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Video: Soil - Its Properties, Composition, Absorption Capacity
Read the previous part. ← On the "usefulness" of vegetables, as a derivative of soil quality
About soil, elements and plants "for health"
To prevent depletion of the soil, to obtain vegetables with a full-fledged content of nutrients on it, it is necessary to apply fertilizers, including mineral fertilizers, and the use of chelated micronutrients.
It has been established that plants have critical periods in relation to one or another mineral element, that is, there are periods of higher plant sensitivity to a lack of this element at certain stages of ontogenesis. This allows you to adjust the ratio of nutrients depending on the phase of development and environmental conditions.
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With the help of fertilizers, it is possible to regulate not only the size of the crop, but also its quality. So, to obtain wheat grain with a high protein content, nitrogen fertilizers must be applied, and to obtain products with a high starch content (for example, malting barley grains or potato tubers), phosphorus and potassium are needed.
Foliar feeding with phosphorus shortly before harvesting enhances the outflow of assimilates from sugar beet leaves to root crops and thereby increases its sugar content. Thus, with the right approach, we need mineral fertilizers.
Let's take an example from practice. Let's calculate the required amounts of nutrients for, say, a tomato. This plant with a planned yield of 50 kg from 10 m? takes out 225-250 g of nitrogen, 100-125 - phosphorus and 250-275 g of potassium. According to the results of agrochemical analysis in the field where they plan to grow tomatoes next year, it turns out before fertilizing that in the arable soil layer (0-30 cm) per 10 m2 there is about 150 g of nitrogen in digestible forms, 20 - phosphorus and 200 g of potassium …
Consequently, to obtain the planned yield, it is necessary to add 75–90 g of nitrogen, 80–100 g of phosphorus and 25–50 g of potassium to this area. Ultimately, about 250-300 g of ammonium nitrate, 400-500 g of simple superphosphate and no more than 100 potassium salt per 10 m3 should be added to the tuk. Doses of organic fertilizers are determined taking into account the content of basic elements in them. Let's take manure as an example, but good compost can also be used. It is known that from 30 kg of litter manure, 150 g of nitrogen, 75 - phosphorus, 180 - potassium, 60 - manganese, 0.0010 g - boron, 0.06 - copper, 12 - molybdenum, 6 - cobalt, about 0, 5 g of calcium and magnesium (in terms of carbon dioxide).
That is, when 30 kg of litter manure is applied per 10 m2 of tomato beds, the crop's need for basic nutrients is almost completely covered. However, taking into account the fact that manure supplies the soil-absorbing complex with the main elements of plant nutrition within three years, together with organic fertilizer, adjusted doses of mineral fertilizers are added, i.e. mineral fertilizers are required much less when applied together with organic matter.
The advantage of organic fertilization consists in a positive effect on the agrophysical properties of the soil (the micro-aggregate composition and water resistance of the macro- and microstructure improve, the water-holding capacity, the content of available soil moisture, the rate of infiltration, porosity, etc.). When applying the above-mentioned manure rate, 1.6-1.7 kg of humus is formed. It should be noted that the amount of humus formed will vary depending on the soil cover and the quality of the manure.
The removal of nutrients from the soil with the harvest must be compensated for by the appropriate introduction of organic and mineral substances, otherwise we impair soil fertility. It is clear that in summer cottages, where there is not so much cultivated land, the consumption of fertilizers is small, which means that it is quite possible to find several buckets of good humus. 10 m 2 requires 30 kg, but 10 hectares will require 300 tons of manure and, accordingly, 3 tons of mineral fertilizers.
In Poland, for example, green manures are used on large areas, they plan to sow peas, lupine, vetch, seradella, rana, clover, mustard and other plants, the green mass of which is plowed into the soil. When decomposing, this material will improve the water-physical properties of the soil, enrich it with useful microflora and nutrients. Indeed, in terms of nutritional value, green manures are close to manure.
Green manure crops are sown in spring, and then, having plowed them into the soil, late vegetable plants and potatoes are placed there. They are also sown as secondary crops after early vegetables, in wide aisles of row crops, etc. It should be noted that green manure enriches the soil mainly with nitrogen, and therefore phosphorus and potassium fertilizers are added to them in optimal doses for the culture grown.
To obtain a good green manure mass during dry periods, the soil is watered (400–450 m3 / ha). The number of irrigations can vary between 3-5. In general, mineral fertilizers in the form of dressings are indispensable for correcting plant growth in its various phases. The effect of organic fertilizers strongly depends on the biological activity of the soil, and in the North-West, especially in spring when the temperature drops, mineral nitrogen fertilization is necessary, fertilizing with microelements for many crops.
