A CROP-WEATHER MODEL TO ESTIMATE THE YIEL D OF POTATO VARIETY DESIREE

1. Under Hungarian weather conditions basic correlations were determin ed for potato variety Desiree between weather factors (heat sum and re lative soil moisture) and harvest index, and dry matter content of tub ers, respectively. 2. Based on the relation between the transpiration of plant stand and the accumulation of dry biomass, a dynamic-statisti c potato model was developed. To run a direct transpiration potato mod el of simple structure needs only three kinds of input data: daily ave rage temperature, daily average of vapour pressure and precipitation s um. The deviation among the calculated results of the model and the ac tual yield averages was under 20% in 78.3 percent of the cases. The co rrelation among the calculated and measured values is fairly close (r= 0.803). According to the results of the model, the weather determines the size of the yield only in 64%, the remaining 36% is the sum of eff ects cased by other factors. 3. To operate a simulation model it is in dispensable to have a potato stand free of diseases, while its nutrien t supply should be more favorable than limit level. Due to these facts , the model ensures a realistic yield result only in case of non-deter iorated potato, therefore the application of the model may be recommen ded first for seed potato producing fields. The model in its present s tage may be used mainly for research purposes. 4. By using the model, theoretically attempts were made to estimate the possible yield in pot ato at optimal water supply. Based on the results, the average of pota to yields at proper water supply exceeded the 50 t/ha in each county. The ratio of actual and potential yields is suitable to evaluate the p roduction site.