Choosing high-quality water-soluble fertilizers with major elements is only the first step. Scientific application methods can maximize the fertilizer efficiency and avoid problems such as seedling burning and root damage. According to the guidance of agricultural experts, the scientific application of WSF should focus on mastering the following key points.

Firstly, select the appropriate application method according to the irrigation method. Different irrigation methods have different requirements for the water insoluble matter content of WSF: drip irrigation requires water insoluble matter less than 0.2%, micro-sprinkler irrigation less than 0.5%, and sprinkler irrigation less than 5%. It is recommended to give priority to products with low water insoluble matter to reduce pipeline blockage. Common application methods include drip irrigation, sprinkler irrigation, foliar spraying, flushing application and hole application. Among them, drip irrigation and sprinkler irrigation are the most recommended, which can realize uniform fertilization and improve nutrient absorption efficiency; foliar spraying is suitable for emergency nutrient supplement, such as crop nutrient deficiency or post-disaster recovery; flushing application and hole application need to control the dosage to avoid local excessive fertilizer concentration.

Secondly, adopt the "secondary dilution" method. Many growers directly flush WSF like traditional compound fertilizers, which easily leads to uneven fertilization: crops with too much fertilizer will have root burning and yellow leaves, while those with too little fertilizer will have poor growth. The correct method is to first dissolve WSF in a small amount of water and stir evenly, then add it to the irrigation system or dilute it to the required concentration for application. This method can ensure uniform fertilization and improve fertilizer utilization rate.

Thirdly, follow the principle of "small amount and multiple times". WSF has strong quick-acting properties and is difficult to remain in the soil for a long time. Therefore, it is necessary to strictly control the application amount and avoid excessive fertilization. The general application amount per mu is 3-6 kg, and it should be adjusted according to the crop growth stage and soil conditions. For example, in the vigorous growth period, the frequency can be increased and the single dosage can be reduced to meet the continuous nutrient demand of crops.

Fourthly, grasp the application time and matching skills. Before fertilization, first drip clear water to fill the pipeline; after fertilization, drip clear water for 20-30 minutes to flush the residual fertilizer in the pipeline and avoid pipeline blockage and root damage. In dry seasons, fertilization should be completed within 2-3 hours of drip irrigation to keep the soil layer 20-40 cm moist and prevent nutrient loss. WSF should be applied separately as much as possible or mixed with non-alkaline pesticides. Before mixing, compatibility test should be carried out to avoid precipitation caused by reaction with metal ions. In addition, fertilization should be avoided in rainy days; in high temperature and drought weather, the fertilization concentration should be reduced to prevent seedling burning.

Different crops have different nutrient needs. For example, watermelons and tomatoes need low-concentration nitrogen-potassium fertilizer in the early stage and high-concentration balanced fertilizer in the later stage; for grapes, attention should be paid to supplementing magnesium to avoid leaf yellowing. Scientific application of WSF can not only improve crop yield and quality, but also extend the service life of soil.