Summary:

The work was carried out in order to determine the frequency of droughts in the period of increased water needs of spring cereals. In addition, based on the time variation of the standardized precipitation index SPI assessed the needs and the expected production results of the plants irrigated in the Kujawsko-Pomorskie region. Data consisted of the results of standard measurements of rainfall from 1 May to 30 June in the period 1981-2010. Rainfall data were obtained from the branches COBORU in Chrząstowo, Głębokie and Głodowo and also from the Research Station of University and Technology and Life Science in Mochełek. Based on the results of the study, it was found that, during the period of high demand for water of spring cereals, the frequency of drought conditions in the region accounted of 23,3-30,0%, depending on the locality. Extreme droughts occurred in years 2000 and 2008, strong in 1983, moderate in 1989 and weak in 1992, 2003 and 2006. Among the analyzed 30 years, in 4 years were identified very high- and high-level requirements of irrigation in spring cereals corresponding to periods of extreme, strong and moderate droughts (SPI ≤ -1.0). The expected increase in grain yield of spring cereals cultivated on light soils under irrigation is assessed at the level higher than 1.8 t•ha-1. In the subsequent 8 years, occurred medium-level irrigation needs, which in the period of May-June corresponded to the values of the SPI at the level between 0.0 and -1.0.