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1 Magombeyi, M. S .; Rasiuba, T.; Taigbenu, A. E. 2009. Maize productivity under supplementary irrigation in the Olifants River Basin, South Africa. In Humphreys, E.; Bayot, R. S. (Eds.). Increasing the productivity and sustainability of rainfed cropping systems of poor smallholder farmers: proceedings of the CGIAR Challenge Program on Water and Food, International Workshop on Rainfed Cropping Systems, Tamale, Ghana, 22-25 September 2008. Colombo, Sri Lanka: CGIAR Challenge Program on Water and Food. pp.99-110.
Rainfed farming ; Water stress ; Supplemental irrigation ; Water productivity ; Maize / South Africa / Olifants River Basin
(Location: IWMI HQ Call no: 631 G000 HUM Record No: H042439)
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A daily field water balance experiment was conducted for three consecutive cropping seasons to study the effects of supplementary irrigation on grain yield and water productivity of maize (Zea mays L.) in the semi-arid Olifants River Basin, South Africa. Maize yield was affected by seasonal total rainfall and its distribution. Average maize yields under rainfed and supplementary irrigated conditions were 0.7 t ha (standard deviation of 0.44 t ha) and 1.7 t ha (standard deviation of 0.28 t ha) respectively. Supplementary irrigation during dry spells increased average yields by 196%. The benefits of supplementary irrigation were greatest during a season with low rainfall which was poorly distributed. Average evapotranspiration under rainfed and supplementary irrigation for the three seasons was 344 mm and 431 mm, respectively. However, crop water productivity with respect to evapotranspiration was significantly greater for supplementary irrigation (4.0 kg mm?1 ha) than for rainfed (2 kg grain mm?1 ha?1). The mean incremental water productivity from supplemental irrigation of 12.8 kg mm?1 ha?1 implied that timely application of 1 m3 of irrigation water can produce ZAR 2.56 (US$ 0.26) worth of maize, 5 times the cost of the water used. The values demonstrate the monetary gains from timely and adequate supplementary irrigation to bridge dry spells. The results show significant yield increases irrespective of the season under supplementary irrigation, demonstrating the potential of supplementary irrigation to improve and stabilise smallholder farmer maize yields, thereby enhancing livelihoods.
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