Among the urgent problems of modern agro-industrial production, the scientifically based application of fertilizers deserves special attention. Analyzing the state of soil fertility, it is worth noting that today the trend towards dehumification, increasing nutrient deficiency, increasing acidity, soil contamination with radionuclides, heavy metals and pesticides is more pronounced, which activates erosion processes.

The reason is a number of factors that have both a direct and an indirect effect on the assimilation of nutrients contained in the soil by plants. To neutralize their negative effect, it is necessary to use mineral and organic fertilizers, as well as alternative sources of mineral and organic plant nutrition.

SOIL TYPE AND ITS PROPERTIES

One of the determining factors of influence is clearly the type of soil and its properties, which are closely related to the nutrition system. The processes of interaction with fertilizers on different types of soil have their own characteristics, and their digestibility directly depends on the content of mobile forms of nutrients in it, in particular, nitrogen, phosphorus and potassium. It is the basic nutrients present in the soil that determine the availability of fertilizers for plants. Therefore, the choice of their form and method of application must be made taking into account the agrochemical parameters of the soil.

It has been scientifically established that the maximum effect of applied fertilizers is obtained on sod-podzolic, gray forest, podzolized and leached chernozems. On these soils, nitrogen is mostly present in minimal concentrations. For chernozems, the problem of applying nitrogen is not so acute, but there are significant requirements for phosphorus. A feature of podzolized sandy soils is the increased influence of nitrogen and potassium, but the opposite effect is observed on peat soils. At the same time, the minimum and maximum indicators of the available nutrients directly depend not only on the properties of the soil, but also on one or another group of crops represented in the crop rotation.

As for phosphorus fertilizers, their high efficiency is typical for chernozems; they are less effective on gray forest and sandy podzolic soils. Interestingly, the effectiveness of such fertilizers decreases as the level of phosphates in the soil increases.

Fertilizers with a high potassium content show the best effect on sandy, peat-swamp and floodplain soils. If you work on podzolic soils, you should take into account the fact that the mobility of potassium increases during liming. At the same time, the opposite effect is observed on acidic soils, and the specified element is found here mainly in gross forms. The role of potassium can also significantly increase if the rate of application of nitrogen and phosphorus fertilizers is increased. The effect of potash fertilizers increases in crop rotation with grasses, which remove a large amount of this element from the soil.

At the same time, the type of soil and its physical properties (porosity and granulometric composition), chemical composition, as well as the water regime play a primary role in the effective assimilation of nutrients from fertilizers, which determine the maximum penetration of nutrients into the soil, and ultimately, their effective absorption by plants through the root system.

The productivity of mineral fertilizers is also determined by the granulometric composition of the soil, which varies somewhat even within the same soil and climate zone. This property affects the mobility of nutrients, which, in turn, determines the nature of their absorption by plants and, therefore, the efficiency of their use.

Soils with different granulometric composition require an individual approach to fertilizer application planning. This indicator is also taken into account when calculating the dose of fertilizer, as well as when determining the term and method of application. Fertilizers are absorbed and fixed more on medium loamy and clayey soils because they move with water at a slower rate than on sandy and sandy soils. Therefore, clay soils require a specific approach: fertilize not often, but in relatively large doses, while sandy soils - more often and in small "portions".

As you know, nitrogen fertilizers are the most mobile, so they can be washed out on light soils with high humidity. A rational way out of such a situation would be the application of nitrogen fertilizers in the spring. As you move from light to heavy soils, the efficiency indicators of spring and autumn application of nutrients are smoothed out, and already on heavy soils preference is given to the autumn application period.

The direct effect on the effectiveness of fertilizers is the relationship between the granulometric composition and the form of the fertilizer. For example: on light soils, phosphate flour has an effect almost identical to that of superphosphate, but on heavy soils, the effectiveness of superphosphate is many times higher. Potash fertilizers, although less mobile by their nature than nitrogen fertilizers, can also be washed out on soils of light granulometric composition with increased humidity.

