The effects of repeated soil wetting and drying on lowland rice yield with system of Rice Intensification (SRI) methods
International Journal of Agricultural Sustainability
In lowland rice farming, water control is the most important management practice that determines the efficacy of other production inputs such as nutrients, herbicides, pesticides, farm machines, microbial activity, mineralization rate, etc. Poor drainage that keeps soil saturated is detrimental to crops and degrades soil quality. In many rice irrigation systems, drainage mechanisms and practices are dysfunctional or inadequate because farmers believe that rice grows best when water is supplied
... n abundance. Rice fields are therefore kept continuously flooded and are drained only at time of harvest. This practice is not only wasteful, but also leads to leaching of soluble nutrients, blocks soil microbial activities, and slows down mineralization and nutrient release from the soil complexes. The natural nitrogen supply for plants and microorganisms results principally from the mineralization of organic nitrogen compounds. The water management practices proposed for the System of Rice Intensification (SRI), cycles of repeated wetting and drying, were found to be beneficial to rice plant growth through increased nutrient availability leading ultimately to higher grain yields. The phenomenon of having a large flush of nitrogen mineralization occurring after rewetting of dry soil was first reported by Birch in 1958. This intensive pathway of nitrogen mineralization and nitrogen availability has potential to increase lowland rice yields. In a series of lowland rice experiments conducted in a semiarid region of Africa, repeated wetting and drying increased grain yields by up to three hundred percent in comparison with continuous flooding.