30 under 100% NPK to 0.67 under MR at 5 t ha−1 application in MR block. The regression model (2) of yield as a function of seasonal rainfall, soil N, P, and K nutrients gave a predictability in the range of 0.11 under FYM at 10 t ha−1 to 0.52 under 100% NPK in FYM block compared to 0.18 under MR at 5 t ha−1 + 50% NPK to 0.60 under MR at 5 t ha−1 application in MR block. An assessment of yield sustainability under different crop seasonal rainfall situations indicated that FYM at 10 t ha−1 + 100% NPK was efficient in FYM block with a maximum Sustainability Yield Index (SYI) of 41.4% in <500 mm, 64.7% in 500–750 mm, 60.2% in 750–1000 mm and 60.4% in 1000–1250 mm rainfall, while MR at 5 t ha−1 + 100% NPK was efficient with SYI of 29.6% in <500 mm, 50.2% in 500–750 mm, 40.6% in 750–1000 mm, and 39.7% in 1000–1250 mm rainfall in semi-arid Alfisols. Thus, the results obtained from these long term studies incurring huge expenditure provide very good conjunctive nutrient use options with good conformity for different rainfall situations of rainfed semiarid tropical Alfisol soils for ensuring higher finger millet yield, maintaining higher SYI, and maintaining improved soil fertility.

Influence of Tillage and Nutrient Sources on Yield Sustainability and Soil Quality under Sorghum–Mung Bean System in Rainfed Semi‐arid Tropics

The crop production in rainfed semi‐arid tropical (SAT) Alfisols is constrained by low soil organic matter, poor soil fertility, soil structural infirmities, and scarce moisture availability. To offset some of these constraints, a long‐term study of tillage [conventional (CT) and reduced (RT)] and conjunctive nutrient‐use treatments was conducted in SAT Alfisol at Hyderabad, India, under sorghum–mung bean system. The order of performance of the treatments in increasing the sorghum yield was 2 Mg gliricidia loppings + 20 kg nitrogen (N) through urea (T4) (93.2%) > 4 Mg compost + 20 kg N through urea (T3) (88.7%) > 40 kg N through urea (T2) (88.5%) > 4 Mg compost + 2 Mg gliricidia loppings (T5) (82.2%). In the case of mung bean, where half as much N was applied as was to the sorghum, the order of performance of the treatments in increasing the grain yields was T3 (63.6%) >T5 (60.3%) >T4 (58.0%) >T2 (49.6%). Tillage significantly influenced the hydraulic conductivity only, whereas the conjunctive nutrient‐use treatments significantly influenced the predominant physical, chemical, and biological soil‐quality parameters. Among the conjunctive nutrient‐use treatments, T5 was found to be superior in influencing the majority of the soil‐quality parameters and increased the organic carbon by 21.6%, available N by 24.5%, dehydrogenase activity by 56.1%, microbial biomass carbon by 38.8%, labile carbon by 20.3%, and microbial biomass nitrogen by 38.8% over the unamended control and proved superior most in improving soil quality.

Prediction of nitrogen availability in soil after crop residue incorporation

Controlled study was conducted with five farm-based organic residues to predict the expected nitrogen availability with time, based on N concentration and C/N ratio of the residues under two moisture availability situations. Two kg of red loamy sand soil representing Alfisol and related soil was incubated with the residues to supply 40 kg N ha−1 at 28 ± 1°C at field capacity (FC) and 50% FC moisture conditions. Results obtained indicated that N content in soil released from residues increased with the time allowed for decomposition reactions at both FC and 50% FC moisture regimes. Relatively higher amount of N release was observed in case of legume residues like mungbean (Vigna radiata),L. leucocephala and perennial pigeonpea (Cajanus cajan), although the rate of N release was more with low N concentration residues. Sorghum stover with C/N ratio of 72.1 resulted in immobilization of N upto 90 days. Nitrogen release was higher at FC than 50% FC. The critical N concentrations of the residues at which N neither released nor immobilized decreased with the length of incubation. At 50% FC the critical concentrations were higher than at FC.

Soil fertility and quality assessment under tree-, crop-, and pasture-based land-use systems in a rainfed environment.

