Summary:

Reduction of evapotranspiration due to soil water deficit is quantified by CDI (Crop Drought Index). It is an agricultural drought index. The relationship was examined between precipitation P and CDI for sugar beet in Kujawy region for different soils. Evapotranspiration reduction was estimated on the basis of model research conducted for the growing season of sugar beet (21.04–30.09) in the years 1954–2003 and for 4 soils, with different total available soil water (103, 137, 165, 203 mm) in the 1-m profile. Relations between P and CDI were studied in 5 time periods, created by adding another subsequent phenological phases of sugar beet. The significance of the relationships was evaluated by using statistical analysis. The correlation coefficients showed the share of precipitation in the reduction of evapotranspiration of sugar beet in relation to potential evapotranspiration. The determined monograms can be useful in determining CDI on the basis of current measurements of precipitation.