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Subject and methods of agrochemistry

Agrochemistry, or agronomic chemistry, is the science of interaction between plants, soil and fertilizers in the cultivation of crops, the cycle of chemicals in agriculture and the use of fertilizers to increase yields, improve their quality and increase soil fertility, taking into account the bioclimatic potential.

In the process of development of agrochemistry, the meaning of the concept has been constantly improving due to the tasks and formation of its new functions, which reflects the complex relationship of plants, soil, climate and agrochemical means. The main task of agrochemistry is to study this relationship.

Subject and methods of agrochemistry (Русская версия)

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Subject and methods of agrochemistry (Русская версия)

Subject of agrochemistry

D.N. Pryanishnikov called the task of agrochemistry the study of the cycle of substances in agriculture and the identification of ways to influence the chemical processes occurring in the soil and plants that affect the crop and its quality.

Fertilizers create an optimal nutrient regime, directionally regulate the exchange of organic and mineral compounds, thereby allowing to realize the potential productivity of plants. In turn, fertilizers are affected by plants, for example, hard soluble forms of plants can translate into available, and the selective absorption capacity in relation to certain elements, create a physiological acidity or alkalinity of mineral fertilizers.

Agrochemicals affect the chemical and physical properties of the soil, the activity and direction of microbiological processes, at the same time changing themselves under the influence of soil properties. Exchange reactions occurring in the soil between cations of salts of mineral fertilizers and soil absorbing complex can lead to negative or positive results. For example, displacement of aluminum from absorbing complex by potassium when potassium chloride is applied leads to additional acidification of soil solution, and exchange reactions between calcium from applied fertilizers and sodium of absorbing complex of alkaline soils improve their physical and chemical properties and increase biological activity. This is the basis of chemical reclamation of saline soils – gypsum.

D.N. Pryanishnikov showed the relationship between three interacting factors: soil, plant, and fertilizer in a simple scheme reflecting the essence of agrochemistry. The task of agrochemistry is to create optimal conditions with fertilizers for plant nutrition. The same approach must be taken with the soil. By satisfying the biological requirements of plants, it is possible to realize the potential productivity of plants.

C.K. Giedroytz noted that yield is determined by three factors: climate, soil, and the plant itself. Climate is difficult to change, but it is possible to mitigate its effect by improving soil properties. By changing the properties of the soil, the farmer can to a certain extent regulate the impact of climatic conditions on plants. C.K. Giedroytz considered the impact of fertilizers indirectly through the change of soil properties.

Agrochemistry
Scheme of relationships between plants, soil and fertilizers as the essence of the subject of agrochemistry (according to D.N. Pryanishnikov)

The development of theoretical provisions of quantitative and qualitative formation of crop production has caused the need to introduce the bioclimatic potential in the concept of agrochemistry. The theory of programmed yields has been developed and successfully applied, static models of soil fertility by agrochemical and agrophysical indicators, taking into account the level of yield of individual crops and the productivity of specialized crop rotations as a whole are created and improved. The work on modeling of productivity processes for some crops, the implementation of which will make it possible to achieve the highest possible yields, is under way.

Numerous experiments with fertilizers in different climatic zones of the country allow to a certain extent taking into account the climate as one of the factors in the climate-plant system.

The 1983 state standard included climate in the definition of agrochemistry: “Agrochemistry – the science of interaction between fertilizers, soil, plants and climate, the cycle of substances in agriculture and the rational use of fertilizers” (Resolution No. 3110 of the USSR State Standards Committee of July 13, 1983).

Underestimation of climatic features in relation to a particular farming area can lead to errors in determining the value of mineral fertilizers.

