Long continued stationary feeding trial, established in arid conditions of the Southern Moravia (average yearly temperature is 9.1-degrees-C, average yearly sum of precipitation is 540 mm) on sandy loam degraded chernozem. was performed to study the effects of NPK-gradated rates, phosphorus alone and potassium and irrigation on the changes in agrochemical soil properties and on the crop rotation production at gradated nutrient intensity by fertilizers and nutrient uptake by plants. The crop rotation production was converted into cereal units. Comparing the production obtained is given in Tab. I. A lack of NPK fertilizers led to the lowest production reached in the given combinations. Gradated NPK-aplication rates caused a growth in production in the area with no irrigation up to the third level of nutrition, whereas this was not applied in irrigated area. Gradated application rates of phosphorus and potassium alone had no significant effect on the given crop rotation production. The effect of irrigation was positive, an irrigation caused an increase by 12.0 % on an average for all combinations. However, gradated nutrition intensity through fertilizers did not reduce the effect of irrigation. A negative yield response was recorded in lucerne and spring barley. Tabs II and III give the balance of nutrients in both - the irrigated and non-irrigated areas. In both areas, a balance deficit in nitrogen is evident (in irrigation yearly 110- 220 kg, with no irrigation 66 to 183 kg per ha) and in potassium (yearly in irrigation 14 to 129 kg, with no irrigation 66 to 183 kg per ha). An average uptake of nutrients was 296 kg of N in the irrigated area along with 41 kg of P and 213 kg of K, in nonirrigated area these values were as follows: 271 kg of N, 39 kg of P, and 246 kg of K. Better performance of nutrient supplied was recorded in the irrigated area, when biomass was formed. A lack of irrigation, and thus also the deterioration of agroecological conditions reflected in the lower production efficiency of nutrient supplied, especially of potassium. Tabs IV and V bring the agrochemical properties of the soil before the trial establishment and an average for three years of these values after ending the crop rotation (1984 do 1986). The soil reaction decreased in the irrigated area almost proportionally to increasing intensity of fertilizers applied. Irrigation water, containing comparatively a high amount of cations, negated this oxidizing effect of fertilizer. 72.5 kg of Ca, 50.0 kg of Mg, 36.5 kg of K and 25.0 kg of Na per ha penerated into soil through irrigation water yearly. This supply amounted to 9.0 kg per ha in nitrogen yearly. Gradated phosphorus fertilizing increased phosphorus supply in soil in the P3 combination in the irrigated area by 2.7 mg per kg, and by 1.3 mg per kg of soil in nonirrigated area per year. This fact well corresponds with the results of phosphorus balance where for replacement of phosphorus withdrawal by harvests, P1 is sufficient (43 kg of P), or 37 kg of P in commercial fertilizers, further increase in this rate means an increase in phosphorus supplied in thc soil. Potassium reserve decreased in both areas, that is in all combinations what complies with the balances found. After fininishing the crop rotation, soil samples were analysed by the method of cation exchangeable capacity. In nonirrigated areas, the folowing proportion of cations was found on an average for all combinations in sorption complex: 58.6 % of Ca, 3.7 % of K, 8.8 % of Mg; in irrigated area 64.8 % of Ca, 2.85 % of K, 16.6 % of Mg. Irrigation for a long time by eutrophicated water with high calcium and magnesium supply influenced significantly the proportion of these cations in the sorption complex.
