Effect of irrigation intervals and nitrogen fertilizer rates on fresh forage yield of sudangrass [sorghum sudanense (piper) stapf.]

Abstract

A field experiment was conducted in the Agricultural Experiments and Research Station, of the College of Food and Agricultural Sciences, King Saud University, at Dirab, for two consecutive summer seasons of 2001 and 2002 to investigate the effect of three irrigation (3, 7 and 11 days) intervals, and three urea (%46 N) fertilizer levels (200, 400 and 600 kg ha-1) applied in three equal doses (15 days after emergence, after the first cut, and after the second cut) on forage yield of sudangrass [Sorghum sudanense (Piper) Stapf.]. The forage yield was determined over three successive cuts at 60, 105 and 135 days from planting. The experimental design used was a split plot with four replications, in which the main plots were the irrigation intervals, and the sub-plot were the N-fertilizer treatments. The results showed significant effects for growing season and irrigation intervals on the forage yield, while the nitrogen treatments were not effective. Expanding irrigation interval from 3 to 7 and 11 days decreased the potential yield from 143.6 to 123 and 85.3 ton ha-1, respectively. Moreover, both 1st and 2nd cut yield was about 85% of the total obtained forage. According to this study, the growers are advised to take only two sudangrass forage cuts, using the 7-days irrigation interval. This practice will conserve more than 50% of irrigation water while the reduction in forage may be less than 15% of potential yield.