Effects of Nitrogen Rates on Nitrogen Utilization Efficiency in Different Types of Rice Germplasms at Seedling Stage

Nitrogen utilization efficiency (NUE) in rice germplasms with different ecological types were determined and analyzed during seedling stage under low nitrogen rate (20 mg/kgN), medium nitrogen rate (40 mg/kgN) and high nitrogen rate (60 mg/kg N). The results showed that NUE in different ecological rice germplasms reduced with increasing nitrogen rate and had significant or greatly significant differences with different nitrogen rates. NUE in upland rice was significantly higher than that in paddy rice under low nitrogen rate, whereas NUE between upland rice and paddy rice was not significantly different under medium and high nitrogen rates. NUE in contemporary breeding variety was significantly or greatly significantly smaller than that in ancient local variety under different nitrogen rate. NUE in hybrid combination was significantly or greatly significantly higher than that in conventional variety under different nitrogen rate. NUE in Indica rice was greatly significantly smaller than that of Japonica rice under medium and high nitrogen rates, but NUE between Indica rice and Japonica rice was not significantly different.