Application skills and precautions of water-soluble fertilizer

Water soluble fertilizer refers to water-soluble compound fertilizer, including solid and liquid forms. Generally speaking, the formula of water-soluble compound fertilizer is more reasonable, the nutrients are more diversified, and it is more targeted to crops. However, unreasonable use in production will cause waste of fertilizer and even play a negative role.
Fertilization requirements:
Small amount and multiple application is an important fertilization principle of water-soluble fertilizer, which is in line with the characteristics of continuous nutrient absorption by plant roots and reduces the leaching loss caused by large amount of one-time fertilization. A small amount of repeated application is an important reason for the high utilization rate of water-soluble fertilizer. Generally, the dosage per mu is 3 ~ 6 kg each time. There are few seedling stages and more vigorous growth stages.
Pay attention to nutrient balance. Water soluble fertilizers are usually applied by watering, sprinkling or through irrigation equipment. Especially under the condition of drip irrigation and fertilization, the root growth is large and dense, and the nutrient supply to the soil depends more on the nutrients provided by drip irrigation, especially in sandy soil, which has higher requirements for the reasonable proportion and concentration of nutrients. If the fertilizer formula is unbalanced, it will affect crop growth and produce element deficiency.
When applying fertilizer, especially sprinkler irrigation and micro sprinkler irrigation, attention should be paid to prevent fertilizer from burning leaves and roots. Generally, the EC Value of the soluble salt concentration of the fertilizer solution is controlled at 1 ~ 3MS / cm (millisiemens per cm), or 1 ~ 3kg per cubic meter of water is dissolved, which is equivalent to 350 ~ 1000 times dilution, or spray clean water once after spraying fertilizer. When spraying, it is also necessary to prevent excessive concentration from burning roots and seedlings. The insurance method in production is to test with a small amount of fertilizer and reduce the concentration when it is found to be harmful to the leaves. Some large growers can buy handheld conductivity meter to monitor fertilizer concentration, especially in areas with high salt concentration in water source.
Precautions for drip irrigation application:
When applying fertilizer in drip irrigation, first drop clean water, and then start applying fertilizer after the pipeline is full of water. After fertilization, drip clean water immediately for 20 ~ 30 minutes to discharge the residual fertilizer * * in the pipeline (whether it is discharged can be monitored by conductivity meter). If the pipe is not washed, moss, algae and other plants or microorganisms may grow at the emitter and block the emitter. During the rainy season, the soil is not short of water. At this time, fertilization is required to be fast. It shall be completed within half an hour, and no water shall be dropped after fertilization. Or instead of applying fertilizer through drip irrigation, use soil surface fertilizer. The nitrogen fertilizer is mainly ammonium nitrogen fertilizer, and urea and nitrate nitrogen fertilizer should not be used.
The long-term use of drip irrigation for fertilization in greenhouse or greenhouse will cause the accumulation of surface salt and affect the growth of roots. Drip irrigation under film can be used to prevent the migration of salt to the surface.
Pay attention to the uniformity of fertilization. In principle, the slower the drip irrigation fertilization is, the better. Especially for the elements with poor mobility in the soil (such as phosphorus), prolonging the fertilization time can greatly improve their utilization rate. Drip irrigation and fertilization in dry season are recommended to be completed in 2 ~ 3 hours. The soil is not short of water. On the premise of ensuring uniformity, the faster the better.
Avoid excessive irrigation and generally keep the root layer moist. The root layer depth varies greatly according to different crops. You can dig the soil with a shovel at any time to understand the specific depth of the root layer. Excessive irrigation not only wastes water, but also leaching nutrients below the root layer, wasting fertilizer and reducing crop yield. Especially urea and nitrate nitrogen fertilizer (such as potassium nitrate, calcium ammonium nitrate, nitrophosphate fertilizer and water-soluble fertilizer containing nitrate nitrogen) are easy to lose with water.
Understand the hardness and pH of irrigation water to avoid precipitation and reduce fertilizer efficiency. If the pH value of irrigation water is greater than 7, it indicates that the water is alkaline, which may cause the volatilization loss of ammonium nitrogen in water-soluble fertilizer. Foreign practice is to dissolve * * amount of sulfuric acid in irrigation water and adjust the water to slightly acidic. If the hardness of water is high, the content of calcium and magnesium is high, and the water is alkaline, calcium phosphate precipitation may occur when applying water-soluble phosphate fertilizer. Generally, the precipitation cannot be filtered out by the filter, and it is inconvenient for the naked eye to observe. Fine precipitated particles enter the drip irrigation pipe through the filter and slowly deposit in the flow channel of the emitter, accumulate to the degree of * * and block the emitter. This is one of the reasons for the blockage of drippers in many saline alkali land areas. At the same time, phosphate precipitation is also an important reason to reduce the effect of phosphate fertilizer in water-soluble fertilizer. In view of this situation, it is recommended to use acid fertilizers, such as urea phosphate, urea sulfate, acid water-soluble fertilizer, etc.
Combined with other fertilizers, water-soluble fertilizer is usually only used as topdressing. When recommending fertilization, it should be combined with base fertilizer and topdressing, organic fertilizer and inorganic fertilizer, and water-soluble fertilizer and conventional fertilizer. Do not emphasize the substitution of water-soluble fertilizers for other fertilizers, but use them together to reduce costs and give full play to the advantages of various fertilizers. Generally, organic fertilizer, phosphate fertilizer and magnesium fertilizer are applied as base fertilizer, water-soluble fertilizer is applied as top dressing, and a small amount is applied for many times.
Inorganic water-soluble fertilizer and organic water-soluble fertilizer are applied together. Now the commonly used organic water-soluble fertilizers include amino acid, yellow humic acid, seaweed polysaccharide and so on. These substances have the functions of stimulating root growth, chelating metal trace elements and improving crop stress resistance. The combined application of the two will significantly promote nutrient absorption and improve fertilizer utilization efficiency.
Fertilizer can be divided into solid fertilizer, liquid fertilizer and gas fertilizer (CO2). Liquid fertilizer includes clear liquid fertilizer in which nutrient elements are dissolved in water as solute to become solution, or suspended fertilizer suspended in water to become suspension with the help of suspending agent.
The liquid fertilizer mentioned in this paper is a liquid compound fertilizer based on nitrogen, phosphorus and potassium nutrients, rather than a liquid fertilizer. Urea ammonium nitrate solution (known as nitrogen solution abroad) is the main nitrogen raw material of liquid compound fertilizer, ammonium polyphosphate solution is the main phosphorus raw material, most of the potassium raw material is potassium chloride and a small part is potassium nitrate. The content of nitrogen, phosphorus and potassium of various clear liquid fertilizers is generally 25% ~ 35%, and there are many kinds of formulas. The clear liquid fertilizers widely used abroad belong to this category. Suspended liquid fertilizer is suitable for high concentration compound fertilizer, and the content of nitrogen, phosphorus and potassium is 35% ~ 50%. Some suspended fertilizers are completely water-soluble, and some contain * * impurities. Suspended fertilizer can use various fertilizer raw materials containing impurities or insoluble in water, such as zinc oxide, magnesium oxide, lime powder, gypsum powder, etc. Most of the suspended fertilizer is used as base fertilizer or topdressing. For example, seed fertilizer is sown at the same time, which can be used as seedling bed fertilizer and base fertilizer, and can be sprayed before turning over the ground.
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