## 3 Results
### Effect of the Irrigation System and Variety on the Yield, Yield Components, and WUE of Winter Wheat
In the two-year experiment, the average thousand-grain weight and the average yield of the three varieties increased with increasing irrigation amount, and the average thousand-grain weight and average yield in 2020-2021 were generally lower than those in 2021-2022. From 2020 to 2021, the average WUE increased gradually with increasing irrigation amount. The yield and WUE in the W3 treatment were obviously higher than those in the W1 and W2 treatments. In 2021-2022, the thousand-grain weight and yield of the W2 and W3 treatments were significantly increased compared to the W1 treatment. Moreover, the average WUE in the W2 treatment was obviously higher than that in the W1 and W3 treatments (Table 7). Regression analysis was conducted between the yield increase rate and irrigation amount (Figure 4). In 2020-2021, there was a highly obvious linear correlation between the grain yield increase rate and irrigation amount of Hengmai4399 (\(p<0.01\); Figure 4a). The linear correlation between the yield increase rate and irrigation amount of Hengguan35 reached a significant level (\(p<0.05\); Figure 4b). In 2021-2022, a significant linear relationship between the grain yield increase rate and irrigation amount of Hengmai4399 and Hengmai28 was found (\(p<0.05\); Figure 4c,e), and there was no notable linear correlation between the yield increase rate and irrigation amount in Hengguan35 (\(p>0.05\); Figure 4d). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multirow{2}{*}{**Treatments**} & **Thousand-Grain Weight (g)** & **Effective Spikes (10\({}^{4}\).hm\({}^{-2}\))** & **Grains per Spike** & **Gain Yield (kg\(\cdot\)hm\({}^{-2}\))** & **WUE (kg\(\cdot\)m\({}^{-3}\))** \\ \hline \multirow{4}{*}{2020–2021} & V & ns & - & - & ns & ns \\  & W & ns & - & - & ** & ** \\  & V \(\times\) W & ns & - & - & ns & ns \\ \cline{2-6}  & V & * & * & * & ns & ns \\ \cline{2-6}  & W & ** & ns & ns & ** & ** \\ \cline{2-6}  & V \(\times\) W & ns & ns & * & ns & ns \\ \hline \hline \end{tabular}  
* Notes: *: \(p<0.05\); **: \(p<0.01\); ns: not significant, V: variety; W: irrigation treatment; V \(\times\) W: interaction between variety and irrigation system, the same as below.  
\end{table} 
Table 6: Effect of variety, irrigation, and the interaction of both on yield, yield components, and water use efficiency. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Year**} & \multirow{2}{*}{**Treatments**} & **Thousand-Grain Weight (g)** & **Effective Spikes (10\({}^{4}\).hm\({}^{-2}\))** & **Grains per Spike** & **Gain Yield (kg\(\cdot\)hm\({}^{-2}\))** & **WUE (kg\(\cdot\)m\({}^{-3}\))** \\ \hline \multirow{4}{*}{2020–2021 (N = 6)} & W1 & 40.52 \(\pm\) 2.44 a & - & - & 6178.09 \(\pm\) 814.50 b & 1.66 \(\pm\) 0.22 b \\  & W2 & 42.43 \(\pm\) 2.77 a & - & - & 6978.49 \(\pm\) 762.29 b & 1.72 \(\pm\) 0.19 b \\  & W3 & 43.33 \(\pm\) 2.55 a & - & - & 8816.91 \(\pm\) 593.75 a & 2.31 \(\pm\) 0.16 a \\ \cline{1-1} \cline{2-6}  & W1 & 43.66 \(\pm\) 2.76 b & 575.13 \(\pm\) 64.03 a & 35.21 \(\pm\) 2.31 a & 8155.56 \(\pm\) 421.14 b & 1.83 \(\pm\) 0.09 c \\ \cline{1-1}  & W2 & 48.02 \(\pm\) 3.65 a & 570.93 \(\pm\) 48.79 a & 36.61 \(\pm\) 2.24 a & 9048.15 \(\pm\) 508.30 a & 2.12 \(\pm\) 0.12 a \\ \cline{1-1}  & W3 & 50.00 \(\pm\) 4.45 a & 598.18 \(\pm\) 53.47 a & 34.94 \(\pm\) 3.14 a & 9307.41 \(\pm\) 443.17 a & 1.98 \(\pm\) 0.09 b \\ \hline \hline \end{tabular}  
* Notes: Different lowercase letters after the same column of data indicate significant differences at the \(p<0.05\) level between different treatments, the same as below.  
\end{table} 
Table 7: Effects of different irrigation systems on the yield, yield components, and WUE of winter wheat.