EFFECTIVE FERTILITY OF CHESTNUT SOILS
The chestnut soils of the Kulunda dry steppes cover over 1,308,000 ha and are widely used in agricultural production. Rational and efficient use of chestnut soils with their relatively low fertility and the development of ways to improve fertility are impossible without studying the soil and climatic conditions of crop yield formation. It is known that crop yield may vary within a single field. The yield value is determined by the impact of economic activity, and also depends on the weather conditions and soil properties. Therefore, the authors analyzed the hydrothermal conditions for the period from 1971 to 2000; statistical data processing was carried out, the crop yields were studied. It has been proved that the organizational factor (an organizational type of agricultural enterprise) significantly affects the average yield of spring wheat. On average, wheat yields are higher by 0.36 t ha in a peasant (farmer) enterprise than that in a limited liability company. Information-logical analysis of the relationship of yields and soil and climatic factors enabled to develop a model of effective fertility of chestnut soils for spring wheat. The proposed model of effective fertility of chestnut soils (expressed by spring wheat yields) is proved correct with provision for one rank deviation to 77-83%. This model has been developed without considering the variety, forecrop and the impact of organizational and economic factors of effective fertility. The developed model is a prognostic model which reflects effective fertility and may be used to evaluate effective fertility under low and medium technology of spring wheat cultivation.