Characteristics and application features of simple potash fertilizers

Sylvinite nKCl+mNaCl. Contains 12–18% K2O and 35–40% Na2O. The sodium chloride impurity in sylvinite is 75–80%. According to the standard, Solikamsk sylvinite must contain 15% K2O. It is obtained by mechanical grinding of sylvinite potash ore. It is a coarse-crystalline substance with crystals of white, orange, brown, and sometimes bluish color. It has satisfactory physical properties. During long-term storage, it cakes heavily. A disadvantage of this fertilizer is its high chlorine content. Therefore, sylvinite must be applied in autumn to wash out the chlorine not absorbed by the soil. Due to the presence of sodium, this fertilizer is best used on meadows and pastures, as well as for forage and sugar beet, based on their biological characteristics. Due to the low content of the active ingredient, transporting sylvinite over long distances is economically unprofitable.

Kainite KCl∙MgSO4·3H2O is ground kainite-langbeinite ore. As associated compounds, kainite contains NaCl, CaSO4, and MgSO4. This fertilizer contains only 8–10% of the active ingredient, about 40% chlorine, and about 8% MgO. It is a coarse-crystalline substance of gray, white, or orange color. It does not cake and is transported in bulk. The disadvantage of kainite is the same as that of sylvinite – high chlorine content. It should be applied during tillage">primary tillage of the soil to create favorable conditions for leaching out chlorine ions.

Polyhalite K2SO4·MgSO4·2CaSO4·2H2O. Contains 12–15% K2O. It is a chlorine-free potash fertilizer, the value of which is increased by the presence of magnesium, sulfur, and trace elements. Polyhalite has good physical properties and does not cake. It is highly effective for fertilizing potatoes, flax, and grain crops. It is applied in autumn.

Schoenite K2SO4·MgSO4·6Н2О; contains 20–23% K2O.

Langbeinite K2SO4·2MgSO4; contains 22.7% K2O. In its effect and properties, this fertilizer is similar to polyhalite.

Kalimag (potassium-magnesium concentrate) K2SO4·2MgSO4. Contains 17.5–19.5% K2O and 24–26% MgO. It is produced from langbeinite after removing NaCl by leaching. Kalimag has good physical properties: it is non-hygroscopic and does not cake. At the Solikamsk Magnesium Plant, during the processing of carnallite, the production of granulated potassium kalimag with a content of 45–65% KCl and 4.5–15.0% MgCl2 has been mastered. It is a good fertilizer for potatoes, flax, clover, and other magnesium-loving crops, especially when grown on potassium- and magnesium-deficient sandy and sandy-loam soils.

Kalimagnesia K2SO4·MgSO4·6H2O. It is obtained from kainite-langbeinite ore. Contains 29% K2O, 9% MgO, no more than 25% Cl, and up to 5% moisture. Thus, in kalimagnesia, there is approximately 2 times less chlorine per unit of potassium than in potassium chloride. It has good physical properties, is non-hygroscopic, and does not cake. Kalimagnesia is obtained during the dehydration of schoenite. It is a valuable fertilizer for crops sensitive to chlorine (potatoes, vegetables, fruit crops, buckwheat, flax) on soils with a light granulometric composition that are poor in magnesium. It can be used on all soils for all crops using various application methods.

Wood ash is a local potash-phosphorus-lime fertilizer. Potassium is present in ash in the form of carbonate (K2CO3). The amount of K2O in ash varies depending on the fuel source (Table 63; Anspok P.I., Shtikans Yu.A., Vizla R.R., 1981).

Wood ash is the best form of potassium for crops sensitive to chlorine. It must be stored in a dry place, as water leaches potassium and other nutrients from it, reducing its fertilizing value.

It can be used on all soils and for all crops:

• potatoes;
• vegetable crops;
• clover;
• perennial grasses.

As a fertilizer containing lime, it is most effective on acidic soils, especially on sandy, sandy-loam, and peat soils poor in potassium.

Table 63 – Composition of ash from different types of fuel, % Ash K2O P2O5 CaO

 Straw: wheat                            13.6       6.4      5.9
        rye                              16.2       4.7      8.5
        rice*                            18.1       5.1      7.3
        buckwheat                        35.3       2.5     18.5
 Sunflower stalks                        36.3       2.5     18.5
 Wood: birch                             13.8       7.1     36.3
       pine                               6.9       2.0     31.8
       spruce                             3.2       2.4     25.3
       willow                             4.6       2.1     43.5
 Manure, dung                            1.0       5.0      9.0
 Peat: lowland                           1.0       1.2     20.0
       upland                            0.3       0.5      3.0
 Coal: pure                              0.1–0.4   0.1–0.4     –
       together with wood                1.0       2.0       –
 *
     supplemented by A.Kh. Sheudzhen

Ash can be applied as a base fertilizer in autumn before ploughing or in spring before cultivating fallow land, as well as in the form of top dressing for row crops (or during inter-row cultivation), winter crops, and perennial leguminous grasses (applied to the surface early in spring).

The application rate of ash depends on its potassium and phosphorus content. Ash from burning straw and wood is usually recommended to be applied at a rate of 0.5–1.5 t/ha before ploughing or cultivation.

Cement dust is a byproduct of cement plants; it contains 10–15% K2O. Potassium in cement dust is present in the form of carbonate, bicarbonate, sulfate, and silicates. The ratio between the salts depends on the composition of the raw materials and the production technology.

Cement dust: a chlorine-free source of potassium for acidic soils

Cement dust can be used as an effective potash fertilizer. The potassium salts within it are fully water-soluble and easily accessible to the root system of plants. Since this industrial byproduct does not contain chlorine, it is used for feeding chlorine-sensitive crops.

The fertilizer has an alkaline reaction, therefore it is best to apply it to acidic sod-podzolic soils. In addition to potassium, cement dust introduces a whole complex of accompanying substances into the soil.