Improvement of nitrogen fertilizer efficiency with nitrification inhibitors in lowland rice

Rice is a very responsive crop to nitrogen, but the efficiency of the N- fertilizers is low. Greenhouse experiment has been conducted to evaluate some synthetic (N-serve) and natural (neem cake and waste tea) nitrification inhibitors to improve fertilizer efficiency and reduce N-losses in rice fields. Nitrogen was applied as urea and ammonium sulfate at a rate of 60mg/Kg soil. Results revealed that addition of inhibitors with both N fertilizer caused a significantly increase in both grain and straw yields rice, addition of 0.04 per cent neem cake with both urea and as gave the highest grain and straw yields of rice while the waste tea gave the lowest. The percentage increase of total yield with urea + inhibitor treatments ranged between 5.8 per cent to 26 per cent when compared with urea alone, 26 per cent increase was recorded for 0.04 per cent neem cake treatment and 22.4 per cent for N-serve, while 5.8 per cent was recorded for 0.04 per cent waste tea treatment. Also, the percentage increase in total rice yield over AS alone was 14.4 per cent and 25.6 per cent for 0.02 per cent and 0.04 per cent neem cake treatments respectively, while was 8.8 per cent for N-serve treatment. Results also showed that neem cake combined with both urea and AS was more effectiveness on N-uptake especially at applied rate (0.04 per cent ). The percentage increase in total N-uptake over urea alone was 31 per cent , 29 per cent and 5 per cent for 0.04 per cent neem cake, N- serve and 0.04 per cent waste tea respectively. On the other hand, the percentage increase of total N-uptake over all as alone was 29 per cent and 15 per cent for 0.04 per cent and 0.02 per cent neem cake treatments respectively, while, the waste tea a very low increase in total N-uptake. N-recovery by rice plant increased from 285 to 513 mg N/pot as a result of addition of inhibitors, as well as en improved in the utilization efficiency of N from urea and AS fertilizers was recorded.