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

This study was undertaken to characterize the response of organic matter mi neralization to soluble electrolyte concentration. We added salts (either K Cl or KH2PO4) to a non-saline Black Chemozem at rates of 0 to 64 mmol kg(-1 ) and measured the amounts of C and N mineralized in a 40 d incubation (21 degrees C and field capacity), precipitation of calcium phosphate in KH2PO4 -treated soil resulted in electrical conductivity (EC), measured ina 1:2 so il:water extract, being lower than in KCl-treated soil. Dissolved organic C (DOC) was increased (up to twofold) by KH2PO4 addition but KCl had little effect. The relationship between C mineralization and EC appeared to be ind ependent of salt type. Mineralization decreased sharply (by 50%) when EC in creased from 0.5 dS m(-1) (check value) to 1.3 dS m(-1). Inhibition of nitr ification was not detected until EC increased to about 2 dS m(-1).