STUDY OF WATER REQUIREMENT FOR RICE (Oryza sativa) CROP AT CYABAYAGA WETLAND IN NYAGATARE DISTRICT OF RWANDA

Abstract

The water management problems and poor water use efficiency in irrigation command is affecting the rice production of the study area. The objective of the work carried out in the marshland was to assess the rice water requirements, some soil properties, weather parameters and appropriate water use efficiency in the marshland. The research methods adopted were purposely replying to each specific objective. The meteorological data on Nyagatare station were collected from meteorological agency headquarters for the period of 37 years (from 1981 to 2017. The collected samples of soil from the field were examined in CAVM, Busogo soil science laboratory. Evapotranspiration and irrigation needs were determined by using cropwat8.0 software. The actual losses in the field were measured and the conveyance efficiency (Ec) was found to be 70.05% showing 30% of water lost through seepage and evapotranspiration through weeds in unlined channels. The overall deep percolation, seepage and evapotranspiration losses from flooded rice fields were found in the tune of 25mm/day hence considering the highest ETc of 4.8mm, it was indicated that a huge loss of 20.2mm/day was caused by the seepage and percolation within the soil. In the study area the application efficiency (Ea) found was 23.8%. Hence the overall efficiency found was 16.7%. With the current rice yield of 4.25 tons per hectare, a low water use efficiency of 0.089 kg/m3 was found. Therefore, an integrated approach of land and water management, maintenance of irrigation infrastructures is highly recommended.