Distribution of soil organic carbon within water stable soil Aggregates in long-term fertilized and Manured Rice-Wheat rotation
Tarik Mitran, Pabitra Kumar Mani, Kuntal Ganguly
An experiment was conducted in a 22nd cycle of long-term rice-wheat rotation established in the hot humid subtropics of eastern India to evaluate carbon concentration within water stable aggregates in soils undergoes influences of continuous manuring and fertilization. Soil samples were collected at 0-15cm depth from twelve treatments with different type of organic amendments such as farmyard manure, paddy straw and green manure with two levels of Nitrogen substitution (50% and 25%) from. The wet sieving technique was employed to separate soils and catagorized into >2.0, 2.0-0.25, 0.05-0.25 and<0.05mm aggregate fractions. There was an enrichment of organic carbon content in the larger size aggregates (>2 mm) compared to smaller aggregates (<0.25 mm). Higher proportion of organic carbon was occluded within small macro aggregates (0.25-2.0mm) than fine micro aggregates (0.05-0.2mm) as well as silt plus clay sized soil separates (<0.05mm). The effects were more pronounced in organically amended soils rather than unfertilized and solely fertilized soil. Within a size class, aggregated C concentrations of the organically amended treatments were in the order of FYM>PS≥GLM. In all the cases 50% substitution of N by organic amendments recorded much higher values than 25% substitution of N.