Wofost version 6.0 is implemented in the EC Crop GrowthMonitoring System (CGMS) of the MARS project. CGMS uses daily weather data on a 50km x 50km grid. These data are interpolated from weather station data using a special developed procedure. Soil data are derived from the 1:1 Milion EC soil map.
The current version is WOFOST 7.1 and is available at ALTERRA (before SC-DLO):
A simplified version of WOFOST is used for crop growth simulation by the SWAP Soil Water Atmosphere Plant model.
An Updated System Description of the WOFOST Crop Simulation Model as implemented in the E.U. Crop Growth Monitoring System can be found at:
Hijmans R.J., I.M. Guiking-Lens, C.A. van Diepen, 1994. "WOFOST 6.0: User's guide for the WOFOST 6.0 crop growth simulation model". Wageningen, DLO Winand Staring Centre, Technical Document 12. 1994-146 pp.-48 figs.- 78 ref. ISSN 0928-0944
Kraalingen D.W.G. van, 1991. " The FSE system for crop simulation " Simulation reports CABO-TT 23, CABO-DLO, WAU-TPE Wageningen, 77 pp.
2.2 Development of WOFOST
WOFOST originated in the framework of an interdisciplinary study on the potential world food production by the Centre for World Food Studies (CWFS) in cooperation with the Wageningen Agricultural University, Department of Theoretical Production Ecology (WAU-TPE) and the DLO-Centre for Agrobiological Research (CABO-DLO, currently AB-DLO), Wageningen, the Netherlands. After cessation of CWFS in 1988, development of the model has been continued by the DLO Winand Staring Centre (SCDLO) in cooperation with AB-DLO and WAU-TPE.
WOFOST is a member of the family of models developed in Wageningen by the school of C.T. de Wit. Related models are the successive SUCROS models (Simple and Universal CROp growth Simulator), ARID CROP, Spring wheat, MACROS and ORYZA1. The first WOFOST model has been documented by Wolf et al. (1986). Two of the successive model updates have been documented: version 3.0 by Rappoldt (1986) and version 4.1 by Van Diepen et al. (1988).
Documentation of the principles of WOFOST 6.0 is documented by Supit et al.(1994).
...These models all share the same principles and routines, however the submodels describing the soil water balance and crop nutrient uptake vary much in approach and level of detail.
WOFOST was originally developed as a crop growth simulation model for the assessment of the yield potential of various annual crops in tropical countries. ...
In addition to the mainstream of WOFOST versions several models have been elaborated on the basis of WOFOST 4.1. A typical example is the SWACROP2 model formed by linking the WOFOST crop module to the SWATRE soil water and transpirationrate model (Huygen, 1992). Groot (1987) simulated the nitrogen dynamics in crop and soil. Poels and Bijker (1993) developed the model TROPFOR to simulate growth and water use of tropicalrainforest by adapting WOFOST 4.1. De Ruijter et al. (1993) adapted WOFOST for simulating tulip growth.
2.3 Applications of WOFOSTOver the last ten years, the successive WOFOST versions and their derivates have been used in many studies. WOFOST has been applied as a tool for the analysis of yield risk andinterannual yield variability, of yield variability over soil types, or over a range of agrohydrological conditions, of differences among cultivars, of relative importance of growthdetermining factors, of sowing strategies, effects of climate change and critical periods for use of agricultural machinery.The model has also been used for predictive purposes, in quantitative land evaluation, such as regional assessments of crop yield potential in the form of maximum yield levels, estimation of maximum benefits from irrigation or from fertilizer use, detection of adverse growing conditions by simulation-monitoring the agricultural season, and regional yield forecasts. Some WOFOST users have extended the growth model to forest and grass, and have replaced the soil watermodule by more detailed submodels.
Unfortunately, a complete overview of applications of WOFOST is not available, as there has never been a formal network or newsletter for exchange of experiences and (validated) data sets. This has severely hampered feedback to the model developers. Here, we mention the major application studies that influenced its development, and a few examples of other WOFOST applications and extensions.
The first major regional study on the basis of WOFOST (version 3.1) dealt with potential food production increases from fertilizer aid in three African countries, and was carried out by CWFS at the request of the FAO...