TEMPERATURE MODE

One of the leading roles in the effectiveness of fertilizer application is played by the temperature regime, since a significant part of soil bacteria produces at the optimal temperature for them of 25–35°C, and some bacteria can live at 10–20°C. That is why biochemical processes associated with microbiological activity and the production of certain bacteria take place in different periods of vegetation, which are accompanied by different temperature regimes, which, in fact, determine the effectiveness of the applied fertilizer. As a result, the rate of decomposition of organic matter changes, the nitrification process is optimized, the mobilization and immobilization of nutrients increases and, accordingly, the need for fertilizers increases.

The temperature of the soil affects the speed of movement of aqueous solutions, the mobility of salts in the soil and the rate of absorption of nutrients by the plant and, as a result, its full growth and development with a sufficiently developed root system. Under the condition of decreasing temperatures, the intensity of absorption of nutrients in different species and varieties of plants decreases in different ways. If physiologically the plant has a high degree of cold resistance, then absorption processes are practically not disturbed. If the plant is more thermophilic, then they slow down significantly or, under conditions of critically low temperatures, almost stop. And the effectiveness of applied fertilizers decreases to zero.

These processes can be reduced by the justified introduction of mineral fertilizers, which play a significant role in increasing frost resistance. And solve problems with:

• an increase in the solubility of carbon dioxide in water, which leads to an increase in the acidity of the vacuolar juice;
• a decrease in the intensity of breathing, in particular, due to the accumulation of special inhibitors;
• a decrease in the activity of enzymes, which slows down the main metabolic processes;
• violation of the processes of oxidative phosphorylation and the accumulation of less energy by plants;
• by decreasing the intensity of photosynthesis.

CROP CHANGE

As we noted above, the efficiency of fertilizer application directly depends on crop rotation. After all, a well-planned crop rotation changes the water regime of the soil and the level of accumulation of plant residues in it, which determine the rates of mineralization and the dynamics of assimilation of nutrients, thereby regulating the agrotechnical and economic efficiency of fertilization systems. That is why the correct alternation of crops in crop rotation contributes to the improvement of the efficiency of the use of both mineral and organic fertilizers compared to unplanned alternation of crops, and even more so monocultures.

A competent agronomist, when planning sowing, will definitely ask what culture was the predecessor and how and with what it was fertilized. The solution to the issue of both fertilizer application and their rate depends on this. After different crops, obviously, unequal amounts of nutrients and harvest residues remain, which affect the moisture regime and the amount of nutrients for the following crops and create optimal conditions for the manifestation of high efficiency of fertilizers.

The soil is poor in nitrogen after a non-paired predecessor and on occupied pairs. That is why it is worth remembering that leguminous crops play a leading role in balancing nitrogen content in the soil, which bind nitrogen with nodule bacteria, enriching the soil with available forms of nitrogen together with roots and crop residues. Thanks to this, the need for mineral nitrogen fertilizers is reduced and at the same time comfortable conditions are created for the action of phosphorus and potassium fertilizers.

PROCESSING OF THE SOIL

Another factor influencing the efficiency of fertilizer application is soil cultivation. Humidity, air regime, active activity of microorganisms and other indicators that affect the optimal use of nutrients by plants largely depend on the methods of processing. This is primarily due to the optimization of the water regime.

Along with the water regime, the air regime is important, on which the development of the root system of plants depends, and therefore the efficiency of fertilizer absorption. Excessively high soil density and poor aeration slow down root growth, which is why a lack of air inhibits the oxidizing activity of root secretions and reduces the availability of nutrients. With a lack of air, the development of aerobic bacteria, in particular nitrifying bacteria, is inhibited, nitrogen losses from denitrification increase. This has only one consequence - an increase in the need for nitrogen fertilizers.

Therefore, the high efficiency of fertilizers and the rational use of agricultural land - from the point of view of both agronomy and economics - are possible only under the condition of competent, scientifically based consideration of soil, climatic, agrotechnical conditions and biological features of the culture.