Optimizing Tomato Water And Fertilizer Uses In Smallholder Farms In South Africa Using The Piloten Model

The objectives of this paper are twofold: (i) to calibrate and validate the PILOTEN crop model for tomato (Solanum lycopersicum L.), and (ii) to use the model to examine the response of tomato yield to different irrigation and fertilization scheduling scenarios under varying climatic conditions in order to draw up management recommendations for smallholder farms. The calibration and validation were performed by using data collected from field experiments carried out in the north-east of South Africa, on shallow Ferrosol and Luvisol soils. The scenarios dealt with: (i) the initial soil-water availability (fulfilling or not the soil-water reserve at planting); (ii) the irrigation dose frequency (high versus low irrigation doses ranging from 10 to 40 mm per application); (iii) the fertilization dose frequency (full versus split fertilization application). The results indicated that only the fertilization scheduling may significantly affect tomato yields, while irrigation scheduling has a minor role. However, compared to the local official irrigation guidelines, it is recommended to slightly increase the irrigation doses during the first 4 weeks of growth for tomato grown between early September and mid-December, and to slightly decrease the doses in the second part of the growing cycles starting in February and May. It is also suggested to avoid applying the entire fertilizer dose after seedling planting for tomato grown between mid-February and late June. Copyright (c) 2020 John Wiley & Sons, Ltd.