## 2 Materials and Methods
### Measurement of Indicators  
Soil water content of 0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, and 80-100 cm in each growth stage was determined by the gravimetric method. Soil temperature in the soil layer of 0-20 cm was measured by a thermometer during each growth period of maize. Maize of each plot was harvested at the ripening stage, and 6 ears that were growing well were selected randomly in each plot. Drying the grain to constant weight at 85 \({}^{\circ}\)C, weighing by an electric balance for grain yield, the grain yields were then converted to a standard grain water content of 15.50% wet basis [27]. \(ET_{c}\) was calculated daily during the growing season by the soil water balance Equation (1) [28]:  
\[ET_{c}=I+P+C_{r}-D_{w}-R_{f}\pm\Delta s\ldots \tag{1}\]  
where \(ET_{c}\) was the total amount of actual evapotranspiration for the entire season (mm), \(I\) was the amount of irrigation water applied (mm), \(P\) was the precipitation (mm), \(C_{r}\) was the capillary rise (mm), \(D_{w}\) was the amount of drainage water (mm), \(R_{f}\) was the amount of runoff (mm), and \(\Delta s\) was the  
Figure 4: Variation of the reference crop evapotranspiration and precipitation during the growth period of maize. Note: ET\({}_{0}\) represents reference crop evapotranspiration, mm. ET\({}_{0}\) was calculated by means of the FAO Penman–Monteith Equation (2) for the entire growth season of maize. Figure 3: Variation of the temperature and relative humidity of the experimental site during the growth period of maize. Note: T\({}_{\text{max}}\) represents the maximum of temperature; T\({}_{\text{min}}\) represents the minimum of temperature; RH\({}_{\text{max}}\) represents the maximum of relative humidity; RH\({}_{\text{min}}\) represents the minimum of relative humidity. change in the soil moisture content (mm). The soil moisture content measurement was used by the conventional oven-dry method in soil layers (0-20 cm, 20-40 cm, 40-60 cm, 60-80 cm, and 80-100 cm). No runoff was observed during the trials. Capillary rise was considered as negligible due to the deep water table level. Drainage water included precipitation under the effective rooting depth, according to the soil water content measurements in the soil layer at the effective rooting depth, was determined. \(ET_{0}\) was calculated per day during the growing season by using the FAO Penman-Monteith equation. The FAO Penman-Monteith equation is given by (2):  
\[ET_{0}=\frac{0.408\Delta(R_{n}-G)+\gamma\frac{900}{T+273}\mu_{2}(e_{s}-e_{a})}{ \Delta+\gamma(1+0.34\mu_{2})} \tag{2}\]  
where \(ET_{0}\) was the reference evapotranspiration (mm day\({}^{-1}\)), \(R_{n}\) was net radiation at the crop surface (MJ m\({}^{-2}\) day\({}^{-1}\)), \(G\) was soil heat flux density (MJ m\({}^{-2}\) day\({}^{-1}\)), \(T\) was mean daily air temperature at 2 m height (\({}^{\circ}\)C), \(\mu_{2}\) was wind speed at 2 m height (m s\({}^{-1}\)), \(e_{s}\) was the saturation vapor pressure (kPa), \(e_{a}\) was the actual vapor pressure (kPa), \(e_{s}\) - \(e_{a}\) was the saturation vapor pressure deficit (kPa), \(\gamma\) was the slope of the saturation vapor pressure curve (kPa \({}^{\circ}\)C\({}^{-1}\)), and \(\Delta\) was the psychrometric constant (kPa \({}^{\circ}\)C\({}^{-1}\)). Meteorological parameters needed to calculate \(ET_{0}\) were derived from a local meteorological station. Water use efficiency (kg m\({}^{-3}\)) was calculated as (3) [29]:  
\[WUE=Y/ET_{c}\ldots \tag{3}\]  
where \(WUE\) was the water use efficiency (kg m\({}^{-3}\)), \(Y\) was the grain yield (kg hm\({}^{-2}\)), \(ET_{c}\) was the total amount of actual evapotranspiration for the entire season (mm). Net economic profit (yuan hm\({}^{-2}\)) was calculated as (4):  
\[\text{Net profit = total revenue - total cost} \tag{4}\]  
where, total revenue = grain yields \(\times\) average local price. The average local price for maize was 1.70 yuan kg\({}^{-1}\).