Search

High doses of nitrogenous fertilizers are often applied in fishponds but only a small part of the added nitrogen is utilized for improving primary productivity and, thereby, fish yields. A large por- tion of the nitrogen is lost from the pond environment through various mechanisms, especially nitrification. In the present investigation, we studied the effects of three nitrification inhibitors: (a) neem (Azadirachta indica) extract, (b) karanj (Pongamia glabra) extract, and (c) sodium azide (NaN3), on the transformation of applied nitrogen in simulated fishpond conditions. The study revealed that nitrification inhibitors considerably retard the rate of nitrification from the ammoni- um form of nitrogen (NH4+), resulting in a higher amount of nitrogen in the soil and water. The increased nitrogen concentration significantly increased gross primary production and, hence, improved the efficiency of the added nitrogen.