## Result
### GPN, GPP and GPK  
In the two ecological regions of the double cropping rice, a higher N application rate reduced the GPN, GPP and GPK, and the GPN, GPP and GPK under the D\({}_{2}\) and D\({}_{3}\) treatment were slightly higher than those under the D\({}_{1}\) treatment (Figure 2). Compared \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Season**} & \multirow{2}{*}{**Treatment**} & \multicolumn{2}{c}{**Panicle Number**} & \multicolumn{2}{c}{**Spikelet Filling**} & \multicolumn{2}{c}{**Thousand Kernel**} & \multicolumn{2}{c}{**Yield (t ha\({}^{-1}\))**} \\ \cline{3-10}  & & **(\(\times\)10\({}^{4}\) hm\({}^{-2}\))** & & & & **Percentage (\%)** & & **Weight (g)** & & **Yield (t ha\({}^{-1}\))** \\ \cline{3-10}  & & **2018** & **2019** & **2018** & **2019** & **2018** & **2019** & **2018** & **2019** & **2018** & **2019** \\ \hline Early & N\({}_{1}\)D\({}_{1}\) & 331.03e & 321.87e & 131.1a & 130.59a & 70.19d & 70.39b & 25.11a & 25.07a & 6.98c & 6.83c \\ rice & N\({}_{1}\)D\({}_{2}\) & 410.50c & 398.56c & 112.62b & 111.68b & 71.39c & 71.09b & 25.06a & 25.11a & 7.57b & 7.42b \\  & N\({}_{1}\)D\({}_{3}\) & 466.22a & 445.96a & 95.35c & 94.68c & 74.29b & 73.89a & 25.16a & 25.21a & 7.59b & 7.44b \\  & N\({}_{2}\)D\({}_{1}\) & 346.27d & 335.69d & 129.95a & 128.79a & 70.05d & 70.59b & 25.14a & 25.17a & 7.31b & 7.16b \\  & N\({}_{2}\)D\({}_{2}\) & 420.40b & 407.59b & 113.52b & 110.68b & 74.10b & 74.89a & 25.08a & 25.07a & 7.92a & 7.77a \\  & N\({}_{2}\)D\({}_{3}\) & 460.79a & 449.16a & 98.53c & 97.80e & 75.44a & 74.99a & 25.21a & 25.16a & 7.91a & 7.76a \\  & N & 204.48 \({}^{**}\) & 169.73 \({}^{**}\) & NS & NS & 34.55 \({}^{**}\) & 60.69 \({}^{**}\) & NS & NS & 137.11 \({}^{**}\) & 604.84 \({}^{**}\) \\  & D & 250.89 \({}^{**}\) & 108.084g \({}^{**}\) & 207.34 \({}^{**}\) & 1323.97 \({}^{**}\) & 169.28 \({}^{**}\) & 111.80 \({}^{**}\) & NS & NS & 199.10 \({}^{**}\) & 878.29 \({}^{**}\) \\  & N \(\times\) D & 18.21 \({}^{**}\) & 21.22 \({}^{**}\) & NS & 8.56 \({}^{**}\) & 15.26 \({}^{**}\) & 24.57 \({}^{**}\) & NS & NS & NS & NS \\ Late & N\({}_{1}\)D\({}_{1}\) & 389.35d & 399.52d & 129.56a & 126.89 ab & 77.82b & 77.49b & 18.87a & 18.92a & 7.21c & 7.33c \\ rice & N\({}_{1}\)D\({}_{2}\) & 417.95c & 428.20c & 124.42b & 124.42 ab & 80.25 ab & 80.35 ab & 18.92a & 18.93a & 7.81b & 8.01b \\  & N\({}_{1}\)D\({}_{3}\) & 441.83 ab & 452.14b & 117.33e & 117.00b & 81.54a & 82.05a & 18.91a & 18.73a & 7.82b & 8.04b \\  & N\({}_{2}\)D\({}_{1}\) & 411.08c & 422.19c & 129.12a & 128.79a & 78.58b & 78.51b & 18.89a & 18.90a & 7.61b & 7.87b \\  & N\({}_{2}\)D\({}_{2}\) & 437.39b & 451.70b & 124.57b & 124.57b & 80.54 ab & 79.83 ab & 18.92a & 18.94a & 8.26a & 8.47a \\  & N\({}_{2}\)D\({}_{3}\) & 457.70a & 470.29a & 120.32c & 121.32 ab & 81.12a & 80.79 ab & 18.87a & 18.91a & 8.24a & 8.51a \\  & N & 109.51 \({}^{**}\) & 58.40 \({}^{**}\) & NS & NS & NS & NS & NS & 337.43 \({}^{**}\) & 566.67 \({}^{**}\) \\  & D & 248.96 \({}^{**}\) & 108.30 \({}^{**}\) & 121.50 \({}^{**}\) & 20.40 \({}^{**}\) & 51.93 \({}^{**}\) & 16.15 \({}^{**}\) & NS & NS & 342.29 \({}^{**}\) & 454.43 \({}^{**}\) \\  & N \(\times\) D & NS & NS & NS & NS & NS & NS & NS & NS & NS \\ \hline \hline \end{tabular} N\({}_{1}\) and N\({}_{2}\) represent 120 and 150 kg ha\({}^{-1}\) for early rice and N\({}_{1}\) and N\({}_{2}\) represent 120 and 165 kg ha\({}^{-1}\) for late rice. D\({}_{1}\), D\({}_{2}\) and D\({}_{3}\) represent 86, 143 and 200 plants per m\({}^{2}\) for early rice and D\({}_{1}\), D\({}_{2}\) and D\({}_{3}\) represent 57, 114 and 172 plants per m\({}^{2}\) for late rice. Values followed by different lowercase letters are significantly different at the 0.05 level. NS and ** represent no significant difference and significant difference at the 1% levels.  
\end{table}