Soil Fertility
Fertility — is the ability of soil to provide optimal factors of plant life, including a sufficient amount of nutrients in mobile form and to transform them into the soil reserve and back; to exhibit phytosanitary properties, to be resistant to unfavorable factors and suitable for the use of modern crop cultivation technologies.
Natural soil fertility
Natural fertility — fertility formed as a result of the natural soil-forming process over a long period of time and determined by factors such as particle-size distribution, chemical soil composition and climate. Under conditions of natural fertility, part of the nutrients is in a form inaccessible to plants. In some cases, a constant deficiency of certain elements, for example nitrogen, is observed.
Human impact on soils with natural fertility through their cultivation has led to changes in regimes, which affected the provision and availability of plant life factors. Due to the influence of natural factors and human activity, consisting in soil cultivation, use of fertilizers, irrigation, application of crop rotations, etc., effective soil fertility has formed.
Indicators of soil fertility
Soil fertility is assessed by three types of indicators:
- agrophysical;
- biological (composition and amount of organic matter, biota activity, phytosanitary condition);
- agrochemical.
Agrophysical indicators of soil fertility — a complex of soil properties characterizing particle-size distribution, mineralogical composition, structure, density, porosity, air and water capacity, as well as agrotechnological parameters of soils. Agrophysical indicators influence directly or indirectly all factors of plant life and soil cultivation conditions.
Biological indicators of soil fertility — composition and amount of organic matter, biota activity, phytosanitary condition. Biological activity characterizes the intensity of soil biological processes. Beneficial soil microorganisms participate in the cycling of nutrients, release enzymes, antibiotics, growth stimulants and other organic substances that affect plant development.
Agrochemical indicators of soil fertility — content and availability of nutrients, soil reaction (soil acidity), etc.
A number of factors influence the availability of nutrients, one of which is the soil reaction.
The input of nutrients under natural conditions proceeds rather slowly due to processes of nitrogen fixation, input with atmospheric precipitation, dust, ground and runoff waters. Under cultivated land conditions, agrochemical indicators are regulated by applying fertilizers and ameliorants.
In most cases, the integral indicator of fertility is the content of organic matter and its qualitative state. The choice of this particular indicator is explained by the functional significance of organic matter in soil-forming processes. The development of soil as a natural-historical body is the result of a constant process of synthesis and destruction of organic matter, ensuring the continuity of the cycle of matter and energy during soil formation.
Organic matter has a significant effect on the most important agronomic properties of soil: agrophysical, biological and agrochemical, as well as phytosanitary condition.
Increasing the content of organic matter in soil is a long-term task, which should proceed from the real possibilities of reproducing organic matter in arable soils. Effective implementation of this task is possible with long-term, planned and systematic influence of a complex of practical techniques.
The optimal content of organic matter is determined by soil type, the effect of a quantitative increase in yield and the costs of reproducing this indicator.
Fertility indicators correlate with yield and in most cases are interconnected. Some of them are fundamental, determining the state of all soil processes, for example, particle-size distribution and mineralogical composition, phytosanitary condition; others are their derivatives.
Reproduction of fertility
Cultivation of newly developed soils
Soil cultivation — improvement of natural soil properties with the help of agro-ameliorative measures, that is, with the use of cultural-technical impact on arable land, increasing the size of field contours, leveling, removing stones, etc.
Soil cultivation is used for newly developed lands with very low natural fertility, for example on podzolic, solonchak, strongly eroded soils, when plowing in infertile subarable horizon. In these cases, it is not reproduction but creation of fertility that occurs. This task is relevant when restoring soil in mountain areas or peat workings.
Land reclamation — restoration of cultural fertility on previously used soils.
Reproduction of fertility
Restoration of soil fertility is based on achieving optimal soil fertility indicators in relation to specific production conditions and technology of fertility reproduction. It is based on the law of return.
Reproduction of fertility can be divided into simple and expanded.
Simple reproduction of fertility — measures aimed at returning soil fertility to its initial parameters.
Expanded reproduction of fertility — measures aimed at restoring soil fertility above its initial parameters. Expanded reproduction is especially relevant in conditions of intensive agriculture, in which lands with low natural fertility are included in the turnover. For sod-podzolic soils, expanded reproduction is a mandatory condition for conducting stable agricultural activity.
