Effects of P and Cd addition on mineralization of organic N in cultivated red soils

Abstract

The effect of adding P and Cd respectively or together on N mineralization in cultivated red soils derived from different parents(quater-nary red soil,weathering product of granite,weathering product of limestone,weathering product of slate),in Hunan,was studied based on indoor incubation with P concentrations of 0,0.1,0.3,0.5 g/kg and with Cd concentrations of 0,0.5,1.0 mg/kg.Results showed that the average accumulation of N mineralized in quaternary red soil increased first and then decreased with the addition of P,and the maximum N mineralization was happened when the concentration of additive P was 0.1 g/kg.Average accumulation of N mineralized in other red soils increased with the increase of P addition.N mineralization was inhibited by Cd in both quaternary red soil and limestone red soil treated with Cd in a concentration range of 0-1.0 mg/kg,and the largest decline of N mineralization were 4.98 mg/kg and 6.53 mg/kg.Adding the P and Cd together promoted N mineralization in the red soils except the quaternary red soil,and N mineralization were different in red soils derived from different parent soils.Organic N in the red soil with slight Cd pollution mineralized most effectively under the P concentration of either 0.3 g/kg or 0.5 g/kg.