Summary:

The yield of the spring cereals depends mainly on the distribution of at-mospheric precipitation in the growing season according totheir requirements in particular growing stages. Both precipitation excess and deficiency are not de-sirable. The analysis of spring cereals' water requirements fulfillment was made on the basis of IMGW data concerning the sums of atmospheric precipitation in Siedlce in the years 1968-1997. Monthly sums of precipitation were compared with optimum values of precipitation, estimated by Klatt (Water needs..., 1989),for specific spring cerealsin particular vegetation months. The characteristics of water requirements fulfillment for particular cereals was made on the basis of differences between the values of monthly sums of precipitation during the years analyzed and the values considered as optimum. In the months of April, May and June the frequency of precipitation deficiencies was higher than the frequency of precipitation excesses for all the cereals analyzed. However, in July precipitation excesses have been registered more frequently than the deficiencies. During the analyzed thirty years, the highest values of the average precipitation deficiencies for all the spring cereals were registered in May, while the values of precipitation excesses - in July. Meteorological growing season during the analyzed years began on 30th March and finished on 1stNovember. It lasted on average 215 days. An average sum of precipitation in the growing season amounted to 383 mm, with an average air temperature being 13°C.