A review of agricultural research issues raised by the system of rice intensification (SRI) from Madagascar: opportunities for improving farming systems for resource-poor farmers

The system of rice intensification (SRI) originated in Madagascar and was first synthesized in 1983 by Father Henri de Laulanı́e, a French Jesuit priest. Under the drought conditions of that year, he experimented serendipitously with transplanting very young seedlings of only 15 days old. To everyone’s surprise, the yields surpassed all expectations and in subsequent years reliable yields, ranging from 7 to 15 t/ha, were obtained by small farmers cultivating soils with low inherent fertility, using much reduced irrigation rates, and no mineral fertilizers or other agricultural chemicals. The average national yields remained about 2 t/ha. In the last 2 years some development-oriented organizations have successfully repeated this method in half a dozen Asian countries.

Until recently, few agricultural research scientists have shown an interest in understanding how SRI works. Scepticism is understandable, as SRI practices differ greatly from what have been understood to be the optimum conditions and techniques for rice cultivation. Moreover, SRI depends on neither of the two pillars of the crop-improvement paradigm of the Green Revolution: varietal improvement, and external inputs.

This has prompted us to make a critical review of the possible mechanisms that may be involved in SRI. Within the context of integrated crop management systems, the SRI case indicates how synergies may contribute to a shift in what have been considered agronomic “yield ceilings”. This paper considers:

• 1.the growth and development processes of the rice plant, particularly the interdependence between tillering and root growth, and how this enhances grain formation;
• 2.how these processes may be affected by environmental factors such as temperature, light intensity, day length, humidity, soil moisture and aeration, and plant nutrient availability; and
• 3.how the various agronomic management practices, when taken together, can benefit the development and yield of a rice crop through synergistic effects.

The crops’ microenvironment will be crucially influenced by the agronomic management practices, setting in motion important interactions. For example, the water management regime will affect soil aeration, the soil microbial communities, the organic matter mineralization process, and as a result the dynamics and availability of soil nutrients. It will also affect the build-up of various insect pests, diseases and weeds.

In view of the large diversity in the world’s rice production systems, SRI first needs to be understood in terms of a set of principles and a set of mostly bio-physical mechanisms that should be tested under a range of different agro-ecological environments. On-farm participatory research following a farming-systems approach would be required to validate the practical relevance and risks of SRI practices, before any attempts are made to promote their integration into specific production systems.

This review has identified several fundamental gaps in present rice production knowledge. Subsequently, a number of research hypotheses are formulated through which SRI could be validated or discounted, and which would define the conditions under which it might be applied successfully. Resolving these issues would contribute to improved input-use efficiency and factor productivity for farmers; likewise the detrimental effects of a high external-input, “modern” agriculture on the environment and on the health of both producers and consumers could be reduced. Understanding SRI dynamics thus may provide insights into better ways of growing rice as well as other crops. As such it would contribute towards realising a future agriculture, as envisioned by Bonte-Friendheim and Kassma, 1994a, Bonte-Friedheim and Kassam, 1994b, that is more sustainable, more profitable and in greater harmony with nature than is presently the case.

read more here: https://www.sciencedirect.com/science/article/abs/pii/S0308521X01000701