LAUSR

ABSTRACT To select optimal fertilization management for soil productivity and fertilizer-nitrogen use efficiency (NUE) improvement in rice fields, we conducted a microplot experiment by growing rice in soils from different long-term fertilizations with the same inorganic fertilizers. The NUE was accurately evaluated using 15N labeled urea. The variations of the chemical compositions of soil organic carbon (SOC) under different long-term fertilizations were investigated by three-dimensional fluorescence measurement. The results indicated that the treatments containing organic materials could maintain high soil productivities and displayed higher NUE than inorganic treatments. Total phosphorus (TP) was the most important soil factor for soil productivity and the SOC content ranked second, whereas SOC content was the primary soil factor affecting NUE and TP ranked second. Applying organic materials also significantly changed the chemical compositions of SOC as compared with inorganic treatments. Besides the SOC content, the chemical compositions of SOC also affect the soil productivity and NUE. In summary, long-term balanced application of inorganic fertilizers and organic materials increased the quantity and changed the chemical composition of SOC, and thus maintained high soil productivity and NUE.