Water is an indispensable factor for plant life activities, and its impact on crop growth is manifested in many aspects. In addition to directly participating in the growth and metabolism of crops, water can also regulate other environmental factors, which in turn affect crop growth. Therefore, there are four main ways to change whether crops need irrigation and water replenishment.
Judging by the senses of soil moisture
- Observe the color characteristics of the soil in the field with your eyes, if the color of the surface soil becomes light or gray or gets fine cracks, it means that the soil is short of water. If the soil is darker than normal or brownish, there is no water shortage.
- Insert a thin wooden stick into the soil below 10cm, and then pull out the wooden stick to see if the soil brought out is relatively wet. If the soil is relatively wet, it means that the soil is not short of water and does not need to be watered temporarily. If the soil is relatively dry or there is no soil on the stick, it means that the soil is short of water and the crop needs to be watered in time.
- Grab a handful of soil under 10cm with your hand and place it in the palm of your hand. If the palm of the hand does not feel moist and the soil cannot be held into a ball with force, it will scatter immediately after letting go, indicating that the water shortage is serious, and the soil moisture content is below 30% of the field water holding capacity. At this time, it is necessary to water in time. If the palm of the hand has a slight feeling of dampness, the soil can be held into a ball, and it can be naturally spread after letting go, indicating that the humidity can be, and the soil moisture content is about 50% of the field water holding capacity, which generally does not need to be watered. But if the palm of the hand is very moist, hold the soil hard and the water is squeezed out, the soil cannot be spread when you release the hand and there is soil adhesion in the palm, indicating that the moisture content is relatively high, and the soil moisture content is more than 85% of the field water holding capacity, and it is necessary to reasonably control the amount of water at this time.
- If conditions permit, soil can be taken and measured by drying method or a soil moisture sensor can be used to visually reflect the state of soil moisture content.
Judging by the growth of the crop
When crops are short of water, leaves and shoots become wilted, drooping, and tarnished. When there is a severe water shortage, the leaves will fade green and turn yellow or even wither. When planting crops in greenhouses, you can observe whether there are condensed small water droplets on the edge of the leaves on the plant in the early morning, if there are small water droplets on the edge of the leaves, it means that the crop is not short of water. If there are no small water droplets on the edge of the leaves, it means that the crop is short of water and needs to be irrigated in time.
Judging by moisture test data
According to the measurement principle, soil moisture detection instruments can be divided into the following types:
- Time Domain Reflectance Instrument ( TDR )
- Time Domain Transport Instrument ( TDT )
- Frequency Domain Reflectometry ( FDR )
- Neutron Probe
- Negative pressure instrument ( Tension meter )
- Resister Method
Among them, time-domain reflectometry (TDR) and frequency-domain reflectance (FDR) are the most commonly used. Therefore, on-demand irrigation of crops can be realized using automation, and the moisture in the soil can be monitored in real-time online by using soil temperature and humidity sensors. When the soil moisture is detected below the lower standard limit, the system automatically turns on the irrigation equipment to irrigate the crop. When the soil moisture is detected to reach the standard upper limit, the system automatically turns off the irrigation equipment, so that according to the actual situation of the field moisture, the irrigation automation is realized through the automatic control system, which is a more reasonable irrigation.
Judging by the calculation of crop water consumption (or evapotranspiration) obtained from meteorological data
The daily evapotranspiration (ET) is calculated from the solar radiation, air temperature, and relative humidity data of the field weather station, and then the allowable soil water loss of the crop (MAD, soil water loss is generally 30%-50%). When the accumulated soil water loss in the field reaches the normal value, the water supply device is activated for irrigation. The amount of irrigation is the cumulative water consumption, that is, how much water the crop consumes, and how much water is irrigated. When the amount of irrigation is equal to the cumulative water consumption, the water supply device is turned off.
