PHOSPHORUS BALANCE IN ROTATION
The effect of ammonium nitrate, double superphosphate and phosphogypsum on the phosphorus balance has been studied in conditions of Zauralye in a four-field grain-fallow crop rotation. It is done on leached cherno-zem of light loamy. The studies were carried out in a stationary experiment on the experimental field of the Kurgan State Agricultural Academy in 2012-2014. The calculation of the economic phosphorus balance was carried out taking into account the yields of main and minor products of each crop of rotation, as well as the determination of the element in the grain and straw. Fertilizers applied in the experiment had different effects on the phosphorus bal-ance in the crop rotation. The phosphorus balance was negative on the variants without fertilizers (-46.3 kg/ha) and using phosphogypsum (-33.1-40.7 kg/ha). With the annual use of nitrogen fertilizer, phosphorus removal increased to 53.6-53.8 kg/ha. The largest removal of the element was noted in the variant with the use of mineral fertilizers on the background of phosphogypsum - 60.7 kg/ha. The use of mineral fertilizers and phosphogypsum led to a significant change in the structure of the phosphorus balance in crop rotation. The intensity of the balance at the rate of making superphosphate (120 kg) for three years was 222%, using phosphogypsum the intensity was 20-38%. Combined use of mineral fertilizers and phosphogypsum increased the intensity of the balance up to 235%.