Computer-aided model system N-PROG® for estimating the requirements of nitrogen, crop yields and post-harvest nitrogen residues with respect to ecological parameters, economic and crop management factors

In crop management the calculation and distribution of nitrogen fertilisers in time relative to the site-specific spatial variability of cropping areas are uncertain factors. The main reason for this uncertainty arises from weather cycle conditions and their interaction with different qualities of soil and parameters of plant production on nitrogen dynamic and growth of cereals. For this reason a model has been developed with the help of measured data and multiple regression analyses techniques in first order. The model is based on the following data sets: (1) a long-term 48 nitrogen-systems trial set up in 1974 (the amounts of fertilised nitrogen range from 0 to 320 kg N/ha); (2) a complex production system trial of the Collaborative Research Project 192 (SFB 192) set up in 1991; (3) the back flow from N-fertiliser rates recommended to farmers in the Federal Republic of Germany since 1985; and (4) existing and additional field trials made in the FRG. The required and significant model input are ecological data (weather and soil), duration of nitrogen fertilised intensity, genetic data, production technique data and economic data. With respect to the production goal (e.g. high quality, maximal yield) and the administrative conditions (e.g. minimal N-residues), economic or ecological rates of nitrogen fertiliser, the model predicts the optimal N-rates at three development stages: N1 after winter, N2 at development code 30, and N3 at development code 49. The introduced simulation runs from long-term experiments will allow modelling of the nitrogen residues equivalent to simple N-balance = N-fertilisation minus N-uptake. In the near future the nitrogen leaching rates will also be modelled with the data and the expanded N-balance calculated as follows: N-balance = N-fertilisation minus N-uptake minus N-leaching.