Ammonium bicarbonate is a low grade nitrogen fertilizer. It is easily volatile and of poor physical properties. However, at present, a large number of small nitrogen factories are still operating to produce this fertilizer for local usage in China. Recently, deep drill of NH₄HC0₃ pills bellow soil surface has been found much more effective to crop growth than top dress of NH₄HC0₃ powder. The pills weigh about lgm, are pressed out by a double-roll prilling machine. Present investigation deals with the coating technique of NH₄HC0₃ pills for preparing a slow-release fertilizer and the factors affecting the release rate of N from coated pills. The efficiency of this controlled nitrogen ferrilizer has also been studied.