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Agrochemistry and Soil Science

HISTORY OF SOIL SCIENCE

From Wikipedia, the free encyclopedia

The history of soil science began from the contributions of chemist Justus von Liebig. It also includes the work of other scientists like Vasily V. Dokuchaev, Curtis F. Marbut, Hans Jenny, and Guy Smith.

Justus von Liebig

The early concepts of soil were based on ideas developed by a German chemist, Justus von Liebig (1803–1873), and modified and refined by agricultural scientists who worked on samples of soil in laboratories, greenhouses, and on small field plots. The soils were rarely examined below the depth of normal tillage. These chemists held the "balance-sheet" theory of plant nutrition. Soil was considered a more or less static storage bin for plant nutrients – the soils could be used and replaced. This concept still has value when applied within the framework of modern soil science, although a useful understanding of soils goes beyond the removal of nutrients from soil by harvested crops and their return in manure, lime, and fertilizer.

The early geologists generally accepted the balance-sheet theory of soil fertility and applied it within the framework of their own discipline. They described soil as disintegrated rock of various sorts – granite, sandstone, glacial till, and the like. They went further, however, and described how the weathering processes modified this material and how geologic processes shaped it into landforms such as glacial moraines, alluvial plains, loess plains, and marine terraces. Geologist N. S. Shaler's (1841–1906) monograph (1891) on the origin and nature of soils summarized the late 19th century geological concept of soils.

Early soil surveys were made to help farmers locate soils responsive to different management practices and to help them decide what crops and management practices were most suitable for the particular kinds of soil on their farms. Many of the early workers were geologists because only geologists were skilled in the necessary field methods and in scientific correlation appropriate to the study of soils. They conceived soils as mainly the weathering products of geologic formations, defined by landform and lithologic composition. Most of the soil surveys published before 1910 were strongly influenced by these concepts. Those published from 1910 to 1920 gradually added greater refinements and recognized more soil features but retained fundamentally geological concepts.

The balance-sheet theory of plant nutrition dominated the laboratory and the geological concept dominated field work. Both approaches were taught in many classrooms until the late 1920s. Although broader and more generally useful concepts of soil were being developed by some soil scientists, especially E.W. Hilgard (1833–1916) and G.N. Coffey (George Nelson Coffey) in the United States and soil scientists in Russia, the necessary data for formulating these broader concepts came from the field work of the soil survey.

V.V. Dokuchaev

The scientific basis of soil science as a natural science was established by the classical works of Dokuchaev. Previously, soil had been considered a product of physicochemical transformations of rocks, a dead substrate from which plants derive nutritious mineral elements. Soil and bedrock were in fact equated.

Dokuchaev considers the soil as a natural body having its own genesis and its own history of development, a body with complex and multiform processes taking place within it. The soil is considered as different from bedrock. The latter becomes soil under the influence of a series of soil-forming factors: climate, vegetation, country, relief and age. According to him, soil should be called the "daily" or outward horizons of rocks regardless of the type; they are changed naturally by the common effect of water, air and various kinds of living and dead organisms. (Source: Krasil'nikov, N.A. (1958) Soil Microorganisms and Higher Plants)

Beginning in 1870, the Russian school of soil science under the leadership of V.V. Dokuchaev (1846–1903) and N.M. Sibirtsev (1860–1900) was developing a new concept of soil. The Russian workers conceived of soils as independent natural bodies, each with unique properties resulting from a unique combination of climate, living matter, parent material, relief, and time. They hypothesized that properties of each soil reflected the combined effects of the particular set of genetic factors responsible for the soil's formation. Hans Jenny later emphasized the functionally relatedness of soil properties and soil formation. The results of this work became generally available to Americans through the publication in 1914 of K.D. Glinka's textbook in German and especially through its translation into English by C.F. Marbut in 1927.

The Russian concepts were revolutionary. Properties of soils no longer were based wholly on inferences from the nature of the rocks or from climate or other environmental factors, considered singly or collectively; rather, by going directly to the soil itself, the integrated expression of all these factors could be seen in the morphology of the soils. This concept required that all properties of soils be considered collectively in terms of a completely integrated natural body. In short, it made possible a science of soil.