A study was conducted to assess the long‐term impact of land‐use systems on soil physicochemical properties and chemical properties (exchangeable and total nutrients) and overall chemical soil quality in a rainfed Alfisol (Typic Haplustalf) representing the semi‐arid tropical region at Hayathnagar Research Farm of the Central Research Institute for Dryland Agriculture, Hyderabad, India, situated at 17° 18′ N latitude, 78° 36′ E longitude with an elevation of 515 m above mean sea level. Four, 10‐year‐old land‐use systems were adopted for this study. Soil samples were collected from 12 soil profiles (4 systems × 3 replications) from depths of 0–0.05, 0.05–0.15, 0.15–0.30, and 0.30–0.60 m. Study revealed that physicochemical properties such as pH, electrical conductivity (EC), cation exchange capacity (CEC), and organic carbon (OC) were significantly influenced by the land‐use systems. Among the land‐use systems, agroforestry system resulted in the highest pH (7.5), CEC (13.6 cmol kg−1), and organic carbon (C) content (9.6 g kg−1). Exchangeable nutrient cations [calcium (Ca), magnesium (Mg), and sodium (Na)] and total nutrients [nitrogen (N), phosphorus (P), potassium (K), Ca, Mg, copper (Cu), manganese (Mn), zinc (Zn), and iron (Fe)] were also significantly influenced by land‐use systems. The greatest Ca content was found (7.4 c mol kg−1) in arable land system, whereas greatest Mg content (4.7 c mol kg−1) was found in the agroforestry system. Total N content was greatest (607.5 mg kg−1) in the pastoral system and decreased with soil depth. Total P content varied from 473.5 mg kg−1 in arable land to 880.0 mg kg−1 in the pastoral system and decreased with depth. The effect of land‐use systems on total hydrolyzable‐N pool was significant only up to the 0‐ to 0.15‐m soil depth. Despite being statistically nonsignificant, the agroforestry system recorded greater humic acid (12.8%) and fulvic acid (7.9%) contents than the agrihorticultural system. Chemical soil quality index (CSQI) varied from 0.76 in arable land to 0.92 in the agroforestry system. From the viewpoint of aggradation of soil chemical quality, the agroforestry system (CSQI: 0.92) was most superior, followed by the agrihorticultural system (CSQI: 0.86) and pastoral system (CSQI: 0.80).

Effect of Soil and Nutrient-Management Treatments on Soil Quality Indices under Cotton-Based Production System in Rainfed Semi-arid Tropical Vertisol

Rainfed semi-arid tropical Vertisols of the Indian subcontinent encounter many problems on account of the physical, chemical, and biological soil qualities and consequently have poor crop yields. To ensure sustainable crop production, there is a need to improve and periodically assess the quality of these soils by adopting suitable soil and nutrient-management practices on a long-term basis. Hence, soil quality assessment studies were conducted at the Central Research Institute for Dryland Agriculture, Hyderabad, India, by adopting an ongoing long-term experiment from Akola Centre (Maharashtra) of All-India Coordinated Research Project for Dryland Agriculture (AICRPDA) for the rainfed Vertisol. This long-term experiment was initiated in 1987 with six soil and nutrient management treatments: T1, control; T2, 50 kg nitrogen (N) + 25 kg phosphorus pentoxide (P2O5) ha−1; T3, 25 kg N ha−1 through leuceana; T4, 25 kg N ha−1 through farmyard manure (FYM); T5, 25 kg N + 25 kg P2O5 + 25 kg N ha−1 through FYM; and T6, 25 kg P2O5 ha−1 + 50 kg N ha−1 through leuceana under cotton + greengram intercropping (1:1). Out of the 19 soil quality parameters studied, significant influence of the soil and nutrient-management treatments was observed on almost all the parameters except exchangeable calcium (Ca), available iron (Fe), labile carbon (LC), and bulk density (BD). A standard methodology using principal component analysis (PCA) and linear scoring technique (LST) was adopted to identify the key indicators and for computation of soil quality indices. The various key soil quality indicators identified for these Vertisols under cotton + green gram system were pH, electrical conductivity (EC), organic carbon (OC), available K, exchangeable magnesium (Mg), dehydrogenase assay (DHA), and microbial biomass carbon (MBC). The soil quality indices as influenced by different long-term soil and nutrient-management treatments varied from 1.46 to 2.10. Among the treatments, the conjunctive use of 25 kg P2O5 ha−1 + 50 kg N ha−1 through leuceana green biomass (T6) maintained significantly higher soil quality index with a value of 2.10 followed by use of 25 kg N + 25 kg P2O5 + 25 kg N ha−1 through FYM (T5) (2.01). The order of percent contribution of these identified indicators to soil quality indices was OC (28%) > MBC (25%) > available K (24%) > EC (7%) > pH (6%) = DHA (6%) > exchangeable Mg (4%). Thus, the findings of the present study could be of immense use to the researchers, land managers, farmers, nongovernment organizations (NGOs) and other stakeholders for making periodical assessment of key indicators of soil quality, identifying the best soil and nutrient-management treatments and practices, and planning for improving soil quality to achieve higher productivity goals on a sustainable basis in rainfed semi-arid tropical Vertisol regions. The methodology of the study could also be useful for other rainfed semi-arid tropical Vertisol regions of the world.

