Main technologies of water-saving irrigation

Canal water conveyance is the main way of farmland irrigation in China. The water utilization coefficient of traditional soil canal system is generally 0.4-0.5, and the difference is only about 0.3, which means that most of the water is lost through leakage and evaporation. Canal leakage is the main aspect of farmland irrigation water loss. After the canal seepage control technology is adopted, the water utilization coefficient of the canal system can generally be increased to 0.6-0.85, which is 50%-70% higher than that of the original soil canal. Canal seepage control also has the advantages of fast water delivery, being conducive to agricultural production to seize the season and saving land, and is one of the main measures for water-saving irrigation in China.

According to the materials used, the canal seepage control can be divided into: ① concrete cover seepage control; (2) Seepage prevention of masonry (pebbles, stones and flaky); (3) concrete seepage control; (4) Anti-seepage with plastic film (lining with film, and then protecting the surface with soil, concrete or stone), etc. Pipeline water delivery is to send water directly to the field for irrigation through pipelines, so as to reduce the leakage and evaporation loss of water during open channel transportation. In developed countries, pipelines have been widely used for irrigation and water delivery. At present, the popularization and application of pipeline water delivery in North China well irrigation area is also very fast. Commonly used pipes are concrete pipes, plastic hard (soft) pipes and metal pipes. Compared with canal water delivery, pipeline water delivery has the advantages of fast water delivery, water saving, land saving and increased production. Its advantages are: the water utilization coefficient can be increased to 0.95; Save electricity by 20%-30%; 2%-3% land saving; The increase is 10%. At present, if low-pressure plastic pipes are used to deliver water, the investment per mu is 100 yuan-150 yuan, excluding the investment in water source engineering construction (the same below).

Where conditions permit, we should actively develop pipeline water transport in light of actual conditions. However, pipeline water delivery only reduces the water loss in the process of water delivery. In order to realize efficient use of water, field water-saving measures such as spraying and drip irrigation should be supported. Where there is no spray and drip irrigation equipment at present, the pipeline layout and pressure bearing capacity of the pipeline should take into account the requirements of future development of spray and drip irrigation to avoid waste. Sprinkler irrigation is to send pressurized water to the irrigation area through pipes, disperse it into fine water droplets through nozzles, and spray it evenly to the fields to irrigate crops. As an advanced mechanized and semi-mechanized irrigation method, it has been widely used in many developed countries.

The main advantages of sprinkler irrigation are as follows: ① The water-saving effect is remarkable, and the water utilization rate can reach 90%. Generally speaking, compared with surface irrigation, 1 m3 of water can be used as 2 m3 of water. (2) The crop yield has been greatly increased, generally reaching 20%-40%. The reason is that the agricultural canal, capillary, field irrigation ditch and ridge are cancelled, and the sowing area is increased by15%-20%; Uniform irrigation, no soil hardening, is beneficial to grab the season and protect the seedlings; The field microclimate and agricultural ecological environment were improved. ⑶ The workload of field canal system construction, management, maintenance and land leveling is greatly reduced. (4) The irrigation cost and labor force are reduced, and the income of farmers is increased. 5] It is conducive to accelerating the realization of agricultural mechanization, industrialization and modernization. [6] Avoid secondary salinization of soil caused by over-irrigation. Commonly used sprinkler irrigation has pipeline type, translation type, central support shaft type, scroll type and light and small unit type.

Mobile pipeline sprinkler irrigation usually buries the water main pipe underground, and the field branch pipes and nozzles can be disassembled, moved and reused, thus reducing investment. Tens of thousands of acres of grain fields in Shunyi County, Beijing are all using this irrigation method. The practice of 10 years has proved that mobile pipeline sprinkler irrigation not only has the advantages of saving water, increasing production, saving labor, reducing farmers' burden, and being beneficial to agricultural mechanization, industrialization and modernization, but also has the advantages of simple equipment, simple operation, less investment, strong adaptability to the size and shape of fields, and can be used by one or more households. It is a form of micro-sprinkler irrigation which is suitable for China's national conditions and can be popularized vigorously.

Fixed pipe sprinkler irrigation is to install pipes and nozzles in the field, which has high irrigation efficiency and simple management, and is suitable for irrigation of vegetables, fruit trees and cash crops. However, the investment is high (the investment per mu is generally around 1000 yuan), which is not conducive to mechanized farming.

Large-scale sprinkler irrigation machinery with central support shaft and translation can only walk within a predetermined range, and there can be no tall obstacles in the walking area, so the land requirements are relatively flat. High degree of mechanization and automation, suitable for large-scale farms or farmland with high degree of large-scale operation. Domestic equipment is used, and each mu is invested in 300 yuan -400 yuan.

