Changes in the properties of a crusty solonetz with soda salinization after single and repeated amelioration with phosphogypsum

Abstract

Different effects of single and repeated application of various rates of phosphogypsum to a crusty meadow chernozemic high-sodium solonetz with soda salinization formed in the zone of insufficient moistening in the forest-steppe zone of Western Siberia (the Ishim-Irtysh interfluve area) with the mean annual precipitation of 325 mm are revealed. Repeated phosphogypsum application provided a higher saturation of the soil exchange complex with exchangeable calcium, deeper desalinization of the soil profile, and more intensive removal of the exchange products beyond the 1-m-thick layer as compared to a single phosphogypsum application. The soil reclamation results in the soil profile’s differentiation into three zones with respect to the salt content: the desalinization, transit, and accumulation zones. The greater the ameliorant rate, the higher the soil desalinization upon a single application of phosphogypsum. Upon the repeated phosphogypsum application, the zones of desalinization and salt transit are thicker irrespectively of the ameliorant rate. Despite the additional salt application, the degree of salinization in the upper 2 m does not increase. Data of the long-term investigations show that a single gypsum application exerts a favorable and long-term ameliorative effect. In the solonetz repeatedly ameliorated with phosphogypsum at the rates of 8 and 16 t/ha, the amount of the reacted phosphogypsum considerably exceeds the applied calculated rate and is almost equal to that upon a single application of phosphogypsum at the double rate (32 t/ha). It has been shown that not only the repeatedly applied phosphogypsum but also the soil calcium participates in the exchange reactions. This makes it possible to apply smaller rates of the ameliorant or calculate its rate for the upper 10-cm-thick layer.