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MICROORGANISMS IN THE PRODUCTION PROCESS OF AGRICULTURAL CROPS
The importance of microorganisms in providing the production process of agricultural crops began to pay attention relatively recently - after establishing the facts of close interaction of bacteria and microscopic fungi with plants. Today, it is reasonably considered that symbiosis and association of microorganisms with plants are the basis of their vital activity. In this case, one of the main functions of rhizosphere microorganisms (those that develop in the root-zone soil and on the surface of the roots) is to provide the plant organism with nutrients in the optimal form. The chains of bacterial cells, hyphae and mycelium of microscopic fungi are a kind of continuation of the roots of plants, that result in the fact that the absorption capacity of a well-formed plant-microbial association differs significantly from the one of plants not provided with the corresponding microorganisms. If we take into account that several billion bacterial cells actively function in one gram of rhizosphere soil, and the average surface area of the bacterial cell is about 6 μm2, we conclude that the total surface area of the bacteria in this volume reaches several dozens of square decimeters. Taking into account the amount of the root-zone soil, we get remarkable numbers. If we compare those numbers with the area of the root absorption surface (it can be from 1 to 10 dm2) of a single plant, we can understand what role rhizospheric microorganisms play in the absorption of nutrients. It should also be taken into account that microorganisms actively transform indigestible compounds of biogenic elements (for example, phosphorus) into easily digestible ones, some of them are able to assimilate nitrogen from the atmosphere, produce physiologically active substances that influence the development of the root system and the activity of a number of enzymatic reactions in a plant organism.
However, the above-described conditions for the development of cultivated plants are only in biologically active soils, the areas of which are now minimized. The biological state of most arable soils on the planet should be considered as degradative. In the absence of fresh organic matter and in conditions of an unbalanced application of mineral fertilizers, unjustified use of pesticides, ignoring crop rotations, minimizing the areas of growing leguminous grasses, burning straw, etc., radical changes are taking place in soils. At the same time, the composition of biocenoses of soils is significantly impoverished, the minimization and even disappearance of certain types of beneficial microorganisms is observed. Their place is occupied by atypical species, including pathogenic ones. Many agrocenoses have turned into reservations for pathogens. One way out of this situation is the use of microbial preparations based on the cultivated bacteria and micromycetes for the presowing treatment of crop seeds. This provides a significant correction of communities of microorganisms in the root zone and improves plant nutrition. According to our experiments with the 15N isotope, the degree of nitrogen assimilation from fertilizers by bacterized plants increases by 20-30%, depending on the culture (we recall that in the conditions of the traditional cultivation of agricultural crops, these rates are in the range of 35-50%). At the same time, by increasing the assimilation of nutrients, it is possible to save significant quantities of fertilizers - up to 40-60 kg/ha, depending on the crop and soil.
To demonstrate the maximum effectiveness of biological preparations, the level of the agricultural background is also important. According to our data, microbial preparations show the greatest efficiency when mineral fertilizers are applied in doses not exceeding the physiological needs of plants. For example, for cereals, these rates are in the range of 50-60 kg of active ingredient per hectare when applied in partial manner, for corn and potatoes - up to 100 kg/ha. Under these conditions, the reaction to bacterization can sometimes be explosive.
A natural question may arise: if bacterized plants have a higher level of assimilation of biogenic elements (for example, nitrogen), then do they accumulate nitrates? According our surveys, nitrates do enter the bacterized plants in large quantities, but do not accumulate because they are intensively involved in metabolic processes (unlike in the case of non-bacterized plants, when the danger of forming a reserve pool of nitrates is very high). In the case of bacterization, nitrates become a substrate in the synthesis of amino acids and, accordingly, proteins. Today we can state that bacterization is a reliable agricultural technique for reducing the concentration of nitrates in plants with a simultaneous increase in the protein content.
It should be noted that we do not observe large increases in yields when using preparations on the background of manure application. This is due to the fact that a large number of microorganisms are entering the soil with manure (recall the words of V. Dokuchaev "Undoubtedly, along with manure, bacteria are also introduced into the soil, and their role is apparently not less than the role of the introduced fertilizers"). Today we understand that the application of manure provides peculiar bacterization of soils, and its systematic use guarantees a high level of biogeneity and stability of agrocenoses. In the absence of manure, the importance of microbial preparations in the formation of crop yields increases.
The above features of the influence of beneficial microorganisms on the production process of agricultural crops are primarily related to non- leguminous plants. Concerning the role of rhizobia in providing leguminous plants with nitrogen from the atmosphere, the need for the use of microbial preparations in their growing technologies should also be emphasized. In addition to increasing yield, this promotes active protein synthesis. The grain of soy, pea, lupine, obtained from bacterized plants, always has a high protein content, has better quality characteristics and other indicators.
It should be noted that the seeds of crops harvested from bacterized plants are characterized by the best parameters of the sowing qualities, including microbiological indices. This is due to the fact that in nature there is a cycle of microorganisms - from the root zone to the seeds, and from there (when sowing into the soil) into the root zone. That is why representatives of pathogenic microflora are removed from the seeds obtained from bacterized plants.
We are convinced that microbial preparations should become an indispensable element of modern technologies for growing crops. This is confirmed by the results of production tests of the presowing bacterization effectiveness, conducted during the last three years in 250 farms (Table).
Table. Averaged yield increases from the use of microbial preparations in 2014-2016.