Lithium fertilizers

Lithium fertilizers — micronutrient fertilizers that satisfy the requirement of agricultural crops for the trace element lithium.

Lithium is a biologically important element in plant vital activity; it influences the content and heterogeneous composition of proteins and nucleic acids, and the enzymatic activity of enzymes associated with protein–nucleic acid metabolism.

There are data on the role of lithium in plant carbohydrate metabolism, in increasing the intensity of photosynthesis during the reproductive period, and in affecting the rate of photorespiration and the grain productivity of winter wheat. A specific role in alkaloid metabolism has been noted. An effect on the accumulation of ascorbic acid in plants and a positive effect in combating viral infections have been established.

The necessity of lithium for humans and animals has been proven. The effectiveness of lithium in various diseases depends on its effect on neuroreflex activity, as well as on its adrenolytic, noradrenolytic, antihistamine, and antiserotonin actions and its regulatory effect on the hormonal activity of the endocrine glands, especially the adrenal cortex. In hypertension of various origins, lithium has an antistress and sedative effect. Its positive effect in certain pathological processes is determined by a stimulating effect on the immune system and on nonspecific defense reactions of the body.

When lithium is in excess in the human body, it exerts a toxic effect. Symptoms of poisoning indicate a neurotoxic effect of lithium. Its elevated content in feed leads to decalcification of bone tissue and morphogenic changes in animals. Correction of lithium intake into the human and animal body by means of agricultural products enriched with lithium is promising.

At present, there is no information on the necessity of lithium for agricultural plants: the response to the application of lithium fertilizers depends on habitat conditions, age, and systematic position. A positive effect of lithium fertilizers on tobacco, cotton, sugar beet, tomato, sweet pepper, and potato has been noted.

On the other hand, the use of lithium fertilizers as a micronutrient fertilizer requires taking into account its possible toxicity. An excess of lithium salts leads to morphological changes in plants—disruption of mitosis. Very sensitive to lithium are the cypress family (Cupressaceae), crucifers (Brassicaceae), honeysuckle family (Caprifoliaceae), lily family (Liliaceae), iris family (Iridaceae), and grasses (Poaceae).

Lithium uptake by plants depends on the content of mobile forms in the soil. Lithium content in soils increases from north to south—from 10–25 mg/kg for soddy-podzolic soils to 65–90 mg/kg for ordinary chernozems. The amount of the element depends on the lithium content in soil-forming rocks, particle-size distribution (heavy soils contain more lithium), the amount of organic matter, and the degree of leaching. Along the soil profile, the concentration of exchangeable lithium decreases; in horizons with maximum accumulation of calcium carbonates, it is least mobile. Soil salinization reduces mobility. In addition, there is a relationship between lithium and potassium contents in the soil.

In plants, lithium content depends on systematic affiliation and nutritional conditions. Among plants, those that concentrate it under any conditions and prefer its elevated content in soils stand out—nightshades (Solanaceae), violets (Violaceae), and buttercups (Ranunculaceae). Their lithium content is about 60 mg/kg dry matter. Malvaceae and Chenopodiaceae accumulate it only when its content in the soil is high. Plants indifferent to lithium—long-leaved mint (Mentha longifolia) and camel thorn (Alhagi sp.)—contain 20–45 mg/kg dry matter. Legumes consume it in small amounts—4.8–7.9 mg/kg dry matter—but do not avoid lands enriched with it. Grasses (Poaceae) and the mint family (Lamiaceae) consume it in insignificant amounts and avoid places with high soil content.

Lithium accumulation in plants is influenced by soil and climatic conditions. Its distribution among plant organs follows this pattern: leaves > roots > stems > fruits. Therefore, leafy vegetables and root crops serve as the main source of lithium in the diet of animals and humans.

The application of lithium fertilizers to various crops gives mainly a positive result, which depends on the method of application and doses. For this purpose, lithium chloride, sulfate, and carbonate are used. For pre-sowing soaking (moistening) of seeds or potato tubers, solutions from 0.001 to 0.05% lithium are used depending on the crop. For foliar feeding—solutions from 0.005% for grapes and potatoes to 0.1% for tobacco. It is applied to the soil in doses of 0.1–40.0 mg/kg soil depending on the crop and salt.