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

摘要

An on-farm investigation was carried out during 1999 and 2000 on water supply, expense components, water productivity and water cost for growing summer 'IET 4786' rice (January 3rd week to middle of April) under high, medium and low land situation andsoil type in the tube well commands of Lower Gangetic Plains. Irrigation water requirement for of summer rice was 1 928, 1 461 and 773 mm under high, medium and lowland situation respectively when potential crop evapotranspiration was 344 mm for 90 daysduration crop. Water expense for summer 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 19.7% of totalwater requirement as seepage gain from adjoining fields. Expenditure towards evapotranspiration was 55.5, 27.6 and 19.3% of total 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 medium and upland situations. Water productivity value (0.73 kg/m~3) in physical term was 50-66% higher under lowland situation than the medium and high lands. Economics (Rs 4.41/m~3 water) was also high in lowland situation. Summer rice growing with the help of private owned shallow tube well irrigation in medium 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 Government owned deep tube well.