Effect of Combined Use of Organic and Inorganic Sources of Nutrients on Sunflower Yield, Soil Fertility, and Overall Soil Quality in Rainfed Alfisol

Abstract To study the response of inorganic and organic nitrogen (N) sources both alone and in conjunction and their influence on soil quality, a field experiment was conducted during kharif and rabi seasons using sunflower (MSFH‐8) as test crop. The experimental site soil was Typic Haplustalf situated at Hayatnagar Research Farm of Central Research Institute of Dryland Agriculture, Hyderabad, India, at 17° 18′ N latitude, 78° 36′ E longitude. The experiment design was a simple randomized block design with 11 treatments replicated four times. Among all the treatments, vermicompost (VC)+Fert at 25+25 kg N ha−1 recorded the highest grain yields of 1878 and 2160 kg ha−1 during both kharif and rabi seasons, respectively, which were 43.9 and 85.1% higher than their respective control plots. Apparent N recovery varied from as little as 38.30% (FYM at 50 kg N ha−1) to 62.16 (25 kg N ha−1) during kharif and 49.65 (75 kg ha−1) to 83.28% (VC+Fert at 25+25 kg N ha−1) during rabi season. Conjunctive nutrient treatments proved quite superior to other set of treatments in improving the uptake of N, phosphorus (P), potassium (K), sulfur (S), and micronutrients in sunflower and their buildup in the soil. Highest relative soil quality indexes (RSQI) were observed under VC+Fert at 25+25 kg N ha−1 (1.00) followed by VC+Gly at 25+25 kg N ha−1 (0.87). Considering the yield and relative soil quality indices (RSQI), conjunctive applications of VC with either inorganic fertilizer, FYM, or Gly at 25+25 kg N ha−1 could be a successful and sustainable soil nutrient management practice in semi‐arid tropical Alfisols. Besides this, the fertilizer N demand could be reduced up to 50%.

Influence of fly ash mixtures on early tree growth and physicochemical properties of soil in semi-arid tropical Alfisols

The beneficial effects of planting mixtures comprising of fly ash at the rate of 66%, 33% and 17% by soil volume were assessed for the early growth of two economic tree species, teak (Tectona grandis) and leucaena (Leucaena leucocephala) in rainfed Semi-Arid Tropical (SAT) Alfisols in India. Measurements of tree growth were made at six monthly intervals over a 3-year period. Fly ash at 66% by soil volume of the planting pit significantly increased the diameter of teak at breast height (dbh). In leucaena, application of fly ash at 17% by soil volume was found to be effective in increasing dbh during most of the study period. Changes in soil physicochemical properties (bulk density, water retention at 0.033 and 1.5 MPa, profile moisture content, pH, soluble salt content and organic carbon) were simultaneously studied. Among these soil properties, plant available water (PAW) and organic carbon (OC) contents explained variations in diameter at breast height (dbh) in teak during most of the sampling period, while none of the soil properties significantly explained dbh in leucaena. The highest dose of fly ash applied (66% by volume) decreased bulk density (BD) and increased PAW in teak and to an extent in leucaena during the first 2 years of tree growth. Higher profile moisture content was noted in pits treated with 66% fly ash during the dry period of November (after the end of seasonal rainfall which occurred from June to October) during the first and second year after application.