EVALUATION OF SPEED EFFECT ON THE TECHNICAL EFFICIENCY OF CENTRE PIVOT IRRIGATION AT UBOMBO SUGAR ESTATE, SWAZILAND

As part of an ongoing research on centre pivot irri gation system performance at Ubombo Sugar estate, this paper reports on the results of an evaluation of sp eed effect on the technical efficiency of the syste m. Four speeds (15%, 20%, 30% and 40%) were studied on three centre pivot systems to compare maximum water application depth required to prevent runoff, revol ution time, net depth of application, distribution uniformity (DU), coefficient uniformity (CU) and application efficiency which were adopted as indices for the determination of technical efficiency. Results reve aled a general decline in CU and DU with an increase in centre pivot speed as opposed to an increase in app lication efficiency. SMB declined from a CU of 88.9 % at 15% speed to 86.9% at 40% speed setting. This was evident for both NKA21 and EEL09. PELQ for SMB increased from 93.1% to 98.0%%, AELQ from 92.6% to 100% and a parallel trend was observed for NKA21 and EEL09. Analysis of variance for these results showed that the performance indicators were not statistically significant at (P = 0.01) between tre atments although a general trend was evident. This demonstrated the ability of centre pivot irrigation system to apply water uniformly and efficiently ac ross the field at different speeds, hence the system can be used with ease for other field operations such as f ertigation and chemigation which might require some adjustments on speed.