Analysis of manufacturers of sand and gravel filter plates and protected land irrigation and fertilization techniques

In recent years, the application of fertilization during irrigation has been widely used in protected cultivation. Fertilizing with irrigation water has advantages such as simultaneous water and fertilizer application, reduced fertilizer volatilization, improved fertilizer utilization rate, and labor saving. We will mainly introduce the fertilizer requirements, application rates, and irrigation fertilization methods for protected crops.

Protected Land Irrigation Fertilization Methods

1. Overview of Fertilization Methods in Protected Land The fertilization methods for crops in protected land generally include soil fertilization, topdressing, and foliar fertilization. A brief description of each method and its requirements is as follows:

(1) Soil Fertilization Soil fertilization is a method of applying fertilizer to the root distribution layer according to the characteristics of root distribution. This method facilitates absorption by the root system and maximizes fertilizer efficacy. In the case of fruit trees, the horizontal roots are generally concentrated slightly outside the canopy. The root system also has a tendency to seek fertilizer, and its growth direction often shifts towards the fertilized area. Therefore, organic fertilizers are generally applied slightly deeper and further away from the concentrated root distribution layer to induce deeper and wider root growth, forming a strong root system, expanding the absorption area, improving root absorption efficiency and tree nutrition levels, and enhancing the fruit tree's resistance. The depth and breadth of fertilization are related to tree species, variety, tree age, rootstock, soil, and fertilizer type. Fruit tree fertilization methods generally include ring fertilization, radial trench fertilization, strip fertilization, and whole-orchard fertilization. Vegetable fertilization methods generally include basal fertilizer and topdressing. Basal fertilizer is a method of applying fertilizer to the soil before sowing or planting in conjunction with soil tillage. It is the nutritional foundation for excellent and high-yield vegetables. Basal fertilizer should mainly consist of organic fertilizer. The application method of organic fertilizer generally depends on the degree of decomposition and quantity of organic fertilizer. Organic fertilizer that is not well decomposed and is large in quantity should not be applied in concentrated trenches; it should be spread on the surface and incorporated into the soil with plowing. Well-decomposed organic fertilizer in small quantities should be applied in concentrated trenches. If the quantity is large, half can be used for trench application and half for broadcasting, meeting the nutritional needs of vegetables while improving the soil. When applying fertilizer in holes, well-decomposed organic fertilizer must be used, and not too much should be applied to avoid burning seedlings. When applying fertilizer in holes, the fertilizer and soil must be mixed evenly.

(2) Topdressing Fertilizer applied during the seedling stage or after planting is called topdressing. It generally consists mainly of quick-acting chemical fertilizers, primarily nitrogen fertilizer, followed by potassium fertilizer. Topdressing should also be applied multiple times according to the different growth and development stages of vegetables, following the principle of applying small amounts frequently. The number of topdressings can be determined based on the length of the vegetable growth period. Vegetables with short growth periods can be topdressed 1-3 times during the growth period, while vegetables with long growth periods can be topdressed 3-5 times or more during periods of high nutritional demand. Generally, topdressing is applied once every 15-20 days. If the amount of topdressing is too large, not only will the vegetables not be able to absorb it, but it will also cause burning, waste, and increase soil salinity, hindering root growth.

(3) Foliar Fertilization Also known as foliar spraying, this method is simple and easy to implement. It can improve leaf photosynthetic efficiency and enzyme activity, thereby improving root nutrition, promoting root development, enhancing absorption capacity, and promoting the overall metabolic process of plants. The amount of fertilizer used is small, the effect is quick, and it is not affected by the nutrient base, so it can meet the needs of crops in a timely manner and prevent the loss or fixation of certain elements in the soil. However, foliar fertilization cannot replace soil fertilization. Both have their own characteristics and complement each other. When used properly, they can maximize the effect of fertilization.

