WATER-USE AND YIELD RESPONSE OF SUGARCANE UNDER DIFFERENT IRRIGATION SCHEDULES AND NITROGEN LEVELS IN A SUBTROPICAL REGION

Field studies were carried out for 3 years (1986-1989) on silty loam s oil (udic Haplustalf) in the north-western foothill region of India to determine the water use, water use efficiency and yield performance o f sugarcane (Var. COS 767) in response to irrigation schedules and nit rogen fertilization. Irrigation scheduling was based on different rati os between irrigation water (IW) and cumulative pan evaporation (CPE), e.g. IW/CPE. Irrigation of 6 cm depth was applied on the basis of IW/ CPE ratio of 0, 0.6, 0.8, 1.0 and 1.2. Pan evaporation data was record ed daily using standard USWB-Class A open pan. CPE values were compute d after accounting for rainfall in each year, individually. Nitrogen w as applied at the rate of 0, 100, 200 and 300 kg/ha to the test crop. Irrigation and nitrogen had favourable effects on growth and yield of sugarcane. The yield and yield attributes were highest and irrigation efficiency was maximum when irrigation was applied at IW/CPE ratio of 1.0. Water use efficiency decreased with increase in irrigation effici ency. Nonetheless, relatively more water was extracted from the upper layer in IW/CPE ratio of 1.2 treatment as compared to other treatments . However, soil moisture extraction from deeper layer was comparativel y more under lower ratios (0.6 and 0.8) than 1.0 and 1.2 ratios. Nitro gen applied up to 200 kg/ha increased the yield of sugarcane significa ntly. Irrigation and nitrogen had no pronounced effect on the quality of juice; however, the highest dose of nitrogen (300 kg/ha) resulted i n poor quality of cane juice.