Verification of 10- and 20-day forecasts of the standardized precipitation index SPI

Vegetables are considered to be plants with high water requirements. A greater susceptibility to water deficit occurs in the periods of intensive growth and yield formation. At that time even a slight reduction in water supply can deteriorate yielding, thus those periods are referred to as critical periods in terms of water supply. The aim of this paper has been to analyse the pattern of precipitation deficits for the ground cultivation of cucumber, tomato, beans and peas in the Bydgoszcz region in the thirty-year period 1981-2010. The basic of analysis were results of standard meteorological measurements from the Research Station of the Faculty of Agriculture and Biotechnology 'Mochełek', University of Technology and Life Sciences. Values of optimal precipitation for medium soils were calculated according to Klatt. Atmospheric precipitation deficits in subsequent month of selected vegetables cultivation were calculated by diminish between the real and optimal precipitation. The trends of deficiency of precipitation in the examined period were estimated too. Very frequent occurrence of the atmospheric precipitation deficits during the entire cultivation period of selected vegetables, and especially in critical periods was demonstrated. Slight decreasing tendency of precipitation deficits in a vegetation periods was indicated, however in a critical periods in terms of water supply, the trend line remains at a practically constant level. The results obtained indicate the necessity of the irrigation in the cultivation of peas, beans, cucumbers and tomatoes.