The Effect of Different Furrow Irrigation Regimes on Infiltration and Sugarcane Yield at Ubombo

In surface irrigation, the soil serves as a medium for infiltration and conveying water from upstream to the downstream end of a field. In this study, infiltration properties of the Sibaya (Si) soil series (Glenrosa in the South African soil classification system) were determined by a volume balance method using a two-point approach technique. The purpose of the study was to examine the effect of different irrigation scheduling on infiltration characteristics, and on irrigation performance. A trial was conducted on a field with predominately Sibaya soil from 1999 to 2001. The five irrigation treatments were the Ubombo system, Penman Monteith (PM) derived irrigation scheduling factors of 1.25, 1.00 and 0.75, and alternate inter-row irrigation using Ubombo and 1.00 x PM scheduling on plant and first ratoon cane, respectively. Treatments were arranged in a randomised complete block design with four replications. The Ubombo scheduling method had the highest number of irrigation events followed by the 1.25 x PM, whilst the 0.75 x PM had the least. The infiltration variables indicated that, for the Ubombo and 1.25 x PM treatments, irrigation often occurred when the soil water content was still less than 50% depleted plant available water (DPAW). Frequent irrigation resulted in the crop depleting soil water, predominately at the 0.15-0.30 m soil depth and hardly any at 0.45 m, particularly when the crop was still young. There were no significant differences in yield between any of the treatments either in the plant or the ratoon crops. The plant crop consistently recorded higher yields than the first ratoon in all the treatments. Ubombo scheduling recorded the highest sugarcane yield in both seasons at 84 t cane ha for the plant crop and 82 t cane ha for the first ratoon. The 0.75 x PM had the lowest yield (77 t cane ha) in the plant crop as well as in the first ratoon (74 t cane ha).