Surface irrigation is an ancient field water application technology, but it is still a widely used irrigation method in the world, especially in developing countries, accounting for more than 90% of the world's irrigated area. In China, more than 98% of the irrigated area still uses traditional surface irrigation technology.
In view of the shortage of water resources and energy in China, the lack of economic strength, and the fact that the level of technical management in rural areas is relatively low, large-scale promotion of advanced irrigation techniques such as spraying and micro-irrigation is also subject to great restrictions, and therefore it will be a long time in the future. Within China, we must still increase the construction of field projects and vigorously research and promote water saving ground irrigation technology.
I. Leveling land, designing reasonable ditch, concrete size and irrigation technical parameters
Leveling the land is an important measure to improve the surface irrigation technology and irrigation quality, shorten the irrigation time, improve the efficiency of irrigation labor and increase water production. In combination with land leveling, field project reconstruction, long ditch (ditch) is short ditch (ditch), widening ditch is narrow ditch, a reasonable design of ditch size and ditch (ditch) flow rate, can greatly improve the uniformity of irrigation and Irrigation efficiency.
The study of Luohui Canal in Shaanxi Province shows that when the single-wide flow rate is 3~5L/s, the irrigation quota varies with the length of the plant. When the plant length is changed from 100 meters to 30 meters, the irrigation quota is reduced by 150~204m3/hm2. When the head length is 30 to 100 meters, the single-wide flow rate increases from 2L/s to 5L/s, and the irrigation quota can be reduced by 150~225m3/hm2.
The comparative test of deep leakage in Baojixia Irrigation District, the irrigation quota is less than 675m3/hm2, basically no deep leakage; when the irrigation quota is 825~990m3/hm2, there is about 150m3/hm2 water deep leakage; irrigation quota 1350m3/hm2 At that time, half of the water became deep leaking water.
China has a vast area, and there are large differences in terrain and soil around the country. Therefore, it is difficult to have uniform standards. Computer models should be established based on the results of field trials. Through experiments and computer simulations, suitable sluice size and irrigation technical parameters suitable for the local area should be given.
Second, improve the wet method of surface irrigation and develop local moist irrigation
The improvement of the traditional method of surface irrigation with all wet methods, alternate irrigation with alternate trenches or partial wetting irrigation not only reduces the proportion of soil evaporation occupies the total evapotranspiration during the class, but also significantly improves the utilization efficiency of soil water in the field. Improve the permeability of the soil in the root zone of the crop, promote the deep rooting of the root, facilitate the use of deep soil water for the root system, and combine the characteristics of water saving and production increase, and it is worth promoting. Practice has proved that spring wheat and spring maize are interplanted with alternate irrigation, and cotton, corn and other wide-ranging crops are alternately filled with furrows or alternate furrows. The wetted area can be reduced by 50%, water saving can be as high as 30%, and the yield increase can be 5% to 10%. With corn sitting on the water, it can save water 900m3/hm2, save 90~105 kWh, increase production by about 16%, and increase income by about 28%.
Third, improve the way of water release and develop intermittent irrigation
To improve the way of water discharge, the traditional ditch and ditch water transfer to intermittent water release, intermittent irrigation (also known as surge irrigation), is known as a major breakthrough in the 1980s ground irrigation technology. Intermittent discharge of water will promote the flow of water into a surge, because the soil pores will be automatically closed, forming a thin closed layer in the surface of the soil, the water flow is advancing quickly. When irrigation with the same amount of water, the distance of intermittent irrigation flow is 1-3 times of continuous irrigation, which greatly reduces the deep leakage, improves the uniformity of irrigation, and the field water utilization coefficient can reach 0.8-0.9.
IV. Improvement of Gully Drainage Facilities
Improve gully drainage facilities and use siphons (for open channel water transfer) or ground moving gate hole pipes (for pipelines) to discharge water. Field water utilization rate can be increased by 5% to 10% compared with manual opening of water. At present, these facilities are still in the experimental stage in China and have not yet been mass-produced. Therefore, it is necessary to carry out joint research, conduct in-depth research on the materials and processing technology of these facilities, and develop in the direction of technical standardization, production scale, and popularization and application.
V. Vigorously develop water-saving protection film on irrigation
Membrane irrigation is a new type of surface irrigation method developed on the basis of mulching technology in China. It is to lay a mulch in a raft or in a ditch. The raft and ditch are all covered by a mulch, thereby realizing the irrigation method of using the mulch film to transport water and infiltrating the crop through the seedling hole and professional irrigation hole. Since the seedling hole and professional irrigation hole only account for 1% to 5% of the irrigated area in the field, other areas mainly rely on the side seepage water to moisten, so the membrane irrigation is actually a kind of local irrigation. At present, 23.33 hectares of farmland using membrane irrigation has been used in Xinjiang, and Gansu, Henan, and other provinces have begun to promote it. Membrane irrigation situation has open irrigation irrigation membrane membrane irrigation, culture membrane irrigation, membrane hole irrigation, irrigation membrane in the trench, membrane irrigation, grate membrane irrigation, membrane irrigation on the membrane and so on. Membrane irrigation crops include cotton, vegetables, corn and wheat. Film-mulching and membrane irrigation combine to save water, preserve fertilizer, increase ground temperature, inhibit weed growth, and promote crop yield, quality, and early maturity. The production test showed that compared with conventional furrow irrigation, the irrigation of the film was 40.8% water-saving, 5.12% increase in lard production, 15% increase in pre-frost production, 58% increase in corn water use, and 51.8% increase in water production. As membrane irrigation is a new irrigation technology, there are still many immature and imperfect places, and their technical mechanism, technical elements and design methods need further study.