Potassium nitrate, potassium chloride, potassium sulfate, and potassium dihydrogen phosphate are all important potassium fertilizers. What are the differences between them? How do you know which potash fertilizer to choose? Today, let’s learn about the characteristics and usage of these potassium fertilizers.
Potassium nitrate
Potassium nitrate is easy to clump and is a good water-soluble potassium fertilizer. Potassium nitrate is chlorine-free and is a potassium and nitrogen compound fertilizer. The total content of plant nutrients potassium and nitrogen can reach about 60%, including 13.5% nitrate nitrogen and 46% potassium. It is a chemically neutral and physiologically neutral fertilizer that can be used for a long time. Application does not cause soil acidification.
It is suitable for the expansion stage of young fruit trees to the early stage of coloring, and can promote the expansion of pulp cells. Because it contains nitrate nitrogen, it is not recommended to be used in the later stages of coloring, as it can easily cause greening.
Advantages of potassium nitrate:
(1) It can be applied directly to the soil surface without covering.
(2) It can be applied to various soils and crops with good results. It is especially suitable for chlorine-resistant 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) It will not cause the accumulation of salts in the soil.
(5) Potassium nitrate is more expensive than potassium sulfate, but it is also more cost-effective.
Potassium dihydrogen phosphate
Potassium dihydrogen phosphate contains 52% phosphorus (P2O5) and about 34% potassium (K2O). It is a chemically neutral and physiologically neutral fertilizer with good water solubility. Using it before and after fruit trees bloom can increase the fruit setting rate. Using it during the coloring period can promote powdering and coloring and increase fruit sweetness. Using it after fruit picking can promote the aging of branches and increase the degree of lignification of fruits.
Which one is better, potassium nitrate or potassium dihydrogen phosphate?
The two fertilizers have different contents. There is no better one. You can only choose according to the needs of the crops. Potassium nitrate is a binary compound fertilizer of nitrogen and potassium. Potassium dihydrogen phosphate is a binary compound fertilizer of phosphorus and potassium. It depends on what the crops need to supplement. . The nitrate nitrogen in potassium nitrate is easily lost by rain, so it is not recommended for use in paddy fields.
About potassium nitrate and potassium dihydrogen phosphate, you can understand it like this:
When a large amount of nitrogen is needed for crop growth, potassium nitrate is used.
When crops require more phosphorus for growth, potassium dihydrogen phosphate is used. Use potassium nitrate during the expansion stage and potassium dihydrogen phosphate during the coloring stage.
Use potassium nitrate during the normal growth period and potassium dihydrogen phosphate during the flowering and fruiting period.
Strictly speaking, these two products cannot be regarded as simple potash fertilizers. Even potassium dihydrogen phosphate is classified as phosphate fertilizer in many categories.
Both fertilizers are quick-acting fertilizers, and the market price is higher than ordinary potassium fertilizers. Therefore, it is not recommended to be used as a base fertilizer, especially potassium nitrate, which is used as top dressing or extra-root fertilization.
If possible, you can use the two together, and the effect will be better. Many high-end water-soluble fertilizers use both of them as raw materials.
Potassium sulfate
Theoretically, the potassium content is 54%, usually 50%; it is a chemically neutral, physiologically acidic fertilizer with good water solubility. However, long-term use will aggravate soil acidification. It is suitable for the late stage of grape coloring to the fruit maturity stage. Promote fruit powdering and coloring, and increase fruit sweetness.
Reactions of potassium sulfate application in different soils and matters that should be paid attention to:
(1) In acidic soil, excess sulfate radicals will make the soil acidic and even intensify the poisoning of crops by active aluminum and iron in the soil. Under flooded conditions, excess sulfate will be reduced to hydrogen sulfide, causing the roots to become damaged 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 field drying measures to improve ventilation.
(2) In calcareous soil, sulfate radicals and calcium ions in the soil generate insoluble calcium sulfate.
(3) Use it mainly on chlorine-resistant crops, such as tobacco, tea trees, grapes, sugar cane, sugar beets, watermelons, potatoes, etc. Increased application of 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 cash 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 in the United States is the long-term use of potassium sulfate. Therefore, it is best to rotate fertilizers.
Potassium chloride
Potassium chloride [KCl, containing K2O60.0% (K, 50.0%)] occupies a dominant position among potash fertilizers because of its high potassium content, abundant resources, easy processing, and low price.
Potassium chloride is currently the most widely used potassium fertilizer in the world, accounting for more than 90% of all potassium fertilizer consumption. Potassium chloride is not only used directly as a basic fertilizer for potash fertilizers or blended fertilizers, but also as a basic source of potassium for the production of chlorine-free potassium fertilizers such as potassium sulfate, potassium nitrate or potassium phosphate.
Precautions when applying potassium chloride:
(1) Do not apply to chlorine-sensitive crops such as tobacco, sugar beets, and sugar cane.
(2) Suitable for base fertilizer and top dressing, but not suitable for seed fertilizer. Because the chloride ions in potassium chloride fertilizer will affect seed germination and seedling growth. When used as base fertilizer, potassium chloride should be applied into the soil in combination with cultivated land 10 to 15 days before sowing. When applying rubber antioxidant fertilizer, it is best to apply it after the seedlings grow up.
(3) Master the dosage. General application rate per muThe limit is 7.5-10 kg. For sandy soils with poor fertilizer and water retention capabilities, small amounts should be applied multiple times. The amount of basal fertilizer per mu is 8 to 10 kilograms, and the amount of top dressing per mu is 5 to 7 kilograms. The applicable range is smaller than that of potassium sulfate.
Pay special attention not to apply it on chlorine-sensitive crops such as watermelons, grapes, potatoes, etc. to avoid “chlorine damage”. Potassium chloride contains 45%-47% chlorine. Continuous large-scale application will affect the product quality of some economic crops, such as reducing the sugar content in grapes and fruits, reducing the flammability of tobacco, and increasing the moisture content of potatoes. wait.
(4) Whether it is used as base fertilizer or top dressing, it must be applied as early as possible to facilitate the leaching of chloride ions to the lower layers of the soil through rain or irrigation water, thereby removing or reducing the harm of chloride ions to crops.
(5) The fertilizer effect will be better when applied in conjunction with nitrogen fertilizer and phosphorus fertilizer.
(6) Potassium chloride should not be applied to saline-alkali soils with poor water permeability because it will increase salt damage to the soil.
(7) When applying potassium chloride to sandy soil, organic fertilizer should be applied.
(8) It is generally not suitable to apply potassium chloride to acidic soil. If it is applied, lime and organic fertilizer can be applied together.
