Soil health and sustainability of the rice-wheat systems of the indo-gangetic plains

Abstract

The consecutive cropping of wheat after rice is one of the world’s principal agricultural production systems. This system is practised across an area of about 13 million hectares in South Asia and provides food, income and employment to over 200 million rural and urban producer and consumers. About 50 million farm families rely on this agricultural system for their subsistence. Typically in the region wheat is grown from November to April followed by rice during the monsoon from June-July to October-November. However, concerns have emerged regarding the sustainability of the rice-wheat systems. They are showing signs of stress and their sustainability is at risk, especially where there is a continuous rice-wheat rotation and system diversity is low. Problems include low water and nutrient use efficiency, groundwater depletion, water logging, poor water control, salinity and the build-up of weeds, pests and diseases. Yield stagnation and in some cases decline are reducing rural incomes and threatening food security in many areas. Many agricultural research institutions have worked to address these serious concerns. Much of this work has focused on developing resource conserving technologies (RCT) helping to produce cereals at a lower cost while attempting to improve soil health through reduced tillage and stubble retention. Pioneering work by the Govind Ballabh Pant University of Agriculture and Technology (Pantnagar), Haryana Agricultural University, the Rice-Wheat Consortium for the Indo-Gangetic Plains (RWC) and other research organisations have identified new tillage and crop establishment options for rice and wheat that address system ecology problems. These technologies mostly involve reducing tillage and are being widely and rapidly adopted by farmers across the Indo-Gangetic Plains in what has been described as a new green revolution. The Rice-Wheat Consortium has worked in close collaboration with South Asian National Agricultural Research Systems (NARS). These joint initiatives and participatory research involving scientists and farmers through several special projects have accelerated the adoption of the new and improved tillage methods. They include DFID CRF project (R6406) “Crop Establishment and Reduced Tillage Activities in the Rice-Wheat Systems in the Indo-Gangetic Plains” and DFID CRF funded project (R7259) “Harnessing Tillage by Nutrient Management Interactions using Participatory Approaches to Improve Rice-Wheat Systems Productivity and Sustainability”. Several kinds of these resource conserving technologies are being adopted according farmers’ needs and situations. In zero tillage, wheat seeds are drilled into unploughed fields which retain the residues from the rice crop. In reduced tillage, the seeds are surface sown onto rota-tilled soil using a two wheel power tiller or Chinese seed drill (CSD) a technique that is particularly suitable in smallholdings. The surface seeding of wheat into standing rice or after rice harvest has been long used by farmers in parts of South Asia where soil moisture is too high and hampers conventional tillage. These practices are overall referred to as resource conservation technologies (RCT) and form a basket of options to farmers. These practises offer a number of benefits. Farmers save on tillage costs and can sow their wheat, on average, two weeks earlier than under conventional tillage to give a longer growing season and thus more yield. The savings on production costs and increased yields are making an important contribution to livelihood improvement amongst small farmers. The technologies are also more sustainable as they use less energy and are more environmentally friendly. However, concern is being felt that the reduction in tillage and changes in soil physical conditions or crop residue management may be lead to a build up of soil borne pathogens or pests in the rice stubble. Tillage is traditionally seen as an important way of keeping crop pathogens in check. This could become particularly harmful to the many small and resource poor farmers who have adopted the new technology.