Evapotranspiration of Safflower at three densities of sowing

In a low latitude environment, evapotranspiration from irrigated crops of safflower growing at low, middle, and high densities was determined from changes in soil water storage. Evapotranspiration was related to potential free water evaporation as calculated by the Penman formula. Except at the rosette stage and during the transition period leading to elongation, there was no measurable difference in evapotranspiration between densities. The ratio of evapotranspiration to free water evaporation was 1.57 during elongation and 1.25 between elongation and flowering, falling to less than 1 before the last irrigation and before any marked depletion of soil water in the root zone. Average evapotranspiration over the cropping period was 3.1 mm day-l and the transpiration ratio 342. Leaf area index and evapotranspiration rates were related by a Mitscherlich type curve with an evapotranspiration plateau of 4.2 mm day-1. The high ratios of evapotranspiration to potential evaporation were due to bulk advective conditions in this environment. The observed evapotranspiration is discussed in relation to the growth of the crop and the variations observed in the field.