POTASSIUM BALANCE IN THE SOIL AND THE EFFECTIVENESS OF POTASSIUM DEFICIENCY SYSTEM OF FERTILIZATION

The influence of long-term application of different doses and ratios of mineral fertilizers in field crop rotation on the content of basic nutrients in grain and straw of spring barley has been established. The study was held in the conditions of podzolic black heavy loam soil of the Right-Bank Forest-Steppe of Ukraine. The relative nutrients removal by spring barley depending on the doses of different types of fertilizers and their combinations in the field crop rotation is calculated. It is shown that the content of basic nutrients in the harvest of spring barley (grain and straw) significantly depends on the content of their mobile compounds in the soil. This is especially true of nitrogen and less of potassium. Economic removal of nutrients from the grain harvest of spring barley depends on the doses of fertilizers in the field crop rotation and the ratio of nutrients in them. The largest share is nitrogen (65–122 kg / ha), followed by K2O - 47–92 and P2O5 26–51 kg / ha. From 1 ton of grain and the corresponding amount of straw, spring barley of the Commander variety removes 19.2–22.4 kg of nitrogen, 7.8–9.2 - P2O5 and 14.0–16.8 kg of K2O from the soil, depending on the fertilizer and saturation of field crop rotation with different types of fertilizers. Straw is an important source of soil organic matter reproduction and the return of nutrients used for crop formation. Depending on the system of fertilization, 17–25% of nitrogen, 25–30% of phosphorus and 68–69% of potassium are returned to the soil with spring barley straw via economic removal. It is specified that spring barley of the Commander variety absorbs N, P2O5 and K2O in the following ratio: 1: 0,4: 0,3 to form a unit of grain yield and the corresponding amount of straw in the conditions of podzolic black heavy loam soil of the Right-Bank Forest-Steppe