Subsurface Evapotranspiration Irrigation System Design in System of Rice Intensification (SRI) Salibu Paddy Cultivation

The System of Rice Intensification (SRI), a water-saving paddy cultivation system, has been implemented in Indonesia. The application of SRI  can increase water productivity. The Salibu method applied to paddy cultivation can save seeds, costs, labour and increase the planting index of paddy. However, when used in other areas, the yield is reduced by up to 50 per cent from the first harvest. A combination of cultivation and water management is needed to save water and increase paddy production. The method used in this research is experimental research. The design of the irrigation system was made according to the technical design, then tested for automatic water management. The design was tested with the SRI Salibu method. The data are climate data, water level, water discharge, and water content. The climate data used are temperature and solar radiation to determine potential evapotranspiration. The results of observations of water depth, the volume of water in the system, the water content in the media, water entering the system (rain infiltration, irrigation discharge), and water leaving the system (runoff, discharge) are entered into the water balance equation (water balance). The plant coefficient value is included in the water balance equation as a plant coefficient factor multiplied by the potential evapotranspiration value. Then the plant coefficient value for each observation is optimized by reducing the error value to get the coefficient value for SRI Salibu. The results showed that the appropriate evapotranspiration irrigation system for SRI Salibu paddy cultivation is the fifth irrigation system design. The fifth irrigation system design can produce 4.7 tons/ha of paddy (SRI method) and produce SRI Salibu paddy yields of 8 tons/ha. The irrigation water for SRI paddy cultivation is 1738 litres, and the water production is 1.2 kg/m3.