How extensive are yield declines in long-term rice-wheat experiments in Asia /

Yield stagnation has set in the rice-wheat system in all the LTEs and decline in some LTEs,
particularly in rice. It is difficult to attribute any single reason for this decline. The reasons
may be more location-specific. Depletion in soil nutrients, reduced availability of P, delay in
planting, decrease in solar radiation and higher temperatures may be the causes of the
decline in some locations. Depletion of soil K seems to be a general cause.
The main bottleneck in the identification of specific reasons for declining yield trends can
only be identified if historical soil and plant samples are available for analysis. Therefore,
more detailed data collection and archives of soil and plant samples should be determined
to find out this cause-and-effect relationship.
􀁺 Greater stability in wheat yields does not mean conditions are favorable for wheat.
Yields are still below potential.
􀁺 Assessment of pest and disease pressures and interactions with nutrient management is
essential.
􀁺 Greater attention should be given to the role of organic matter in rice-wheat system.
􀁺 New experiments to assess long-term effects of zero-tillage and reduced tillage
practices are required to probe further to this phenomenon.
􀁺 Accurate assessment of nutrient budgets is required. Non-nutritional benefits of some
of the nutrients need further study.
􀁺 More experiments with residue management are needed.