Soil fertility management — a complex of measures aimed at controlling soil fertility and its simple or expanded reproduction under the conditions of a specific enterprise. It is based on a model built taking into account the actual values of fertility indicators.
Example of a fertility model for sod-podzolic medium loamy soils of the Non-Chernozem zone of Russia. Model productivity is 4.5-6.0 t of grain, or 6500-7500 FU.
| Fertility indicators and their parameters | Technological and material factors of simple reproduction of fertility |
|---|---|
| Agrophysical | |
| 1. Density — 1.1-1.2 g/cm3, porosity — 50-55%, air capacity — 25-30%. | Soil cultivation — uniform-depth, combining moldboard and non-moldboard techniques, soil-protective, with elements of minimization |
| 2. Structure — fine-crumbly, water stability of macrostructure — more than 40%. | |
| 3. Thickness of arable layer — 25-30 cm. Podzolic horizon absent. | |
| Biological | |
| 1. Content of humus in arable layer — 2.5-3%, reserve — 75-90 t/ha. | Application of organic fertilizers — 10-12 t/ha. Sowing of perennial grasses — 25-30% of the total sowing structure |
| 2. Soil biota activity high. | |
| 3. Phytosanitary condition — weed population at the level of economic threshold of harmfulness, pathogens and pests absent. | |
| Agrochemical | |
| 1. State of @abbr[Soil absorption complex|SAC] and acidity: @abbr[Hydrogen potential|pH] = 6.0-6.5, 7-12 mg-eq, V = 80-90%. | Liming according to full hydrolytic acidity once every 5-6 years. |
| 2. NPK content, mg/kg soil: mineral nitrogen — 30-50; mobile forms of phosphorus — 150-250; mobile forms of potassium — 200-250. | Application of mineral fertilizers: NPK — 250-300 kg/ha of crop rotation area. N:P:K ratio = 1 : 0.5-0.6 : 1.2-1.3. |
| 3. Trace element content, mg/kg soil: copper — 0.8-1.2; molybdenum — 0.2-0.4; boron — 0.5-0.6; zinc — 5-7. | — |
Methods of fertility reproduction
Reproduction of fertility in modern agriculture is carried out in two ways: material and technological.
The material method of fertility reproduction is based on the use of fertilizers, ameliorants, pesticides, etc. It has the most complete and diverse effect on soil fertility by replenishing nutrient reserves.
The technological method of reproduction is based on the use of crop rotation, various methods of soil cultivation and methods of sowing, catch crops, etc. It mobilizes soil resources but does not replenish them, therefore the use of only this method is not capable of ensuring a long-term effect of fertility reproduction.
Optimization of fertility
Soil fertility is assessed by a complex of indicators in accordance with the specialization of crop rotation.
Optimal fertility indicators are achieved by applying a complex of agrotechnical techniques and agrochemical means. The Soil Institute named after V. V. Dokuchaev proposed parameters of soil fertility indicators that ensure high crop yields.
Table. Indicators of fertility of different soils and yields of agricultural crops.
| Soil fertility indicator and yield | Types of loamy soils | |||
|---|---|---|---|---|
| ordinary chernozem | gray forest | sod-podzolic | typical sierozem | |
| Agrophysical properties of soils | ||||
| Arable layer, cm | 35 | 30 | 27 | 35 |
| Density, g/cm3 | 1.10 | 1.20 | 1.25 | 1.30 |
| Total porosity, % | 59 | 55 | 50 | 46 |
| Water capacity, % of mass | 30 | 29 | 27 | 25 |
| Water-stable aggregates 0.25 mm, % | 60 | 50 | 40 | 25 |
| Agrochemical and physicochemical properties of soils | ||||
| Humus, % / t/ha | 7.0/270 | 3.0/90 | 2.5/75 | 1.3/60 |
| Nitrogen, % / t/ha | 0.30/12.0 | 0.20/7.2 | 0.15/5.0 | 0.14/6.3 |
| Mobile phosphorus, mg/kg soil | 200 | 200 | 200 | 40 |
| Exchangeable potassium, mg/kg soil | 350 | 200 | 150 | 4000 |
| Crop yield, t/ha | ||||
| Winter wheat | 6.0 | 5.0 | 4.5 | 5.0 |
| Barley | — | 4.5 | 3.2 | 4.0 |
| Perennial grasses | 12.0 | 7.5 | 5.5 | 12.0 |
| Potato | — | 25.0 | 25.0 | 12.0 |
| Cotton | — | — | — | 4.5 |
Table. Optimal parameters of properties of the arable horizon of forest-steppe soils (according to Karmanov N. I., 1993).
