Video: Soil Types, Mechanical Processing, Fertilization And Fertilizing
Read the previous part. ← Soil - its properties, composition, absorption capacity
Compared to wild plants and weeds, cultivated plants have a much lower ability to assimilate nutrients from hard-to-reach compounds.
Their productivity is more susceptible to fluctuations in environmental conditions and especially weather. They cannot withstand the competition with weeds without human help.
Compared to natural phytocenoses, agrocenoses are a less stable ecosystem and are very demanding on soil properties.
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Cultivated plants in single-species crops with good growth consume a very large amount of nutrients in readily available forms, especially during critical early periods of growth. Cultivated plants are sensitive to an increase in soil density, to a deterioration in aeration.
To satisfy the great need of cultivated plants for nutrients, it is necessary that the arable soil has a high biological activity - a high number and activity of microorganisms that transform soil nutrients into forms readily available to plants, including chelated forms of microelements.
Cultivated plants make high demands on the content of organic matter in the soil and its quality. The activity of microorganisms and the nutritional regime of the soil, its biological activity and water-physical properties are closely related to it. When you begin to develop a site, its fertility changes depending on the intensity of soil cultivation activities.
During this period, the soil is dominated not by the cultural, but by the natural process of soil formation, which mainly determines the properties and fertility of the newly developed soil. Further soil development depends on how it is used, and its evolution can go in opposite directions: towards the development of the cultural process of soil formation and an increase in soil fertility, or, conversely, towards soil degradation and a decrease in its fertility.
Three main and indispensable factors always affect the soil during the cultivation of cultivated plants - mechanical tillage, fertilizers and the cultivated plants themselves. Each of these factors can create both positive and negative consequences. Mechanical processing contributes to the destruction of the structure and mineralization of humus. With crops, nutrients are removed from the soil, the introduction of acidic mineral fertilizers can increase the toxicosis of the soil, etc.
In this regard, it can be noted that humic substances, especially calcium humates, mycelium of microscopic fungi and bacterial mucus, are of great importance in the formation of structural aggregates and imparting strength and porosity to them. In the first years of the development of virgin lands, organic detritus (small organic particles) accumulated over a long period of formation of natural soil is intensively mineralized, and then, in the process of its agricultural use, a part of specific humic substances is also mineralized.
With the harvest of cultivated plants, many nutrients are removed from the soil, and the more, the higher the harvest. In addition, a large number of nutrients are lost as a result of leaching by precipitation, the release of volatile nitrogen forms into the atmosphere, due to soil erosion.
In addition to the depletion of plant nutrients, the degradation of arable soils and their fertility are associated with improper, often one-sided unbalanced use of fertilizers. The fact is that the systematic use of acidic mineral fertilizers even on soils saturated with bases, such as chernozem, acidifies the soil, leads to the replacement of exchangeable calcium by a hydrogen ion, reduces the absorption capacity and negatively affects the biological properties of the soil and its structure.
On limed and well-cultivated soil, the negative effect of mineral fertilizers does not manifest itself, and they increase the yield of crops. Their effectiveness increases when combined with organic fertilizers. Mineral toxic mobile compounds of manganese and iron oxide, hydrogen sulphide and methane, toxic salts in waterlogged, but rich in organic matter, soils, with an incorrect irrigation regime, also accumulate in soils.
When acidic mineral fertilizers are applied, the number and activity of toxic bacteria and fungi increases, which sharply negatively affect the germination of seeds, the growth and yield of cultivated plants. At the same time, the toxic effect of compounds of mercury, zinc, chromium of industrial origin increases.
Each crop leaves behind a soil with its changed properties. These changes may be insignificant, but the crops of subsequent sowing are very sensitive to them and, even under favorable cultivation conditions, can reduce the yield. The loss or a strong decrease in soil fertility with repeated or with a short break in the cultivation of some crops is called soil fatigue.
