Effects of Irrigation Interval, Urea and Gypsum on N, P and K Uptake by Forage Sorghum on Highly Saline–Sodic Clay

Abstract

SUMMARYThe effects of three irrigation intervals (7, 10 and 15 days), four nitrogen levels (0N, 1N, 2N and 3N where 1N = 43.8 kg N/ha), and 0 or 11.9 tons/ha gypsum on leaf N, P and K uptake by forage sorghum grown on a highly saline–sodic clay soil were investigated in two successive seasons. The two seasons' data consistently showed that both leaf-N and leaf-K increased significantly with increasing N-rate and by splitting the same quantity of irrigation water into more frequent irrigations. Gypsum had no consistent effect. The responses of both leaf-N and leaf-K to nitrogen rates were significantly linear and a linear response of dry matter yield to leaf-N was also observed. P uptake was improved by more frequent irrigations in the first cutting of 1978, but was not otherwise affected by treatments.