The subject of agrochemistry
Dialectical relationship of the system soil - climate - fertilizers - plants in the modern view of the essence of the subject of agrochemistry

Tasks of agrochemistry

At the present stage of development agrochemistry solves the problem of studying the properties of various types of organic and mineral fertilizers and their effect on: 

  • cycle and balance of nutrients in farming;
  • soil properties and fertility reproduction;
  • plant nutrition and exchange of organic and mineral substances during vegetation;
  • biological activity of soil and its biodiversity;
  • formation of yield and quality of products;
  • agro-ecological functions of agrochemistry in the soil-plant system;
  • economic and energy indicators of agrochemicals efficiency.
Agrochemistry studies
Subjects of study of agrochemistry

In recent years, the increasing importance of economic and environmental problems of agrochemistry and evaluation of the effectiveness of fertilizer application has been noted.

The task of the modern agrochemist is reduced to determining the exact parameters of the cycle of biogenic elements, taking into account specific agroclimatic conditions and the specificity of agricultural plants, their varieties at given levels of productivity.

Purpose of agrochemistry

The purpose of agrochemistry – the creation of optimal conditions of plant nutrition, taking into account the properties of types and forms of fertilizers, the peculiarities of their interaction with the soil, the definition of effective forms, methods, timing of fertilizer use.

Methods of agrochemistry

Laboratory methods

Among the methods of agrochemistry of particular importance are laboratory: chemical, physical and chemical methods of analysis of plants, soils and fertilizers. The creation of modern high-precision instruments for various methods of analytical chemistry has greatly expanded the range of possibilities in agrochemistry.

Among the analytical chemistry methods widely used in agrochemistry are:

  • photometry,
  • chromatography,
  • spectroscopy,
  • atomic absorption spectrophotometry,
  • X-ray fluorescence,
  • neutron-activation method,
  • mass spectrometry.
Methods of agrochemistry
Basic methods of agrochemistry

Stable and radioactive isotope methods are used to study plant metabolism. High-performance modern analytical equipment and computers make it possible to process a large volume of in-line analysis results. Portable measuring instruments make it possible to conduct express analyses directly in the field, quickly determine the content of chemical substances in plants or soil, soil properties such as acidity, and quickly make adjustments to fertilizer application rates.

In recent decades, began to apply a comprehensive soil-vegetation diagnostics of plant nutrition and fertilizer application, which consists of laboratory analysis of the soil to determine the optimal rate of the main fertilizer and the subsequent adjustment of doses in the feeding during the growing season after the analysis of plants in the field.

Physiological-agrochemical methods

Physiological and agrochemical methods include vegetative and lysimetric methods. At vegetative methods experiments are carried out in special vessels placed in pavilions-houses or greenhouses. In the lysimetric methods, studies are carried out in large vessels, for example, 1 m3 in volume, with vertically isolated walls to create conditions close to natural.

The lysimetric method has found wide application in research institutions of the world. With its help the processes of migration, transformation of nutrients, changes in soil properties in dynamics are studied, balance experiments as well as metabolism in plants and formation of product quality are carried out.

In practice, the vegetative and lysimetric methods are often used in combination with each other. Physiological and agrochemical methods include experiments in phytotrons, in which all indicators of the plant production process are controlled and regulated: water supply, root nutrition, intensity and quality of light, temperature regime, photosynthesis, gas exchange, etc. These researches are carried out under full automation of processes with registration of plant growth and development parameters. These methods are the most precise and allow to reveal the process of metabolism with participation of all factors of plant life, to determine the potential productivity of plants and ways of its realization for a particular genotype, to create a dynamic model of the productive process. Phytotrons are also used in breeding and genetic studies. Phytotrons are used, as a rule, in large research institutions and institutions of higher education.

Field experiences

A field experiment is an experiment carried out under field conditions to determine the effectiveness of fertilizers on crop yields, crop quality and soil fertility.

Small-scale experiments are performed for in-depth, more often exploratory, experiments. As a rule, they combine vegetative and lysimetric experiments, but under conditions identical or close to natural. Small-scale experiments can use labeled atom methods, create and test models of soils of high fertility, test types and forms of fertilizers and their combinations, including with other chemical agents or microbiological preparations. Small-scale experiments are carried out on plots of up to 10 m2.

