Changes of Soil Moisture in Irrigated Farmland at Different Stages
Changes of Soil Moisture in Irrigated Farmland at Different Stages
Research on soil moisture changes has always been an important issue in agricultural production. In order to understand more intuitively and accurately the numerical changes of soil moisture in each time period, we used a soil moisture meter in standard farmland to irrigate different periods of time. Changes in soil moisture are measured and analyzed.
The time-course characteristics of soil moisture change rapidly after irrigation and no external water supply (July 31 to August 4), and reached their respective minimum values ​​on August 4; after the rainfall on August 5, The soil moisture in each layer increases significantly and then enters the stage of loss of water consumption. On the one hand, at the beginning of August, the flowering period of sunflowers is very strong, the water demand is large, and the absorption of soil moisture is strong; on the other hand, the evaporation in summer is intense, which leads to a significant change in soil moisture during this period.
The time series of water content in each soil layer and the mean value of the profile are consistent, but the degree of change is different. The time series curve of surface soil water content is fluctuating, while the rest of the layers are flat, resulting in different direct causes of the environment. difference.
Statistical characteristics of soil temperature The statistical characteristics of soil temperature show that the temperature of each soil layer is significantly different. The values ​​of surface temperature and the temperature difference are all greater than 0cm. The difference between the highest ground maximum temperature (55.5e) and the minimum ground temperature (10.50e) during the observation period is 45.0e; the ground temperature between 5 and 40cm fluctuates between 19.27e and 28.83e, and the temperature difference is 9.56e. 21.24% of the ground temperature difference (Table 4). At the same time, the variation of ground temperature in different soil layers was different, and the variation index (variance, standard deviation, coefficient of variation) was significantly different. The ground temperature was highly variable, 0cm (CV=0.10), highest ground (CV=0.12), lowest (CV=0.17 ) is moderately variable; soil temperature below 0cm is weakly mutated, and its variability decreases with increasing soil depth, and the coefficient of variation is reduced from 0.09 at 5 cm to 0.04 at 40 cm. This is the same as the variability of soil moisture in each section of the profile, which is directly affected by the soil environment.
The vertical change of soil temperature shows that the temperature usually decreases with the increase of soil depth, but in the period of sudden change of temperature (rainfall) and temperature decrease (August 6th), the deep soil temperature is higher than the shallow layer. . The soil temperature energy comes directly from the solar radiation absorbed by the earth's surface. The ground temperature below the ground depends on the downward transfer of surface energy. Therefore, the farther from the surface, the lower the amount of heat and the lower the temperature; on the contrary, when the temperature of the surface decreases, The deep soil has a certain degree of insulation effect due to its relatively stable environment, and its temperature is higher than that of the shallow layer. The rainy weather on August 5 reduced the temperature of shallow soils and did not recover on August 6, resulting in the farmland's 40-cm higher than the 20-cm ground temperature.
In addition, there are differences in the vertical variation of soil temperature under different temperatures and soil moisture content. The change intervals of soil temperature at the three characteristic dates of farmland were 9.20e, 11.37e, and 6.57e, respectively, indicating that when the temperature is low and the soil water content is high, the vertical variation of soil temperature is small and the variation is weak, whereas the variation of soil temperature is the opposite. Big, strong variation.
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