Modelling production of field crops and its requirements

Abstract Simulation models are being developed that enable quantitative estimates of the growth and production of the main agricultural crops under a wide range of weather and soil conditions. For this purpose, several hierarchically ordered production situations are distinguished in such a way that the results of simulations on one hierarchical situation are used as input for the calculations of another. For the highest hierarchical production situation, water and plant nutrients are optimally available; in the next situation water may be limiting at times, whereas in further situations limited supplies of the main plant nutrients are also taken into account. The reclamation activities and the yield-increasing inputs that are needed to achieve the simulated yield levels for the various situations are estimated. The weather data and the physical soil data that are needed for the calculations in the first two hierarchical production situations are specified. It is shown that environmental heterogeneity contributes considerably to the complexity of the problem and that especially the averaging of weather data over time and soil data over space leads to distortion or even destruction of data. To avoid this, the data from the original observation sites should remain accessible at all times. The easy accessibility of computers and data base management systems implies that there is no excuse anymore to average first and then calculate, instead of the other way round.