The history of the formation of agricultural chemistry science and the application of fertilizer in Russia

Modern methods of working the land are largely based on rules formulated at the dawn of agricultural chemistry. Vast expanses with diverse soil cover have always required domestic researchers to have a deep understanding of the laws of plant nutrition. As early as 1910, foreign experts acknowledged that thanks to Russian scientists, soil science had turned into a global science. Today's practitioner must remember these foundations, as the basic principles of maintaining soil fertility have not changed.

How the foundations of plant mineral nutrition were born

The formation of domestic agronomic science began in the second half of the XVIII century, when in 1770 the university began to hold lectures on agriculture and domestic management. During the same period, scientists began to actively investigate the properties of soils and the effect of fertilizer. In the scientific works of that time, created in 1738–1833, the principles of plant nutrition were described for the first time, which were ahead of many foreign theories. These studies laid the foundation for our modern understanding of how plants interact with the soil solution.

• Beginning of agronomy teaching — 1770
• Works by one author on fertilizers — over 20
• Key conditions for crop growth — 2

In the fundamental work "On Land Fertilization" (1770), scientists described in detail the mechanism of nutrient consumption. They concluded that crop development depends directly on the presence of certain particles in the ground. To obtain a stable harvest on a specific field, it is necessary to follow two basic rules.

1. Ensure a sufficient quantity of nutrients in the soil, remembering that their deficiency or excess is equally harmful to crops.
2. Maintain the state of the soil in which these nutrients transition into a form accessible for plant assimilation.

Already in the second half of the XVIII and early XIX centuries, all applied fertilizers were divided into ordinary (manure, humus) and artificial (ash, lime). Researchers refuted the opinion that liquid manure juice alone increases soil fertility. They proved that the active ingredient of organic matter is the mineral salt contained within it. Rules were developed for preserving the value of fertilizers that are still relevant today.

Chemical properties of soils and the preservation of soil fertility

The first professor of agriculture in the country (life period 1739–1810) considered the study of the chemical properties of arable land to be the most important task. In his work on chernozems, he described the process of humus formation from plant residues under the influence of water, air, and living organisms. These findings help modern specialists understand the processes of organic matter accumulation in the soil. At that time, the idea was also born regarding the necessity of creating a "passport" for every field in terms of its natural properties.

When studying chernozems, scientists identified for the first time areas with increased acidity. As a good fertilizer for such acidic soils, they proposed using the ash of burnt peat. This experience shows that an individual approach to every field contour was established back at the inception of agronomy. Modern precision farming continues to develop these historical principles.

Ivan Mikhailovich Komov (1750–1792) was an ardent supporter of studying plant nutrition, as well as the mechanical and chemical analysis of soils; he gave the first recommendations on the application of organic fertilizer and finely ground limestone. He considered the restoration and maintenance of the soil to be the most important task of agriculture: "the main business of the farmer consists in fertilizing poor land and, once fertilized, striving to ensure it does not lose its goodness." In his book "On Agriculture" (1788), I.M. Komov defines the essence of agriculture as follows: "...agriculture is the mother of every craft and trade.... The farmer has a close union with high sciences, such as natural history, medical science, chemistry, mechanics, and almost all of physics, and it itself is nothing other than a part of experimental physics, only the most useful of all." Here he detailed the importance of individual agricultural crops, spoke about the necessity of fertilizing "poor" land, and emphasized the value of manure not only as a fertilizer, but also its role in conserving soil moisture and improving soil structure. I.M. Komov describes in detail the preparation of fecal composts. He suggests applying chicken manure for winter crops during sowing along with the seed, or in the spring, after the snow has melted, as top dressing. The scientist recommends hauling manure to the field fresh, rather than burnt or rotted, as the "power of nutrition" disappears in such cases. After being hauled to the field, the manure must be immediately incorporated into the soil. I.M. Komov also noted the important role of lime in increasing the yield of agricultural crops. He devoted much attention to the liming of acidic soils and the use of ash, peat, and other local fertilizers: "Lime not only makes clayey soil loose, but also destroys any acid that is for the most part found in clayey land."

