Comparing water input and water productivity of transplanted and direct-seeded rice production systems

Abstract

Increasing water scarcity threatens food production in irrigated rice systems in Asia. It is, therefore, important to identify rice production systems that require less irrigation water than traditional transplanted (TP) rice. This study investigated the effect of crop establishment methods on irrigation input and water productivity (weight of produce per unit volume of water used) in three irrigation service units (ISU) from 1988 to 1994 in the Muda Irrigation Scheme, Malaysia. Water balance components, crop establishment method, the progress of farming activities, and rice yield of individual farmers and over the whole ISU were monitored. Yields in TP ISU were higher than in wet-seeded (WS) ISU and those in WS ISU higher than in dry-seeded (DS) ISU, but the difference was significant ( P<5%) only between TP and DS ISU. Land preparation duration was significantly reduced in DS and WS ISU compared with TP ISU. This led to a significant reduction in irrigation and total water input (rainfall and irrigation) before crop establishment. However, during the crop growth period in the main field, TP ISU had a significantly shorter crop growth duration and total water input than DS and WS ISU. Over the whole crop season, the three crop establishment methods had a similar total water input, but DS ISU had significantly less irrigation water and higher water productivity with respect to irrigation water than WS ISU and TP ISU. This was attributed to the ability of DS rice to capture more rainfall after crop establishment. Site-specific management of WS rice versus TP rice has to be taken into account in assessing their relative advantage for water input and water productivity.