How to choose a compound fertilizer? These four key factors must be considered

. Compound fertilizers have many advantages, such as containing many types of nutrients, being able to supply crops with multiple nutrients at the same time, and fully leveraging the mutually promoting effects among nutrient elements; they have high available nutrient content and obvious economic benefits. In high-concentration compound fertilizers, the content of effective components accounts for at least 30%, most exceed 40%, and some reach as high as 60%; currently, domestically produced single-element chemical fertilizers have available nutrients accounting for about 20%, and their weight and volume are more than twice those of high-concentration compound fertilizers with the same nutrient content. Using compound fertilizers can save on fertilizer packaging, transportation, distribution and application costs, and reduce production costs; compound fertilizers have small side effects, little adverse impact on soil, low hygroscopicity, are not prone to caking, and are convenient to store and use, and are therefore very popular.

????How should compound fertilizers be rationally selected and used?

1. Consider the soil type

For slightly alkaline soil with low organic matter content and deficient in available nitrogen and phosphorus, acidic nitrogen-phosphorus compound fertilizers should generally be selected, such as monoammonium phosphate or humic acid-based NPK compound fertilizers, nitrogen-phosphorus compound fertilizers, etc.

But for a small number of red clay soils or acidic brown earth soils, chemically alkaline compound fertilizers should be selected, such as diammonium phosphate, etc.

2. Consider the crop variety

Generally, field crops should use nitrogen-phosphorus compound fertilizers; wheat fields or high-yield fields should use nitrogen-phosphorus-potassium ternary compound fertilizers; densely planted crops such as wheat, rice and millet are suitable for powdered compound fertilizers; widely spaced intertilled crops such as corn should use granular compound fertilizers; leguminous crops should preferably use phosphorus-potassium compound fertilizers; certain cash crops should use ternary compound fertilizers suited to the local soil and crops; root and tuber crops (lotus root, fragrant solomonseal rhizome), corn, late rice, etc. should preferably use compound fertilizers with relatively high potassium content.

Relatively speaking, crops such as early rice, peanuts, sesame, rapeseed and chili peppers should use compound fertilizers with relatively high phosphorus content; leafy vegetables should preferably use compound fertilizers with relatively high nitrogen content; chlorine-sensitive crops such as watermelon, strawberry, citrus, flue-cured tobacco, tea and grapes should use compound fertilizers that contain no chlorine or low chlorine.

3. Mix with single-element fertilizers

The nutrients in compound fertilizers are fixed. To better exert their yield-increasing effect, they should also be applied together with single-element fertilizers to regulate the crops' needs for different nutrients at different growth stages. For crops such as rice, corn and wheat, which need more nitrogen during the growing period, if diammonium phosphate, which is low in nitrogen and high in phosphorus, is selected, the application rate must first be calculated based on phosphorus, and the insufficient nitrogen must be supplemented with single-element nitrogen fertilizer. If the application rate is calculated first to meet the crops' nitrogen needs, then phosphorus will be excessive, causing waste of fertilizer.

4. Consider the application method

If used as a base fertilizer, granular compound fertilizer must be selected, and the higher the hardness of the granules the better, so as to prolong the fertilizer effect; compound fertilizers containing ammonium nitrogen are easily adsorbed by soil and not easily leached, and are suitable for various soils and crops, but deep application is best to help improve the utilization rate; nitrate nitrogen compound fertilizers are not adsorbed by soil and are easily leached with water, so they are not suitable for paddy fields but are suitable for dryland crops.

For nitrogen-phosphorus compound fertilizers with more phosphorus and less nitrogen, they can be applied deeply as a base fertilizer, and nitrogen fertilizer can be used as a topdressing to supplement the insufficient nitrogen. For relatively expensive compound fertilizers such as potassium dihydrogen phosphate, they are generally not used as a base fertilizer, and are best used for seed soaking or foliar topdressing. When selecting nitrogen-phosphorus-potassium ternary compound fertilizer as a seed fertilizer, consider that the nitrogen content should not be too high, otherwise it is likely to cause seed burn and seedling burn. (Liu Qixun)