In short-term field experiments, the effect of fertilizers on yields and product quality is studied for at least three years in specific soil conditions. Data from the Geographic Network of Experiments in Russia are widely used to determine the need for different types and forms of mineral fertilizers in the zoning aspect, as well as to determine the country’s needs for mineral fertilizers. 

Small-scale and short-term field experiments are also used to improve methods of comprehensive soil and plant diagnostics of plant nutrition and fertilizer application.

Stationary experience is a field experiment with systematic application of fertilizers, which is carried out on one plot, in a crop rotation, in a crop rotation unit or in a permanent crop.

Long-term field experiment is a stationary experiment carried out during several rotations of crop rotation. Long-term stationary experiments allow you to get information to assess the effectiveness of different systems of fertilizers in crop rotations, the level of saturation of crop rotations with fertilizers, the optimal distribution of organic and mineral fertilizers on crops of the rotation and forms of fertilizers. These experiments are the basis for developing static models of soil fertility, for studying the regularities of changes in fertility and product quality under long-term fertilizer use, for carrying out balance studies, migration of nutrients along the soil profile and accumulation of ballast toxic elements, including heavy metals and agrochemicals, that is for solving environmental problems of agrochemistry. Experiments are set in conditions close to production conditions.

Production experiments with fertilizers are carried out under production conditions to test the recommended doses of application and economic evaluation of fertilizers. They have a brief character and are designed to test and refine scientific recommendations in production and specific soil and climatic conditions. The results of these experiments are of great importance in the implementation and justification of the effectiveness of the complex of methods of chemicalization of agriculture.

Relationship of agrochemistry with other sciences

The content of agrochemistry as a science can be presented in three sections:

  • plant chemistry,
  • soil chemistry,
  • fertilizer chemistry.

Plant chemistry is a section of plant physiology, soil chemistry is a section of soil science, and at the same time they are an integral part of agrochemistry. Fertilizer chemistry is fully part of agrochemistry. Research in this section is carried out in conjunction with soil chemistry, plant physiology and agriculture.

Agrochemistry cannot be considered separately from soil science, plant physiology, farming, soil microbiology. 

Agrochemistry became a separate discipline because of theoretical and practical expediency.

The range of agrochemical research is very wide. It includes the study of transformation of nutrients in the soil and metabolism in the plant, optimization of plant nutrition, reproduction of soil fertility, application of fertilizers for the planned yield and regulation of product quality.

Relationship of agrochemistry with other sciences
Relationship of agrochemistry with other fundamental and applied sciences

Relation to the basic sciences

Linking agrochemistry with the basic sciences
Linking agrochemistry with the basic sciences

The relationship between agrochemistry and soil science is that the effectiveness of fertilizers is determined by chemical, physical, physical and chemical properties of the soil, its biological activity, which in turn are related to the content and mobility of nutrients in the soil. The interrelation of soil properties and fertilizers is manifested in the processes of mobilization, immobilization, transformation, migration of nutrients, which are influenced by plants of agrocenosis.

The efficiency and payback of fertilizers depend on soil fertility, humus content, absorption capacity, buffering capacity and environmental reaction. Therefore, the task of agrochemistry is to study soil properties and fertility, the balance of nutrients in agrocenosis, ways to regulate and reproduce soil fertility.

The relationship between agrochemistry and soil science is that the effectiveness of fertilizers is determined by chemical, physical, physical and chemical properties of the soil, its biological activity, which in turn are related to the content and mobility of nutrients in the soil. The interrelation of soil properties and fertilizers is manifested in the processes of mobilization, immobilization, transformation, migration of nutrients, which are influenced by plants of agrocenosis.

