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 15N isotope method to evaluate the application of organic fertilizer on N distribution patterns of labelled and unlabeled N fertilizer, ammonium sulfate -15N uptake by rice, N use efficiency (NUE), and the fate of (15NH4)2SO4 applied. 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 significantly increased N and P concentrations over control (CK) and chemical fertilizer (CF). Moreover, no-significant differences were found in 15N fresh grain and husk concentration. Both organs ranged of 14.2-14.4 g kg-1 and 6.2-6.3 g kg-1, respectively. N derived from the fertilizer and soil significantly affected fresh grain compared to fresh husk. However, N uptake and N use efficiency did not show any differences. We concluded that organic fertilizer has a significant influence on rice growth and promote crop productivity.