The data on sugar beet yield were taken from Stations of Cultivar Assess-ment situated in south-west Poland. Using the method of multiple regression with interactions, models of root and leaf yield and sugar content percentage were con-structed, where the independent variables were precipitation total in the periods April-June and July-September or the number of days with rainfall in the stated periods. The optimum for obtaining highest yields of beetroots proved to be the set of factors: rainfall April-June 222 mm (the highest studied) and rainfall July-September 260 mm (a bit higher than average). As regards the number of days with rainfall, the optimum values were 35 days in the period IV-VI (values lower than average) and 50 days in VII-IX (value close to the maximal studied). The yield of roots was lowest with the lowest precipitation totals in both the periods (122 and 152 mm), and also when the highest number of days with rainfall in the spring season (46) was accompanied by low number of days with rainfall in the summer period (33). For the yield of leaves the best set of factors proved to be the maximum precipitation totals studied, both those of the spring and summer period ...
The data on the yield of potatoes grown on very good and good wheat soil complex as well as very good and good rye soil complexes in 11 experimental stations of varieties evaluation in 1996-2005 were used in this paper. For the wheat and rye soil complexes models of medium early as well as and medium-late and late potato crop were constructed as regression functions (quadratic polynomial with interactions), in which the amount of precipitation in May-June and July-August were independent variables. Models were studied in the range of 75-175 mm precipitation in May-June, and 90-220 mm precipitation in July-August, which corresponds to the average ± standard deviation of these parameters.In all cases, July-August precipitation was the factor more strongly affecting the yield. For medium early potatoes grown on wheat soils the optimum for obtaining the highest yields proved to be the set of factor: low May-June precipi-tation (88 mm) appeared with high July-August precipitation (217 mm). The yield achieved under these conditions amounted to 594 dt•ha-1. Medium late and late potatoes grown on the same soil reacted similarly to water from rain - the optimum set of factors was: May-June precipitation - 76 mm and July-August - 220 mm, ...