The reasons for soil fatigue can be different - one-sided removal and lack of nutrients, including individual microelements, accompanying weeds, etc. But the main ones are the development of phytopathogenic microflora, microorganisms that emit toxic substances, as well as toxins secreted by the plants themselves. The main measures to combat soil toxicosis and soil fatigue are obligatory crop rotation, liming of acidic soils and the introduction of organic fertilizers, including green ones, which have a great influence on stimulating beneficial and suppressing toxic microorganisms in the soil.
The properties of soils in different natural zones are different and, accordingly, the systems of measures for their cultivation are different. Even with this small excursion into soil science, I think the readers were able to wonder if they are working the soil correctly on their plots.
Along with higher vegetation, numerous representatives of soil fauna - invertebrates and vertebrates, inhabiting different horizons of the soil and living on its surface - have a great influence on the processes of soil formation. An example of an unusually intense impact on the soil is the work of earthworms. The Russian soil scientist N.A. Dimo (1938) wrote that under the influence of worms, from year to year, from millennium to millennium, features of biogenic composition and structure, specific biochemical properties that are not reproducible by any other agent of nature, accumulate in soils.
The organic matter processed by the soil fauna is an excellent environment for the settlement of soil microflora. Microorganisms play an extremely important role in soil formation processes. If higher plants are the main producers of biological mass, then microorganisms play the main role in the deep and complete destruction of organic matter. The peculiarity of soil microorganisms is their ability to decompose the most complex high-molecular compounds to simple end products: gases (carbon dioxide, ammonia, etc.), water and simple mineral compounds.
And yet, is it possible in our climatic northwestern zone to have black soil on its site? I will answer this question with an excerpt from V. Dokuchaev's book “Russian Chernozem”: “So, there is no doubt that our chernozem was formed from steppe vegetation, and, moreover, from both aboveground and underground parts.
But for the formation of chernozem it is still not enough for a given locality to have a suitable soil and suitable vegetation: typical loess and no less typical steppe flora are found in many other areas of Western Europe and other countries; however, we do not find black soil there. The reason is that there is no suitable climate, that there is no known relationship between the annual increase and the death of wild vegetation."
Let me remind you that on the territory of the Kursk region there is the Central Chernozem State Natural Reserve named after Professor V.V. Alekhin, part of the system of biosphere reserves of the world network of UNESCO. A sample of Kursk chernozem as a standard of fertile soil is kept in the Soil Museum in Paris, as well as in the Natural History Museum in Amsterdam and in the Soil Science Museum near Leipzig.
For thousands of years, nature has created a fertile chernozem soil layer of a meter thickness in the steppes with a certain hydrothermal regime. The virgin chernozems of this reserve serve as a standard, in comparison with which the degree of disturbance of the surrounding arable lands is determined. V.V. Dokuchaev said that not a single gram of chernozem soil has been artificially created in any laboratory in the world.
But the trouble is - the vegetable plants that we grow in the garden - this agrocenosis cannot exist without a person. Another thing is that man drove agriculture to a dead end in pursuit of unprecedented harvests. 100 years ago V.V. Dokuchaev wrote that black soil reminds us "… of an Arab thoroughbred horse, driven and slaughtered." What can be said here? Much depends on competent agricultural technology, you do not need to chase record harvests, you need to protect soil fertility.
In what way does the organic matter decay? Bacteria, actinomycetes, fungi, soil-dwelling algae, invertebrates and vertebrates actively participate in the transformation of organic matter in all soils. Along with the processes of decomposition of organic residues and reduction of complex organic molecules in the soil, the process of synthesis of humic substances proceeds.
They are formed from "fragments" of biological macromolecules or their monomers, which end up in the soil due to the metabolism of its living population and the activity of exoenzymes. The percentage of humus and various humic fractions varies greatly from one soil type to another. The humus of forest soils is characterized by a high content of fulvic acids, while the humus of peat and steppe soils has a high content of humic acids.
I will not delve into the chemistry of humus formation, especially since these are only some of its schemes. One of the hypotheses of high fertility of humus is associated with the biogeocenological principle formulated by academician V.N.Sukachev. This is the so-called microbiological theory. Perhaps the most important role of humus is to create a favorable regime, favorable conditions for the life of microorganisms.