Anton Pavlovich Poshman (1792–1852) published a book in 1809 titled "Instructions on the preparation of dry and moist fertilizers for the enrichment of arable land." This work is the result of the author's independent inquiries into the application of fertilizers in agriculture. A. P. Poshman writes: "Nothing hinders a farmer as much in the fertilization of his land as the lack of necessary fertilizer. Who is not aware that even the best soil, in order not to be deprived of its good properties, must be manured from time to time; it is all the more necessary to improve and saturate poor and bad soil so that it may bear good fruits and reward the hard labor of the farmer." He categorizes manure as ordinary and dry. The former is obtained from livestock, and the latter by burning plants. In essence, A. P. Poshman was one of the first to express the idea of the high efficiency of using an organic-mineral fertilizer system. He clearly formulated the tasks facing the science of field fertilization: "One must look more at the properties of the soil or how little it requires manure. Everything in excess in nature is not only useless but also harmful." "Many owners," he continues, "think that abundant manuring of land is very useful; but experience shows the opposite. Grain grown on heavily manured land grows too much into straw and yields few seeds." A. P. Poshman pointed out that "alkaline-saline substances" serve as food for plants and are contained in manure and ash from burning plants. Thus, many years before Justus von Liebig published the theory of mineral nutrition, A. P. Poshman wrote about the importance of mineral salts in plant nutrition. He considered lime to be "a driving force of growth" and recommended its use on heavy, cold soils. A. P. Poshman was the first in science to propose the preparation of dry fertilizers. For this purpose, the scientist suggested a portable furnace. He burned various substances: moss, heather, fern, peat, pine cones, leaves, tops, reed, and cane. A. P. Poshman added marl and clay to the burned organic matter to prepare dry fertilizers.

Mikhail Grigoryevich Pavlov (1793–1840) was a professor at Moscow State University in the Department of Physics, Mineralogy, and Agriculture. He alternately lectured on physics, mineralogy, forestry technology, and agriculture. In the lectures of M. G. Pavlov, the course of agriculture was, for the first time in Russia, presented as an independent scientific discipline. "Agriculture," he said, "must be taught as a science." "Whoever wants to be an agronomist without knowledge of nature is merely an agromaniac... Conscious (rational) agriculture, undertaken with an understanding of the matter, begins with experiments. Everything in agriculture is a deduction from particular cases, from special productions, from local circumstances. Reason, examining details and local peculiarities, with a wondrous power of abstraction, converts them into concepts or knowledge, subordinating them to one another: the particular to the general, the lower to the higher, and finally to the principles by which everything thus acquired is bound into a harmonious whole, forming a system of management – a science..." "To teach agricultural science means to introduce the century-old experience of predecessors," M. G. Pavlov wrote in the journal "Russian Farmer" in 1838. M. V. Pavlov was the first in Russia to link chemistry with agronomy and published the book "Agricultural Chemistry with a preliminary presentation for this part, and for the whole science of agriculture – preparatory knowledge from known sciences, with an indication of various methods of soil improvement and an outline of rules for ploughing" (1825). Here he wrote that "agricultural chemistry is the science of the matter of those objects exclusively that have relevance to agriculture, and knowledge of the matter of which can guide one to the most profitable organization of the production of this art."

Regarding soil fertility and plant nutrition, M. G. Pavlov initially proceeded from A. D. Thaer's theory of humus nutrition of plants. Subsequently, the scientist moved away from it. In the aforementioned book "Agricultural Chemistry...", he wrote: "The main material of plant nutrition is chernozem; the root is in direct contact with it; consequently, chernozem passes into the plant through the root; but by cutting the root, we do not find chernozem in it. And the very structure of this organ is enough to convince us that it cannot absorb solid substances." Elsewhere in the same work, he wrote: "Chernozem is not absorbed by the root in its real form, but in an altered one, namely, in the form of mucus dissolved by water." By chernozem, M. G. Pavlov, in accordance with the teachings of M. V. Lomonosov, understood "a black-colored, earth-like residue of decayed plants and animals." Later, in his "Course of Agriculture," the scientist moved even further away from A. D. Thaer's theory and developed his own, more realistic concept of plant nutrition using soil mineral compounds and certain elements of the air. He notes that "plants do not always originate from chernozem"; many, especially the lower ones, "originate even where there is sufficient humidity with favorable air and warmth. Here, consequently, inorganic matter is turned into organic matter by the power of growth. Plants that have originated not from chernozem, when decaying, turn into chernozem. Those growing on chernozem also do not feed on it alone, but especially broad-leaved ones absorb much food from the atmosphere as well; consequently, when decaying, they return to the earth more chernozem than they absorb from it: thus, they increase the richness of the land." The mutual influence of soil and plant is constant. The soil is a "medium of plant digestion," a "storehouse of growth conditions." "Plant food, before it is absorbed by the root, is processed in the soil. And therefore it is quite rightly that the soil is compared to the stomach of animals." M. G. Pavlov understands the soil in its development. The scientist's stated concepts on plant nutrition, the mutual influence of plant and soil, and the dynamic nature of the soil process are vivid and close to our modern understanding.

