Compound fertilizer

1. Concept

Compound fertilizer refers to a chemical fertilizer that simultaneously contains two or more nutrients in nitrogen, phosphorus, potassium, and other nutrient elements. Some countries are also called comprehensive fertilizers or multi-nutrient fertilizers, and sometimes in addition to N, P, and K, composite fertilizers can also contain one or several micronutrients that can be labeled.

2. The type of the compound fertilizer material

        The compounds generated by the established production process are the components of compound fertilizer, and the nutrient content and proportion are fixed. Such as diammonium 18-46-0 [(NH4)2HPO4]; That is, the conventional compound fertilizer.

    The content and proportion of nutrients in compound fertilizer are composed of several single fertilizers or compound fertilizers in the production process according to a certain process formula System, within a certain range can be adjusted according to different requirements. The 15-15-15 compound fertilizer that China has imported and produced in large quantities in recent years is a kind of compound fertilizer.

    There are two ways of mixing the base material into the compound fertilizer, one is the early use of mixing the original base material. The other is the modern application of bulk mixing of granulated basic materials. The material used for compound fertilizer can be simple fertilizer or compound fertilizer. The content and proportion of nutrients can be greatly adjusted, which is suitable for the nutrient requirements of soil and crops in the service area. The formula can be easily changed according to time and place. It is often used with and without long-term storage.

3. the characteristics of the compound fertilizer material

    1. Advantages 

        (1) One application can supply all or most of the nutrients needed by the crop, and reasonable application generally does not have adverse effects on the soil. 

        (2) High nutrient concentration, few side components, small body volume of fertilizers with the same nutrients, low

        (1) The nutrient ratio of compound fertilizer is fixed, which cannot be applied to the nutrient demand of various soil and crops. Generally, it is applied with simple fertilizer, which is the basic fertilizer for the production of mixed fertilizer 

        (2) It is difficult to meet the needs of fertilization technology, and the best fertilization effect of various nutrients.

4. Types and application of common compound fertilizer materials

    (1) Ammonium phosphate

        (1） Nature Ammonium phosphate fertilizer has monoammonium phosphate (NH4H2PO4, abbreviated MAP) and diammonium phosphate (NH4)2HPO4, abbreviated as DAP), they are formed by the reaction of phosphate acid and ammonia into compound fertilizer. Ammonium phosphate fertilizers are gray-white or gray particles, easily soluble, neutral to slightly alkaline, stable properties, ammonia is not volatile.

At present, domestic ammonium phosphate is a mixture of mono ammonium salt and diammonium salt, and the total nutrient concentration is 60% -80%, of which nitrogen (N) is 14% -18%; phosphorus (P2O5) Is 46%-50%. Ammonium phosphate is a phosphate-based binary compound fertilizer with a high concentration of nitrogen and phosphorus, and its N+ P2O5 content is about 64%, soluble in water.

        (2) Features

Ammonium phosphate can be used as base fertilizer and topdressing fertilizer, but its phosphate content is mostly higher than nitrogen, mono ammonium N∶P2O5The ratio is about 1∶5 and diammonium is about 1∶2.5, which is not suitable with the demand for nitrogen to phosphorus ratio in most crops. 

Therefore, in order to make the phosphorus contained can play a role in the seedling stage to meet the needs of crops in the phosphorus nutrition critical period, it is generally advisable to make seed fertilizer; on the other hand, when ammonium phosphate fertilizer is used as base fertilizer, a certain amount of nitrogen fertilizer should be applied to make N∶P2O5The proportion of which is adjusted to the appropriate degree. 

Therefore, in the compound fertilizer, ammonium phosphate is only a raw material, rarely applied alone.

    Potassium dihydrogen phosphate is suitable for all kinds of crops and soil use, especially in areas where phosphorus and potassium nutrients are deficient and phosphophiliaPotassium crops. When it is used for root fertilization, it can be used as base fertilizer, seed fertilizer, or middle and late topdressing. Because KH2PO4 is more expensive, it is often used by economic methods such as seed soaking or topdressing outside the root. The concentration of field crops is commonly 0.2%, soaked for 18-20 hours, and can be sown after drying. For external topdressing, if sprayed alone, up to 0.5% can be used. For example, in the jointing booting period of wheat and rice, the first flowering period of cotton and rape can be sprayed 1-2 times. It can also be combined with other nutrients to form a compound nutrient solution for external topdressing. In recent years, KH2PO4 has been used as a kind of phosphate and potassium fertilizer source with high concentration and good hydrophilicity