The early enthusiasm for the new concept and for the rising new discipline of soil science led some to suggest the study of soil could proceed without regard to the older concepts derived from geology and agricultural chemistry. Certainly the reverse is true. Besides laying the foundation for a soil science with its own principles, the new concept makes the other sciences even more useful. Soil morphology provides a firm basis on which to group the results of observation, experiments, and practical experience and to develop integrated principles that predict the behavior of the soils.

C. F. Marbut

Under the leadership of C. F. Marbut, the Russian concept was broadened and adapted to conditions in the United States.This concept emphasized individual soil profiles to the subordination of external soil features and surface geology. By emphasizing soil profiles, however, soil scientists at first tended to overlook the natural variability of soils which can be substantial even within a small area. Overlooking the variability of soils seriously reduced the value of the maps which showed the location of the soils.

Furthermore, early emphasis on genetic soil profiles was so great as to suggest that material lacking a genetic profile, such as recent alluvium, was not soil. A sharp distinction was drawn between rock weathering and soil formation. Although a distinction between these sets of processes is useful for some purposes, rock and mineral weathering and soil formation are commonly indistinguishable.

The concept of soil was gradually broadened and extended during the years following 1930, essentially through consolidation and balance. The major emphasis had been on the soil profile. After 1930, morphological studies were extended from single pits to long trenches or a series of pits in an area of a soil. The morphology of a soil came to be described by ranges of properties deviating from a central concept instead of by a single "typical" profile. The development of techniques for mineralogical studies of clays also emphasized the need for laboratory studies.

Marbut emphasized strongly that classification of soils should be based on morphology instead of on theories of soil genesis, because theories are both ephemeral and dynamic. He perhaps overemphasized this point to offset other workers who assumed that soils had certain characteristics without examining the soils. Marbut tried to make clear that examination of the soils themselves was essential in developing a system of Soil Classification and in making usable soil maps. In spite of this, Marbut's work reveals his personal understanding of the contributions of geology to soil science. His soil classification of 1935 depends heavily on the concept of a "normal soil," the product of equilibrium on a landscape where downward erosion keeps pace with soil formation.

Clarification and broadening of the concept of a soil science also grew out of the increasing emphasis on detailed soil mapping. Concepts changed with increased emphasis on predicting crop yields for each kind of soil shown on the maps. Many of the older descriptions of soils had not been quantitative enough and the units of classification had been too heterogeneous for making yield and management predictions needed for planning the management of individual farms or fields.

During the 1930s, soil formation was explained in terms of loosely conceived processes, such as "podzolization," "laterization," and "calcification." These were presumed to be unique processes responsible for the observed common properties of the soils of a region.

Hans Jenny

In 1941 Hans Jenny's (1899–1992) Factors of Soil Formation, a system of quantitative pedology, concisely summarized and illustrated many of the basic principles of modern soil science to that date. Since 1940, time has assumed much greater significance among the factors of soil formation, and geomorphological studies have become important in determining the time that soil material at any place has been subjected to soil-forming processes. Meanwhile, advances in soil chemistry, soil physics, soil mineralogy, and soil biology, as well as in the basic sciences that underlie them, have added new tools and new dimensions to the study of soil formation. As a consequence, the formation of soil has come to be treated as the aggregate of many interrelated physical, chemical, and biological processes. These processes are subject to quantitative study in soil physics, soil chemistry, soil mineralogy, and soil biology. The focus of attention also has shifted from the study of gross attributes of the whole soil to the co-varying detail of individual parts, including grain-to-grain relationships.

Guy Smith

In both the classification of Marbut and the 1938 classification developed by the U.S. Department of Agriculture, the classes were described mainly in qualitative terms. Classes were not defined in quantitative terms that would permit consistent application of the system by different scientists. Neither system definitely linked the classes of its higher categories, largely influenced by genetic concepts initiated by the Russian soil scientists, to the soil series and their subdivisions that were used in soil mapping in the United States. Both systems reflected the concepts and theories of soil genesis of the time, which were themselves predominantly qualitative in character. Modification of the 1938 system in 1949 corrected some of its deficiencies but also illustrated the need for a reappraisal of concepts and principles. More than 15 years of work under the leadership of Guy Smith culminated in a new soil classification system. This became the official classification system of the U.S. National Cooperative Soil Survey in 1965 and was published in 1975 as Soil Taxonomy: A Basic System of Soil Classification for Making and Interpreting Soil Surveys. The Smith system was adopted in the U.S. and many other nations for their own classification system.