To fertilize the soil, according to M.G. Pavlov, means to make it more fertile. "Land fertilization" can be carried out with the aim of improving physical properties, eliminating acidity, or increasing soil fertility. The purpose of the latter, in his opinion, "is to multiply nutrients in the soil or, at least, to compensate for what is being extracted from the land by the plants growing on it through the use of organic fertilizer." M.G. Pavlov promoted a progressive system of crop rotation, pointing out the need to replace the three-field system that existed in Russia; he made proposals for the fundamental improvement of tillage, and in particular, he designed a special type of plough, which was named the "Pavlov plough"; he organized an agricultural school for the education of serf children. In the experimental farm he organized on previously waterlogged soil, he achieved high yields by employing drainage, liming, deepening of ploughing, manure and bone meal, gypsum application, and green manure (a mixture of vetch and buckwheat). His recommendations regarding the use of semi-decomposed manure have retained their significance to this day. He considered the main task of fertilizer application to be "...the correction of deficiencies in soils that do not possess all the qualities of fertile land."

Yaroslav Albertovich Linovsky (1818–1846) was a proponent of the widespread introduction of grass seeding and the application of fertilizers. In less than three years of his work at Moscow University, he published two major, unique works: "Conversations on Agriculture" (1845) and "A Critical Analysis of Scientists' Opinions on the Conditions of Soil Fertility with Application of a General Approach to Agriculture" (1846). In these works, he identifies the question of the conditions of soil fertility as the "essential subject" of agricultural science and practice. Y.A. Linovsky provides a critical analysis of theories on plant nutrition and soil fertility, starting from ancient Greek naturalists and ending with the agricultural chemistry schools of J. Liebig and J.B. Boussingault. He was the first to propose measures for various regions of Russia for the restoration, maintenance, and increase of soil fertility. He pointed out the need to develop irrigation and afforestation in the conditions of steppe agriculture and to carry out drainage measures in the non-chernozem zone; he compiled the first map of peatlands in the Moscow Governorate and outlined methods for their utilization.

Prominent scientists in the field of agricultural chemistry in the second half of the 19th century include D.I. Mendeleev, P.A. Ilyenkov, I.A. Stebut, A.N. Engelhardt, A.E. Zaykevich, P.A. Kostychev, A.V. Sovetov, and P.S. Kossovich.

Pavel Antonovich Ilyenkov (1821–1877) headed the Department of Organic and Agronomic Chemistry at the Petrovskoye Academy of Agriculture and Forestry from 1865 to 1875. In 1865, he developed a method for producing fertilizer by processing bones with alkalis, prepared a number of manuals on agronomic chemistry, translated his teacher J. Liebig's book "Chemistry in its Application to Agriculture and Physiology" into Russian, and taught a course in agronomic chemistry for 10 years. P.A. Ilyenkov was the first in Russia to introduce a course on agricultural analysis into the curriculum – the foundations of the methodology for agrochemical research.

Speaking of the quality of P.A. Ilyenkov's translation of J. Liebig's book "Chemistry in its Application to Agriculture and Physiology," A.N. Engelhardt (1863) wrote: "P.A. Ilyenkov enjoys well-deserved fame in Russian scientific literature; his scientific dissertation, his remarkable course on chemical technology, and his popular articles on natural science in 'Sovremennik' are highly valued. The name of P.A. Ilyenkov serves as a guarantee that the translation of J. Liebig's book has been done conscientiously and with complete expertise."

Grass seeding and green manure crops: how science replaced intuitive experience

A scientific approach to agriculture allows for increased yield where simple practical experience is powerless. In the period from 1826 to 1901, researchers theoretically justified the introduction of crop rotations, the sowing of legumes and cereal grasses, and began a systematic study of steppe chernozem soils. Perennial grasses began to be considered not just as a forage crop, but as a source for increasing soil fertility. A comparative analysis of domestic and European practices showed that scientific knowledge provides an agronomist with more reliable solutions than blindly following old recipes.

Another pressing problem was the constant removal of nutrients from fields along with grain and meat without their replenishment. To cover this deficit, researchers (1832–1893) proposed using alternative sources of plant nutrition — ash and bones — and developing green manuring. Special attention was paid to the northern regions, where the combination of phosphate rock powder and green manure (sideration) made it possible to cultivate vast areas of wastelands.

