A Model and Its Performance of Evapotranspirative Irrigation Tested to Grow Water Lettuces

Abstract

Efficient use of irrigation water is crucial to face the uncertain trend of a declining water resource. Ensuring a supply of water that matches crop evapotranspiration (<i>ETc</i>) while optimizing soil moisture is challenging. This study aimed to come up with a model of an irrigation system that can supply water immediately to meet <i>ETc</i> without using electricity. To test the proposed water balance model a trial was established in water lettuces. The system consisted of 15 pots connected in serial using water pipes and hoses through the bottoms of the pots. The first pot was used as a water level controller and the last pot used as a drain water collector. Irrigation water would flow immediately to the pots that had water levels lower than the setting level. Testing carried out on rainy days resulted in considerably higher rainwater (99.8%) being utilized compared to the irrigation water (0.2%). For water lettuces, the yield was 258.9 g/m<sup>2</sup>, water use efficiency reached 95% while the economical and physical water productivity were 2.17 g/L and 2.28 g/L, respectively. The water level in the pots could be maintained within the expected range while the soil moisture maintained an unsaturated condition. Further tests however are still needed, which currently is underway.