Production and application of potassium fertilizer in agriculture

Potassium is critically important for yield formation, as crops extract it from the soil in large quantities. Significantly more potassium is lost with the harvest than phosphorus, and in some cases, even more than nitrogen. Naturally, this element returns to the soil in very scarce amounts—only with fallen leaves, straw, and other crop residues. Therefore, regular application of potash fertilizers remains a mandatory practice for maintaining the productivity of all crops.

The requirement for this element varies greatly depending on the crop. It is important for agronomists to consider the requirements of the so-called group of potassium-loving plants, which are sensitive to its deficiency. These include:

• sugar beet and forage root crops;
• potato;
• maize;
• vegetable crops;
• gooseberry (notable for its particularly high requirement).

The primary raw materials for the production of potash fertilizers are natural potassium salts. The industry processes a whole spectrum of minerals with varying chemical composition. This list includes both simple chlorides and complex sulfate compounds:

• halite NaCl;
• sylvinite alunite 2SO4·Al2(SO4)3·4 3;
• polyhalite K2SO4·MgSO4·CuSO4·Н2О;
• carnallite КС 2·6Н2О;
• kainite КС 4·3Н2О;
• schoenite K2SO4·MgSO4·6Н2О;
• langbeinite K2SO4·MgSO4;
• glaserite 3K2SO4·Na2SO4;
• nepheline 2O·Al2O3·2SiO2.

The Russian Federation possesses the largest raw material base for the production of potassium chloride salts. The Verkhnekamsk deposit, with reserves of 12 billion tons, is located on the left bank of the Kama River, near the cities of Solikamsk and Berezniki (the western slope of the Northern Urals). It was discovered in 1925, and fertilizer production started there in 1929. The salts lie beneath a layer of alluvial deposits. The upper part of the stratum is represented by carnallite, while the thick lower stratum consists of variegated sylvinite, which serves as the main raw material for producing potassium chloride at the Solikamsk and Berezniki plants.

Other raw material sources are used for the production of sulfate potash fertilizers. They are obtained from kainite, langbeinite, and mixed langbeinite-kainite rocks, as well as from alunites. Deposits of these minerals (polyhalite, kainite, and glaserite) are concentrated in the Saratov and Orenburg regions, as well as in Bashkiria at the Zavolzhskoye deposit.

Classification and production of potash fertilizers

Finished potash fertilizers are categorized by several key characteristics. Depending on the raw material used, they are divided into chloride-containing and chloride-free types. However, the main classification criterion is the concentration of the active ingredient (K2O), according to which simple and concentrated forms are distinguished.

Production volumes of potash fertilizers in Russia (calculated in terms of active ingredient K2O) have stabilized over recent decades. After the decline in the nineties, the domestic industry reached stable production figures. The production dynamics are characterized by the following key indicators:

• Verkhnekamsk deposit reserves — 12 billion t
• Average annual output in 1986–1990 — 4.5 million t a. i.
• Average annual output in 1993–1996 — 2.5–2.7 million t a. i.
• Stabilized output level — 3.5–4.0 million t a. i.