• Work of the agricultural department of the scientific society — about 30 years (since 1860)
• Joint soil research — 1885–1896 and 1898–1900
• Launch of the first phosphorite meal plants — 1868–1869

The organization of experimental work in the northern Non-Chernozem belt helped prove that plants absorb nutrients only in the form of specific, available chemical compounds. Surveys conducted on phosphorite deposits in four provinces led to the establishment of the first processing plants in 1868–1869 in two provinces and in the Baltic region. This laid the foundation for the large-scale application of mineral fertilizers.

Chemical land reclamation and theoretical foundations of plant nutrition

For the restoration of soil fertility, chemical land reclamation is of key importance. In the works of researchers (1833–1923), the mechanisms for the application of lime and gypsum were described in detail. It was proven that liming and gypsuming improve soil structure and make nutrients more available to crops. During the same period, the active development of agronomic education and the organization of experimental work began.

Simultaneously, the educational base was being formed. The first specialized department of agrochemistry functioned at the university in 1863–1872 under the leadership of its founder (1814–1903). And in 1904, the first Higher Women's Agricultural Courses opened, which made it possible to train professional personnel to work directly in the fields.

A fundamental basis for agrochemistry was provided by discoveries in the field of general chemistry (1834–1907). For the understanding of plant nutrition processes, the announcement of the discovery of the periodic law of chemical elements on January 17, 1869, became critically important. Also playing an important role was the defense of a doctoral dissertation on the mixture of alcohol with water on January 31, 1865, which served as the basis for the invention of vodka, and the publication of fundamental educational materials.

During this period, landmark works and textbooks were published that shaped the domestic agronomic school:

• textbook "Organic Chemistry" (1861);
• teaching aid "Principles of Chemistry" (part 1 in 1869, part 2 in 1871);
• book "Private Crop Science and Field Husbandry" (1888);
• journal "Russian Agriculture" (published in 1869–1870).

A major role also belongs to him in the development of agrochemistry. The scientist's name is associated with the first establishment of field experiments with mineral fertilizers in Russia. Over three years, experiments were conducted in the Smolensk, St. Petersburg, Moscow, and Simbirsk provinces using a unified methodology, which he viewed as a "special method of investigating soil composition." His thoughts on the production and application of fertilizers have not lost their significance to this day.

D.I. Mendeleev predicted in the development of agrochemistry, experimental work, and agricultural practice what was destined to begin implementation on a large scale only half a century after his agrochemical experiments. As early as 1866, while speaking at the Free Economic Society, he pointed out that the progress of agriculture is possible only on a solid scientific basis, consisting not only of theoretical knowledge and observations but also of data from direct, specially designed experiments.

When conducting experiments, he attached great importance to studying the physical and chemical properties of soils and fertilizers, the availability of nutrients for plants, and the development of effective preparation technologies and methods of fertilizer application. "By chemical analysis of the soil," the scientist wrote, "one must be able to judge the fertilizer and treatment necessary for the soil, just as it is possible to judge the method of extracting metal from ore by analyzing the ore..., just as one has been able to judge the properties of steel by analyzing steel. This task has still been little touched upon, although others may think of it differently."

He pointed out the necessity of simultaneously providing plants with all the essential elements, the list of which was already known, thus fully acknowledging the law of replaceability and equal significance of plant life factors. However, the analysis of soil in comparison with harvests convinced D.I. Mendeleev that soil fertility depends not so much on the total content of nutrient elements as on the presence of substances available to plants. To the latter, he attributed water-soluble salts and substances that dissolve in acids, even if weak, such as carbonic acid. This is why in the soil analyses conducted under the guidance of D.I. Mendeleev, primary attention was paid to the study of acid extracts.

Attaching great importance to the forms of nutrients and the soil, he distinguished effective soil fertility, calling it the "ripeness or maturity" of the soil, from potential fertility ("quantity of constituent parts"). D.I. Mendeleev did not forget about the enormous agronomic significance of physical properties of the soil, the influence of their mechanical composition and the presence of organic matter on them. He correctly evaluated the adsorption capacity of the soil as a factor preventing the leaching of cations, which remain (like potassium) available to plants. Even from a modern perspective, adsorbed potassium is the immediate reserve of potassium nutrition for plants.

