The effects of growing Jatropha in on-farm and on-station degraded lands were evaluated on carbon (C) sequestration and soil properties. Jatropha accumulated and added to soil significant amounts of C (305 kg ha −1 year −1) from the year one itself. Overall, a 3-5-year old plantation added per year around 4000 kg plant biomass equivalent to 1450 kg C ha −1-800 kg C through leaves, 150 kg C through pruned twigs, and 495 kg C as deoiled Jatropha cake. Biodiesel C replacement in the fossil fuel was 230 kg ha −1. Besides adding biomass to the soil, and C replacement in fossil fuel; the standing Jatropha rendered ecosystem service by fixing 5100-6100 kg ha −1 C as the aboveground plus belowground biomass. Carbon additions by Jatropha during 4 years increased C content in the degraded surface soil layer by 19%, resulting in about 2500 kg ha −1 C sequestered. Huge C additions and live root activity under Jatropha increased microbial population, respiration rate and microbial biomass C and N in soil. Along with C additions, 4000 kg ha −1 year −1 plant biomass recycled into the soil 85.5 kg nitrogen, 7.67 kg phosphorus, 43.9 kg potassium, 5.20 kg sulphur, 0.11 kg boron, 0.12 kg zinc and other nutrients. The C additions improved water holding capacity of the soil under Jatropha as compared with the adjacent control soil which increased by 35% at 30 kPa and 21% at 1500 kPa soil water potential.
Soil degradation in the semi-arid tropics (SAT) is mainly responsible for low crop and water productivity. In Madhya Pradesh and Rajasthan states in India, the soil analyses of farmers' fields revealed widespread deficiencies of S (9-96%), B (17-100%) and Zn (22-97%) along with that of P (25-92%). Soil organic C was deficient in 7-84% fields indicating specifically N deficiencies and poor soil health in general. During on-farm evaluations in rainy seasons 2010 and 2011, the soil test based addition of deficient nutrient fertilizers as balanced nutrition (BN) increased crop yields by 6-40% (benefit to cost ratios of 0.81-4.28) through enhanced rainwater use efficiency. The integrated nutrient management (INM), however, decreased the use of chemical fertilizers in BN by up to 50% through on-farm produced vermicompost and recorded yields at par or more than BN with far better benefit to cost ratios (2.26-10.2). Soybean grain S and Zn contents improved with INM. Applied S, B, Zn and vermicompost showed residual benefits as increased crop yields for succeeding three seasons. Hence, results showed INM/BN was economically beneficial for producing more food, while leading to resilience building of SAT production systems.
In dryland tropics, integrated watershed management approach enabled farmers to diversify the systems along with increasing agricultural productivity through increased water availability, while conserving the natural resource base. Household incomes increased substantially, leading to improved living and building the resilience of the community and natural resources.
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Widespread multinutrient deficiencies in the semi-arid tropics (SAT) are among major factors for large gaps between farmers' current crop yields and potential yields. In this study, we adopted a stratified soil sampling method to assess soil fertility-related constraints in farmers' fields in eight districts of Andhra Pradesh in the semi-arid tropics of India. Most of the fields across all eight districts were critical in sulfur (61%-98% deficient fields); and up to six districts each in boron (83%-98% deficient fields), zinc (50-85% deficient fields), and soil organic carbon (55-97% deficient fields). Low soil organic carbon specifically indicates nitrogen deficiency. Phosphorus deficiency was critical in three districts (60-84%) while potassium in general was adequate. Soil test-based nutrient balancing through the application of sulfur, boron, and zinc in addition to farmers' practice of adding only nitrogen, phosphorus, and potassium increased crop productivity by 8%-102%. Benefit-cost ratio (1.60-28.5) proved favourable to scale-up balanced nutrition. Better post-harvest soil health and residual benefits of sulfur, boron, and zinc up to four succeeding seasons indicated sustainability of the practice. Results showed that balanced nutrition is a way forward for sustainably improving farm productivity and livelihoods.
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