What are the main technologies of agricultural water-saving irrigation?

Irrigation water mainly includes water resources allocation, water transmission and distribution, field irrigation and crop absorption. Take corresponding water-saving measures in each link to form a complete water-saving irrigation technology system, including water resources optimal allocation technology, water-saving irrigation engineering technology, agronomic and biological water-saving technology and water-saving management technology. Among them, water-saving irrigation engineering technology is the core of the technical system, which has been relatively mature and popularized, while other technologies are relatively weak, and it is urgent to strengthen research, development and popularization.

1, canal seepage control technology

Canal seepage control technology is a variety of technical measures to reduce the water permeability of channels or establish waterproof protective layers. The main means of water conveyance for farmland irrigation in China is canal, and the leakage loss of traditional soil canal water conveyance accounts for about 50% ~ 60% of the total water diversion. The impervious layer of canal is usually constructed of rigid materials such as concrete, cement soil, masonry, asphalt concrete, PE, PVC and its modified membrane materials, and the cross section of impervious canal is mostly U-shaped. After adopting canal seepage control technology, the water utilization coefficient of canal system can generally be increased to 0.6-0.8, and the leakage loss can be reduced by 70% ~ 90%. Canal seepage control also has the advantages of fast water delivery, reducing the cost of canal maintenance and management, regulating groundwater level and preventing secondary salinization, which is the main measure to be taken in agricultural water saving in China.

2. Pipeline water delivery technology

Low-pressure pipeline irrigation technology is a technical measure to send water directly to the field by using low-pressure water pipelines such as plastic or concrete to reduce the leakage and evaporation loss of water during transportation. There are three types of low-pressure pipeline irrigation systems: mobile, fixed and semi-fixed. Commonly used materials are PVC pipes, cement sand pipes and cast-in-place concrete pipes. Pipeline water delivery can reduce leakage and evaporation loss, and the water use efficiency can reach 90%-97%. At the same time, it can also save agricultural land, generally reduce the area by about 5%, and the water delivery speed is fast, which greatly improves the water delivery capacity. After the mid-1980s, most of the newly-built irrigation canals were transported by pipeline, and about 1/2 large irrigation districts in the United States realized pipeline water delivery. Pipeline water conveyance technology has been popularized and applied rapidly in well irrigation areas in northern China, and has been basically popularized at present.

3. Sprinkling irrigation technology

Sprinkler irrigation is a mechanized, efficient and water-saving irrigation technology. It uses special equipment to pressurize the water or uses natural water dripping to send the pressurized water to the irrigation area, which is sprayed into the air through the nozzle, dispersed into fine water droplets and evenly distributed in the field for irrigation. There are many forms of sprinkler irrigation system, among which pipeline type, translation type, central support shaft type, coil type and light and small unit type are widely used in China. Sprinkler irrigation system relies on pipeline to deliver water, which basically has no water loss, and can control irrigation intensity and irrigation quantity well, with even irrigation and no leakage. The water-saving effect is obvious, and the general water consumption is 30%-50% less than that of surface irrigation. Sprinkler irrigation has strong adaptability and can be used for various types of soil, topography and crops. It is widely used to irrigate field crops, cash crops, vegetables and garden grasslands. However, sprinkler irrigation is greatly affected by wind power, and evaporation loss is large, so the moisture in the bottom layer of soil may be insufficient.

4. Micro-irrigation technology

Micro-irrigation is a local irrigation technology that uses micro-irrigation system to transport and distribute water and various nutrients needed for crop growth to the field, and moistens the soil near the roots of crops with a small flow through emitters. Micro-irrigation can be divided into drip irrigation, micro-sprinkler irrigation and infiltration irrigation. Drip irrigation is to send irrigation water directly to the roots of crops for local irrigation. There is almost no evaporation loss and deep leakage, and the utilization rate of water resources can reach 95%. However, the emitter is easy to scale and block, and the requirements for water source are strict. Micro-sprinkler irrigation has the advantages of both sprinkler irrigation and drip irrigation, which is more water-saving and more uniform than ordinary sprinkler irrigation. Because the fog drops are fine, it has little impact on crops and will not hurt seedlings, so it can be combined with fertilization. Infiltration irrigation is a new and effective underground irrigation technology after sprinkler irrigation and drip irrigation, which changes the previous irrigation of land into direct irrigation of plant roots under the condition of meeting the physiological growth needs of plants. Micro-irrigation is all transported by pipeline, and there is basically no leakage and evaporation loss along the way. Local irrigation is generally used in irrigation, which is not easy to produce surface runoff and deep leakage. It saves water by 50% ~ 70% compared with surface irrigation and 15% ~ 20% compared with sprinkler irrigation. However, due to the high investment, it is mainly used for crops with high economic benefits such as fruit trees and flowers in water-deficient areas, and less used for field crops. Developed countries such as Israel and the United States have also adopted it in field cotton.

5. Agronomic techniques

It mainly includes tillage and mulching technology, improved surface irrigation technology, water-saving tillage system, excellent drought-resistant varieties, high-efficiency utilization technology of water and fertilizer coupling, soil protective agent and crop transpiration control technology. Tillage and moisture conservation technology can loosen soil, cut off capillary, reduce soil moisture evaporation and significantly improve soil water use efficiency. Covering and moisture conservation technology is to cover the surface of cultivated land with plastic film, straw or other materials to inhibit soil moisture evaporation, reduce surface runoff and store water and moisture conservation. Improving surface irrigation technology includes improving border specifications (such as changing long border to short border, widening border to narrow border, short border irrigation and drip irrigation, etc.). ) and adopt advanced surface irrigation technology (such as surge irrigation, furrow irrigation, film irrigation, thin line irrigation, horizontal border irrigation, etc.). ) is the most popular in China at present. According to the local precipitation distribution, drought occurrence law and crop moisture characteristics, the water-saving crop variety screening technology compresses crops with large water demand according to local conditions, expands crops with synchronous rain and heat and autumn maturity, selects crops with low water consumption and high water use efficiency, and establishes a highly adaptable and efficient planting system by adjusting crop layout. Water-retaining and water-saving technology of chemical preparations is the rational application of water-retaining agent, composite coating agent, fulvic acid and multifunctional steam-inhibiting and drought-resistant agent. Inhibition of excessive transpiration in crop growth and development, prevention of excessive water consumption, reduction of drought damage, promotion of root system to improve the utilization rate of deep soil water storage, has a significant role in enhancing crop drought resistance and improving water production efficiency.

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