Analyzing the results of experiments with fertilizers, he wrote: "Regarding the influence of various fertilizers taken for the experiment, the highest yield was obtained from the most complex fertilizer composed of manure, lime, ash, superphosphate, and horn shavings." He paid special attention to phosphate fertilizers. He repeatedly noted the role of nitrogen in poor soils as a necessary background for the effective action of phosphate fertilizers, which was subsequently confirmed by numerous experiments in the Non-Chernozem zone. The significance of the forms of phosphorus in the fertilizers themselves also did not escape D.I. Mendeleev's attention. He attached great importance to the presence of weak acids, particularly carbonic acid, in the soil solution as a factor promoting the conversion of water-insoluble and, therefore, unavailable for plants salt Ca3(PO4)2 into a form they can assimilate.

Promoting nitrogen fertilizers, D.I. Mendeleev ingeniously foresaw that eventually "a method will be found that allows the introduction of those conditions or substances into the earth that will force the inactive nitrogen of the air to turn into assimilable ammonia and nitric acid." And indeed, with the expansion of clover sowing and green manure, new methods of enhancing the fixation of atmospheric nitrogen in the field appeared, such as inoculation, nitraginization, and the application of free-living nitrogen fixers.

D.I. Mendeleev recommended potash fertilizers for those fields where rapid depletion of potassium salts is expected due to the lack of manure application or the cultivation of grasses and root crops. Specifically for Russia, which did not yet have its own potash salts, he recommended using ash, which is simultaneously a potash, phosphate, and lime fertilizer. Ash, which D.N. Pryanishnikov once called an "unrecognized Stassfurt," has not lost its significance for us, even after the discovery of the Solikamsk salts.

D.I. Mendeleev attached great importance to the application of organic fertilizers in increasing crop yields and soil fertility. "Manure," D.I. Mendeleev pointed out, "will never lose its significance, as it is the cheapest, most widely distributed, suitable for various crop rotations, and the most complete fertilizer in terms of the set of ash elements, which also improves the physical properties of the soil and replenishes the naturally occurring loss of organic matter in it." For Russia, which did not have its own chemical industry, he considered the use of manure a matter of primary importance and closely linked it to the development of livestock and forage crops. He was a convinced proponent of liming. He considered the most important reasons for the action of lime on non-chernozem soils to be: 1) systematic depletion of the soil of lime due to its leaching from the tilled layer by waters containing carbonic acid, 2) improvement of the physical properties of the soil under the influence of lime, 3) neutralization of excess acidity by lime, 4) improvement of conditions for nitrification in the soil during liming. "In summary, in my opinion," he wrote, "the influence of lime can be expressed by that imprecise but, for a practitioner who knows the land, understandable expression that it promotes soil maturity." For non-chernozem soils, he considered lime to be the "most appropriate... fertilizing agent." All the considerations provided about the nature of the action of lime and the national economic significance of liming are correct even from a modern point of view.

Touching upon the issue of fertilizer application, D.I. Mendeleev repeatedly emphasized that fertilizers must be evenly distributed in the ground so that roots find them in all directions. He also considered techniques for application at sowing, such as moistening the seed or mixing it with dry fertilizers, to be promising. He paid serious attention to fertilizer dosage: "...for each fertilizer, one must know its possible maximum and its minimum for profitability and not exceed it; otherwise, one might pay for it with a loss." D.I. Mendeleev developed a special program to determine the effectiveness of fertilizers in various regions of Russia. For this purpose, he established experimental stations in the St. Petersburg, Moscow, Smolensk, and Simbirsk provinces, i.e., he laid the foundations of the Geographical network of field experiments to clarify the patterns in the action of fertilizers across soil-climatic zones. Among Russian scientists, D.I. Mendeleev was the first to foresee the colossal benefits that soil fertilization could bring and was the first to predict that, over time, the question would arise of building an entire system of agriculture based on the application of fertilizers. We are witnesses to how the scientific system of fertilization, being part of a general system of measures to increase yields, is increasingly becoming a part of our domestic agriculture. D.I. Mendeleev specifically noted the importance of tillage as a factor in fertilizer effectiveness. In this regard, he wrote: "I rise against those who preach in print and verbally that it is all about the fertilizer, that by fertilizing well, one can plough anyhow."

Nikolay Eustafievich Lyaskovsky (1839–1893) was a student of J. Liebig. He began his scientific and pedagogical career by organizing a soil-chemical laboratory at the Department of Agricultural Chemistry of Moscow State University. This was a significant event in the life of the department; it became possible to conduct experimental work. N. E. Lyaskovsky was the first to establish that the protein content in wheat grain increases as one moves from the North-West to the South-East of the European part of Russia. His master's thesis "On the Chemical Composition of Wheat Grain" and his doctoral thesis "On the Germination of Pumpkin Seeds in Chemical Respect" have not lost their scientific significance even today.