Efficiency and payback of fertilizers depend on soil fertility, humus content, absorption capacity, buffering capacity and environmental reaction. Therefore, the task of agrochemistry is to study soil properties and fertility, the balance of nutrients in agrocenosis, ways to regulate and reproduce soil fertility.

The relationship between agrochemistry and plant physiology is manifested in the influence of nutrients on all life processes of plants, which ensures the formation of quality indicators of products. Such agrochemical methods as root and foliar feeding allow to regulate nutrition of plants, directionally optimizing the conditions of active growth and development, forming a larger yield of better quality. On the knowledge of the laws of plant nutrition during the growing season the methods of plant diagnostics of the availability of nutrients to the crop have been developed.

Many sections of agrochemistry are related to soil biology and microbiology. Thus, the state and regulation of nitrogen regime in agrocenoses is a task of agrochemistry, the successful solution of which is possible with correct evaluation of biological sources of nitrogen in the soil-plant system: symbiotic and associative nitrogen fixation or by free-living microorganisms. The activity of these processes is determined by the right fertilizer system. The same applies to the processes of humification and mineralization of humus and phosphorus nutrition of plants.

The increasing role of ecological aspects of farming connects agrochemistry with ecology. For example, technogenic pollution of agrocenoses with heavy metals, radionuclides and agrochemicals causes the need to develop a set of agrochemical tools and techniques aimed at reducing the penetration of pollutants into plants and trophic chains.

Ecological assessment is especially necessary when using non-traditional types of fertilizers – waste from industry, municipal services, when using local organic and mineral raw materials as fertilizers.

Ecological functions of agrochemistry:

  • maintaining the biological cycle of substances,
  • preservation of biodiversity and improvement of soil microbiocenosis,
  • immobilization of toxic substances,
  • preservation of soil biological activity,
  • activation of nitrogen-fixing capacity of soil,
  • preventing eutrophication of natural waters.

Creating optimal cultural agrolandscapes in different natural zones is possible with the help of agrochemicals. By applying fertilizers in the complex of agrolandscape farming, humans create a cultural agrolandscape with an optimal geochemical regime, which is the best in terms of hygiene and meets the conditions of human life.

The ecological function in agrolandscape farming systems characterizes the relationship between agrochemistry and geochemistry. V.A. Kovda (1984) noted that the behavior of fertilizers in the landscape should be studied with the involvement of biogeochemical methods – agrogeochemistry. He believed that the study of the transformation of fertilizers in all components of the landscape allows to get the greatest benefit from fertilizers with the least negative ecological consequences.

The relationship between agrochemistry and geography manifests itself in the geographic patterns of fertilizer action, which in turn are determined by the soil, biological, and climatic conditions of the zones.

The relationship between agrochemistry and meteorology is determined by the dependence of fertilizer and agrochemical efficiency on weather and climatic conditions.

Relationship to applied sciences

Relationship between agrochemistry and applied sciences

Agrochemistry is closely related to all branches of agricultural applied sciences.

K.A. Timiryazev wrote in 1935 that agriculture became what it is because of agronomic chemistry and plant physiology. The connection between agrochemistry and farming is that the fertilizer system is the most important link in modern farming systems. Thus, the efficiency of fertilizers is determined by the presence of mobile forms of nutrients in the soil, the state of water and air regimes, which in turn depends on the predecessors and tillage system. The same applies to the system of crop rotations, which determines the norms and ratios of fertilizers, distribution of fertilizers and ameliorants on crops in the crop rotation.

The set of agronomic practices used in crop cultivation, including fertilizer application, is determined by biological requirements of the crop, meteorological conditions, soil fertility, and predecessor, thereby linking agrochemistry with crop production.

Intensification of farming determines the complex science-based application of agrochemicals in progressive cultivation technologies on the basis of comprehensive soil and plant diagnostics of plant nutrition, fertilizers and chemical means of protection. In this case the payback of mineral fertilizers and plant protection agents, in particular pesticides or herbicides, increases. Thus the relationship between agrochemistry and plant protection is manifested.

