Effect of organic manures on organic carbon content of submerged pond soil

Application of organic manures (cow dung, poultry manure, mustard oilcake o r compost) at three levels (300, 600 or 1200 kg C/ha) to pond soil with a l ow (0.45%) or medium (1.33%) organic carbon content resulted in a significa nt (p <0.01) increase in organic carbon in both soils. The increase of soil organic carbon was higher in both soils under incubation (5.7-20.41% and 1 5.08-29.93%) than in soils used for rearing of carp spawn (2.65-14.99% and 1.82-6.07%). A similar increase in organic carbon for low-carbon and medium-carbon soils (5.77-7.83% and 2.86-5.15%, respectively) was observed after three months of applying nitrogen (0.2 ppm), phosphorus (0.1 ppm) and 10, 30 or 60 kg C/ ha at monthly intervals. The lowest increases (5.77% and 2.86%) occured in the 30 kg C/ha/month treatment.