| Name of parameters | Gray forest | Podzolized and leached chernozems |
|---|---|---|
| 1. Morphological | ||
| Thickness, cm | 29-35 | 30-35 |
| 2. Agrophysical | ||
| Bulk density, g/cm3 | 1.15-1.25 | 1.05-1.10 |
| Total porosity, % | 52-56 | |
| Number of water-stable aggregates (fraction with particle size 0.25 mm) | 55-65 | |
| 3. Biochemical and physicochemical | ||
| Humus content, % | 5.0-6.0 | |
| Humus reserves, t/ha | 160-230 | 160-230 |
| Humus type CHA : CFA | 1.2-1.6 | |
| Amount of labile humic acids, mg C/kg | no data | no data |
| @abbr[Hydrogen potential|pH] salt | 6.0-6.2 | 6.0-6.5 |
| Hydrolytic acidity mmol/100 g soil | 1.5-2.5 | 2.5-3.5 |
| Sum of exchangeable bases, mmol/100 g soil | 15-25 | 25-35 |
| Degree of base saturation, % | 88-92 | 90-95 |
| 4. Agrochemical | ||
| Mobile forms of phosphorus, mg/kg soil | 200-250 | 180-230 |
| Mobile forms of potassium, mg/kg soil | 200-250 | 150-200 |
For sod-podzolic soils, an important indicator is acidity, which is determined taking into account the specialization of crop rotation, biological characteristics of crops, particle-size distribution of soil, sum and composition of exchangeable cations. The problem of optimizing the reaction of the soil solution is caused by the use of physiologically acid mineral fertilizers, leading to depletion of the arable layer in calcium. Maintaining the optimal reaction of the medium of acidic soils is associated with scientifically substantiated liming technology.
First of all, soil fertility is determined by the content of organic matter. Optimal parameters of humus content in sod-podzolic soils have been established depending on particle-size distribution: in sandy — 1.8-2.0, sandy loam — 2.0-2.5, loamy — 2.6-3.0. To maintain a deficit-free humus balance, it is necessary to apply annually 16-18 t/ha, 13-15 t/ha and 10-12 t/ha of manure, respectively. To maintain the optimal humus content in acidic sod-podzolic and gray forest soils, liming is combined with the application of organic and nitrogen fertilizers in doses covering more than 90% of nitrogen removal by crops, and the inclusion of legume-cereal grass mixtures in the structure of sown areas. Doses of organic fertilizers are determined depending on humus content and particle-size distribution. Assessment of the nitrogen regime of soils is carried out by the content of mineral nitrogen.
One of the characteristics of soil cultivation is the content of mobile phosphorus. In this case, one should focus on the crops of the crop rotation most demanding for phosphorus nutrition under specific soil-climatic conditions. The lower boundary of the content of mobile forms of phosphorus is determined taking into account the assessment of phosphorus content at maximum crop yield and the absence of effect from additional application of phosphorus fertilizers. According to generalized data from long-term experiments, the lower boundary of P2O5 content is 100-150 mg/kg for sod-podzolic loamy soils, 50-100 mg/kg for sandy and sandy loam soils, 100-150 mg/kg for gray forest soils. A further increase in the content of mobile phosphorus does not provide a significant increase in yield.
Table. Crop rotation productivity and content of mobile forms of phosphorus in long-term experiments of the Geonetwork (1993).
