A study on the relative efficiency of organic manures and the effect of salinity on its mineralisation in brackishwater fish farm soil

The influence of salinity on the mineralisation of organic nitrogen in the form of mustard oil cake, poultry manure and cow-dung in brackishwater pond soils was studied under laboratory conditions. The concentration of mineralised nitrogen for mustard oil cake and poultry manure showed a marked increase during 7 to 30 days after which it decreased gradually and in 90 days assumed practically the same value as that of the control over the salinity range of 0–40‰. The mineralised nitrogen of cow-dung treatment was lower than that of the control,till 30 days,after which it increased gradually. The loss of nitrogen is minimum in the higher salinity range for all three types of manure used. Mustard oil cake is a better manure for brackishwater soil than poultry droppings and cow-dung.