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 soil (udic Haplustalf) in the north-western foothill region of India to determine the water use, water use efficiency and yield performance of sugarcane (Var. COS 767) in response to irrigation schedules and nitrogen fertilization. Irrigation scheduling was based on different ratios 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 recorded daily using standard USWB-Class A open pan. CPE values were computed after accounting for rainfall in each year, individually. Nitrogen was 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 efficiency. 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 comparatively more under lower ratios (0.6 and 0.8) than 1.0 and 1.2 ratios. Nitrogen applied up to 200 kg/ha increased the yield of sugarcane significantly. Irrigation and nitrogen had no pronounced effect on the quality of juice; however, the highest dose of nitrogen (300 kg/ha) resulted in poor quality of cane juice.