What is Irrigation?

Technical measures to replenish crops with water. In order to ensure the normal growth of the crop and obtain high and stable yield, the crop must be supplied with sufficient water. Under natural conditions, often due to insufficient precipitation or uneven distribution, it is impossible to meet the crop's water requirements. Therefore, irrigation must be carried out artificially to compensate for natural rainfall. ^[1]

Irrigation, that is, watering the ground. The principle of irrigation is that the amount, frequency and time of irrigation should be determined according to the water demand characteristics, growth stages, climate, and soil conditions of medicinal plants. Its main types are irrigation before sowing, seedling irrigation, growing season irrigation and winter irrigation.

Chinese name: irrigation
Foreign name: irrigation

Pour: guàn Irrigation: irrigation, canal, irrigation
Irrigate: gài irrigation: irrigation. washing.
Earliest Chinese record: More than 2000 BC

Explanation of irrigation words

Number of strokes: 19; radicals:

Inject liquid: perfusion, grout, enema.

Number of strokes: 12; radicals:

Main methods of irrigation

Flood irrigation

Flood Ditch irrigation is required to dig trenches. It used to be manual, then livestock, tractors, and later the most advanced advanced laser ranging. It depends on economic and geographical conditions, such as the size of the area to be irrigated, what technologies are available, and labor costs. Wait. The plants are lined up in the hoe and Longgou or grow on the seedbed. Water enters the farmland along the channel and flows along the edge of the Longgou or the seedbed. You can also use hard plastic or aluminum pipes to conduct water in the field, open holes for irrigation at intervals, and connect the channels with siphons.

The application of pipes can control the flow of water. Due to differences in temperature, wind speed, soil, and infiltration capacity, flood irrigation can easily cause water in some places and water shortage in some places. The pipe can be moved, so it can be controlled to prevent this uneven phenomenon. . Especially if the use of automatic valves can increase efficiency.

However, flood irrigation is a waste of water resources, requires more labor, and easily raises the groundwater level. Therefore, salinization of soil has been gradually eliminated in developed countries. But because it requires only a small amount of funding and technology, it is still widely used in most developing countries.

Sprinkler irrigation

Sprinkler irrigation Sprinkler irrigation is a pipe that sends water to a sprinkler located in the field and sprays it out. There is a difference between high pressure and low pressure, and it can also be divided into fixed and mobile. The fixed sprinkler is installed in a fixed place, and some sprinklers are installed at the height of the ground surface. It is mainly used in places where beauty is needed, such as golf course, racetrack grass irrigation, park, cemetery, etc.

The pressure of the sprinkler can't exceed 200 bar generally. If it is too high, it will generate water mist and affect the irrigation efficiency. The sprinkler can be rotated. The rotation can be 360 degrees or a certain angle. There are also spray gun styles. It can work at a pressure of 275-900 bar, with a long jet and a flow rate of 3-76 liters / second. Spray guns can also be used for industrial dust protection.

If the nozzle is connected to the water source with a pipe so that the nozzle can be moved, for mobile sprinkler irrigation, the plastic tube is rolled onto a reel, which can be released as the nozzle moves, or the nozzle can be moved manually.

The disadvantage of sprinkler irrigation is that a lot of water will be lost due to evaporation, especially in windy weather, and it is not easy to irrigate the entire irrigation area uniformly. Water remaining on the leaves will easily cause the growth of mold. Hot and sunny weather can cause leaf burns.

Micro sprinkler irrigation

Micro sprinkler irrigation uses water refraction, rotation, or radiation to spray water evenly.

Rich gold micro-spray irrigation Irrigation forms sprayed to crop branches and other areas belong to the category of micro-irrigation. Micro-sprinkling irrigation has low working pressure and small flow rate, which can increase soil moisture regularly and increase air humidity and adjust local microclimate. It is widely used in vegetables, flowers, orchards, medicinal planting sites, cutting planting and breeding sites, etc. Humidification and cooling.

Drip irrigation

Drip irrigation Drip irrigation is a form of irrigation that drips water drop by drop evenly and slowly into the soil near the roots of the plant. The drip flow is small and the water drops slowly into the soil, which can minimize evaporation loss. If you add mulching film, you can further reduce Under evaporation and drip irrigation, except that the soil moisture immediately below the dripper is saturated, the other parts of the soil moisture are unsaturated. The soil moisture mainly infiltrates and diffuses by capillary tension.

