Maize yields under supplementary irrigation in the Olifants river basin South Africa

A daily field water balance experiment was conducted for three consecutive years to study the effects of supplementary irrigation on grain yield and water productivity of maize (Zea mays L.) crop in semiarid Olifants river basin, South Africa. Maize average yield under rainfed and supplementary irrigation conditions were 0.78 t/ha (standard deviation of 0.43 t/ha) and 1.90 t/ha (standard deviation of 0.39 t/ha), respectively. Supplementary irrigation with added fertilisation of 14 kg-N/ha during dry spells increased average yields by 185 %. Maize yield was affected by seasonal rainfall and its poor distribution. The average evapotranspiration under rainfed and supplementary irrigation for the three seasons was 574 mm and 640 mm respectively. Nevertheless water use efficiency was significantly greater for supplementary irrigation plots (3.0 kg mm ha) than for rainfed plots (1.3 kg mm ha). Furthermore, with mean incremental water use efficiency of supplemental irrigation of 13.7 kg mm ha, implies that 1 m of irrigation water applied timely can produce ZAR 27.4 (US$ 3.4) worth of maize. 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. Based on these results, the potential of supplementary irrigation exist to improve and stabilise smallholder farmer maize yields, thereby enhancing livelihoods.

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