Flood irrigation has many drawbacks; only by changing the irrigation method can benefits be increased
Flood irrigation has many drawbacks; changing the method increases benefits
Our country is a country poor in water resources, yet it is also a major agricultural country with high water consumption. Agricultural water use accounts for about 60% of total water use, and the effective utilization rate of irrigation water is less than 50%. This is especially true for vegetables that are watered frequently, where the overall utilization rate is even lower.
From the waterwheel irrigation of the past to today's flood irrigation, thousands of years have passed, and this must be said to be a great advance in the speed of watering. However, everything has its two sides. The drawbacks brought by large outflow and high speed are greater water loss and low utilization rate. Among these, the greater harm is that soluble fertilizers move downward with the water into the subsoil and pollute groundwater sources. In response to this situation, agriculturally advanced countries are currently using drip irrigation and sprinkler irrigation on a large scale to water fields.
In order to explore the vertical and horizontal movement of water in the soil layer under different irrigation amounts, the author once carried out measurements. The results showed that after water flows across the surface of the border, it quickly infiltrates downward. In the layer where vegetable roots are concentrated, namely the 0-30 cm soil layer, the water quickly reaches saturation, and the excess water carries fertilizer downward into the subsoil layer with few or no roots and enters the shallow groundwater layer. This is especially true for sandy soil, where the lower part lacks a "water-holding" clay layer, so water and fertilizer are lost even faster. The greater the irrigation amount, the greater the loss. Because the downward seepage loss of water and fertilizer occurs in a "hidden" environment that people cannot see with their eyes, everyone does not feel the harm of flood irrigation. This is also the main reason why vegetable farmers are still unwilling to give up flood irrigation so far.
So how should water-saving irrigation be carried out? Several specific measures are now proposed, and farmer friends can choose according to their own specific circumstances.
Advocate drip irrigation Drip irrigation is a relatively advanced water-saving and fertilizer-saving irrigation technology that can control water volume and achieve integrated fertilizer and water application. Because it has been promoted for many years, the problem of dripper clogging has been solved, and the current price is also relatively cheap, with an input of only four or five hundred yuan per mu. In concentrated protected areas, as long as there is a water tower or pressure equipment for towerless water supply, water can be led directly into the greenhouse through underground pipes, and the water consumption can be shown by a water meter. The advantage of drip irrigation is that because a valve switch is installed at the main pipe inlet and there is a water meter for measurement, scientific water supply can be achieved according to different growth stages of vegetables and different seasons. This can not only reduce the loss of water and fertilizer, but also optimize the environment for root growth in the soil layer.
Improve flood irrigation Flood irrigation is still a main irrigation method in vegetable fields at present. In order to achieve the goal of saving water and fertilizer, the following improvement suggestions are specifically proposed: First, change long borders into short borders. At present, the border length in vegetable fields is mostly about 50 m, and some borders can reach 80 m. In this way, water flows from the head of the border to the tail of the border, and stays in the border for too long, so downward seepage loss will be greater. For this reason, it is suggested to divide long borders into short borders of no more than 10 m each. Second, when watering, change the opening once the water reaches the head of the border; it is not necessary to irrigate until the furrows are full and the borders overflow. Third, alternate wide rows and narrow rows for each watering: water the narrow rows this time and the wide rows next time. In this way, the irrigation amount can be controlled. Fourth, in addition to reasonably supplying water according to different growth stages of vegetables, plastic film mulching should also be carried out across the whole field to reduce the number of waterings.
Farmer friends often say that when watering the field, it should be "watered thoroughly," but how much water per mu counts as "watered thoroughly," and how thick a soil layer being soaked through counts as "watered thoroughly," probably few people can explain clearly. This can be explained with the help of meteorological knowledge. Generally, when the 24-hour precipitation is 20 mm, the amount of water received on one mu of land is 13,340 kg, that is, 13.34 cubic meters. According to the experience of ordinary farmers, this is a "thorough rain," meaning that the water held in the root concentration layer can fully meet the needs of vegetables. If the amount of water for each irrigation is set according to this standard, then irrigating 10 cubic meters of water per mu each time can meet the requirement. After the "amount" is determined, the interval between each watering can be determined according to the water demand of different vegetables, the water requirements of vegetables at different growth stages, different seasons, and the water-holding degree of different soil textures. Grasp the principle of small amounts and frequent watering, and change the habit of flood irrigation.