| Institution, soil | Experimental variants | Crop rotation productivity, dt grain units/ha | Average annual dose of P2O5, kg/ha | Content of mobile P2O5, mg/kg |
|---|---|---|---|---|
| CES VIUA, sod-podzolic heavy loamy | Control | 29.0 | — | 56 |
| NPK — reduced dose | 36.4 | 64 | 103 | |
| NPK — basic dose | 37.8 | 90 | 120 | |
| RIA of the North-East, sod-podzolic medium loamy | Control | 29.0 | — | 46 |
| NPK | 35.0 | 21 | 54 | |
| NPK | 45.0 | 84 | 169 | |
| ARRI of Flax, sod-podzolic loamy | Control | 15.2 | — | 106 |
| NPK | 25.0 | 45 | 111 | |
| Manure + NPK | 32.7 | 75 | 170 | |
| Sudogodskaya ES, sod-podzolic sandy loam | Control | 26.6 | — | 16 |
| NPK | 36.7 | 25 | 24 | |
| 2 NPK | 38.4 | 50 | 50 | |
| Manure + NPK | 40.2 | 75 | 63 | |
| Vladimirskaya ES, gray forest | Control | — | 28.6 | 132 |
| NPK | 34 | 34.6 | 132 | |
| NPK | 37 | 35.8 | 154 | |
| 2 NPK | 68 | 37.2 | 163 |
The importance of optimizing the phosphorus nutrition regime is due to the fact that significant areas of arable land are characterized by low content of mobile phosphorus. The optimal level of mobile phosphorus content in soil is considered to be that at which at least 90-95% of the maximum yield is achieved; the missing 5-10% is compensated by phosphorus fertilizers, which compensate for removal.
Under irrigation conditions, higher levels of mobile phosphorus supply are required. An increase in mobile phosphorus content from low (2-4 mg/100 g soil) to medium (8-10 mg/100 g soil) gives the highest yield increases. A further increase leads to a decrease in the magnitude of increases, and upon reaching optimal values, crop yield stabilizes.
Table. Fertilizer rates for increasing mobile phosphorus content by 10 mg P2O5/kg soil (according to Litvak Sh. I., 1990; Sychev V. G., Shafran S. A., 2013).
| Soil | Particle-size distribution | Determination method | Fertilizer consumption, kg/ha | |
|---|---|---|---|---|
| data variation | normative1 | |||
| Sod-podzolic | sandy and sandy loam | by Kirsanov | 47-90 | 50-70 |
| light loam | 60-108 | 70-80 | ||
| medium loam | 60-110 | 80-90 | ||
| heavy loam | 90-120 | 100-110 | ||
| Gray forest | sandy and sandy loam | by Kirsanov | 70-80 | 70-80 |
| loamy | 80-110 | 90-110 | ||
| heavy loam | 120-140 | 120-140 | ||
| Podzolized chernozem | light loam | by Chirikov | 74-109 | 90-100 |
| loam | 80-120 | 100-110 | ||
| Leached chernozem | heavy loam | by Chirikov | 90-135 | 110-120 |
| Typical chernozem | heavy loam | by Chirikov | 103-141 | 120-130 |
| Ordinary chernozem | loam | by Chirikov | 94-122 | 100-110 |
| heavy loam | 100-140 | 120-130 | ||
| Carbonate chernozems | On average | by Machigin | — | 110-120 |
| Chestnut soils | On average | by Machigin | — | 90-110 |
Notes.
1 Taking into account phosphorus removal by the crop and coefficients of its return.
Table. Gradations of soil supply with mobile phosphorus, mg/kg soil (Methodological guidelines for integrated monitoring of soil fertility of agricultural lands, 2003).
| Degree of supply | Kirsanov method | Chirikov method | Maslova method | Egner-Riehm method |
|---|---|---|---|---|
| Very low | < 25 | < 20 | < 50 | |
| Low | 26-50 | 21-50 | 51-100 | < 70 |
| Medium | 51-100 | 51-100 | 101-150 | 71-140 |
| Increased | 101-150 | 101-150 | 151-200 | > 140 |
| High | 151-250 | 151-250 | 201-300 | |
| Very high | > 250 | > 250 | > 300 |
An indicator of plant potassium supply is its content in soil in exchangeable form. Soil contains potassium reserves, and there is a dynamic equilibrium between potassium in the soil solution, exchangeable and non-exchangeable (fixed and potassium of natural clay minerals). During plant nutrition, the dynamic equilibrium is disturbed and all forms of soil potassium are involved. At the same time, the mobility of exchangeable potassium and the rate of its restoration from non-exchangeable forms are important.
Table. Gradations of soil supply with mobile (exchangeable) potassium, mg/kg soil (Methodological guidelines for integrated monitoring of soil fertility of agricultural lands, 2003).
| Degree of supply | Kirsanov method | Chirikov method | Machigin method | Maslova method | Egner-Riehm method |
|---|---|---|---|---|---|
| Very low | < 40 | < 20 | < 100 | < 50 | |
| Low | 41-80 | 21-40 | 101-200 | 51-100 | < 70 |
| Medium | 81-120 | 41-80 | 201-300 | 101-150 | 71-140 |
| Increased | 121-170 | 81-120 | 301-400 | 151-200 | > 140 |
| High | 171-250 | 121-180 | 401-600 | 201-300 | |
| Very high | > 250 | > 180 | > 600 | > 300 |
The supply of soils with mobile potassium is determined by different methods depending on soil type. Optimal levels of exchangeable potassium supply can be refined with crop rotation specialization, liming of acidic soils, nitrogen and phosphorus supply, and biological characteristics of crops.
