Managing Soil and Water Resources for Sustainable Intensification of Agroecosystems in India

摘要

Despite impressive increase in grain production and achieving food self-sufficiency since early 1970s, 250 million people in India are vulnerable to hunger and malnutrition. Yet, India is also endowed with vast land and water resources. The problem lies in low and variable crop yields, large yield gap between actual and attainable yields, low use efficiency of inputs (water, fertiliser, energy), degraded and depleted soils, and strong vulnerability of agriculture to changing and uncertain climate. The widespread problem of soil degradation is caused through accelerated erosion by water and wind, salinization, depletion of soil organic carbon (SOC), acidification, nutrient imbalance and mining by extractive farming, and lack of stewardship of natural resources. The SOC concentration in soils under continuous cropping may be <1g kg~(-1) in the root zone, leading to a low biodiversity and poor soil health. The interactive problems of degraded soils low and variable agronomic yields and polluted environment are being exacerbated by the historic and projected climate change. Enhancing and sustaining agronomic yields, and improving use efficiency of inputs necessitate increasing SOC stocks in the root zone, improving soil fertility, and enhancing soil health by restoring biodiversity. Plant nutrients harvested in produce and lost by erosion/ leaching must be replaced. While judicious use of chemical fertilisers is important, adopting the strategy of integrated nutrient management (INM) is crucial. The latter involves use of biofertilisers (compost, farmyard manure, Rhizobium, mycorrhizae) in combination with chemical fertilisers. Review of the data from long-term experiments indicates that best management practices (BMPs) include a combination of organic amendments (3-5 Mg C ha~(-1) yr~(-1)) with appropriate rates of chemicals fertilisers (NPK, micronutrients), cover cropping, conservation agriculture (CA) based on retention of crop residues, and silviculture/agroforestry systems. Food needs of the future populations must be met through sustainable intensification (SI) of agroecosystems. The goal is to produce more food from less land, water, fertilisers and energy by reducing losses and improving the use efficiency of inputs. Agriculturally marginal and degraded soils must be set aside for nature conservancy and carbon sequestration. There is a strong need for a paradigm shift. In addition to improved varieties, the focus must be on climate-smart agricultural systems (CSA). Rather than a cause of global warming, agriculture can be a solution through reduction of gaseous emissions and sequestration of atmospheric CO, in vegetation and soil. Any option of SI of agro-ecosystems is a triple-win strategy: it adapts/mitigates climate change, advances food and nutritional security, and improves the environment.