Impact of Meteorological factors on wheat growth period and irrigation water requirement —A case study of the Beijing-Tianjin-Hebei region in China

This study analyzes the irrigation water requirement of wheat in the growth stage in the Beijing-Tianjin-Hebei region under the changes of meteorological factors conditions, using the growth period data, and meteorological data from 80 meteorological stations, from 2000 to 2019. The results show that: (1) The annual average precipitation, average wind speed, and average relative humidity of the growth period in the Beijing-Tianjin-Hebei region show a downward variation trend, while the temperature variation shows an upward trend. Moreover, relative humidity and radiation exhibit a negative spatial correlation. (2) Wheat irrigation water requirement in the Beijing-Tianjin-Hebei region gradually decreases from north to south and east to west. However, the eastern region shows a gradually increasing trend, while the western region shows a decreasing trend. (3) Meteorological factors are negatively correlated with irrigation water requirement, potential evapotranspiration, effective precipitation, and relative humidity, and significantly positively correlated with sunshine hours, average temperature, and wind speed. The overall variation in irrigation water requirement has the highest correlation with potential evapotranspiration. However, the yearly variations in regional irrigation water requirement are dependent on factors such as wind speed, relative humidity, and radiation.


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The United Nations defines climate change as the variation in the Earth's atmospheric and minimum) and precipitation were interpolated using Kriging interpolation.

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The growth period data for wheat was obtained from the Chengde, Tangshan, Zunhua, Baoding, observation stations and ground weather stations (Beijing Station, Tianjin Station, Shijiazhuang

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In the equation, 0 is the net radiation on the surface of the canopy (MJ/(m 2 ·d)); is the soil The crop water requirement is determined by the crop coefficient method as follows: In the formula, is the crop water requirement (mm/d); 0 is the reference crop 145 evapotranspiration (mm/d); and is the crop coefficient.

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The piecewise single-value average crop coefficient method recommended by the Food and

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Agriculture Organization (FAO), is adopted for . Hence, the variation of during the entire 148 growth period is divided into 6 stages. The values of are shown in Table 2.
149 where, 10 is the ten-day scale effective precipitation (mm/10 d); 10 is the ten-day crop 157 water requirement (mm/10 d); and 10 is the ten-day precipitation (mm/10 d). 158 The effective precipitation during the crop growth cycle is the sum of the effective precipitation 159 on the ten-day scale: 160 EP = ∑ 10 (4) 161 162

Calculation of irrigation water requirement 163
A portion of the water needed for agricultural production is obtained from precipitation, and 164 the remaining portion from artificial irrigation. Precipitation is sufficient for crop growth during 165 high-water period, but artificial irrigation is required during low-water period. Therefore, irrigation 166 water requirement, effective precipitation during the crop growth and development stages, the actual 167 area, and the amount of precipitation are closely related factors. Setting the effective precipitation 168 as P 1 and the actual regional precipitation as P 2 , the irrigation water requirement, Q can be expressed in Figure 5(c). Hence, it can be concluded that relative humidity and radiation are inversely correlated in space; that is, areas with high relative humidity have low radiation, and areas with low

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The radar chart was used to analyze the changes in irrigation water requirement of wheat from 248 2000 to 2019, as shown in Figure 9. It can be clearly seen from the shape of the chart that irrigation 249 water requirement in the study area is closest to potential evapotranspiration. However, for 250 individual years, wind speed, relative humidity, and radiation contributions were different. The shows an upward trend. Relative humidity and radiation show negative spatial correlation, that is, 267 areas with high relative humidity have low radiation, and vice versa.

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(2) The irrigation water requirement of wheat in the Beijing-Tianjin-Hebei region gradually 269 decreases spatially from north to south and from east to west. The temporal variation in irrigation 270 water requirement in the eastern and western regions shows an opposite trend. The eastern region 271 shows a gradually increasing trend, while the area is decreasing.

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(3) Meteorological elements have significant impact on irrigation water requirement. They

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show negative correlation with irrigation water requirement, potential evapotranspiration, effective 274 precipitation, and relative humidity, and positive correlation with sunshine hours, average 275 temperature, and wind speed. The overall change in irrigation water requirement has the highest 276 correlation with potential evapotranspiration. However, for yearly variations in regional irrigation 277 water requirement, wind speed, relative humidity, and radiation are the common influencing factors.