However, if the drip irrigation time is too long, the infiltration phenomenon may occur under the root system, so the drip irrigation is generally completed by high-tech computer manipulation, and it is also manually operated. Drip irrigation has low water pressure and saves water. It can be used to irrigate each plant in areas where different plants are grown, but pressure compensation is required for slopes. Computers can be controlled by adjusting valves in different areas. The key is to control the pressure and Remove particulate matter from the water to prevent clogging of drip holes. Plastic pipes are usually used for water transportation. They should be black or covered under the mulch to prevent the growth of algae and prevent the pipes from aging due to ultraviolet radiation. Drip irrigation can also be done with a porous ceramic tube buried underground, but the cost is higher, and it is only used for turf and golf courses.

Irrigation seepage

Infiltration irrigation technology has been applied in places with high groundwater levels for many years. It is a method of artificially raising the groundwater level and directly supplying plant roots from the bottom.

Infiltration irrigation is commonly used in commercial greenhouse products, such as irrigating potted flowers, fertilizing, soaking the pots with an aqueous solution containing fertilizer for 10 to 20 minutes from the bottom, and then water can be recovered. This operation requires high-tech automatic operation and expensive equipment , But it saves manpower, water and fertilizer, while maintaining and operating costs are very low, the principle is the same as underground drip irrigation.

Regulated deficit irrigation

Regulated deficit irrigation reduces irrigation (deficit) during the non-critical period of the crop, is in a state of drought stress, reduces transpiration water consumption and delays vegetative growth, and supplies limited water to the crop's critical period of water demand to meet the formation of reproductive organs And growth requirements. This technology can significantly improve water use efficiency without reducing or even increasing yield

Controlled Root Splitting Irrigation

When this technology was originally proposed, part of the root system was in a dry area (dry area) of the soil, the crops were subject to water stress, a large amount of ABA was formed in the roots, transmitted to the leaves, the stomatal opening was reduced, and transpiration water consumption was reduced; On the one hand, part of the root system is placed in an irrigated area (humid area), and the crop absorbs water from the soil to meet the needs of normal physiological activities. Dry and humid areas are irrigated alternately. After alternate stress, the number of secondary roots increased greatly, the ability of roots to absorb water and fertilizer was increased, and water use efficiency was significantly improved.

In practice, the technology is changed to a ditch alternate irrigation system, an alternate irrigation system, and the like.

Gansu Province implemented the field corn alternate furrow irrigation technology, which saved 33.3% of water while maintaining high yield. The effect was significant and the investment did not increase. Therefore, it was listed as a local water-saving technology promotion plan a few years ago. ^[2]

Irrigation equipment

Hour hand sprinkler

Hour hand sprinkler (2 photos)

The hour hand sprinkler is a kind of mobile sprinkler. The sprinkler head is installed on an electroplated steel pipe or aluminum pipe supported by wheels. It rotates around a center and conveys water from the center pivot. The entire sprinkler irrigation area forms a circle. This type of sprinkler irrigation is common in the United States.

This kind of mechanical sprinkler can be hung on the steel pipe, spraying only on the plants, and some can be almost lifted to the ground and spray directly on the ground between the plants, so the water lost due to evaporation can be saved.

The rotation of the hour hand sprinkler can be driven by water or by a motor. Most of them use a motor. The mechanical irrigation area is a circle, so the gap between each circle cannot be used for irrigation, and it is only suitable for use in areas with sufficient arable land.

Translational sprinkler

It is also called a continuous linear moving sprinkler. It is a long pipe with a bracket at regular intervals. The bracket has wheels. The sprinkler is on the pipe. The whole pipe is sprayed in parallel. Water is input from one end of the pipe, so the sprinkler irrigation area can be as large as Thousands of hectares.

Winch sprinkler

The winch sprinkler is also called a reel sprinkler, which uses a water turbine power drive system. The design of large cross section and small pressure can achieve high recovery speed at a small flow rate. The speed of the water turbine leads from the water turbine shaft to a two-speed belt drive to the reducer. After the speed is reduced, the chain The transmission generates a large torque force to drive the winch to rotate, thereby achieving automatic recovery of the PE pipe. At the same time, the high-pressure water flowing out of the water turbine flows directly through the PE pipe to the sprinkler head. The sprinkler sprays the high-pressure water stream evenly over the crops, spreads into small droplets and drops uniformly, and performs the spraying operation intermittently as the PE pipe moves.

Side effects of irrigation

Competition for surface water

cause groundwater level to drop

Land subsidence

Soil salinization in areas with large evaporation

Pesticide and fertilizer pollution caused by agricultural wastewater caused by over-irrigated areas.

History of irrigation development

China is a large agricultural country with a large population, little arable land, scarce water resources, frequent floods and droughts, and special natural conditions such as climate and geography, as well as social conditions, determine that China's agriculture must follow the path of irrigated agriculture.

