Effects of Combined Application of Inorganic Fertilizer and Organic Manures on Nitrogen Use and Recovery Efficiencies of Hybrid Rice (Palethwe-1)

We conducted two field experiments to investigate combined effects of or- ganic and inorganic fertilizers on nitrogen use and recovery efficiencies of hybrid rice (Palethwe-1) during dry and wet seasons, 2015. Four levels of in- organic fertilizer (0%, 50%, 75%, and 100% NPK), based on recommended rates of 150 kg N ha−1, 70 kg P2O5 ha−1, and 120 kg K2O ha−1, were used with cow manure, poultry manure, and vermicompost (5 t•ha−1each) in a split-plot design with three replicates. In both seasons, with 50% NPK, the N uptake level achieved with poultry manure was similar to that obtained with 75% and 100% NPK. The greatest N use, internal, agronomic N use, and recovery effi- ciencies were obtained with 50% NPK + poultry manure, but were similar to those obtained from cow manure and vermicompost subplots. As the amount of applied N from organic and inorganic fertilizer increased, the N use effi- ciency and related parameters decreased, due to similar yields among plots with different NPK application levels. Poultry manure resulted in the highest significant correlations between applied N and N accumulation, followed by cow manure and vermicompost, in both seasons. Neither chemical fertilizer nor organic manure alone led to optimum N use and N recovery efficiencies. The combination of 50% inorganic fertilizer (75 kg N ha−1) and poultry ma- nure (5 t•ha−1) enhanced the N uptake, the N use and recovery efficiencies of hybrid rice. Cow manure (5 t•ha−1) in combination with 75% inorganic ferti- lizer (112.5 kg N ha−1) was an adequate substitute for reduced chemical ferti- lizer usage. Therefore, this study highlighted combined application of inorganic fertilizers and organic manures had the benefits not only in reducing the need for chemical fertilizers but also in improving N uptake by hybrid rice (Palethwe-1) leading to the better environment