CONSUMPTION AND UTILIZATION OF IRRIGATION WATER BY FIELD CROPS ON LIGHT-TEXTURED SOILS OF THE CENTRAL ELBE BASIN

The regulation of the water regime of light-textured soils is still in the centre of attention of the research. Most of field experiments are aimed at irrigation water consumption by crops to be relatively as low as possible at reaching the highest increments of dry matter. Polyfactorial field experiments were conducted at the research station of the Research Institute for Crop Production Praha-Ruzyne in the years 1967 to 1988 to study the effect of various water regime of soil and nitrogen fertilization on phytomass production of major crops. Experimental fields are situated in the beet-rye growing region, latitude of 50 degrees 16', longitude of 13 degrees 33', altitude 168 m above sea level. The normal of annual air temperature on the experimental site is 8.6 degrees C, 14.8 degrees C for the growing season, long-term annual sum of precipitation is 542 mm,while it is 352 mm for the growing season. Soils on the experimental plots are included in sod chernozem, created on gravel-sand terrace, topsoil is loam-sandy, well-supplied with major nutrients, pH value (KCI) is 6.5 to 7.7. Retrospective analysis was used to assess the quantity of irrigation water applied in chosen crops, followed by consumption of irrigation water per unit of dry matter increment and the effect of nitrogen fertilization on the irrigation water consumption. It follows from the results obtained that the highest consumption of water (220 mm) was achieved by meadow clover and sugar beet, the greatest range of irrigation water used was found out in cereals (40 to 270 mm). The proportion of moistening irrigation in the total quantity of water supplied (precipitation and irrigation) was the highest in silage maize (50%), followed by sugar beet, meadow clover and grain maize (Tab. IV). Moistening character of irrigations in climatic and soil conditions of the Elbe Basin with respect to the consumption of irrigation water affects significantly the time of irrigation. In cereals a close correlation between deficit (surplus) of quantity of precipitation water, used doses of irrigation water and winter wheat grain yields (Tab. V) has not been proved. Irrigation water consumption per unit of above-ground production of phytomass is summed up in Tab. VI. The lowest irrigation water consumption per 1 t of dry matter exhibited sugar beet (20 to 40 mm), the highest values of irrigation water consumption were recorded with cereals (40 to 50 mm). By using the lower nitrogen rates water consumption for phytomass production was falling (Tab. VI). Application of lower nitrogen rates in interaction with irrigation decreased the irrigation water consumption per production unit by 55% in winter wheat, by 37% in spring barley, in grain maize by 38%, by 31% in sugar beet.