The influence of carbon-humic fertilizers on the dynamics of soil microflora under wheat crops

Development of soil microflora

Observations of the dynamics of microflora development in fields of light-gray forest soil occupied by wheat crops show that under the influence of carbon-humic fertilizers, the total number of microorganisms in the arable horizons of fertilized areas increases significantly (Table 1).

Development of soil microflora in differently fertilized soil occupied by wheat

Unfertilized soil is characterized by weak biogeneity. The best indicators of growth and development of microorganisms growing on a nutrient medium were in areas fertilized with ammonia water. The total number of microorganisms against the background of different doses of carbon-humic fertilizers was almost the same, but quite high compared to the control.

Later, the total number of microorganisms in the gray forest soil decreases somewhat; however, the emerging dependence of their numbers on the type and dose of the studied fertilizers persists until the end of the growing season.

Effect on various groups of microorganisms

The increase in the total number of soil microflora during the initial period of interaction of ammonia water with soil occurs due to spore-bearing ammonifiers, which are the most resistant to the antiseptic action of ammonia. Microorganisms growing on MPA developed well in soil fertilized with ammonia water, subsequently carrying out vigorous mineralization of soil organic matter and the mass of microbes killed by ammonia.

Carbon-humic fertilizers, despite the fact that the coal was treated with ammonia until complete saturation, do not have such an antiseptic effect on the soil microflora. Therefore, against the background of carbon-humic fertilizers, fungi and nitrifying bacteria intensively developed, which are particularly sensitive to the antiseptic effect of ammonia.

With a higher dose of carbon-humic fertilizers, the total amount of fungal flora increases and its species diversity changes somewhat.

The development of pathogens of butyric acid fermentation was equally active for all types of the studied fertilizers. Thus, under the influence of the tested fertilizers, significant changes occur in the development of microorganisms, which are of great importance in the implementation of the processes of development of plant residues and the formation of humus substances.

It is generally accepted that nitrifying bacteria are the only causative agent of nitrate formation processes. Therefore, taking into account the development of nitrifiers is of great importance for characterizing the effect of the studied fertilizers.

Under the conditions of our experiments, the number of nitrifying bacteria (on leached agar with ammonium-magnesium salt of phosphoric acid) increases against the background of a higher dose of carbon-humic fertilizers.

Their development against the background of ammonia water, especially in the first half of the vegetation season, was weak. Nevertheless, compared to the indicators in unfertilized soil, ammonia water somewhat activated the processes of nitrogen mobilization in the soil.

Weak development of nitrification processes in unfertilized soil and their activation by the studied fertilizers indicate a lack of energy material for nitrification in light gray forest soil.

The content of mineral nitrogen in the plots fertilized with a higher dose of carbon-humic fertilizers increased to 4% in relation to the total nitrogen in the first period of the study and to 3.5% in the second period, while in the plots fertilized with ammonia water, the mineral nitrogen content was somewhat lower at the beginning and almost twice as low at the end of the study. Consequently, the effect of carbon-humic fertilizers on the processes of mobilization of mobile nitrogen in the soil is more effective than the effect of ammonia water (Table 2).

Mobilization of nitrogen in the soil

The use of a new type of organic fertilizers had a certain effect on the dynamics of actinomycetes development, recorded on a starch-ammonia medium. Thus, the growth of their colonies on control dishes was barely noticeable, whereas against the background of ammonia water, their colonies reached significant sizes and had a greater diversity of species. In soil samples fertilized with different doses of carbon-humic fertilizers, there were no differences in the intensity of actinomycetes development.

However, when determining the effect of the studied fertilizers on the number of individual representatives of the two main communities of soil microflora, no special differences were found for the types of fertilizers tested. However, the intensity of ammonification processes for carbon-humic fertilizers does not reach the intensity of these processes in soil fertilized with ammonia water.

The high ammonifying activity of the soil fertilized with ammonia water indicates the activation of the processes of organic matter decomposition occurring under the influence of ammonia. This conclusion is confirmed by the increasing active development of actinomycetes and cellulose bacteria in the soil that received ammonia water as a fertilizer by the end of the growing season. In addition, a study of the dynamics of humus transformations establishes a significant increase in the content of water-soluble humus in the soil fertilized with ammonia water by this time.

Based on the data from the study of the microbial association that destroys cellulose, it is possible to judge the stimulating effect of carbon-humic fertilizers on the development of microorganisms that make up this association (Table 3).

Thus, in unfertilized soil, fungi and bacteria participated in the destruction of fiber at the tillering stage of wheat. But in fertilized soil, fungi did not appear at all at this time of the study.

