A field experiment was conducted in Ninghe, Tianjin, China, using the 15N 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 15N 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.

A field experiment was conducted in Ninghe, Tianjin, China, using the 15 N 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 15 N 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.2 of 13 fertilizer (CF) in China is more intensive and wide-spread than in any other country [6]. However, excessive use of N fertilizer has the consequence of severe environmental degradation with high potential for N loss in many pathways [7], decreased N use efficiency (NUE), decreased crop quality, and creation of environmental hazards in rice growing countries [8][9][10][11]. Therefore, an appropriate fertilizer input should be required and controlled to maintain rice yield. Adequate nitrogen (N) supply may enhance the rice growth and improve grain yield, and the application of appropriate levels of N fertilizer through improved management is key to increasing N use efficiency [12,13]. In addition, nitrogen is required to produce more food in agricultural systems. Therefore, the lack of N responds quickly to the addition of N fertilizers if applied in a timely manner and properly. Furthermore, nitrogen transformation in soil-plant systems involves the complex N cycling process, which increases the difficulty of N management. Basically, processes involving N in the soil-plant system are: mineralization, nitrification, immobilization, leaching, denitrification, and volatilization. In the present study, ducks were introduced to the field. Duck activities include walking, swimming, eating, grooming, paddling, and rubbing which can influence soil structure and fertil...