Farm Table says:
Rice-wheat rotation is the principal agricultural production system in South Asian countries. This system occupies around 13.5 million ha in the Indo-Gangetic plains of Bangladesh, India, Nepal, and Pakistan, and 10.5 million ha in China. The sustainability of the rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotation is important to Asia’s food security.
The purpose of the study was to document the adverse effects and long-term management strategies of WS, GM, FYM, or FYM and urea N on crop yields, nutrient balances, and soil properties as they relate to the sustainability of the rice-wheat cropping system.
Discussion of Result:
The study demonstrated that rice yields and N-use efficiency decreased with wheat straw incorporation when compared with straw removal. Wheat straw can be incorporated concurrently with GM with no adverse effects on rice yields. Nitrogen from green manure and urea was equally efficient in increasing yield and N-use efficiency in rice. Organic manuring with farmyard manure plus green manure without the application of any inorganic fertilizers proved quite effective in producing high rice yields. The regular incorporation of crop residues and FYM increased (though at a slow rate) SOM contents. Though the available K supply may be maintained from the nonexchangeable soil pools and from irrigation water for some time, a reduced supply of K will eventually occur due to a K deficiency.
The results clearly reveal that current fertilizer recommendations for P and K are inadequate in the long run The total input of N, P, and K should be optimal to ensure a sufficient nutrient supply for higher yields. Rice yields in this long-term rice-wheat experiment declined with the application of urea as well as organic materials. These data seem to rule out the possibility of a decline in SOM as a reason for negative yield trends.
The adverse changes in climatic parameters along with a decreased soil supply of available K may be the possible reasons associated with the yield decline. The effect of decreased soil K supply as a result of large negative K balance on yield decline was, however, not apparent in the present study. Wheat yields were more stable during 1988–2000.
Further studies are needed to understand the causes of yield decline in a rice-wheat system. Regular monitoring of climatic factors would help in predicting problems in achieving high yields and allow measures to be taken to improve productivity.