In the second half of the growing season, with an increase in the content of difficult-to-mineralize forms of organic matter such as humic compounds, fungi appear and the number of cellulose bacteria and actinomycetes increases. By this time, humic compounds introduced into the soil with carbon-humic fertilizers undergo significant changes (Table 4).

In soil samples fertilized with carbon-humic fertilizers, the content of free humic acids and fractions of their mobile forms increases. At the same time, there is an increase in the content of water-soluble humus compounds, increasing from a lower to a higher fertilizer rate, the accumulation of which indicates an increase in the mineralization processes of the organic matter of the soil itself.

The direct effect of ammonia on the composition of the bioorganomineral complex of the soil when using ammonia water significantly increases the intensity of humus mineralization. The destruction of the organic matter of the soil observed in this case occurs due to fractions represented by mobile compounds of humic acids.

When using carbon-humic fertilizers, on the contrary, an accumulation of humic acids is observed (Table 5).

Microorganisms that destroy fiber

Dynamics of humus compounds

Thus, the organic matter of the soil fertilized with ammonia water becomes more accessible to soil microflora and therefore its mineralization occurs faster.

An idea of ​​the intensity and direction of the transformation of humus compounds is also provided by data that determine the biogenicity of the soil and the density of its microscopic population per unit of organic matter and nitrogen (Table 5).

Total number of microorganisms

As can be seen from the calculations given in Table 5, the coverage of the soil by life reaches the largest sizes in the soil samples fertilized with ammonia water. Against the background of different rates of carbon-humic fertilizers, there are no significant differences in the content of microorganisms in 1 g of dry soil. However, compared to unfertilized soil, carbon-humic fertilizers activate microbiological activity. The total number of microorganisms increases tens of times when using carbon-humic fertilizers.

The number of microorganisms per unit of organic matter and per unit of soil nitrogen in fertilized soil indicates a high intensity of microbiological processes and determines the rate of inclusion of humus and nitrogen-containing compounds in new biological cycles.

Differences in the density of microorganisms per unit of humus and nitrogen in differently fertilized soil also determine different durations of the period of intensive biological activity. In soil fertilized with carbon-humic fertilizers, microbiological processes proceed more evenly throughout the entire vegetation season.

The action of ammonia water is characterized by an uneven course of individual microbiological processes, apparently due to the fact that ammonia, during the initial period of interaction with the soil, partially sterilizes it and changes the state of organic matter, causing increased mobility of humus and regrouping among soil microorganisms.

Table 6 presents data characterizing the effect of the studied fertilizers on the activity of nitrification processes, taken into account in the differently fertilized soil before the experiment (control soil in each experimental variant) and after keeping it in optimal moisture and temperature conditions for a month (Table 6).

A large accumulation of nitrates when maintaining soil in favorable conditions for the development of nitrifiers is established in samples fertilized with carbon humates. The increase in the nitrifying activity of gray forest soils, when using carbon humate fertilizers, is determined by the action of ammonium humates contained in the fertilizers as an energy material that simultaneously causes an increase in general microbiological activity.

In the soil fertilized with ammonia water, the nitrification processes in the early stages of the study were suppressed by the antiseptic action of ammonia. Therefore, in the soil that received ammonia as an energy material for the process and was maintained in optimal temperature and moisture conditions, the amount of nitrates in the early stages of wheat development did not exceed their amount in the control soil of this variant of the experiment.

At the same time, plants on the background of ammonia water had the most characteristic differences in color and power precisely in this period of time. Obviously, in this period of wheat development, the main form of nitrogen nutrition of plants was the ammonia form. In subsequent periods of the study, the effect of ammonia water was noted on the accumulation of nitrates, but without advantages over the options of carbon-humic fertilizers.

Activity of microbiological processes

The increase in the energy of the nitrifying capacity of the soil when using carbon-humic fertilizers in conditions of low annual precipitation and dry springs is a factor that characterizes the new type of organic fertilizer as a highly effective fertilizer.

Key findings

Research has shown that carbon-humic fertilizers:

• Increases the total number of soil microorganisms by 10-15 times compared to unfertilized soil
• Promotes the development of nitrifying bacteria, increasing the NO3 content _in the soil
• Increases the content of humic acids in the soil by 30-50%
• Ensure a more uniform flow of microbiological processes during the growing season
• Increases the availability of nitrogen to plants, especially in the form of nitrates
• Stimulates the development of actinomycetes and cellulose-destroying bacteria
• Less aggressive impact on soil microflora compared to ammonia water