Farm level water footprints of rice production based on measured and estimated crop evapo-transpiration

Abstract

Studies have been conducted to quantify water footprint (WF) on high spatial scale in which crop evapo-transpiration (ETc) was computed indirectly using empirical formula. In this study attempt has been made to quantify field level WF of rice production (varieties: ‘Lalat’ and ‘Gayatri’) in eastern India based on measured ETc. The measured values were compared with other 3 methods like Pan Evaporimeter, Bowen ratio and Penman Monteith methods. Based on measured field water balance study, 562 and 688 mm of ETc were recorded for ‘Lalat’ and ‘Gayatri’ varieties, respectively and water footprints of 2470 and 2704 m3 t-1 were computed in these two respective varieties when no nitrogen was applied. But WFs of 1316 and 1394 m3 t-1 were recorded under 150 kg N ha-1 in these two respective varieties. Thus it can be concluded that WF of a crop to a large extent was influenced by agricultural management adopted. Among different methods, the pan-evaporimeter method estimated ETc values very close to the measured one, whereas, Bowen Ratio and Penman-Monteith methods overestimated ETc values by 11-12 percent.