The value of irrigation water in Nyanyadzi smallholder irrigation scheme, Zimbabwe

The low performance of smallholder irrigation schemes is largely attributable to unreliable and inadequate water delivery. This is evidenced in Nyanyadzi smallholder irrigation scheme in eastern Zimbabwe, where unreliable water supply resulted in significant yield reduction during the summer season of 1999/2000. This paper reports the study of yield, rainfall, irrigation water and soil moisture status of 13 plots with maize. Based on these data, the marginal yield of maize per unit of water (rainfall+ irrigation) could be established and was found to be 1.5 kg m-3• Assuming a world market price of maize of 0.10 US$ kg-1, it follows that an additional I m3 of water at the right time and at the right place yields US$ 0.15. The marginal yield of maize per unit of net irrigation water applied was found to be 1.9 kg m-3 This means that I m3 of irrigation water applied at the right time at the right place can produce US$ 0.19 worth of maize. These values indicate the potential magnitude of the gains if the reliability and adequacy of water supply is enhanced through rehabilitation of the infrastructure and improvement of the management of the irrigation scheme