Productivity Trends in Intensive Rice-Wheat Cropping Systems in Asia

摘要

The rice—wheat system occupies 24 million ha in South Asia and China and is important for the food security of the region. Recently, concerns have been raised regarding the stagnation and, in some cases, decline in the productivity and sustainabilityof this system. To understand the productivity trends of the rice-wheat cropping system, we reviewed (i) yield trends in long-term experiments (LTE), (ii) trends in climatic constraints to the potential yield, and (iii) trends of on-farm yields. Gaps between climatic potential yields and on-station and on-farm yields were also estimated. Data showed that, in treatments in which the recommended rates of N, P, and K were applied, yields of rice and wheat declined in several LTE. In the rice-wheat system,particularly in the Indo-Gangetic Plains (IGP), rice yields tended to have more of a declining trend than wheat yields. There was also a negative trend in climatic potential yields of rice across a west-east transect of the IGP. On-farm yields of rice also showed mixed trends, with trends in some districts negative but positive in others. At the provincial level, yields have stagnated since 1990 in both Punjab and Haryana. However, the wheat yield trends were mostly positive. More detailed data collection and archives of soil and plant samples in the LTE and regular on-farm monitoring of crops and climatic factors are required to identify the specific cause of the yield decline and to develop suitable agronomic and soil management interventions for improving and sustaining productivity.