Increased efficiency of rockphosphate in presence of ammonium sulphate in carp culture system.

摘要

The combined fertilizer value of Mussoorie Phosphate Rock (MPR) and nitrogen (N) was evaluated using growth criteria for carp. Forty-four carp fry (Labeo rohita, Cirrhinus mrigala, Cyprinus carpio in a 2:1:1 ratio) were introduced in each of twelveexperimental tanks used for monthly application of fertilizers for one year growth cycle in four combinations, in triplicate: high dose MPR (MPR-H), low and high doses of MPR amended with nitrogen (MPRL-N and MPRH-N), and mixed application of MPR and single superphosphate (SSP) with nitrogen (MPR+SSP-N). Primarily contributed by Labeo rohita (64-69%), the total yield of fish was maximum and minimum in MPRH-N and MPRL-N, respectively. Stepwise multiple regression analysis revealed that the mechanism of orthophosphate to fish growth via net primary productivity (NPP) was functional in MPRH-N. Apart from these two variables N: P ratio and COD were responsible for fish growth in MPR+SSP-N. In MPRL-N and MPR-H, the available-P and N: P ratio of soil or available-N of water were responsible for fish growth mediated through NPP.