The influence of mineral and organic fertilizers in the grain crop rotation on the properties of leached chernozem of the Western Caucasia

The purpose of the research is to assess the humus state and functioning of the soil absorbing complex of leached chernozem during the rotation period of the six-field grain crop rotation. Traditional methods of soil research were used in field long-term experience. The medium and high rates of the mineral fertilizers of nitrogen, phosphorus, potassium, as well as the organic fertilizers (litter, liquid manure, straw) and their combinations with mineral solid fertilizers were used. The application of the mineral fertilizers for a circle of the crop rotation contributed to an increase in all types of soil acidity. The use of the litter manure and straw significantly reduced the indicators of an active, metabolic and hydrolytic acidity, respectively, by 6.8-1.7, 15.2-13.0, and 18.4-8.2% relative to the control. The joint application of the organic and mineral fertilizers slows down the rate of acidification of the soil, but does not eliminate them. The use of the litter manure and its combination with a mineral fertilizer caused an increase in the carbon content of humus, respectively, by 3.9 and 11.6%. The use of the straw in a combination with the mineral fertilizer and liquid manure increased the carbon content of humus, respectively, by 1.4 and 14.5% relative to the control. The degree of humification with increasing rates of the mineral fertilizers decreased from 24.2 to 22.3, and with the use of the organic fertilizers increased from 22.3 to 25.2.