Green manure production systems for Asian ricelands

Progress in adapting green manures (GMs) to Asia’s changing rice production systems has been limited. Recent research has concentrated on the soil fertility implications of GMs, neglecting the socioeconomic and agronomic aspects that ultimately determine the feasibility and cost effectiveness of GM systems. Recogni- tion, holistic evaluation, and extrapolation of areas where GMs have a comparative advantage over mineral fertilizer or other nonrice crops are needed. This paper reviews the strategy for including GMs in rice farming systems and develops a framework for analyzing the fit of soil-improving legumes across a range of ecological niches. Macroeconomic factors, such as oil prices and national policy, set the general framework. Other important factors determining the specific adaptation of GMs are the socioeconomic environment, farm-level economic and biophysical conditions, and availability of appropriate GM species and production technology. The prognosis for soil-improving legumes is seen to follow two key possibilities: 1) multiple-use solutions where the GM also provides grain, fodder, or fuel; and 2) specificity of GMs to well-defined niches within the cropping system. Agronomic research in the hitherto neglected areas of species improvement, seed production, crop establishment, and pest management may expand the options for GMs in all niches. The complexity and scale of the work require an international research effort that provides leadership, stimulates coordinated work, and involves sharing priority responsibilities among participating research institutions.

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