Validation of the aquacrop model for the irrigated african eggplant(solanum macrocarpon) at the UNZA field station

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Bwalya, Angela
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African Eggplant (Solanum macrocarpon) is a minor vegetable crop in most African countries which is currently receiving interest. Given the effects of climate change and decreasing crop water availability, there is need to consider the efficiency of use of the available water. The high dependence on farming and on highly unreliable rainfall in Zambia is risky but continued investment in improved water storage and irrigated agriculture, as a means of adaptation to climate change, raises crop productivity. The effect of water application rate on biomass and yield of African eggplant was evaluated at the University of Zambia, Field Station for partially irrigated, fully irrigated and rain fed eggplant crop under three water application rates at 50 percent, 75 percent and 100 percent of crop evapotranspiration (ET). The 100 percent ET treatment had sub-treatment with plastic cover (100 percent ET+) and without plastic cover (100 percent ET) as control. The experimental design was a Randomized Complete Block Design (RCBD) with four replications. Amount of applied irrigation water for four treatments varied from 197 to 364 mm. The biomass produced varied from 6.59 to 8.07 ton/ha, while the fruit yield varied from 0.89 to 1.46 ton/ha. Reduction of applied water by 25 and 50 percent resulted in yield reduction of 17 and 23 percent respectively. The results showed that decreasing the amount of water applied through irrigation resulted in decrease in total dry matter and final fruit yield produced. Results showed significant differences (P<0.05) in fruit yield and harvest index (HI) as affected by water application rate. These results therefore suggest that irrigation water requirements of African eggplant can easily be reduced by 25 percent in situations where water supply is limited, without significant yield reduction if the 100 percent of ET and 75 percent of ET irrigation practices are adopted, to save on costs. Therefore, increasing the irrigated area with the saved water could compensate for any yield loss. In terms of biomass, no significant differences were observed in stem girth diameter, plant height, stover and dry matter produced. Furthermore, the water use efficiency increased with decrease in water application rate. Keywords: African eggplant, Climate change, Crop evapotranspiration (ET), Irrigation, Solanum macrocarpon,
Eggplant. , Plant anatomy.