Table. Soil supply with exchangeable potassium and crop rotation productivity.
| Soil | K2O, mg/kg | Productivity, dt/ha grain units per year |
|---|---|---|
| Sod-podzolic sandy loam and loamy | 150-200 | 35-45 |
| Gray forest | 100-150 | 40-50 |
| Leached and typical chernozems (forest-steppe) | 150-200 | 45-60 |
| Thick, ordinary and carbonate chernozems (steppe) | 150-200 | 35-45 |
| Ordinary and carbonate chernozems (steppe, under irrigation) | 250-300 | 50-65 |
| Chestnut, light and dark chestnut soils (steppe, under irrigation) | 250-300 | 65-90 |
The consumption of potassium fertilizers for increasing potassium content in soil is presented in the table.
Table. Fertilizer rates for increasing mobile K2O content by 10 mg/kg soil (according to Litvak Sh. I., 1990).
| Soil | Particle-size distribution | Determination method | Fertilizer consumption, kg/ha @abbr[Active ingredient|a.i.] |
|---|---|---|---|
| Sod-podzolic | sandy loam | by Kirsanov | 40-60 |
| light and medium loam | 60-80 | ||
| heavy loam | 80-100 | ||
| Gray forest | sandy loam | by Kirsanov | 60-70 |
| light and medium loam | 70-80 | ||
| heavy loam | 80-90 | ||
| Podzolized and leached chernozem | on average | by Chirikov | 80-90 |
M. Kh. Shaimukhametov and D. S. Travnikov (1977) proposed optimal parameters of exchangeable potassium content depending on its share in the cation exchange capacity (CEC) of soils with different particle-size distribution.
Table. Optimal indicators of exchangeable potassium content in soils (M. Kh. Shaimukhametov, L. S. Travnikova, 1997).
| Soils (particle-size distribution) | Optimal exchangeable potassium content | |
|---|---|---|
| K2O, mg/kg | % of @abbr[Cation exchange capacity|CEC] | |
| Sandy | 140-160 | 5-10 |
| Sandy loam | 160-190 | 3-5 |
| Loamy | 190-220 | 1.8-3 |
| Heavy loamy and clayey | 220-250 | 1.2-1.8 |
The ranges of variation of the minimum content of exchangeable potassium for sod-podzolic soils are presented in the table.
Table. Levels of variation of the minimum content of exchangeable potassium for sod-podzolic soils of different particle-size distribution (Nikitina L. V., 2011).
| Particle-size distribution | Content of physical clay (particles < 0.01 mm), % | Levels of K2Omin, mg/kg soil |
|---|---|---|
| Sandy loam | 10.1-20.0 | 50-70 |
| Light loam | 20.1-30.0 | 55-85 |
| Medium loam | 30.1-40.0 | 55-105 |
| Heavy loam | 40.1-50.0 | 70-110 |
Based on generalized experimental data, gradations of the degree of soil supply with mobile forms of trace elements in the soil-climatic zones of Russia have been determined.
Table. Gradation of supply of Russian soils with mobile forms of trace elements (Yagodin, Zhukov, Kobzarenko, 2002).
