Healthy Soil – A Key to Resilient Agricultural System

–Chinmoy Kumar Sarma

Based on past experience, the impact of climate change on agriculture is going to be one of the major deciding factors which will influence the food security of mankind in future. Agriculture is not only responsive to climate change but also one of the major drivers for climate change. Impacts of climate change on agriculture have been experienced all over the globe. Changes in mean rainfall and temperate as well as the increase in extreme weather events affect agriculture, livestock, forestry as well as fisheries. The Intergovernmental Panel on Climate Change (IPCC) predicted that during the next decades, billions of people, particularly those in developing countries, will face changes in rainfall patterns that will contribute to severe water shortages or flooding, rising temperature that will cause shifts in crop growing seasons (F.A.O., 2008).

Agricultural practices are the key determinants of the level of food production and are mainly responsible for the status of our environment. Unfortunately, most of these practices, like using higher doses of inorganic fertilizers and other chemicals, that guarantee higher yields are not environment-friendly and sustainable and thus, luxuriant use of farm inputs poses a great threat to our environment. At present, soil health poses a serious threat to agricultural production and farm profit. Decreased soil fertility and organic matter content, loss of soil structure, loss of soil through wind and water erosion, development of acidic, saline and sodic soils, and soil contamination with pesticide residues and heavy metals are some major issues which are often linked to soil degradation. Indiscriminate use of N fertilizers aggravates soil fertility depletion, and proves detrimental in terms of low nutrient use efficiency, poor quality of produce, enhanced susceptibility of crops to biotic and abiotic stresses, and a potential threat of groundwater pollution due to excessive leaching of nitrates beyond effective root zone.

Building resilience in soil is vital for crop production under changing climate and soil health is the key property that determines the resilience. Building up of soil organic carbon, controlling soil loses due to erosion and improving water holding capacity of soil enhance resilience in soil. Climate variability manifests in terms of deficit or excess water, so water saving technologies like direct-seeded rice, zero tillage and other resource conservation practices should be promoted which also reduce GHG emissions besides saving of water. Rainwater harvesting and recycling through farm ponds, percolation tanks/ponds for recharging open wells, bore wells and ground water are some important management practices for enhancing farm level water storage in rain fed/dry land areas.

A healthy soil has the ability to perform or function according to its potential and soil health can be improved by proper management practices and land-use decisions that consider the multiple functions of soil and that take into account that soil is a living entity. Soil health ailments could be effectively addressed though judicious management for improving chemical, physical and biological properties of soil. Precision nutrient management (PNM), on the other hand, ensures a better synchrony between nutrient supply and crop demand which involves assessment of soil fertility variation and suggesting nutrient prescriptions following the principle of 4R (right rate, right source, right time and right method). Soil Testing for Soil Health Monitoring is very much crucial to assess the soil fertility status and also gives an appraisal of soil problems and nutrient availability. Site-specific nutrient management (SSNM) is a field-specific management of nutrients to increase profit through high yield and enhanced nutrient use efficiency. Apart from soil test based prescriptions, plant analysis-based SSNM approach would help move towards greater accuracy. Soil organic matter (SOM) is the epicentre of soil health. It serves as soil conditioner, nutrient source, substrate to soil microbes, preserver of environment and a major determinant for sustaining agricultural productivity. Farm Yard Manure (FYM), compost, vermicompost, green manuring, crop residues, etc. are some important sources of organic matter which improve soil health. Skipping fertilizer input altogether or imbalanced use often caused a decline in soil organic carbon, obviously due to poor yield and lesser quantity of biomass incorporation. Combining use of fertilizers and organic manure maintained invariably higher soil organic carbon levels compared with fertilizer alone. Practice of using one or more sources of plant nutrients such as bulky and concentrated organic manures, legumes, crop residues/wastes, industrial by-products, municipal solid wastes and bio- fertilizers etc. along with chemical fertilizers often leads to improvement of soil health for sustaining crop productivity on long-term basis. Management of problem soils like acid soil, saline soil, sodic soil, waterlogged soil etc. should aim at realization of production potential either by addition of amendments or manipulation of agricultural practices to enhance nutrient use efficiency and crop yields. Physical environment of soil can be manipulated by proper tillage practice at right time to produce as favourable habitat as possible for successful crop production. Conservation agriculture (CA) is a production system involving minimum soil disturbance, soil cover through crop residues or other cover crops and crop rotations for achieving high productivity with most efficient resource use. Crop residue management has emerged as a major challenge in recent years, especially in machine-harvested areas. In absence of viable alternatives, farmers opt for residue burning, thus losing precious nutrients and causing severe environmental problems. Whereas technologies for faster in situ decomposition of residues need to be perfected, equally important is to incentivize residue retention by way of subsidizing conservation agriculture machinery and promoting custom hiring services to facilitate large-scale use of machinery. Initiation of community-level ‘waste-to-wealth’ model of composting will be helpful for efficient utilization of on-farm and off-farm by-products and wastes in rural areas which can contribute to soil health improvement.