Water balance and water productivity of summer rice as influenced by land situation in tube well commands

Abstract

An on-farm investigation was carried out during 1999 and 2000 on water supply, expense components, water productivity and water cost for growing summer 'lET 4786' rice (January 3rd week to middle ofApril) under high, medium and low land situation and soil type in the tube well commands ofLower Gangetic Plains. Irrigation water requirement for ofsun1mer rice was 1 928, 1461 and 773 film under high, medium and lowland situation respectively when potential crop evapotranspiration was 344 mm for 90 days duration crop. Water expense for sunlmer rice was 89-152% higher in high land situation than lowland. Percolation and seepage loss was accounted to be 62.1-69.9% of total water supply under different land situations. Lowland crop received 19.70/0 of total water requirement as seepage gain from adjoining fields. Expenditure towards evapotranspiration was 55.5, 27.6 and 19.30/0 oftotal water requirement under low, medium and high land situation respectively. The productivity of summer rice in lowland (5.92 tonnes/ha) was 7.8-19.7% more than the nlediu111 and upland situations. Water productivity value (0.73 kg/m3 ) in physical tenn was 50-66% higher under lowland situation than the medium and high lands. Economics (Rs 4.41/m3 water) was also high in lowland situation. Summer rice growing with the help of private owned shallow tube well irrjgation in mediun1 and high lands increased the water cost for cultivation (Rs 6 750-7 500/ha) and produce (Rs 1 510/tonne/ha) by 70-120% compared with the water cost of Govemment owned deep tube well.