A Comparison of Nitrogen Transfer and Transformation in Traditional Farming and the Rice-Duck Farming System by 15N Tracer Method

A field experiment was conducted in Ninghe, Tianjin, China, using the N-15 isotope method to determine the fate of N sources, application effect of organic fertilizer on the growth of rice plant organs, N uptake by rice, and N use efficiency. The experiment included eight treatments: CK-N (control + no-duck), CK-D (control + ducks), CF-N (chemical fertilizer + no-ducks), CF-D (chemical fertilizer + ducks), CM-N (chemical fertilizer + organic fertilizer + no-ducks), CM-D (chemical fertilizer + organic fertilizer + ducks), CD-N (chemical fertilizer 30% off + organic fertilizer + no-ducks), and CD-D (chemical fertilizer 30% off + organic fertilizer + ducks). The results showed that the application of organic fertilizer whether CM or CD in grain and leaf significantly increased N concentration; leaf and root P concentrations over control (CK) and chemical fertilizer (CF). In contrast, straw and root N concentrations, including grain and straw P concentrations did not show any difference between duck and no-duck treatment. Moreover, non-significant differences were found in N-15 fresh grain and husk concentration. Both organs ranged from 14.2-14.4 g.kg(-1) and 6.2-6.3 g.kg(-1), respectively. Likewise, N uptake and N use efficiency in fresh grain and husk were not significantly differed within duck and without duck treatment. However, N uptake in fresh grain and husk ranged at the rates of 54.90-93.69 and 6.43-11.04 kg ha(-1) with duck and without duck treatment. N use efficiency in fresh grain and husk ranged from 21.55%-34.61% and 2.61%-4.24%, respectively. Overall organic fertilizer has a significant influence on rice growth and promotes crop productivity.