## 4 Discussion  
In this research, the water content of the soil profile of each treatment was uniformly distributed in the pre-pointing stage. After irrigation, the increase in the soil moisture content above the 60 cm soil layer was significantly greater than that below the 60 cm soil layer, which was in agreement with the results of [PERSON] et al. [23] and [PERSON] et al. [24] The soil water consumption among the 0-100 cm soil layer during the growth period of winter wheat under the W2 and W3 treatments accounted for 77.06-87.39% and 69.30-94.22% of the total soil moisture consumption, respectively. However, the soil moisture consumption in the 100-150 cm soil layer under the W1 treatment was obviously greater than that under the W2 and W3 treatments, accounting for 15.71% and 26.36%, respectively. This result is because the soil moisture absorbed by the winter wheat mainly depends on the root, but there is a less-deep root system, so the consumption of soil moisture mainly comes from the 0-120 cm soil layer [24; 25; 26]. The W1 treatment did not supplement the shallow soil water after the jointing stage because the reduction in irrigation will promote downward root development of winter wheat, thereby enhancing the capacity of winter wheat to absorb deep soil water [27]. The water consumption in each soil layer is greatly influenced by the soil and climatic conditions for winter wheat [28]. Under the condition of limited water irrigation, sufficient soil water storage before sowing is an important condition for winter wheat to maintain a high yield [11]; it is because sufficient soil water storage before sowing can promote wheat to absorb deep soil moisture. The results of this study showed that there was an obvious and positive correlation between deep soil water consumption and soil moisture storage presowing (Table 3). Due to more autumn rainfall in 2021, the soil moisture before winter wheat sowing was sufficient from 2021 to 2022, which improved the ability of wheat to use the soil moisture storage. Therefore, there was a large difference in the change in soil water content under 140 cm in the two-year test W1 treatment, but irrigation in the late growing period of the W2 and W3 treatments reduced this difference (Figure 2). Water has a regulatory effect on the photosynthetic characteristics of wheat, and high chlorophyll content in flag leaves is one of the foundations of efficient photosynthesis [29]. Because the photosynthetic products in the late growing period account for 80% of the grains [30], leaf senescence caused by the decrease in chlorophyll content in the late growth period will reduce the production of winter wheat. In this research, the SPAD value in the W3 treatment was the lowest among the three irrigation treatments, but it maintained a high SPAD value after the filling stage, which effectively enhanced the photosynthesis of winter wheat in the late growing stage and promoted its dry matter accumulation [13]; this was a main reason for the high yield of the W3 treatment. [PERSON] et al. [31] showed that the SPAD value of the flag leaves of winter wheat first increased and then reduced from the heading stage to the maturity stage. The W1 and W2 treatments obtained the same results, \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Year** & **Variety** & **Relational Expression** & \(\mathbf{R^{2}}\) & **F Value** \\ \hline
2020–2021 & Hengmai4399 & y = 20.510x + 4299.371 & 0.806 ** & 29.119 ** \\  & Hengguan35 & y = 14.674x + 5071.979 & 0.591 * & 10.119 * \\ \hline  & Hengmai4399 & y = 9.963x + 7246.296 & 0.748 ** & 20.762 ** \\
2021–2022 & Hengguan35 & y = 3.667x + 8312.963 & 0.185 & 1.589 \\  & Hengmai28 & y = 9.407x + 7496.296 & 0.655 ** & 13.267 ** \\ \hline  & \multicolumn{3}{c}{Notes: y: yield, x: irrigation rate, *: \(p<0.05\); **: \(p<0.01\)} \\ \end{tabular}
\end{table} 
Table 9: Regression analysis of yield and irrigation amount.