Spring and Autumn and Warring States Period

China is the world's earliest country engaged in agriculture and water conservancy construction. As early as the Dayu era 5000 years ago, there were farmland water conservancy content such as "best effort in gully", "Jiangju Jiuze, Fengjiu Jiuyu", At that time, there were facilities for arranging ditches in wells for irrigation and drainage. During the Western Zhou Dynasty, there were already many small-scale irrigation projects in the Guanzhong area of the middle reaches of the Yellow River. For example, "The Book of Songs, Xiaoya? , Soak in the paddy field. " It means that the Weihe River tributary mud water irrigates the rice fields. The Spring and Autumn and Warring States Period was a period of change in China from a slave society to a feudal society. Due to the improvement of productivity, a large amount of land was reclaimed, and irrigation and drainage have developed accordingly. The famous Ximen leopard of Wei Kingdom repaired Zhang 12 Canal for irrigation of farmland and improvement of saline-alkali land in Yi County (now Linzhang, Hebei Province). The Chu State built a water storage irrigation project in Shou County, Anhui Province today. Dujiangyan has made the Chengdu Plain a "land of heaven and earth", "where fertile fields and thousands of miles, floods and droughts follow people."

Qin and Han Dynasties

The Qin and Han Dynasties were China's first period of strong national unity and the first major development period of irrigation and drainage projects. Especially the construction of water conservancy in the early Western Han Dynasty greatly promoted the social and economic development at that time. Zheng Guoqu (built in 246 BC) was an irrigation project built before Qin Shihuang unified the Six Kingdoms. At that time, it was said to irrigate 40,000 hectares, making the Guanzhong area the earliest basic economic zone in China. Therefore, "Qin was prosperous and strong, and he died as a prince." When Emperor Wu of the Han Dynasty, the diversion channel for diversion and irrigation was opened by the Weishui River. Later, the Longshou canal of the Beiluo River, the Baishui channel for diversion water, and the Chengguo channel for irrigation were introduced. In addition to the construction of irrigation projects in the Weihe and Fenhe valleys of the Han Dynasty in the Han Dynasty, in order to consolidate border defense and military reclamation, some large-scale canal diversion projects were also built in the Hexi Corridor of the Northwest Frontier and the Yellow River Hetao.

The Sui, Tang and Northern Song Dynasties

China's second irrigation and drainage project development period was from the Sui Tang to the Northern Song Dynasty. In the early years of the Tang Dynasty, Chang'an was the capital, and the Guanzhong irrigation and drainage project was vigorously developed. After the Anshi Rebellion, a large number of people moved south. The agricultural and water conservancy projects in the Jiangsu and Zhejiang areas developed rapidly. universal. At the same time, water-lifting tools have also been improved and promoted, which has expanded farmland irrigation areas. By the late Tang Dynasty, the tax revenue of the Taihu Lake area had surpassed the Yellow River Basin and became a new basic economic zone. By the Northern Song Dynasty, the proportion of the population in the Yangtze River Basin to the national population had increased from less than 20% in the Western Han Dynasty to over 40%. Emperor Shenzong of Song supported Wang Anshi's reform and promulgated the "Farmland Benefits Treaty" (also known as "Farmland Water Conservancy"), which is the first farmland water conservancy law officially promulgated by the central government. At the same time, it also established a palace history of farmland water conservancy in each country To further develop the water conservancy construction of farmland. After the Southern Song Dynasty favored Jiangnan, it further promoted the development of water conservancy in the south of the Yangtze River. Not only the water conservancy development in Jiangsu and Zhejiang has been greatly developed, but also the water conservancy construction in the southeast coast and the Pearl River Delta has begun to develop.

Ming and Qing Dynasties

The Ming and Qing dynasties were the third development period of irrigation and drainage engineering in China's history. During this period, the country s population increased significantly, from more than 50 million in the Yuan dynasty to 90 million in the Ming dynasty, to over 100 million in the Kangxi reign of the Qing dynasty, and 400 million in the late Qing dynasty. The population has increased more than 7 times in more than 500 years. The increase in population, the area of arable land and the yield per mu must be correspondingly enlarged and increased, so it has also promoted the large-scale development of water conservancy. Water conservancy in the middle and lower reaches of the Yangtze River has been extensively developed during the Ming and Qing dynasties. There were only 200 dykes built in the Dongting Lake area. There were 200 in the Ming dynasty and 400 to 500 in the Qing dynasty. Become another basic economic zone in the country. At the same time, the Pearl River Basin in the south, the Beijing-Tianjin area in the north, and the northwest and southwest border areas have all witnessed great developments in irrigation. After the Songliao Plain in the northeast began to ban immigration, irrigation and drainage projects also developed.

