Conservation agriculture in dryland ecosystem: Prospects and opportunities

Abstract

Conservation agriculture (CA) comprises zero or reduced or minimum tillage, crop–residue retention and crop rotation which offers an alternative sustainable system to conventional tillage (CT) without crop–residue retention or with residue burning. The literature available on CA in rainfed dryland areas has been reviewed critically with a particular reference to India. Unlike irrigated systems, very limited research work has been done on CA in rainfed areas. In majority of studies under rainfed conditions, zero tillage (ZT) or reduced tillage (RT) or minimum tillage (MT) resulted in lower mean crop yield as compared to CT after 4–15 years of experimentation on Alfisols, Vertisols and Inceptisols. The reduction in yield under ZT/ MT/ RT was probably due to less infiltration of water and poor root growth owing to compact surface and sub–surface and higher weed growth. The quantity of crop–residue retained in rainfed crop rotations was not sufficient to improve the performance of MT in highly degraded, very shallow and poor–fertile soils. The review further indicated that retention of 4–6 t/ha crop–residue under MT resulted in higher yields of sorghum [Sorghum bicolor (L.) Moench]–cowpea [Vigna unguiculata (L.) Walp.] rotation throughout the experimentation. Undoubtedly, ZT or RT or MT with retention of residue at any rate maintained better soil physical, chemical and biological quality and higher organic C pool, nutrient pool and their availability. Therefore, under rainfed conditions, MT or RT with higher dose of N application or soil–moisture conservation intervention with desired limits of soil disturbance was found to be a viable option to produce sufficient quantities of crop–residue to retain and sustain higher crop yields while maintaining better soil quality. Very limited on–farm trials were conducted to evaluate CA practices on farmers’ fields in rainfed areas. Therefore, packaging efficient practices of different components of location–specific CA such as tillage level, zero till planter–cum–herbicide applicators, and weed, nutrient and pest management for validating on farmers’ fields in different rainfed crop rotations should be the major focus in future.