Potassium nitrate, potassium chloride, potassium sulfate, potassium dihydrogen phosphate, these four fertilizers are all important potash fertilizers. What are the differences between them? How do I know which potash fertilizer to choose? Today, let’s take a look at the characteristics and usage of these potash fertilizers.

Potassium nitrate

Potassium nitrate is easy to agglomerate and is a good water-soluble potassium fertilizer. Potassium nitrate is chlorine-free and belongs to potassium and nitrogen compound fertilizer. The total content of phytonutrient potassium and nitrogen can reach about 60%, which contains 13.5% of nitrate nitrogen and 46% of potassium; it is a chemically neutral and physiologically neutral fertilizer. Application will not cause soil acidification.

It is suitable for fruit tree young fruit expansion stage to early coloring stage, which can promote the expansion of pulp cells. Because it contains nitrate nitrogen, it is not recommended to use it in the later stage of coloring, which will easily cause blueness.

Advantages of potassium nitrate:

(1) It can be directly applied to the soil surface without covering.

(2) It can be applied to various soils and crops, and the effect is good. It is especially suitable for chlorine-free crops, such as tobacco, tomatoes, citrus, grapes, sugar beets and other crops.

(3) Provide nutrients quickly, suitable for spring, summer, autumn and winter crops.

(4) Will not cause salt accumulation in the soil.

(5) The price of potassium nitrate is higher than that of potassium sulfate, but it is also cost-effective.

Potassium Dihydrogen Phosphate

It contains 52% phosphorus (P2O5) and about 34% potassium (K2O). It is a chemically neutral and physiologically neutral fertilizer with good water solubility.

Use before and after the fruit tree blooms can increase the fruit-setting rate, use during the coloring period can promote powder coloring and increase the sweetness of the fruit; use after the fruit is picked can promote the maturity of the branches and increase the degree of fruit lignification.

Which one is better, potassium nitrate or potassium dihydrogen phosphate?

The content of the two fertilizers is different. No one is better. You can only choose according to the needs of the crop. Potassium nitrate is a binary compound fertilizer of nitrogen and potassium, and potassium dihydrogen phosphate is a compound fertilizer of phosphorus and potassium, depending on what the crop needs to supplement. The nitrate nitrogen in potassium nitrate is easily lost by rain, so it is not recommended to be used in paddy fields.

Regarding potassium nitrate and potassium dihydrogen phosphate, it can be understood as follows:

When crops use a lot of nitrogen, potassium nitrate is used.

When crops need more phosphorus, potassium dihydrogen phosphate is used. Potassium nitrate is used in the swelling period and potassium dihydrogen phosphate is used in the coloring period.

Potassium nitrate is used in the normal growth period, and potassium dihydrogen phosphate is used in the flowering and fruiting period.

Strictly speaking, these two products cannot be regarded as pure potash fertilizers. Even potassium dihydrogen phosphate is classified as phosphate fertilizer in many classifications.

Both of these fertilizers are quick-acting fertilizers, and the market price is higher than ordinary potassium fertilizers. Therefore, it is not recommended to use as base fertilizer, especially potassium nitrate, which is used as topdressing or extra-root fertilization.

If you have the conditions, you can use the two together, the effect will be better. Many high-end water-soluble fertilizer raw materials will use both of them.

Potassium sulfate

Theoretically 54% potassium, generally 50%; it is a chemically neutral, physiologically acidic fertilizer with good water solubility, but long-term use will aggravate soil acidification. It is suitable for grapes from late coloring to fruit ripening to promote fruit growth Powder color, increase fruit sweetness.

The reaction of applying potassium sulfate in different soils and the matters needing attention:

(1) In acidic soil, excess sulfate radicals will increase the acidity of the soil, and even aggravate the toxicity of active aluminum and iron in the soil to crops. Under flooding conditions, excessive sulfate radicals will be reduced to form hydrogen sulfide, which will damage the roots and turn black.

Therefore, long-term use of potassium sulfate should be combined with farmyard manure, alkaline phosphate fertilizer and lime to reduce acidity. In practice, it should also be combined with drainage and drying measures to improve ventilation.

(2) In calcareous soil, sulfate and calcium ions in the soil produce calcium sulfate, which is not easily soluble.

(3) Focus on the use of chlorine-free crops, such as tobacco, tea trees, grapes, sugarcane, sugar beets, watermelons, potatoes, etc. Increasing potassium sulfate will not only increase the yield, but also improve the quality. Potassium sulfate is more expensive than potassium chloride and has less supply. It should be used mainly on economic crops that are sensitive to chlorine and prefer sulfur and potassium, and the benefits will be better.

(4) Potassium sulfate should not be mixed with calcium-rich fertilizers. It is said that manganese poisoning in many fruit tree areas is caused by soil acidification, and the direct cause of soil acidification is the perennial use of potassium sulfate. Therefore, fertilizers are best used in rotation.

Potassium chloride

Potassium chloride [KCl, containing K2O60.0% (K, 50.0%)] Because of its high potassium content, abundant resources, simple processing, and low price, it occupies a major position in potash fertilizer.

Potassium chloride is currently the world's most used potash fertilizer, accounting for more than 90% of all potash fertilizer consumption. Potassium chloride is not only used directly as potash fertilizer or as a basic fertilizer for blending fertilizers, but also as the basic potassium source for the production of chlorine-free potassium fertilizers such as potassium sulfate, potassium nitrate or potassium phosphate.

Precautions for potassium chloride application:

(1) Do not apply it on crops that are sensitive to chlorine, such as tobacco, sugar beet, and sugar cane.

(2) Suitable for base fertilizer and top dressing, but not suitable for seed fertilizer. Because the chloride ion in potassium chloride fertilizer will affect seed germination and seedling growth. When making base fertilizer, apply potassium chloride to the soil 10 to 15 days before sowing, combined with the cultivated land. When topdressing, it is best to topdress after the seedlings grow up.

(3) Master the dosage. The general application rate per mu is controlled at 7.5-10 kg. For sandy soils with poor fertility and water retention capacity, a small amount of multiple applications should be used. The amount of base fertilizer is 8-10 kg per mu, and the amount of top-dressing fertilizer is 5-7 kg per mu. The scope of application is smaller than that of potassium sulfate.

Pay special attention not to apply it on crops such as watermelons, grapes, potatoes, etc., which are sensitive to chlorine to avoid "chlorine damage". Potassium chloride contains 45%-47% chlorine, and continuous large-scale application will affect the product quality of some cash crops, such as reducing the sugar content in grapes and fruits, reducing the combustibility of tobacco, and increasing the moisture content of potatoes Wait.

(4) Whether it is used as base fertilizer or top dressing, it should be applied as soon as possible to facilitate the leaching of chloride ions to the lower layer of the soil through rainwater or using irrigation water to remove or reduce the harm of chloride ions to crops.

(5) It will be more effective if combined with nitrogen fertilizer and phosphate fertilizer.

(6) Potassium chloride is not suitable for saline soil with poor water permeability, because it will increase the salt damage to the soil.

(7) When applying potassium chloride to sandy soil, organic fertilizer should be used in conjunction.

(8) It is generally not suitable to apply potassium chloride to acid soil. If it is to be applied, lime and organic fertilizer can be used in combination.