Humus, phosphorus, and potassium in cultivated soils of Ciscaucasia

The progressing alkalization in the soils of Ciscaucasia is accompanied by a significant increase in the concentration of labile forms of phosphorus a nd potassium in the soil solution, despite a strong decrease in the applica tion of fertilizers after 1991. The reasons and particular mechanisms of th is process remain unclear. The 20-year-long survey data witness that the hu mus content is relatively stable in the noneroded soils, while the annual l oss of humus in the eroded soils can reach 0.14%.