2. Common Irrigation Fertilization Methods in Protected Land In recent years, fertilization methods combined with irrigation have been widely used in protected land. Soil fertilization methods in protected land can generally be combined with various irrigation methods such as furrow irrigation, sprinkler irrigation, drip irrigation, and seepage irrigation.

(1) Irrigation Fertilization Method Combined with Furrow Irrigation Generally, various fertilization equipment, such as fertilizer tanks, is set up at the head of the field. Sometimes, a small pit can be dug in the field and covered with plastic film as a substitute. Various fertilizers are placed in the water tank to dissolve, and then they flow into the field and into the root layer of the crops with the water. In protected land furrow irrigation fertilization, the following points should be noted:

① The concentration of the fertilizer solution should be strictly controlled between 0.2% and 0.3%;

② The fertilization period during irrigation must be noted.

(2) Irrigation Fertilization Method Combined with Drip Irrigation This method combines irrigation and fertilization, resulting in higher water and fertilizer efficiency. At the same time, the fertilizer concentration can be adjusted, which is relatively safer and can effectively reduce the air humidity in protected land and prevent the spread of diseases and pests. In drip irrigation fertilization, fertilization equipment is generally added to the system to achieve this. Commonly used fertilization (pesticide) equipment includes pressure-differential fertilizer tanks, open fertilizer barrels, Venturi fertilizer applicators, and injection pumps. A brief description of the structure of various common fertilization equipment is as follows:

① Pressure-Differential Fertilizer Tank: A pressure-differential fertilizer tank consists of a storage tank, an inlet pipe, an outlet pipe, and a pressure regulating valve. The pressure-differential fertilizer tank fertilization process is as follows: After the irrigation system is operating normally, first, the soluble fertilizer or fertilizer solution is added to the storage tank 1, and then the tank lid is closed; the valve 6 is opened to connect the fertilizer supply pipe 7, and then the valve 4 is opened and the inlet pipe 2 is connected. At this time, the pressure in the storage tank and the water supply pipeline is balanced. Then, the fertilizer pressure regulating valve 5 is slightly closed to create a pressure difference between the inlet and outlet pipes of the valve, causing the fertilizer in the tank to Enter the outlet pipe under pressure, resulting in a decrease in pressure in the storage tank. This cycle continues until the fertilizer in the tank is used up, and then new fertilizer is added. The advantages of the pressure-differential fertilizer tank are that it is simple to manufacture, has a low cost, and does not require external power equipment. The disadvantages are that the concentration of the fertilizer solution changes greatly and cannot be controlled. The volume of the tank solution is limited, and the frequency of adding fertilizer is high.

    ②Open-type fertilizer tank self-pressurized fertilization equipment: In a self-pressurized irrigation system, using an open-type fertilizer tank or building a fertilizer pool is very convenient. Simply place the fertilizer tank in an appropriate position under the self-pressurized water source, connect the fertilizer supply pipe to the water source through a control valve, connect the infusion tube and valve to the main pipe of the irrigation system, and open the fertilizer valve to the required degree to complete fertilization. Open-type fertilizer tanks are generally used in single-shed independent irrigation systems or self-pressurized irrigation systems.

    ③Venturi fertilizer injector: The Venturi fertilizer injector can be used in conjunction with an open-type fertilizer tank to form a fertilization system. Its structure is simple, easy to use, and inexpensive. It is mainly used as a fertilization device for small irrigation systems. Its drawback is that if it is directly connected to the main pipe, it will cause a large pressure loss.

    ④Injection pump: Piston pumps or diaphragm pumps are often used in irrigation systems to inject fertilizer solutions or pesticides into irrigation pipes. The advantages of using this type of equipment are that the fertilization equipment can uniformly supply fertilizer to the irrigation water source, ensuring that the fertilizer concentration of the irrigation water remains stable, the fertilization quality is good, and the efficiency is high; the disadvantage is that additional power equipment and an injection pump are needed, so the cost is higher.