From the waterwheel irrigation of the past to today's flood irrigation, thousands of years have passed, and this must be said to be a great advance in the speed of watering. However, everything has its two sides. The drawbacks brought by large outflow and high speed are greater water loss and low utilization rate. Among these, the greater harm is that soluble fertilizers move downward with the water into the subsoil and pollute groundwater sources. In response to this situation, agriculturally advanced countries are currently using drip irrigation and sprinkler irrigation on a large scale to water fields.
In order to explore the vertical and horizontal movement of water in the soil layer under different irrigation amounts, the author once carried out measurements. The results showed that after water flows across the surface of the border, it quickly infiltrates downward. In the layer where vegetable roots are concentrated, namely the 0-30 cm soil layer, the water quickly reaches saturation, and the excess water carries fertilizer downward into the subsoil layer with few or no roots and enters the shallow groundwater layer. This is especially true for sandy soil, where the lower part lacks a "water-holding" clay layer, so water and fertilizer are lost even faster. The greater the irrigation amount, the greater the loss. Because the downward seepage loss of water and fertilizer occurs in a "hidden" environment that people cannot see with their eyes, everyone does not feel the harm of flood irrigation. This is also the main reason why vegetable farmers are still unwilling to give up flood irrigation so far.
So how should water-saving irrigation be carried out? Several specific measures are now proposed, and farmer friends can choose according to their own specific circumstances.
Advocate drip irrigation Drip irrigation is a relatively advanced water-saving and fertilizer-saving irrigation technology that can control water volume and achieve integrated fertilizer and water application. Because it has been promoted for many years, the problem of dripper clogging has been solved, and the current price is also relatively cheap, with an input of only four or five hundred yuan per mu. In concentrated protected areas, as long as there is a water tower or pressure equipment for towerless water supply, water can be led directly into the greenhouse through underground pipes, and the water consumption can be shown by a water meter. The advantage of drip irrigation is that because a valve switch is installed at the main pipe inlet and there is a water meter for measurement, scientific water supply can be achieved according to different growth stages of vegetables and different seasons. This can not only reduce the loss of water and fertilizer, but also optimize the environment for root growth in the soil layer.
Improve flood irrigation Flood irrigation is still a main irrigation method in vegetable fields at present. In order to achieve the goal of saving water and fertilizer, the following improvement suggestions are specifically proposed: First, change long borders into short borders. At present, the border length in vegetable fields is mostly about 50 m, and some borders can reach 80 m. In this way, water flows from the head of the border to the tail of the border, and stays in the border for too long, so downward seepage loss will be greater. For this reason, it is suggested to divide long borders into short borders of no more than 10 m each. Second, when watering, change the opening once the water reaches the head of the border; it is not necessary to irrigate until the furrows are full and the borders overflow. Third, alternate wide rows and narrow rows for each watering: water the narrow rows this time and the wide rows next time. In this way, the irrigation amount can be controlled. Fourth, in addition to reasonably supplying water according to different growth stages of vegetables, plastic film mulching should also be carried out across the whole field to reduce the number of waterings.
Farmer friends often say that when watering the field, it should be "watered thoroughly," but how much water per mu counts as "watered thoroughly," and how thick a soil layer being soaked through counts as "watered thoroughly," probably few people can explain clearly. This can be explained with the help of meteorological knowledge. Generally, when the 24-hour precipitation is 20 mm, the amount of water received on one mu of land is 13,340 kg, that is, 13.34 cubic meters. According to the experience of ordinary farmers, this is a "thorough rain," meaning that the water held in the root concentration layer can fully meet the needs of vegetables. If the amount of water for each irrigation is set according to this standard, then irrigating 10 cubic meters of water per mu each time can meet the requirement. After the "amount" is determined, the interval between each watering can be determined according to the water demand of different vegetables, the water requirements of vegetables at different growth stages, different seasons, and the water-holding degree of different soil textures. Grasp the principle of small amounts and frequent watering, and change the habit of flood irrigation.