Late 19th century

After the middle of the 19th century, due to the invasion of imperialism, China became a semi-feudal and semi-colonial society. Although water conservancy developed in some areas during this period, it was generally declining. In the late 19th century, as western modern science and technology were introduced to China, a group of water conservancy scholars returned from studying abroad, opened water conservancy schools, and spread advanced science and technology. In 1914, Hohai Engineering College, the first water conservancy college in China, was established in Nanjing. After 1917, the Yangtze River, Yellow River and other river basins have successively established water conservancy institutions to carry out planning and engineering design work for water conservancy development in the river basin. In 1930, Mr. Li Yizhi presided over the construction of Luhui Canal in Shaanxi Province with modern technology, and later built Weihui Canal, Luohui Canal and other irrigation areas.

Challenges in Irrigation Development

Irrigation achievements

After several ups and downs in history, by 1949 the country had 16 million hectares (240 million acres) of irrigated area.

Since the founding of the People's Republic of China, it has carried out extensive and durable basic construction of irrigation and drainage projects, and achieved great achievements that have attracted worldwide attention. It has provided irreplaceable infrastructure and material guarantees for the sustainable development of China's agriculture and national economy. By the end of 2003, the country's irrigated area had reached 55.8 million hectares, and 40% of the arable land had irrigation facilities. In 1949, the amount of irrigation water was less than 100 billion cubic meters, accounting for 16.3% of the area of arable land at that time. Per capita irrigated area is 0.03 hectares (0.44 acres). By 2003, it had reached 330 billion cubic meters.

Since 1980, the effective utilization rate and production efficiency of irrigation water have gradually improved. Calculated based on the actual irrigation area, the average national irrigation water per hectare of farmland was 8,745 cubic meters in 1980, and in 1997 it was reduced to 7,800 cubic meters. During the same period, the grain production per cubic meter of irrigation water increased from about 0.6 kg to about 1 kg. A total of 5,686 irrigated areas with an area of over 10,000 mu (667 hectares) were constructed nationwide, with an irrigated area of more than 22 million hectares, accounting for 43% of the country's farmland irrigated area. There are a total of 84905 reservoirs in the country, with a total storage capacity of 457.1 billion cubic meters. Except for a few large reservoirs that are mainly used for flood prevention and power generation, most of them have irrigation and water supply functions. By the end of 2002, the country had developed more than 18.6 million hectares (280 million acres) of water-saving irrigation, of which more than 2.47 million hectares (more than 37 million acres) were spray-irrigated, more than 300,000 hectares were micro-irrigated, and more than 6.14 million were irrigated by low-pressure pipelines. Hectares (more than 62 million acres), and channel anti-seepage control area of more than 7.56 million hectares (more than 113.5 million acres). The non-engineering water-saving area reached 16.7 million hectares, of which 8 million hectares were paddy fields using controlled irrigation methods. The waterlogging removal reached 20.27 million hectares, accounting for 83% of the flood-prone area requiring treatment.

Irrigation challenge

Although China has made great achievements in irrigation and drainage, it also faces serious challenges. The shortage of water resources has become a major constraint on the sustainable development of China's society and economy. In 2002, the country's total water consumption was 549.7 billion cubic meters, accounting for 19.5% of the total water resources of the year, of which 5.8% was used for urban living, 5.4% was used for rural living, 20.8% was used for industrial use, and 61.4 was used for farmland irrigation. %, Forestry, animal husbandry and fishing account for 6.65. Although the total water supply will increase in the future, with the development of industry and urbanization and the improvement of people's living standards, more and more water will be used to meet the needs of industry and residents. Irrigation water shortages amount to more than 30 billion cubic meters per year, but agricultural water is wasted, and the national irrigation water utilization rate is only about 40%. In the 1970s, the average drought-stricken area of the country was about 11 million hectares per year, and by the 1980s and 1990s, it averaged about 20 million hectares and 27 million hectares per year, respectively. In addition, water pollution in China has not been effectively controlled. According to the water quality evaluation results in 2002, of the 123,000 kilometers of river lengths surveyed and evaluated, the lengths of four types of rivers accounted for 12.2%, and the lengths of five or worse types of rivers still accounted for 23.1%.

The area of flooded, saline-alkali, and flood-damaged farmland in the country is nearly 33 million hectares. After more than 40 years of ditch drainage and comprehensive treatment, most of these low-yield farmlands have been improved to varying degrees. However, with the increase in the requirements of governance standards for agricultural development and the destruction of the natural environment due to human activities in some areas, the task of further governance is still very large.