To more fully illuminate the issue of the impact of humic fertilizers on the activity of microbiological activity, a study was undertaken of the activity of enzymatic processes occurring directly in the soil. It is well known that microorganisms participate in the transformation of substances in the soil, carried out by enzymatic catalytic reactions that underlie the metabolism of soil microflora, as well as any living organism.
The introduction of fertilizers into the soil dramatically changes the combination of absorbed cations characteristic of these conditions and, naturally, changes the enzymatic activity of microorganisms, which is a manifestation of the interaction of the organism with the external environment.
When studying the enzymatic activity of soils, the ability of plants to release certain substances through the root system was taken into account. Therefore, the studied soil samples were carefully cleared of roots and other organic remains.
In specially prepared soil, enzymes were determined that catalyze the breakdown of substances containing starch, sugars, fats and protein compounds.
The action of proteolytic enzymes was taken into account in total the ability of soil microflora to carry out hydrolysis of protein compounds and further splitting of their decay products to form amino acids and amino groups. The amount of amino nitrogen was determined by the formol method according to Soerensen.
The activity of carbohydrate decomposition in the soil was determined by the activity of carbohydrate metabolism enzymes - amylase and sucrase. The activity of amylase was determined by the amount of maltose formed. The activity of sucrase by the amount of reducing sugars. The activity of lipase in the studied soil samples was determined by the amount of fatty acids formed during the hydrolytic action of enzymes.
Accounting for catalase activity was introduced into the definition of soil biological activity as an enzyme associated with the act of respiration of many microorganisms. The action of catalase was taken into account using the Euler and Josephson method.
Soil in the amount of 5 tons from the control and fertilized plots was used as preparations of the studied enzymes. Sterile soil served as the control in the experiment. In all cases of studying the enzymatic activity of the soil, an exposure of 72 hours at a temperature of 30° C was adopted. The enzymatic activity of 5 tons of soil was taken as a unit of measurement of enzyme activity. The results of the study of the biological activity of light gray forest soil are given in Table 7.
Effect of fertilizers on the enzymatic activity of soil (72 hours exposure at 30° C)
(Sowing wheat)
| Experience options | Enzyme activity | Proteolytic (by the amount of amino nitrogen), mg | Lipases (by amount of hydrolyzed fat), % | Catalase (by the amount of decomposed H2O2 ) , mg | |
|---|---|---|---|---|---|
| Amylase (in mg maltose) | Sucrases (in mg reducing sugars) | ||||
| June 12 | |||||
| Without fertilizers | 75.6 | 4.3 | 50.0 | 2.6 | 0.7 |
| Carbonaceous fertilizers 0.5 t/ha | 95.8 | 7.6 | 100,0 | 2,3 | 0.5 |
| Carbonaceous fertilizers 1 t/ha | 115.9 | 10.3 | 160,0 | 2.1 | 0.5 |
| 25% ammonia water 240 l/ha | 136.2 | 12.8 | 150,0 | 1.6 | 0.4 |
| August 11 | |||||
| Without fertilizers | 14.3 | 1.7 | 12.5 | 1.6 | 1,1 |
| Carbonaceous fertilizers 0.5 t/ha | 22.0 | 1.8 | 35.0 | 1.8 | 1.4 |
| Carbonaceous fertilizers 1 t/ha | 29.6 | 1.6 | 48.0 | 2.0 | 2.6 |
| 25% ammonia water 240 l/ha | 34.6 | 2,2 | 74.0 | 3.1 | 2.4 |
When comparing the effect of the studied fertilizers on the enzymatic activity of light-gray forest soil, it is clear that the conditions for the action of enzymes on a differently fertilized background develop differently.
Based on the results of studies of the activity of individual soil enzymes, it seems possible to establish that the enzymatic activity of the soil is subject to the same sharp periodic fluctuations as the growth and development of individual physiological groups of microorganisms.
The highest activity of carbohydrate metabolism enzymes of microorganisms is observed in soil samples fertilized with ammonia water.
Of the tested doses of humic fertilizers, the advantages in enhancing the activity of amylase and sucrase are determined by a larger dose. Such a pattern in the manifestation of the hydrolytic action of these enzymes with a significant decline in their periodic activity in all variants of the experiment is also noted in the second term of the studies.
A similar picture emerges when determining the effect of the studied fertilizers on the ability of the soil to break down protein compounds. The soil fertilized with ammonia water has greater proteolytic activity, as shown by the final results of the action of proteolytic enzymes.
In soil fertilized with a higher dose of humates, the activity of proteolytic enzymes in the early stages of the studies was also quite high.
A comparison of the degree of intensity of enzymatic processes of hydrolysis of substances containing carbohydrates and protein compounds leads to the conclusion that the studied fertilizers significantly increase the enzymatic activity of gray forest soils.
The catalytic action of enzymes hydrolyzing fats, as well as the action of catalase in the first term of the study, was weakly active for all types of fertilizers under study. Later, the activity of lipase and catalase increases against the fertilized background. As can be seen, the change in soil conditions under the influence of the fertilizers under study has a great influence on the biological activity of the soil, which is a reliable indicator of the intensity of the microbiological factor of transformations in the soil of a number of compounds and the formation, ultimately, of substances of plant root nutrition.