Another factor has had an immense impact on soil survey, especially during the 1960s. Before 1950, the primary applications of soil surveys were farming, ranching, and forestry. Applications for highway planning were recognized in some States as early as the late 1920s, and soil interpretations were placed in field manuals for highway engineers of some States during the 1930s and 1940s. Nevertheless, the changes in soil surveys during this period were mainly responses to the needs of farming, ranching, and forestry. During the 1950s and 1960s nonfarm uses of the soil increased rapidly. This created a great need for information about the effects of soils on those nonfarm uses.

Bioturbation

A major re-evaluation of soil formation and the role of biota commenced in the 1980s, as soil-geomorphologists began to re-evaluate Charles Darwin's and Nathaniel Shaler's early ideas on the role of bioturbation in soil formation. There is now ample evidence to support Darwin's conclusions, and in many areas biota that burrow in soil are major agents of pedogenesis.

DARWIN, CHARLES ROBERT

Darwin was born on February 12, 1809 on the same day that Abraham Lincoln was born in Kentucky. He was the son of a doctor and the grandson of the poet-doctor, Erasmus Darwin.

Darwin showed no particular promise in his youth. At first he studied medicine, but found that unlike his father and grandfather he had no ability for it. He thought next that he would make a carrier in the church but found he had no ability for that either. However, he had made natural history his hobby after reading Humboldt and had grown gradually more interested in the subject during his stay in Cambridge. This was his road to fame. His first scientific work was taking part in a geologic expedition led by Sedwick.

The ship Beagle was about to set out for a voyage of scientific exploration in 1831 and Darwin took part in the voyage as the ship's naturalist. Off he went on a five-year cruise around the world, the most important voyage in the history of geology.

During the voyage of the Beagle, Darwin watched how species changed, little by little, as the ship moved down the coast of South America. Most important of all were his observations during a five-week stay of the animal life of the Galapagos Islands, a group of a dozen or so islands about six hundred and fifty miles off the coast of Ecuador. What Darwin mainly studied there was a group of birds now called "Darwin's finches".

These finches were closely similar in many ways but were divided into at least fourteen species. Not one of these species lived on the nearby continent, or, as far as was known, anywhere else in the world.

But what would cause those evolutionary changes?

Darwin returned to England in 1836 with no answer. He wrote several books on the voyage and the observations he had made. The first of these now usually known as A Naturalist's Voyage on the Beagle, was a great success and made him famous.

Soon he joined the Geological Society of London and was its secretary. There he met the well-known naturalist Lyell and discussed the problem of evolution with him. These discussions helped Darwin to understand that creatures would adapt themselves to different ways of life under the stress of evironmental pressure. Thus nature would select one group over another and by such "natural selection" life would branch out into infinite variety, more efficient groups always replacing less efficient ones in particular environmental conditions.

Darwin used to classify and collect his information endlessly. In 1844 he started a book on the subject, but continued to collect his examples and in 1858 he was still working at it.

His friends knew what he was doing and Lyell in particular was constantly telling him to publish his book, for evolutionary ideas were in the air, and he was right. Another naturalist, Wallace, wrote a paper, embodying Darwin's ideas almost to a letter and then sent a copy to none other than Darwin himself. When Darwin received the manuscript he was thunderstruck". However, he was an ideal scientist. He didn't publish quickly to be the first in discovering the idea of evolution. He passed on Wallace's work to other important scientists and offered to collaborate with Wallace on papers summarizing their mutual conclusions. This was done. The work of both men appeared in the Journal of the Linnaean Society in 1858 and the next year Darwin published his book, the full title of which is "On the Origin of Species by Means of Natural Selection". It is usually known as "The Origin of Species".