| Trace element | Biogeochemical zone | Soil extract | Soil supply, mg/kg soil | ||||
|---|---|---|---|---|---|---|---|
| very poor | poor | medium | rich | very rich | |||
| B | Taiga-forest | H2O | < 0.2 | 0.2-0.4 | 0.4-0.7 | 0.7-1.1 | > 1.1 |
| Cu | 1.0 N HCl | < 0.9 | 0.9-2.1 | 2.1-4.0 | 4.0-6.6 | > 6.6 | |
| Mo | oxalate | < 0.08 | 0.08-0.14 | 0.14-0.30 | 0.30-0.46 | > 0.46 | |
| Mn | H2SO4 | < 1.0 | 1.0-25 | 25-60 | 60-100 | > 100 | |
| Co | HNO3 | < 0.4 | 0.4-1.0 | 1.0-2.3 | 2.3-5.0 | > 5.0 | |
| Zn | 1.0 N KCl | < 0.2 | 0.2-0.8 | 0.8-2.0 | 2.0-4.0 | > 4.0 | |
| B | Forest-steppe and steppe | H2O | < 0.2 | 0.2-0.4 | 0.4-0.8 | 0.8-1.2 | > 1.2 |
| Cu | 1.0 N HCl | < 1.4 | 1.4-3.0 | 3.0-4.4 | 4.4-5.6 | > 5.6 | |
| Mo | oxalate | < 0.10 | 0.10-0.23 | 0.23-0.38 | 0.38-0.55 | > 0.55 | |
| Mn | H2SO4 | < 25 | 25-55 | 55-90 | 90-170 | > 170 | |
| Co | HNO3 | < 1.0 | 1.0-1.8 | 1.8-2.9 | 2.9-3.6 | > 3.6 | |
| Zn | 1.0 N KCl | < 0.15 | 0.15-0.30 | 0.30-1.0 | 1.0-2.0 | > 2.0 | |
| Zn | acetate-ammonium | < 4.0 | 4.0-6.0 | 6.0-8.8 | > 8.8 | — | |
| B | Dry-steppe and semi-desert | H2O | < 0.4 | 0.4-1.2 | 1.2-1.7 | 1.7-4.5 | > 4.5 |
| Cu | 1.0 N KNO3 + HNO3 (by Gyulakhmedov) | < 1.0 | 1.0-1.8 | 1.8-3.0 | 3.0-6.0 | > 6.0 | |
| Mo | < 0.05 | 0.05-0.15 | 0.15-0.50 | 0.5-1.2 | > 1.2 | ||
| Mn | < 6.6 | 6.6-12 | 12-30 | 30-90 | > 90 | ||
| Co | < 0.6 | 0.6-1.3 | 1.3-2.4 | > 2.4 | — | ||
| Zn | < 0.3 | 0.3-1.3 | 1.3-4.0 | 4.0-16.4 | > 16.4 | ||
Table. Efficiency of micronutrient fertilizer application for main agricultural crops according to generalized data of field experiments (1993).
| Crop | Average yield increase from trace elements, dt/ha | |||||
|---|---|---|---|---|---|---|
| B | Mo | Zn | Cu | Co | Mn | |
| Wheat, barley (grain) | 1.4 | 2.1 | 2.5 | 3.7 | 2.7 | 1.9 |
| Maize, green mass | 51 | 49 | 44 | 50 | 40 | 39 |
| Sugar beet, roots | 32 | 23 | 32 | 14 | 20 | 28 |
| Potato, tubers | 20 | 20 | 24 | 13 | 18 | 28 |
| Clover, seeds | 0.5 | 0.5 | — | 0.4 | — | — |
| Perennial grasses, green mass | 25 | 46 | 18 | 32 | 34 | 22 |
Research institutions of Belarus conducted studies to determine optimal indicators and developed a model of fertility of sod-podzolic loamy soils.
Building a soil fertility management system
Building a fertility management system begins with determining the optimal parameters of the fertility model. To build an implementable model, one should take into account the experimental characteristics of specific agricultural regions for the purpose of objective agronomic assessment of soils.
Assessment of the effectiveness of differentiated, experimentally determined fertility models should be supplemented by an economic assessment, which allows comparing the effect obtained from the model with the costs of maintaining it under specific natural-economic production conditions. The agroeconomic assessment of fertility models allows determining the levels of fertility reproduction, both as a whole and by individual indicators — simple or expanded reproduction.
Reproduction of fertility in intensive agriculture should be carried out according to all fertility indicators, but primary importance should be given to the most important of them for specific soils and conditions of agricultural production.
List of sources
- Bazdyrev G. I., Loshakov V. G., Puponin A. I. et al. Agriculture. Textbook for universities. M.: Kolos Publishing House. 2000.
- Niklyaev V. S. Fundamentals of agricultural production technology. Agriculture and crop production. M.: Bylina. 2000.
- Mineev V. G., Sychev V. G., Gamzikov G. P. et al. Agrochemistry. Textbook. / Ed. Mineev V. G. M.: Publishing House of VNIIA named after D. N. Pryanishnikov. 2017.
