Use Of Potash Fertilizers (part 3)

2023 Author: Sebastian Paterson | [email protected]. Last modified: 2023-11-26 20:34

The mysteries of potash fertilizers

Read the previous part of the article

The effect of potash fertilizers on different soils

All agricultural crops are in great need of potash fertilizers on peaty, sandy and sandy loam soils. These fertilizers are also highly effective on floodplain and sod-podzolic soils. On them, potash fertilizers are used in combination with nitrogen and phosphorus fertilizers. Only peatlands, floodplains and meadows sometimes receive only potash fertilizers, where they pay off well.

On all types of soils, the need of plants for potassium is largely covered by the application of manure, therefore, the further in the rotation of the crop rotation a given crop is placed from manure, the higher the increase in yield from potash fertilizers.

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Interaction of potassium with soil

Industrial potash fertilizers, being easily soluble in water, quickly interact with the soil. The K + cation is strongly adsorbed by its colloidal part. This prevents noticeable movement of potassium in the soil and its leaching. It usually does not sink deeper than 4-6 cm from the place of application; with surface application, the largest amount of it is retained already in the upper, two-centimeter layer of soil. It follows from this that potash fertilizers are best applied to the root layer of the soil to a depth of 10-18 cm, i.e. in the spring for digging.

Thus, on heavy and medium soils, deep plowing of potash fertilizers is required, since under these conditions potassium is less fixed in a non-exchangeable form. On light soils, in an area with increased precipitation, potash fertilizers can also be applied under the cultivator (in a layer of 8-15 cm).

Entering into the absorbing complex of the soil, potassium displaces into the solution an equivalent amount of other cations and, first of all, calcium, which is the most in the exchange state in soils. In acidic soils, in exchange for potassium ions, the soil solution is enriched with hydrogen, aluminum and manganese ions, which adversely affect beets, cabbage, as well as many beneficial bacteria - nitrifying, nodule and free-living. Therefore, on acidic soils, the systematic introduction of potassium salts should be accompanied by the introduction of a neutralizing lime additive (the same amount of dolomite flour or other lime fertilizer is added to 1 part of the potassium fertilizer).

After liming the soil, the content of assimilable potassium in the soil increases, here the calcium of lime displaces a lot of potassium from the absorbed state into the soil solution, increasing the assimilability.

The role of impurities in potash fertilizers

The inevitable companion of potassium in fertilizers is chlorine, sodium, magnesium and sulfate ion. All the ions in the fertilizer are essential for plant nutrition. A lot of chlorine contains sylvinite, carnallite, kainite. Excess chlorine for some crops (potatoes, etc.) is sometimes harmful. But it cannot be assumed that the chlorine ions are completely ballast. Recent physiological experiments suggest that chlorine is also needed in small quantities for nutrition and metabolism in the plant organism, although its functions are still not fully understood. But if chlorine ions are completely excluded from the nutrient solution, then all plants begin to develop weaker. It is contained not only in potash fertilizers, but also in manure, phosphate rock, superphosphate and other mineral fertilizers, and also enters the soil and leaves from the atmosphere with precipitation.

The mobility of soil cations increases with the addition of chloride salts, since none of them with the chlorine anion gives insoluble salts. This is the reason for the leaching of increased amounts of calcium and magnesium from the soil when potash fertilizers rich in chlorine are embedded in it.

Sodium, although not included in the elements necessary for all plants, is nevertheless found in all agricultural crops. It has been established that many plants respond positively to the introduction of sodium into the nutrient medium. First of all, this applies to beets, cruciferous vegetables, carrots and some cereals.

The magnesium content in potash fertilizers is very beneficial. When physiologically acidic ammonium fertilizers are applied, a lot of magnesium is leached from the absorbing soil complex. Such losses of magnesium are very noticeable on light soils, their fertility for magnesium decreases. The introduction of potassium-magnesian salts makes up for the losses, especially on sandy loam. Therefore, magnesium-containing fertilizers have a better effect than potash fertilizers that do not contain magnesium. Trace minerals in unrefined potassium salts are also beneficial in improving plant growth and development in many soils.

The less potassium available to agricultural plants is contained in the soil, the larger doses of potash fertilizers must be applied to obtain high yields.

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In the first year of life, beets and other root crops absorb potassium throughout the growing season, but especially a lot in the second half of the growing season, when carbohydrates are intensively accumulated. At this time, with a weak potassium diet, protein synthesis is delayed, the accumulation of soluble non-protein nitrogenous substances in the root increases, which worsens the quality of the crop, especially sugar beets. Potassium starvation (as well as an excess of nitrogen) accelerates the appearance of flowering stems in the first year of life of a beet plant, sharply reduces the yield and sugar content of root crops. Beets respond better to the addition of potassium salts containing sodium chloride. However, on light soils, potassium magnesium acts better than all other fertilizers. A dose of K ₂ O 10-12 g / m² is applied in the spring for digging the soil.

Potatoes are a typical "potash" plant. Potato tubers' ash contains 44 to 74% potassium, which is almost one and a half times more than potassium chloride, the most concentrated fertilizer. During July, potatoes receive 60% of the total amount of potassium in the crop. Therefore, 12-15 g / m² K ₂ O is applied under potatoes in the spring for digging, regardless of whether manure was introduced or not. This is done in order to ensure optimal nutrition for the potatoes during July and during the ripening of the crop. The best forms of potash fertilizers are sulfate forms and contain magnesium (potassium sulfate, potassium magnesium, etc.), since potatoes cannot tolerate excess chlorine.

Vegetables are also high in potassium intake and respond well to it. Potash fertilizers (potassium chloride and other chlorine-containing fertilizers) have a positive effect on tomatoes, cabbage (12-20 g / m² K ₂ O for digging). Potassium increases the sugar content of vegetable crops and reduces their morbidity during long-term storage in winter.

Onions, cucumbers and carrots suffer from an increased concentration of soil solution, therefore, only concentrated potassium fertilizers (potassium sulfate) are applied under them for digging the soil in the spring (8-10 g / m² K ₂ O).

Fruit and berry crops are highly responsive to potassium fertilization. Under the influence of potash fertilizers, the percentage of flowering branches in the apple tree increases, the marketable part (large fruits and lighter ones) increases, the number of fruits in the crop increases, the cold resistance and frost resistance of crops increase. Fertilizers are best applied at the end of April for digging row spacings, excluding near-trunk circles and protective zones near plants.

That's all. Make friends with potash fertilizers. Wish you luck.