WOFOST: crop growth simulation model - 1st part
DOI:
https://doi.org/10.14720/aas.2009.93.2.15047Keywords:
WOFOST, model development, input data, water balance, crop yield, maizeAbstract
The WOFOST crop growth simulation model was selected, when the JRC (i.e. European Commission) requested Alterra (formerly SC-DLO) and Plant Research International (formerly AB-DLO) in Wageningen, The Netherlands, to develop, adapt and calibrate new or existing agro-meteorological simulation models for 10-day routine quantitative forecasting of national and regional yields and qualitative monitoring of the growth conditions for the whole EU for different kinds of crops. WOFOST is a member of the family of crop growth models developed in Wageningen by the school of C.T. de Wit. The first WOFOST model has been documented by Wolf et al. (1986) and it was originally developed to assess yield potential of various annual crops in tropical countries (van Keulen & Wolf, 1986; van Diepen et al., 1988; van Keulen & van Diepen, 1990). Over the last ten years, the successive WOFOST versions have been used in many studies. WOFOST has been applied as a tool for the analysis of yield risk and inter-annual yield variability, of yield variability over soil types, or over a range of agro hydrological conditions, of differences between cultivars, of relative importance of growth determining factors, of sowing strategies, effects of climate change, critical periods for use of agricultural machinery and others. Recently, the version WOFOST 7.1.2. is in use.
WOFOST is a mechanistic model that explains crop growth on the basis of the underlying processes, such as photosynthesis, respiration and how these processes are influenced by environmental conditions. Crop growth depends on the daily net assimilation, which on its turn depends on the intercepted light. The intercepted light is determined by the level of incoming radiation and the leaf area of the crop. We can choose between potential and water-limited simulation. We have to prepare meteorological data in the requested format.
WOFOST uses a water balance, which compares for a given period of time, incoming water in the rooted zone with outgoing water and quantifies the difference between the two as a change in the stored soil moisture amount. Several processes are included: infiltration, evaporation, transpiration, percolation and capillary rise. We have to keep in mind that the model is not meant to calculate the water balance in first place. The procedure which calculates the nutrient requirements is based on the work of Janssen et al. (1990). Phenological phase is calculated from daily temperature and correction factor. Temperature sums needed for each phase are determined in crop files. Appendices to the model description include equations, description of the global radiation calculation, Gauss integration, linear interpolation with AFGEN function, sowing date determination, CGMS (Crop Growth Monitoring System) data base, use of meteorological, crop and soil data in CGMS.
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