Carbon and nitrogen mineralization in soil treated with chloride and phosphate salts

This study was undertaken to characterize the response of organic matter mineralization to soluble electrolyte concentration. We added salts (either KCl or KH 2 PO 4 ) to a non-saline Black Chernozem at rates of 0 to 64 mmol kg −1 and measured the amounts of C and N mineralized in a 40 d incubation (21 °C and field capacity). Precipitation of calcium phosphate in KH 2 PO 4 -treated soil resulted in electrical conductivity (EC), measured in a 1:2 soil:water extract, being lower than in KCl-treated soil. Dissolved organic C (DOC) was increased (up to twofold) by KH 2 PO 4 addition but KCl had little effect. The relationship between C mineralization and EC appeared to be independent of salt type. Mineralization decreased sharply (by 50%) when EC increased from 0.5 dS m −1 (check value) to 1.3 dS m −1 . Inhibition of nitrification was not detected until EC increased to about 2 dS m –1 . Key words: Mineralization, organic matter, salinity, chloride, sulfate