Carbon and nitrogen mineralization in clay loam soil amended with different composts

This study investigates the effects of different composts on chemical and biomass soil properties. This study also measures mineralization of nitrogen (N) and carbon (C) in soils amended with different organic residues including manure and composts. A laboratory incubation experiment was conducted to study the effect of different amendments such as C1: composted greenwaste (GW) C2: composted Posidonia oceanica mixed with poultry manure (70/30%; v/v); C3 compost green waste mixed with Posidonia oceanica (70/30%; v/v), C4: compost of municipal domestic solid wastes, on mineralization of N and C, EC, pH and microbial biomass in soil. Farmyard manure (F) was used as a control test. Eight weeks after incubation, the highest electric conductivity (EC), was recorded in soil amended with C3 (500 μS/cm) while the lowest value was recorded in the sample from the soil treated with C2 (316 μS/cm). The salt content of the green waste compost C1 (422 μS/cm) was not significantly different than soil amended with C2 (427 μS/cm). Organic matter in soil treated with C4 showed high potential mineralization of carbon and nitrogen compared to those observed in a soil (S) treated with manure. After eight weeks of incubation, carbon mineralization of the different organic residues expressed as mg C/kg dry matter (DM) exhibited the following order (values): Carbon mineralization of different soil applied organic residues ranked in the following order: S + F (463) > S + C3 (318) > S + C4 (286 ) > S + C1 (257) > S+C2 (233) > S (167). However; net N mineralization expressed as mg N/kg dry soil after 8 weeks of incubation has the following order: S + C4 (80) > S + C3 (71) > S + F (64) > S + C1 ( 57) > S+C2 (48) > S (47). Posidonia oceanica associated with green wastes increased carbon mineralization from 257 to 318 ppm C, N mineralization from 57 to 71 ppm N. However addition of Posidonia oceanica to the green vegetable pile reduced the biomass C from 667 to 498 mg/Kg DM and biomass N from 34.17 to 24.59 mg/Kg DM.The present study showed significant variation in the mineralization of nitrogen and carbon after addition of different types of organic wastes.

Keywords:

Soil , Green wastes , Posidonia oceanica , Compost , Amendment , Mineralization , Biomass C and N