Fertilizer efficiency under irrigation conditions with an optimal combination of water and nutrient soil regime increases dramatically. The same applies to fertilizer efficiency when they are used on reclaimed drained lands, especially with double regulation of water regime. This explains the relationship between agrochemistry and land reclamation.

Importance of agrochemistry

For expanded reproduction of soil fertility, creating an active balance of biogenic macro- and microelements in the system soil – plant – fertilizer, it is important to maximize the use of local fertilizer resources. Particular importance is given to manure. Well-established and properly organized technology of accumulation, storage and use of manure – an indicator of the culture of agriculture.

The high rate of chemicalization of agriculture requires improvement of mechanization and automation, ie improvement of transport vehicles for transportation of fertilizers; machines for mixing and applying of fertilizers, machinery for accumulation, storage of manure, compost preparation, transportation and application.

Fertilizer efficiency is evaluated primarily by economic indicators. It is possible to implement all methods of chemical agriculture in the farm with a set of organizational, economic and economic measures in the presence of appropriate material and technical base.

Dynamics of wheat yield growth in Western Europe over 200 years
Dynamics of wheat yield growth in Western Europe over 200 years

In the Middle Ages, when the three-field farming system prevailed, the average yield of wheat was 0.7-0.8 t/ha. The introduction of fruit rotation with clover allowed for a doubling of yields. The Norfolk four-field crop rotation, first developed in England in the 18th century, was typical for that time. Doubling of yields was achieved at the expense of biological nitrogen fixed by nodule bacteria on clover roots.

In the early 20th century, the doubling of wheat yields in Western Europe was due to the widespread use of mineral fertilizers. In recent years, the dynamic growth of grain crops yields, reaching 5-6 t/ha and higher, is due to the high culture of farming, the use of scientifically sound system of fertilization, based on soil and plant diagnostics, as well as crop rotation. Integral system of plant protection and achievements in breeding of highly productive crop varieties play a positive role.

Thus, using a set of agro techniques in the progressive technologies of crops cultivation, achieve the realization of their potential productivity. At the same time there is a direct correlation between the level of fertilizer use and yields of cereal crops.

Wheat grain production, crop area, yield and mineral fertilizer consumption

Table. Wheat grain production, sown areas, yields and mineral fertilizer consumption (1961-2010) (FAOstat, 2012; IFADATA)[1]Agrochemistry. Textbook/V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al; ed. by V.G. Mineev. - M.: Publishing house of the All-Russian Scientific Research Institute of Agrochemistry named after D.N. … Continue reading

Country
Grain production, million tons
Sown area, million hectares
Export, mln. tons
Yield, t/ha
Fertilizers applied to wheat (2006-2007), thousand tons a.d.m.
Total fertilizer application, thousand tonnes a.d.m.
N
P2O5
K2O
China
112,10
23,90
0,77
4,69
4258
1194
255
49513
India
77,02
27,76
0,16
2,77
2892
1109
187
23906
USA
58,70
20,32
27,11
2,89
1604
568
224
18795
Russia
52,26
24,18
12,60
2,15
402
169
70
2055
France*
36,73
5,31
16,03
6,92
619
240
206
3249
Canada
24,79
9,25
17,01
2,67
591
173
36
2770
Germany*
23,71
3,17
6,42
7,47
458
117
129
2253
Pakistan
22,57
8,75
0,13
2,58
1004
345
15
3829
Turkey
19,06
8,15
0,27
2,34
584
252
15
1925
Ukraine
18,30
6,31
6,43
2,86
**
**
**
955
Australia
17,92
13,04
13,88
1,36
263
284
28
1908
Great Britain*
14,83
1,93
2,36
7,66
549
89
87
1462
Kazakhstan
13,83
12,98
4,09
1,07
**
**
**
55
Iran
13,40
6,47
0,06
2,05
414
179
48
1614
Argentina
12,68
4,69
8,73
2,70
280
165
1
1321
Poland*
8,79
2,26
0,76
3,87
591
176
140
1968
Egypt
7,87
1,26
0,00
6,27
302
35
10
1409
Italy*
7,29
2,00
0,21
3,65
190
141
81
11,28
Spain*
5,80
1,89
0,48
3,06
515
199
114
1558
Romania
5,35
2,05
1,14
2,59
150
24
7
397
Total in the world
647,30
218,60
134,78
2,96
16614
6261
1261
161313