Let's try, from the point of view of modern genetic soil science, to understand the methods of farming. In his work "Lectures on Soil Science" (1901) V. V. Dokuchaev wrote that the soil "… is a function (result) of the parent rock (soil), climate and organisms, multiplied by time."
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One way or another, according to Academician V. I. Vernadsky, the soil is the bio-inert body of nature, i.e. soil is a consequence of life and at the same time a condition for its existence. The special position of the soil is determined by the fact that both mineral and organic substances are involved in its composition and, which is especially important, a large group of specific organic and organomineral compounds - soil humus.
Greek philosophers, starting with Hesiod and up to Theophrastus and Eratosthenes, have tried for six centuries to comprehend the essence of soil as a natural phenomenon. Roman scientists were more inclined to practicality and over the course of two centuries created a fairly harmonious system of knowledge about soils and their agricultural use, fertility, classification, processing, fertilization.
I will not go deep into the theory of soil science, I will note that interest in the study of soil, as you understand, has been manifested by humanity since ancient times and, as we decided, to obtain useful vegetables and other plants, we need a soil in which plants can find everything substances necessary for their development.
With the accumulation of information about the soil and the development of natural science and agronomy, the idea of what determines soil fertility also changed. In ancient times, it was explained by the presence in the soil of special "fat" or "vegetable oils", "salts" that give rise to all "plant and animal" on Earth, then - by the presence of water, humus (humus) or mineral nutrients in the soil, and, finally, soil fertility began to be associated with the totality of soil properties in the understanding of genetic soil science.
Only in the 19th century, primarily thanks to the works of Liebig, was it possible to eliminate erroneous ideas about plant nutrition. For the first time, two German botanists F. Knop and J. Sachs succeeded in bringing a plant from seeds to flowering and new seeds on an artificial solution in 1856. This made it possible to find out exactly what chemical elements plants need. Soil fertility is understood as its ability to ensure the growth and reproduction of plants with all the conditions they need (and not just water and nutrients).
One and the same soil can be fertile for some plants and little or completely barren for others. Swamp soils, for example, are highly fertile in relation to swamp plants. But steppe or other plant species cannot grow on them. Acid, low-humus podzols are fertile in relation to forest vegetation, etc. The elements of soil fertility include the entire complex of physical, biological and chemical properties of the soil. Of these, the most important, determining a number of subordinate properties, are as follows.
Granulometric composition of the soil, i.e. the content of fractions of sand, dust and clay in it. Light sandy and sandy soils warm up earlier than heavy soils, and they are referred to as "warm" soils. The low moisture capacity of soils of this composition prevents the accumulation of moisture in them and leads to the leaching of soil nutrients and fertilizers.
Heavy loamy and clayey soils, on the contrary, take longer to warm up, they are "cold", since their thin pores are filled not with air, but with very warm water. They are poorly water and air permeable, poorly absorb atmospheric precipitation. A significant part of soil moisture and reserves of nutrients in heavy soils are inaccessible to plants. The best for the growth of most cultivated plants are loamy soils.
Content of organic matter in the soil. The quantitative and qualitative composition of organic matter is associated with the formation of a water-resistant structure and the formation of water-physical and technological properties of the soil favorable for plants. Biological activity of the soil. The biological activity of the soil is associated with the formation of microbial products in it that stimulate plant growth, or, conversely, have toxic effects on them. The biological activity of the soil determines the fixation of atmospheric nitrogen and the formation of carbon dioxide, which is involved in the process of plant photosynthesis.
Soil absorption capacity. It determines a number of soil properties vital for plants - its food regime, chemical and physical properties. Due to this ability, nutrients are retained by the soil and less washed out by precipitation, while remaining readily available to plants. The composition of the absorbed cations determines the reaction of the soil, its dispersion, the ability to aggregate and the resistance of the absorbing complex to the destructive action of water in the process of soil formation.
The saturation of the absorbing complex with calcium, on the contrary, provides plants with a favorable, close to neutral, soil reaction, protects its absorbing complex from destruction, promotes soil aggregation and the fixation of humus in it. That is why it is so important to carry out liming of the soil on time. Thus, practically all physical, chemical and biological properties of soils serve as elements of soil fertility.
Read the next part. Soil types, mechanical treatment, fertilizers and fertilizing →