In agricultural production, the monitoring of soil moisture content is particularly important. Soil moisture and nutrients have the most direct impact on crop yields. In order to further understand the influence of soil moisture on crops and guide farmers in agricultural production, we have laid a foundation for the increase of farmers' income from grain production. In 2008, we used a soil moisture monitor to test soil moisture in Ledu County, Gansu Province. With the determination, the present situation is reported as follows.
1 Basic situation
1.1 The natural conditions in Ledu County
Ledu County is located in the southeastern part of Gansu Province and belongs to the climatic region of the Loess Plateau. Water resources are relatively scarce. The annual precipitation is relatively small, natural disasters are frequent, and natural disasters such as drought, hail, heavy rain, and frost occur frequently.
1.2 Basic Conditions of Monitoring Stations and Farmland Monitoring Sites
The site of the monitoring station was set in the Lechang County improved seed field, and the monitoring instrument and equipment installation site was open around, no high-rise buildings around, with an area of ​​1000m2, convenient transportation, construction of equipment rooms, and fence protection around. Soil moisture monitoring points in farmland were divided into three monitoring areas: Alpine, Mid-Level and Chuandao. 10 monitoring sites were selected in the three monitoring areas. Soil moisture monitoring instruments were installed at the monitoring sites. The three main crops were all field grain crops. There is also a soil moisture and drought management system in the thoroughbred farm, which can manage the timely situation of all public opinion monitoring sites.
2 Monitoring data analysis
2.1 Analysis of the main point fixed moisture monitoring
It can be seen from the measurement results that in the month of May-May in our county, with the decrease of precipitation, the amount of soil moisture evaporates, the soil moisture content in 10cm and 30cm soil layers is obviously insufficient, and the soil moisture content is relieved with the increase of precipitation from June to September. No drought phenomenon occurred. Soil water content at each level was positively correlated with monthly precipitation. Soil water content at 10cm and 30cm soil layers was most affected by precipitation and evaporation. Therefore, according to the characteristics of precipitation and seasons, we must vigorously promote agricultural water-saving technologies, adopt effective drought protection measures, and reasonably adjust planting structures to ensure normal agricultural production.
2.2 Analysis of Changes in Soil Water Content at Farmland Monitoring Sites
From the results of sampling in three levels in 2008, the change of soil moisture in the county showed a low peak during the annual cycle, which reflected the characteristics of drought and drought seasons in the county; Among them, the rainfall in April-April was extremely small, the temperature rose, the monsoon intensified, the soil evaporation on the surface increased, the soil loss was serious, and there was a significant deficit in the moisture content; the average soil moisture content in the 0-20cm soil layer was lower than or close to the crop The soil moisture content at the time of wilting is the most important aspect of agricultural production.
From July to October, with the increase of precipitation, the soil moisture content was significantly improved. During this period, due to the increase of atmospheric humidity, the temperature dropped and the soil evaporation decreased. Therefore, as long as the well-being is completed and the water is flooded and flooded, the water requirement for the normal growth and development of autumn crops can be guaranteed, and favorable conditions for winter wheat sowing can be provided.
2.3 Analysis of Weather Factors
2.3.1 Rainfall
In the first nine months of 2008 from January to September 2008, the accumulated rainfall was 381.50mm, which accounted for 75% of the annual rainfall, indicating that the drought was serious this year. The rainfall was mainly concentrated in June-September, accounting for 81% of the whole year, while the average rainfall in April and May of the crop water demand was only 44.80mm, which had a great impact on the growth of winter wheat. It shows that in the arid climate of our county, soil moisture necessary for crop growth must be guaranteed by rainfall, and rainfall has a great influence on soil moisture content.
2.3.2 Temperature conditions
After March, the temperature gradually increased. According to the reality of our county, the average summer temperature is 21.50°C. The average temperature in June-August is 0.40-0.60°C lower than the normal temperature, and the minimum minimum temperature is 8.30°C. The maximum number of days at 32°C is 9d. It shows that the temperature drop in autumn is faster than the temperature drop in spring. From the perspective of temperature changes in different soil layers, with the increase of soil depth, the effect of ground temperature changes is less affected by temperature, and the temperature is also relatively stable.
2.4 Relationship between meteorological factors and soil moisture content
Each meteorological factor has different degrees of influence on the soil moisture content, but the main direct influence factors are rainfall, outdoor average temperature, outdoor humidity and solar radiation. According to the overall analysis, the precipitation, outdoor average temperature, outdoor humidity, and solar radiation all showed an upward trend from May to August, and the soil moisture content at all three monitoring depths showed an upward trend. From the rainfall analysis, the cumulative rainfall of 215.50 mm in June-August is a critical period for crop water demand, which is very favorable for the growth and development of large autumn crops.
According to the laws of crop growth and development and the law of water demand, we have organized experts to conduct research and research on the biological characteristics of different ecological regions of major crops, climatic and meteorological conditions, farmers' farming practices, fertilization systems, and promotion of applicable agricultural technologies. Monitoring of soil moisture in the mountains, Wuying, Qianhu and other places was conducted. Field trials were conducted on winter wheat, corn, and other major crops. Soil moisture content was measured periodically, and the growth and development indicators and drought status during crop growth were observed. At the same time, relevant data collection and research were carried out, and the water requirement law of winter wheat and corn in Ledu County was initially defined. The requirements for soil moisture and crop performance at each growth stage were proposed. Different crop needs and recommendations were proposed at different stages so as to guide farmers’ production. To do a good job for the increase of farmers' income.
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