Note: * – The amount of mineral fertilizer applied to wheat in each of the 27 European Union countries was estimated from the average fertilizer requirement of the crop (Heffer, 2009) and the total amount of fertilizer applied in each country per year.

** – no data

The possibility of obtaining high yields of grain up to 7-8 t/ha in different soil and climatic conditions of Russia is confirmed by experimental production institutions under the condition of the optimal scientifically based combination of all links of agriculture.

Given the role of mineral fertilizers in increasing agricultural productivity in Russia in the second half of the XX century, measures were taken to increase their production and use.

Table. Dynamics of application (supply) of mineral fertilizers in the Russian Federation[2]Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al; ed. by V.G. Mineev. - M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, … Continue reading

Years
Thousand tons in recalculation on 100% of nutrients
Kg per 1 ha of arable land
1965
2608
19,7
1970
4317
32,9
1975
7869
59,9
1980
8914
67,5
1985
12677
96,0
1986-1990
12800
99,0
1999
1200
10,0
2006
1510
27,0
2011
1970
38,0

Measures were taken to increase the number of livestock, which allowed an increase in the production and use of organic fertilizers.

Application of organic fertilizers in Russia
Application of organic fertilizers in Russia

Attention was paid to chemical reclamation of soils, in particular liming.

Average annual liming of soils in Russia, mln ha

For example, the Ministry of Agriculture of the Republic of Kazakhstan provides data on the use of mineral fertilizers.

In Belarus from 2006 to 2013 used 250-313 kg/ha d.v. of mineral fertilizers, or 1.3-1.5 million tons of d.v. for all agricultural land. In the short term, the technological need for mineral fertilizers for the planned productivity of arable land in the whole country is 1939.1 thousand t a.d., of which nitrogen – 753.3 thousand t a.d., phosphorus – 325.0 thousand t a.d., potash – 860.8 thousand t a.d. In the future as soil reserves of phosphorus and potassium increase the need for these fertilizers can be reduced to the size of the removal of these elements with the planned crop yield, the need for nitrogen fertilizers will remain.

In the XXI century Russia and the former Soviet Union were faced with the need to increase agricultural productivity and achieve food independence. Based on the experience of countries around the world, this goal can be achieved with the full provision of agriculture with mineral fertilizers in the necessary volume and assortment, combined with extensive use of all types of organic and local fertilizer resources, phosphoritization and liming of acidic soils.

Table. Use of mineral fertilizers in the Republic of Kazakhstan (according to the data of the Ministry of Agriculture of Kazakhstan)[3]Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al; ed. by V.G. Mineev. - M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, … Continue reading

Years
Fertilizer application (NPK), thousand hectares
Introduced kg a.d.m. per 1 ha
% fertilized
Fertilized area, thousand hectares
общего
удобренной
1965
107,3
3,6
-
7,0
-
1986
1018,7
29,0
59,0
47,0
17253
1990
672,2
19,1
72,0
26,5
9332
2000
11,5
0,71
133,7
0,53
86
2005
58,5
3,17
89,4
6,23
1150
2010
99,4
4,14
40,2
12
2472
2015
81,1
4,3
33,1
10,3
2453

Sources

Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al. – M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, 2017. – 854 с.

Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry / Edited by B.A. Yagodin. – Moscow: Kolos, 2002. – 584 p.: ill.