And already microbes help the plant, supplying it with nitrogen and other nutrients. True, in our northern regions it is cool enough for such a violent action of microorganisms, and there is very little humus in our soils. More often on our soils, mineral fertilizers are more effective together with organic matter, as well as the use of chelated forms of micronutrient fertilizers.
Soil organic matter reduces the negative side effect of chemical fertilizers, helps to fix their surplus and neutralize harmful impurities. It would be a mistake to identify the soil only with its upper humus or arable layer, while the consumption of water and nutrients by plants is greatly influenced by the deeper soil horizons and the groundwater located at a depth. The fertility of the soil is determined by the nature and characteristics of its entire profile; this is often encountered by summer residents when developing a site, when they carry out reclamation work.
A few words should be said about tillage. Now there are different opinions on this matter. After the development of the soil in a new garden plot, its structure, created over a long time of the formation of natural soil with a large participation of the soil fauna, is gradually destroyed and at the same time a new, lumpy structure is formed in the arable layer, which is characteristic of well-cultivated soils.
In the destruction and formation of structural aggregates, mechanical soil cultivation and the processes of mineralization of organic matter holding the aggregates play an important role. The treatment of dry soil strongly destroys the structure - during the summer stubble plowing immediately after harvesting. However, if "ripe" soil is cultivated after rains or in spring with moisture corresponding to the "optimum moisture content of structure formation" (about 60% HB), then mechanical tillage does not destroy, but, on the contrary, forms structural aggregates. Previously, the peasants cultivated only "ripe soil".
To maintain a positive humus balance and improve the humus state of the soil, its losses must be constantly compensated by the application of organic fertilizers and by increasing the input of plant residues into the soil, by sowing green manure and catch crops. In pre-revolutionary Russia, there were no problems with manure on personal plots, and manure of the best quality - horse manure.
To the north and south of the chernozem zone, the amount of incoming litter decreases and the conditions for the synthesis of humus deteriorate (in the north - excess, in the south - lack of moisture). This determines both a decrease in the total humus content and the predominance of more “simple” fulvic acids in its composition.
Recently, in our climatic zone, more attention has been paid to microelements, especially in a chelated form. Chelates of trace elements have a number of valuable properties. They are non-toxic, readily soluble in water, highly stable (do not change their properties) in a wide range of acidity (pH values), are well adsorbed on the surface of leaves and in the soil, and are not destroyed by microorganisms for a long time.
The role of trace elements in plants mainly lies in the fact that they are part of many enzymes that play the role of catalysts for biochemical processes and increase their activity. Trace elements stimulate plant growth and accelerate their development; have a positive effect on the resistance of plants to adverse environmental conditions; play an important role in the fight against certain plant diseases. And as we found out at the beginning of the article, our body needs in the form of vegetables, in which they are contained.
As for the cultivation of the site, it should be noted that the soil-climatic conditions of the non-chernozem zone determine special requirements for soil cultivation, which are not the same in different subzones. Our soils are characterized by low fertility, excessive moisture, acidity and a tendency to waterlogging. With a lack of heat and air, they need various agromeliorative techniques that help eliminate excess moisture, improve aeration and thermal regime.
On light soils a good effect is provided by non-moldboard cultivation, which preserves the rich organic matter and more cohesive soil layer in the upper part of the arable horizon. Deepening the topsoil yields positive results only where more connected subsoil layers are involved in cultivation. Only with a competent combination of organic and mineral fertilizers, including microelements in a chelated form, with the correct ratios of nutrients, the choice of forms of fertilizers, and adherence to the timing of their introduction, it is possible to obtain environmentally friendly vegetables containing the nutrients necessary for a person.
In the article, I tried not to impose on the readers either the methods of classical farming, or alternative - organic farming. What for? The choice is yours, but my opinion is this: do not go to extremes, and most importantly - be guided by your own experience, study your site, observe the development of plants and help the soil and plants to work for the benefit of your health in time.