CORRELATIONS BETWEEN THE AGROCHEMICAL PROPERTIES OF SOIL AND THE YIELDING CAPACITY OF CEREAL CROPS IN THE FOREST-STEPPE ZONE OF THE CISVOLGA REGION, TATARSTAN REPUBLIC
Parameters of correlation between the content of mobile phosphorus and potassium forms and the average yield of cereal crops were analyzed on the regional and local (administrative) levels of the forest-steppe zone were analyzed. It was found that the correlation increased with elongating period of averaging due to elimination of the weather factor. Higher coefficients of correlation were obtained for potassium compared to phosphorus, which pointed to a lack of potassium in gray forest soils.