Opportunities for ecological intensification: lessons and insights from the System of Rice/crop Intensification - their implications for agricultural research and development approaches.

A growing and increasingly urbanized global population will raise the pressures to intensify agricultural production systems, as the total surface area of arable lands remains constant or even diminishes in many parts of the world. Mainstream agricultural research and development have been emphasizing a 'green revolution' type intensification largely based on new seeds of crop varieties, while relying on agrochemicals to achieve short-term economic sustainability. During the 1980s the 'System of Rice Intensification (SRI)' was empirically developed in Madagascar. This set of practices was initially and widely rejected by mainstream (rice) research in spite of its often spectacular grain yields as obtained in farmer fields across many Asian and African countries. Some of the practices proved equally relevant for other crops such as wheat maize and sugarcane. SRI's popularity among Indian smallholders, originated from its attractive yields at reduced rates/costs for seeds, water, nutrients and chemicals (fertilizers and pesticides). These features have sparked research into both the agronomic/biological as well as socioeconomic/humanity disciplines. This paper seeks to capitalize on the lessons learned from SRI, also with respect to other crops, and explores additional opportunities for intensification based on ecological processes as supported by insights from (soil) microbiological, biochemical and molecular research. Recent studies suggest that soil organic matter, plant roots, soil biota and biodiversity of plants and (micro-) organisms - rather than agrochemicals - will be the critical elements of environment-friendly and sustainable forms of agriculture. To capitalize on these factors, large reductions in plant densities (>50%) would be required to allow expanded root systems as the basis for increased plant physiological efficiency. The paper elaborates also on the socioeconomic/cultural issues involved in possible transitions as farmer's technical/managerial skills and insights were crucial in the successful introduction and dissemination of SRI practices so far. The article is based on an extensive review of literature complemented by field observations and farmer interviews in different parts of India and West Africa.