Research opportunities to improve nutrient-use efficiency in rice cropping systems

This is a summary of discussions and conclusions from a workshop on nutrient-use efficiency of rice cropping systems, held 13-15 December 1995 at the International Rice Research Institute, Los Banos, Philippines [Field Crops Research, Special Issue, 1998]. Workshop participants reviewed current research in crop management and genetic improvement of rice, and concluded that increased rice production will depend on explicit considerations of nutrient supply. For intensive irrigated rice systems, research priorities include understanding how soil nutrient supply is linked to cropping intensity, what pattern of nutrient supply is required to achieve the high yield levels needed to meet the needs of rice consumers in the next century, and how to improve congruence of nutrient supply and crop demand through management. In rainfed environments, nutrient demand is closely linked to water availability, and participants saw a need to characterize environments according to the different patterns of resource Limitations. Soil and climate databases will be important in this effort. An explicit conceptual framework must underlie field work in these variable environments, and simple simulation models were identified as essential tools for targeting experiments and pre-testing improved technologies. Cultivar improvement for efficient nutrient use can complement agronomic approaches. The potential gains in improved nutrient acquisition and/or improved physiological efficiency are not clear for all nutrients, and these need to be estimated in order to set breeding priorities. Improved screening techniques related to specific mechanisms of nutrient efficiency will facilitate genetic improvement. Promising research approaches are described to address each of these constraints to improving nutrient-use efficiency in rice. (C) 1998 Elsevier Science B.V.