Leaf nutrition and the need for its application

The full development of agricultural crops is provided by nutrients entering plants not only through the root system, but also by getting on their aboveground surface (leaves, stems, petioles, generative organs). The main purpose of the leaves is the exchange of gases between the plant and the environment, but they can also serve as an organ of foliar nutrition of plants. The absorbing ability of leaves on the example of water was first discovered in the 17th century, and the process of adsorption of dissolved mineral salts by the leaf surface was described a century later in the 19th century and only at the beginning of the 20th received scientific confirmation. This type of nutrition is called foliar or leaf nutrition.

Nutrient intake is a process of moving the necessary chemical compounds from the environment directly into the plant itself, which also includes qualitative changes associated with the transformation of abiotic material into a cell component capable of further assimilation processes. The supply of oxygen and carbon occurs in molecular form from atmospheric air in the form of CO2, in the same way plants can receive nutrients, including N, P, K, Ca, Mg and trace elements in salt solutions of a certain concentration. This type of nutrition exists in parallel with the root, in which nutrients and water in the soil enter the plant through the root system.

Leaf feeding should be perceived as additional nutrition, which allows you to quickly respond to the shortage of one or another element, not only by visual observations, but also based on the analysis of plant biomass. At the same time, the adjustment of nutrition is carried out in the shortest possible time, allowing you to save labor and consumables. Obtaining the necessary minerals by leaf feeding cannot be a substitute for root nutrition, since the volume of fertilizers absorbed by the aboveground part and their qualitative composition are quite small. The undoubted advantage of foliar nutrition is the available ionic form of fertilizers, which is easily absorbed by the plant and is much more effective than substances coming from the soil. Mineral substances are immediately included in the composition of proteins, enzymes, plastid culture pigments and forming a number of organomineral compounds. In addition, leaf fertilizing can be carried out simultaneously with the treatment of crops with pesticides, as well as in combination with nitrogen fertilizers, excluding options for combining incompatible components in solutions.

With the help of leaf feeding, it is possible to prevent oversaturation of the soil with minerals and reduce the risk of environmental threats. The effectiveness of nutrients in foliar nutrition can reach 85%, while the use of soil fertilizers is only from 30 to 60% efficiency.

One of the rules of foliar nutrition of plants is compliance with the exact dosage of the working solution. It is known that the effectiveness of leaf feeding depends on the concentration and dose of fertilizer, which should not exceed a certain norm in order to protect the leaves from burns. For solutions containing macronutrients, an average value of no more than 2% is recommended, and the optimal concentration of nutrient solutions with trace elements is in the range from 0.1 to 1%.

Environmental factors are also of great importance for the effectiveness of leaf nutrition: humidity, temperature, lighting. The higher the relative humidity, the longer the solution remains on the surface of the leaves, and the amount of nutrients entering the plant increases. At a higher temperature, when the evaporation of water increases, the absorption of ions is limited, which can cause burns on the leaves.

In stressful situations (low temperatures, frosts, lack of moisture, etc.), the assimilation of nutrients by the root system is insufficient, and this slows down the rate of growth and development. At low temperatures, they are not fully absorbed even with the optimal amount of available macronutrient compounds and moisture in the soil. The ability of nitrogen and phosphorus assimilation by the root system is especially reduced. Potassium is comparatively less sensitive to a decrease in temperature.

Critical periods regarding the lack of macro- and microelements in cereals occur in the phase of entering the tube — earing. Due to the intensive, rapid growth of vegetative mass, the reserves of easily accessible nutrients from the soil are exhausted or their assimilation "does not keep up with the growth rate of plants." This is especially noticeable in years with cold nights.

In such a situation, the plant can be helped by foliar (leaf) fertilizing.

The degree (percentage) and rate of assimilation of nutrients from fertilizers through foliage is significantly higher than when assimilating from fertilizers introduced into the soil. But the volume of assimilation of elements through leaves is limited. The leaves absorb nitrogen, magnesium, potassium the fastest, sulfur is slower, phosphorus, calcium and trace elements are even slower. Despite this difference in the rate of penetration of nutrients into the plant, in general, they are absorbed by the leaves much faster than the root system from the ground.

Trace elements in leaf feeding are 10 times more effective than when they are introduced into the ground, where they can bind into inaccessible compounds.

The problem of combining high yields with good grain quality is considered one of the most important tasks. The main signs of high-quality grain are such indicators as protein and gluten content, which determine the food and feed value of winter wheat grain. The main amount of protein in the grain of cereals accumulates due to the outflow of nitrogenous substances from the vegetative organs and only 18-26% is formed due to the root system. Therefore, one of the main elements of improving grain quality at the last stages of plant vegetation is leaf nutrition. After all, if the plants did not have time to accumulate enough nitrogen in the vegetative organs, then the necessary amount of nitrogen can be introduced only through leaf nutrition.

Science does not stand still, and nowadays not only macro- and microelements are used for leaf fertilizing, but also various biologically active substances (biostimulants). Preparations containing these substances themselves work as affordable nutrition for plants, in addition, they contain substances that relieve stress from plants, since stress blocks the assimilation of nutrition from the soil, which leads to a loss of quantity and quality of the crop.

The use of leaf nutrition is a step into the future!