Key points of drip irrigation technology under plastic film for greenhouse vegetables

1. The water supply for drip irrigation under film in greenhouses is mostly well water, but using a pump to lift well water directly to supply drip irrigation inside the greenhouse results in a contradiction of simultaneous water supply and different water use for multiple types of vegetables. Therefore, the water supply for greenhouse drip irrigation should generally choose the following forms:

(1) Pressure irrigation water supply. For areas with multiple and concentrated greenhouses, pressure tanks are generally used for centralized pressurization. The pressure tanks are installed between the water pump and drip irrigation to ensure continuous operation of the pipeline network under unmanned control, and no additional pressurization equipment is installed inside the greenhouse. Install a filtration facility consisting of a cyclone sand separator and a screen filter at the water source. Pressure tank water supply has a small one-time investment and convenient management, but the disadvantage is that it increases the cost of irrigation operation.

(2) Build a water tower for water supply. Build a water tower in the center of the greenhouse concentrated area to supply water for each greenhouse drip irrigation, meeting the pressure water requirements for greenhouse drip irrigation. Install filters and other equipment on the water supply pipes of the water pump and tower. The construction of a water tower requires a large one-time investment, but the operating cost is low, and it can also play a certain role in regulating and storing water.

(3) Single shed small pump water supply. For each greenhouse, a 5-7 cubic meter underground water storage tank should be built near the outside of the greenhouse, and water should be supplied to the tank through a centralized well. During drip irrigation, a micro water pump should be installed in a single greenhouse to pressurize the water, and a filter should be installed at the head of the drip irrigation. Overall, the investment is relatively high, but for each greenhouse, it is easy to build and manage.

2. The application of subsurface drip irrigation

(1) Selection of drip irrigation capillary. For closely planted crops such as vegetables, the root system development range is small, and it is very sensitive to the supply of water and nutrients. It requires a high density of drip heads and a large amount of capillary use. Therefore, the use of drip irrigation belts with lower prices for capillary use can effectively reduce the cost of drip irrigation, and the operation is reliable and easy to install and use.

(2) Layout of subsurface drip irrigation. Before drip irrigation into the greenhouse, ridges should be formed along the span (or length) of the greenhouse, with a width of 40 centimeters and a height of 10-15 centimeters, to form a double high ridge with a lower middle. The drip irrigation belt should be placed in the middle low depression of the double high ridge, and the ridge should be covered with plastic film. The center distance of double high ridges is generally 1 meter, so the spacing between drip irrigation capillary tubes is 1 meter. The length of each drip irrigation capillary is generally equal to the width (or length) of the shed, and sometimes two pipes are arranged for vegetables with high water demand. The layout of branch pipes generally follows the length of the back wall (or span) of the shed, which is equal to the length (or span) of the shed. Install fertilization devices and secondary mesh filters at the head of the branch pipe.

(3) The benefits of drip irrigation for vegetables. Drip irrigation under plastic film in greenhouses generally saves about 70% of water compared to flood irrigation, and can significantly reduce humidity inside the greenhouse, reduce pests and diseases, and improve the quality of vegetables; Compared to flooded greenhouses, the temperature is higher, and fresh vegetables can be released half a month earlier. Drip irrigation of vegetables under plastic film in greenhouses can increase production by 20% -40%, and the investment payback period is generally 4-6 months.

3. Management of subsurface irrigation

(1) Standardized operation. To achieve good results in vegetable drip irrigation, design, installation, and management must be carried out in a standardized manner, and filtration facilities cannot be dismantled or self drilled at any location.