Model-based assessment of water balance components under different cropping systems in north-west India

Water balance components were assessed under main cropping systems of the Punjab state in northwest India with a simplified model using long-term weather data. Ten years' average annual evapo-transpiration (ET) was maximum in sugarcane (136 cm) followed by cotton-wheat (125 cm), rice-wheat (92 cm) and maize-wheat (86 cm) cropping system on a medium textured soil. However, on a coarse textured soil, ET was less by 6-11 cm under different cropping systems. Soil water evaporation (E) constituted the major proportion of the annual water loss during establishment and senescence periods of the cropping cycles and intervening bare periods. Water loss by deep drainage in rice (68.2 cm) was more by 2.4 times than in maize, by 3.1 times than in cotton and by 3.3 times than in sugarcane. Irrigation water required to meet ET and drainage was maximum in rice-wheat (106.8 cm) followed by sugarcane (85.5 cm), cotton-wheat (81.6 cm) and maize-wheat system (61.2 cm). Straw mulching in maize. cotton and sugarcane decreased irrigation requirement further by reducing unproductive E losses. Thus. maize-wheat or cotton-wheat cropping systems having low irrigation requirement can be an appropriate alternative to rice-wheat system for maintaining balanced hydrology in the state. (C) 2002 Published by Elsevier Science B.V.