EFFECT OF THE LONG-TERM USE OF ORGANIC AND MINERAL FERTILIZING SYSTEMS IN A GRAIN-FALLOW CROP ROTATION ON THE DYNAMICS OF EXCHANGEABLE POTASSIUM IN LEACHED CHERNOZEM
The stabilization of potassium status in leached chernozem under long-term application of nitric and phosphoric fertilizers for spring wheat and oat (planned productivity to 4.0 t/ha) in the grain-fallow crop rotation on the background of straw plowing was observed only during ten years. The further cultivation of grain crops on the same agricultural background gradually decreased the content of mobile potassium in the soil, in spite of the plowing of straw. Increase in the level of mineral nutrition (NPK) to 6.0 t/ha enhanced the uptake of potassium from the soil, which negatively affected its reserve already after two cycles of crop rotation. Under conditions of the Transural forest-steppe zone, the plowing of wheat and oat straw in the grain-fallow crop rotation cannot stabilize the potassium status of leached chernozem. This fact should be taken into consideration at the development of a fertilizing system ensuring the fertility reproduction of chernozemic soils involved in the arable land resources.