Calibration and validation of the FAO aquacrop model For tomato (solanum lycopersicon) in the coastal savannah agro-ecological zone of Ghana

Abstract

Two field experiments were conducted to compare the growth and yield of tomatoes using experimentation and FAO AquaCrop model at the University of Cape Coast Teaching and Research Farm in the Cape Coast Metropolitan Assembly of the Central Region of Ghana. The Randomized Complete Block Design was used with four (4) treatments and four(4) replications for the two experiments. The treatments used for both experiments were T1 – Full irrigation (100 %), T2 – 90 % irrigation, T3 – 80 % irrigation, T4 – 70 % irrigation. Data was collected on water requirement, plant height, leaf area, stem diameter, internode length,number of harvested fruits, fruitsdiameter, weight of harvested fruits and yield for both experiments after which the results were compared to that generated by AquaCrop model. At 100 % water application (full irrigation), crop coefficient for tomato was determined to be 0.62 - 0.63, 1.54 - 1.61, 1.23 - 1.34 and 0.92 –0.93 for the initial, development, mid-season and the late season stages respectively. The total amount of water applied for the 116 days ranged between 307 mm and 359.89 mm. Twenty percent deficit (irrigation) had no significant reduction on the yield of tomatoes. T4 had adverse effect on the plant and yield as indicated, which recorded the lowest yield of 3.11 t/ha in the first experiment and 2.10 t/ha in the second experiment. The model did not accurately simulate the yield of tomatoes under deficit irrigation. In the case of T4, however, the level of accuracy was high at 18.09 %. The model was able to simulate the seasonal ETc for T₂ at 9.88 % in Experiment 1 but not for the others.