Differential Yield Response of Groundnut, Maize and Sorghum to Water Management

Abstract

Irrigation scheduling is very critical on groundnut and, at a lesser extent on grain sorghum because of the limited yield response and the risk of yield depression or poor grain quality which can result from over-irrigation. Two experiments were conducted to compare responses of various yield components of groundnut, sorghum and maize to water in order to design optimum field water managements for these crops. The experimental site was a well-drained Millhopper fine sand, Groundnut, sorghum and maize, planted as subplots were subjected to 4 water treatments as main plots in 4 replications: (1) optimum irrigation based on maize water requirements, (2) irrigation allowing 2 days of wilt on sorghum, or (3) on groundnut, and (4) rainfed. Irrigation frequency and seasonal amount decreased from treatment 1 to 4. Yields of groundnut, sorghum and maize increased linearly with seasonal irrigation or ET. Harvest index and ET WUE of the 2 cereals decreased with increasing water stress. These parameters were more fluctuating in groundnut, where the highest harvest index was recorded in treatment 3, followed by 2, 1 and 4, while the ET WUE decreased from treatment 2 to 3, 1 and 4. Irrigation-use efficiency was high for maize (81.7%), but rather low for sorghum (45.2%) and groundnut (29.2%), indicating over-irrigation of these last 2 crops. Treatment 1 was adequate for maize, but resulted in poor grain quality in sorghum and depressed harvestable yield in groundnul. The threshold soil water matric potential at which to irrigate for optimum grain yield was quite high and crop-dependent: -20 kPa for maize (whole crop cycle) and sorghum (from planting to early grain filling period), -50 kPa for sorghum (grain filling and maturing periods) and groundnut (whole crop cycle). These threshold values are greater than those generally found in the literature.

Keywords: Yield, Watar use, Groundnut, Maize, Sorghum.