Validation of crop weather models for crop assessment arid yield prediction under Tanzania conditions

Abstract

Information gatheringfor early warning and crop assessment in Tanzania is based on physical inspection of standing crop in sample yields. This process is subject to human error, inadequate and is also time consuming. Recent developments in computer simulation have paved the way for more efficient methods of analysing data for purposes of early warning and crop assessment. Two such schemes based on soil water balance simulation, viz. IRSIS and CRPSM models were used in this study to see how closely they could predict grain yields for selected stations in Tanzania. Input for the models comprised of weather, crop and soil data collected from five selected stations. Simulation results show that IRSIS model tends to over predict grain yields of maize, sorghum and wheat, a fact that could be attributed to the inadequacy of the model to accurately account for rainfall excess. On the other hand, the CRPSA1 model simulated results were not significantly different (P > 0. 05) from the actual grain yields maize, sorghum, wheat and beans. Although the agreement between actual and simulated yield data was good, it was observed that mean values for predicted grain yields were consistently lower than for actual grain yields. This could be attributed to the use of approximate rather than location specific input parameters required by the CRPSM model. Locally calibrated input parameters in the CRPSM model could further improve the accuracy of the model and hence its ability to predict grain yields.

Keywords: Soil water balance, simulation model, crop assessment, yield prediction

Tanzania J. Agric. Sc. (2000) Vol. 3, No. 2,129-136