NPK compound fertilizer has long effect and should be used as base fertilizer. The compound fertilizer processed and granulated by NPK compound fertilizer production line decomposes slowly than powdered fertilizer, is not easy to lose and volatilize, and has a long duration of fertilizer effect. It is suitable to be used as base fertilizer. Generally, 30-40 kg compound fertilizer is used per mu. Compound fertilizer is not suitable for topdressing at seedling stage and middle and late stage to avoid late crop maturity.
NPK compound fertilizer decomposes slowly and should be used in conjunction with simple nitrogen fertilizer. The crop seedling stage needs a large amount of nitrogen fertilizer. Therefore, when sowing or transplanting a crop with late-effect compound fertilizer as base fertilizer, it should be timely supplemented with quick-effect simple nitrogen fertilizer according to the law of fertilizer requirement of different crops. Usually, urea was applied 5 kg-8 kg/mu at seedling stage.
The concentration of NPK compound fertilizer varies greatly, so the appropriate concentration should be chosen. Most compound fertilizers are formulated according to the average nutrient status of soil types and the proportion of basic crop fertilizer requirements in a region. There are a series of compound fertilizers of high, middle and low concentration on the market. Generally, the total nutrient of low concentration is between 25% and 30%, the total nutrient of medium concentration is between 30% and 40%, and the total nutrient of high concentration is above 40%. NPK compound fertilizer should be selected according to different regions, soils and crops. Soil test before fertilizer plant production, combined with the law of crop fertilizer requirement, adding appropriate ingredients before compound production and granulation, can produce economic and efficient compound fertilizer and improve fertilizer utilization rate.
The concentration of NPK compound fertilizer is high, so it is necessary to avoid direct contact between seeds and seedlings or mixing of fertilizers and seedlings. The nutrient content of compound fertilizer is high. If it contacts directly with the root system of seeds or seedlings, it will affect seed germination and even burn buds and rot roots. When planting or transplanting NPK compound fertilizer, the root system of seeds and seedlings should be about 5-10cm apart from fertilizer when applying it in hole or strip.