The winch sprinkler is driven by the hydrodynamic pressure in the pipeline, which has the advantages of flexibility, adaptability to large and small fields, low equipment investment per mu and so on. Compared with the central support shaft nozzle and the translation nozzle. At present, the investment per mu of imported equipment is about 50 yuan, which can be further reduced after the equipment is localized. This kind of sprinkler irrigation is suitable for China's national conditions and has a broad prospect, which can be applied to field crops, vegetables and so on. There are two kinds of winch sprinklers: spray gun type and folding frame type. The latter has the advantages of good atomization and low energy consumption. Sprinkler irrigation with small light units can be carried by hand or mounted on trolleys or tractors. It has the advantages of flexibility, strong adaptability and low price, and is usually used for drought-resistant sprinkler irrigation in small plots. Investment per mu 100 yuan -200 yuan. Drip irrigation is to use plastic pipes to send water to the roots of crops through small holes or drippers on capillaries with a diameter of about 16mm for local irrigation. It is the most effective water-saving irrigation method in arid and water-deficient areas at present, and the water utilization rate can reach 95%. Drip irrigation is more effective than sprinkler irrigation in saving water and increasing yield, and can be combined with fertilization to improve fertilizer efficiency by more than one time. It can be used for irrigation of fruit trees, vegetables, cash crops and greenhouses, and can also be used for irrigation of field crops in arid and water-deficient areas. Its disadvantage is that the emitter is easy to scale and block, so the water source should be strictly filtered. At present, domestic equipment has basically reached the standard, and areas with conditions should actively develop drip irrigation.

According to the fixed degree of the pipeline, drip irrigation can be divided into three types: fixed, semi-fixed and mobile. For fixed drip irrigation, the positions of pipelines and emitters at all levels are fixed in the irrigation season. Its advantages are simple operation, labor and time saving and good irrigation effect. The investment per mu of domestic equipment is about 700 yuan (fruit trees)-1400 yuan (greenhouse vegetables). Semi-fixed drip irrigation, its main pipe and branch pipe are fixed, and the capillary is manually moved. Invest in 500 yuan -700 yuan per mu. Mobile drip irrigation, the trunk, branches and capillaries are all manually moved, and the equipment is simple, which saves investment compared with semi-fixed drip irrigation, but requires more labor. Invest in 2 yuan -500 yuan per mu.

The semi-fixed and mobile drip irrigation systems developed in combination with the specific situation of large labor force and lack of funds in China have greatly reduced the engineering cost and created conditions for the popularization and application of drip irrigation in field crops and economically underdeveloped areas.

Water storage and drip irrigation is to introduce rainwater collection or other surface runoff into the water cellar (or other micro-water storage projects), or use the water storage tank as a small mobile water source to solve the problem of farmland irrigation in arid and water-deficient areas with drip irrigation. It has the characteristics of simple structure, low cost and can be adopted by every household. It plays an important role in realizing that each person in arid and poor mountainous areas has half an acre to one acre of farmland, solving the problem of food and clothing and developing courtyard economy, and should be vigorously promoted in arid and water-deficient mountainous areas.

Underground drip irrigation is to bury drip irrigation pipe in the active layer of underground crop roots, and irrigation water penetrates into the soil through micropores for crops to absorb. In some places, a small hole is drilled on the plastic pipe at regular intervals and buried near the roots of underground plants for irrigation, which is commonly known as "infiltration irrigation" by the masses. Underground drip irrigation has the advantages of less evaporation loss, water saving, electricity saving, fertilizer saving, labor saving and obvious yield increase benefits, and can be used for fruit trees, cotton and food crops. Its disadvantages are: 2. When the pipeline spacing is large, the irrigation is not uniform enough, so it is not suitable for use in places with large soil permeability or steep ground slope. The investment per mu is 400 yuan-1000 yuan. Its advantages are: water saving 50%-60%; Save electricity by 40%-50%; Increase production by about 30%. According to the different demands for water in different growth stages of rice, the controlled irrigation of "thin, shallow, wet and sunny" not only saves water, but also is beneficial to crop growth, and changes the old habit of flooding and series irrigation of rice in the past. It does not need to increase the project investment, as long as it is irrigated according to the water-saving irrigation system. Techniques such as "thin, shallow, wet and sun-cured" (transplanting rice seedlings in thin water, raising seedlings in shallow water, wetting at the early tillering stage and sun-cured at the late tillering stage) and "dry cultivation and sparse planting" (dry cultivation and sparse planting, appropriate water supplement) all belong to this category, which have been widely popularized in Guangxi, Jilin and other provinces in recent years. Generally, it can save water per mu1100m3, and increase rice production by 25kg, with remarkable benefits. Water-saving irrigation technology of rice won the first prize of national scientific and technological progress, and should be vigorously promoted in rice areas.

In Jiangsu, Shanghai, Zhejiang and other areas with good economic conditions, laying underground pipeline system to control irrigation and field drainage is conducive to water saving, fertilizer saving and crop growth, creating favorable conditions for realizing high yield, high efficiency and high quality agriculture. According to the water demand of crops, timely and appropriate irrigation, monitoring soil moisture and water regime of irrigation water distribution system by advanced scientific and technological means, data collection and computer processing can scientifically and effectively control soil moisture, conduct reasonable scheduling, plan water use and optimize water distribution, thus achieving the purpose of saving water and increasing production. At the same time, we should attach importance to and strengthen water-saving management, change the current situation that the price of agricultural water is too low to save water, and implement policies such as charging according to cost and increasing prices beyond plan. It is necessary to establish and improve water-saving management organizations and technology extension service systems, and improve water-saving management rules and regulations.