Gavriil Gavrilovich Gustavson (1842–1908), from 1875, succeeding P. A. Ilyenkov, headed the Department of Organic and Agronomic Chemistry at the Petrovskaya Academy. He compiled the first curriculum for the course of agronomic chemistry and wrote the book "Twenty Lectures on Agronomic Chemistry," which represents a complete course in agricultural chemistry. In the first lecture, G. G. Gustavson discusses the origins of the mineral constituent of soil. The second and third lectures are devoted to the role of plants in soil formation. The fourth and fifth lectures describe the conditions for nitrate formation in the soil. The sixth and seventh lectures are devoted to humus. After examining the origin and composition of the mineral and organic parts of soil, G. G. Gustavson, in the eighth and ninth lectures, explains issues related to their absorptive capacity. The eleventh and twelfth lectures of the book are devoted to the chemical analysis of soil. All matters related to fertilizers are set out in the thirteenth lecture. G. G. Gustavson devotes the fourteenth and fifteenth lectures to "fertilizers with a predominant content of lime phosphate." To these, he mainly refers phosphorites and bones. Issues regarding the nitrogen cycle in nature and mineral nitrogen fertilizers are addressed by G. G. Gustavson in the sixteenth and seventeenth lectures of his book. The eighteenth lecture is devoted to potash fertilizers. The last two lectures – the nineteenth and twentieth – are dedicated to analytical methods for investigating animal feed and food substances, as well as the composition and analysis of milk and butter. Of undoubted interest is also the appendix "On the Chemical Role of Mineral Salts in Organic Nature," which G. G. Gustavson delivered as an inaugural speech at the Petrovskaya Academy on November 21, 1881.

Chernozem soils, despite their high humus content, respond excellently to the application of mineral fertilizers. The practical basis for this was local row application of superphosphate — this method was first successfully tested on sugar beet crops. The efficiency of such nutrition depends directly on the cultivar characteristics of the plants, the depth of ploughing, and the quality of fallow field tillage. These principles were experimentally proven in the period from 1842 to 1931.

In arid regions, mineral nutrition becomes an important factor in preserving the harvest. During the research period of 1851–1914, the causes of drought were studied in detail, and practical measures for combating it were developed. Based on the results of the analysis of the severe drought of 1891–1892, published in 1893 and 1894, a comprehensive approach was proposed. To protect crops, an agronomist must:

• perform deep ploughing;
• maintain soil structure to support optimal water and nutrient regimes;
• apply mineral fertilizers to increase plant drought resistance.

Nitrogen metabolism, dissolution of phosphorites, and rules for working with organic matter

Agronomic analysis of plant material allows for precise calculation of a crop's nutritional needs. The basic chemical patterns of this analysis were developed in the period of 1861–1938. During this period, normal limiting glycols, unsaturated alcohols, and their isomeric oxides were obtained. Also, the effect of N₂O₅ on unsaturated hydrocarbons was experimentally studied, yielding nitrogen esters of glycols and products of the addition of N₂O₃, N₂O₄, and N₂O₅, and methylcyclopropane was obtained for the first time. Furthermore, the process of amine rearrangement with a change in the cycle by 1 carbon atom was described, and all methods for the analysis of plant material were compiled into a practical guide in 1923.

Research from 1862–1915 shed light on the mechanisms of nitrogen and phosphorus nutrition. It was proven that grain legumes are capable of assimilating molecular nitrogen only through roots bearing nodules. Regarding mineral nutrition, it was established that plants in sterile cultures can assimilate ammonium cations directly, without their prior conversion into nitric acid anions.

To increase the efficiency of phosphorus fertilizers, it is important to utilize the natural mechanisms of plants. The acidic root exudates of lupin and buckwheat are capable of independently dissolving and assimilating hard-to-reach phosphorites. For other crops, a similar effect is achieved through the combined application of phosphorites with acidic ammonium fertilizers.

To prevent clover sickness of the soil, it is necessary to keep records of nutrient intake and removal in dynamics, as well as to monitor the cycle of sulfur and chlorine. Maintaining soil fertility is supported by the application of fertilizers and soil conditioners, taking into account the gross chemical composition of chernozems. The practical foundations of these processes were set out in scientific works on soil science in 1911 and 1912.