Do System of Rice Intensification Practices Produce Rice Plants Phenotypically and Physiologically Superior to Conventional Practice?

The System of Rice Intensification (SRI), an agro-ecological approach to rice cultivation developed in Madagascar, has generated considerable interest worldwide. Having not been developed at a research establishment but rather from observation and testing on farmers' fields, SRI attracted considerable controversy, for example, with unwarranted objections that it lacked of scientific evidence, and being characterized as based on 'unconfirmed field observations' (UFOs). One 2004 article concluded that "the system of rice intensification does not fundamentally change the physiological yield potential of rice". This assertion was not based on any physiological examination of rice plants grown using SRI methodology, however, or on any systematic comparison with what would be considered as best management practices (BMPs), recommended practices (RPs), or farmer practices (FPs). Other dismissals of SRI have had contestable data selection, analytical methods, and presentation of results. The published literature provides abundant evidence that the earlier evaluations of SRI were either not well-informed or objective, and possibly, they discouraged others from embarking on systematic evaluations of their own. This article examines the results of 78 studies in the published literature where SRI results were explicitly compared with RPs, including BMPs or FPs. The results from 27 countries, plus several large-scale evaluations, show that in 80% of the evaluations, grain yield was higher under SRI than with RPs or FPs. SRI gave 24% higher grain yield than RPs and 56% more than FPs, while reducing seed, water, and fertilizer inputs. Beyond the descriptive evidence, this paper considers that the phenotypical changes and physiological improvements in SRI-grown rice plants could account for the reported enhancement in yield. More research remains to be undertaken to elucidate casual mechanisms, but abundant evidence shows that this is a subject deserving considerable scientific effort.