COMPUTER-AIDED MODEL FOR ESTIMATING THE R EQUIREMENTS OF NITROGEN ANDYIELDS OF CEREALS DEPENDENT ON WEATHER CONDITIONS, QUALITY AND KIND OF SOILS AND PARAMETERS OF PLANT-PRODUCTION

In crop management uncertain factors are the calculation and distribut ion of nitrogen fertilizers in time and space. The main reason for thi s uncertainty arises from weather cycle conditions and their interacti on with different qualities of soil and parameters of plant production on nitrogen dynamic and growth of cereals. For this reason a model ha s been developed based on data of a long term experiment, set up in 19 74. At different stages of growth this model is able to estimate the n itrogen requirements and yields of cereals dependent on actual and lon g term weather data. The model is now beeing tested and calibrated (an d has been since 1982) under different conditions of plant production, qualities and textures of soil with the analysis of other field trial s, crop management and weather data and the aid of 250 farmers in the FRG. Recommendations for nitrogen fertilizing and the corresponding an nual results of harvest are used to validate the model and - if necess ary - to calibrate the model further on. For special fields of crop pr oduction the calculation of nitrogen requirements often are calculated unique. But if there are informations about the variability of textur e and quality of soil within the field, it is possible, to calculate a dapted amounts of nitrogen fertilizer dependent on these factors. The proportions weather cycle conditions and their interaction with differ ent qualities of soil can determine the nitrogen requirements, yields and the results of not adapted fertilizing are simulated and discussed .