Within the framework of the Monitoring Agro-ecological resources with Remote sensing and Simulation (MARS) project, WOFOST (version 4.1) has been proposed as a yield estimating tool in an early warning system for food security in Zambia. This system would consist of a GIS (Geographic Information System) and a crop model, and would be fed with data from meteorological satellites (Berkhout et al., 1988). For that purpose the WOFOST model has been calibrated and tested for maize (Huygen, 1990; Wolf et al., 1989). WOFOST 4.1 was also applied to evaluate irrigation and water conservation strategies in support of rural development in small watershedsin the Peruvian Andes (Van der Zel, 1989).
An elaborated calibration and validation study for maize in Kenya was carried out by Roetter (1993) on the basis of WOFOST 4.4. Using data from experimental fields he found that themodel predicted grain yields with an accuracy of 15 percent (Root Mean Square Error) which was considered satisfactory in the light of the quality of the available data. WOFOST wasthen applied to re-evaluate former field trials with varying planting dates and fertilizer treatments and to assess yield risks for specific sites, prior to interpolation to regions using GIS techniques.
The AGRISK project applied WOFOST for risk studies in Burkina Faso, in order to analyze farmer's strategies to cope with drought risks in relation to soil type, crop and cultivar,sowing date, runoff and location of crop fields (Mellaart, 1989). Within the framework of ICRISAT's village level studies in India's semi-arid tropics, Bakker (1992) used WOFOST in a study of the scope for rainfall insurance.
In the NASREC program of ISRIC and UNEP supporting the establishment of National Soil Reference Collections and Databases for education, extension and research, in which 11countries participate, WOFOST has been adopted as the reference crop model. To facilitate the use of the model for detailed land/soil properties studies, ISRIC has developed a user-friendly shell for WOFOST (version 4.3), providing a link to the NASREC database applications (Pulles et al., 1991).
WOFOST (version 5.3) was used for the estimation of the regional production potential of the major field crops in the European Community, as a function of soil and climate con-ditions (De Koning and Van Diepen, 1992; Van Lanen et al., 1992). To that end, data sets for a range of temperate crops (wheat, maize, oilseed rape, potato, sugar beet) weredeveloped as well as a separate model version for grass. In this study the model was linked to a GIS to facilitate generation of model input data and to aggregate model output over regions. The data generated were used to determine input- output coefficients of cropping systems in the EC (De Koning et al., 1994). These coefficients were used in GOAL (GeneralOptimum Allocation of Land use), an Interactive Multiple Goal Linear Programming Model developed by the Netherlands Scientific Council for Government Policy (1992) (Rabbinge and Van Latesteijn, 1992) to explore feasible options for rural land use in the EC. One of the conclusions of the study was that in Europe at least 30 percent of the agricultural land could be taken out of production without endangering food security or compromising other major political objectives.
In other studies WOFOST has been used to asses the effect of climate change on crop growth (Van Diepen et al., 1987; Wolf and Van Diepen, 1991; Wolf, 1993). The model is particularly suited to quantify the combined effect of changes in CO2, temperature, rainfall and solar radiation, on crop development, crop growth and crop water use, as all the relevantprocesses are simulated separately while taking due account of their interactions.
WOFOST version 6 was developed under the contract study "Models for yield forecasting" issued by the Joint Research Centre (JRC) of the European Commission at Ispra, Italy, inthe framework of Action 3 of the Agriculture Project, also called MARS project (Monitoring Agriculture with Remote Sensing). The objective of this study was to generate crop growthindicators for the quality of the current agricultural season over the EC regions as compared to the quality of historical seasons, and to use these indicators for quantitative yield prediction per region and per country. To this end WOFOST has been incorporated in the Crop Growth Monitoring System (CGMS). In CGMS, that runs on a SUN-UNIX computer, WOFOST is linked to an ORACLE relational data base and an ARC/Info GIS (Van der Wal, 1994; Van Diepen, 1992). The stand-alone version of WOFOST 6.0 is maintained for learning, demonstration, test and validation purposes, and as a starting point for its application in other studies.