CATION-EXCHANGE PROPERTIES OF UNIRRIGATED AND IRRIGATED ORDINARY CHERNOZEM

The insignificance of the differences between genetic horizons of Ordi nary Chernozems with respect to the coefficients of selectivity of Nik ol'skiy (k(N)) exchange for the pairs of (Ca + Mg)-Na, Ca-Na, and Mg-N a is demonstrated. In horizon A, the value of K(Ca+Mg)-Na(N) is 10-15 percent lower in irrigated plots than in unirrigated plots, whereas in horizon B it is higher. Determining the CEC of Chernozems by the Pfef fer method yields understated values; the Gillman method (1979) yields better results.