The learned world was waiting for the book. Only 1,250 copies were printed and everyone was sold on the first day of publication. It went through printing after printing, and it is still being reprinted now, a century later. It is one of the classics of science.

Darwin died in 1882 and was buried among England's heroes and near Newton and Faradey, as well as his friend Lyell.

VARIATIONS IN ORGANISMS

Darwin brought back from his scientific travels the conception that plant and animal species are not constant but subject to variation. In order to make further researches along these lines after his return home there was no better field available than that of breeding of animals and plants. Darwin found that this breeding produced artificially, among animals and plants of the same species, differences greater than those found in what are generally recognized as different species. Thus was established, on the one hand, the variability of species, and on the other, the possibility of a common ancestry for organisms with different specific characteristics.

Darwin then investigated whether there were not possibly causes in Nature which would in the long run¹ produce in living organisms changes similar to those produced by artificial breeding. He discovered these causes in the disproportion between the immense number of germs² created by Nature and the insignificant number of organisms which actually attain maturity. But as each germ strives to develop, there necessarily arises a struggle for existence. And it is evident that in this struggle those individual organisms which have some particular characteristic, however insignificant, which gives them an advantage in the struggle for existence will have the best prospect of reaching maturity and propagating themselves. Those individual organisms which do not possess these characteristics succumb more easily in the struggle for existence and gradually disappear. In this way a species is established through natural selection, through the survival of the fittest.

Notes and Commentary

¹ – in the long run – з часом

² – germ – зародок, ембріон; зав’язь

SOIL: ECOLOGICAL ASPECT

Soil is a mixture of humus, decayed organic matter, and particles of weathered rock, sand, silt, and clay. Clay is perhaps the most important component of soil because it helps hold water in the soil and containes many minerals required by plants for growth. The types of minerals found in clays are largerly dependent on the climate. Humus is equally important because it helps separate clay and sand partcles, allowing more water and air to enter the soil. It also provides food for soil organisms, as well as minerals for plants.

The kind of soil (determined by varying mineral contents, nutrients, and amounts of water) helps determine the organisms that live there. Roses and asparagus grow in different types of soil. Prairie dogs and earthworms live in different types of soil. Specialized grasses and ground covers grow best in specific soil types.

Some herd animals such as cattle change the physical environment when they overgraze. Overgrazing results in the destruction of plant life, which in turn changes the soil. Without plants, soil will erode and the ecosystem will change. Humans are responsible for changes in the ecosystem.

PROSPECTING WITH PLANTS

One day in the summer of 1959, geologist Helen Cannon was returning home after a day's field work on the Colorado Plateau, USA. Stopping to rest a moment, she let her horse to eat some grass growing along the road. Shortly afterward the animal died. Mrs. Cannon collected some of the grass that caused her horse die and asked a chemist to analyse it. It was found to be rich in selenium, a highly poisonous metallic element. Mrs. Cannon learned why her horse died. But she learned also a more interesting fact, for she knew that selenium usually lies together with uranium. And so a valuable deposit of uranium was found near the place where the grass had grown.

This incident shows that mineral deposits can be found by using plants.

The use of plants in looking for minerals is called botanical prospecting. It can be done by one of three methods. First, analyse the chemical composition of plants to find the minerals. Second, map the places of growth of particular species of plants – indicator plants – that grow only in soil that is rich in this or that mineral. And third, note changes that are made by certain soil minerals in the size or form of plants.

Why not just analyse the soil, then? This method is not always good. One sample of soil may differ fully of the soil over a wide area. A plant, on the other hand, sends roots down into the soil. It absorbs minerals from a large part of ground together with water which contains minerals in solution¹. In this way minerals become concentrated in the plant.

The first who used botanical prospecting was the Russian scientist S.M. Tkalitch in 1938. He used the first and the second methods in looking for deposits of iron-containing minerals in eastern Siberia. He found that grasses growing above iron deposits contain iron.

Today it is common to have a geobotanist, a man trained in both geology and botany, the science of plants, in every geological expedition. Botanical prospecting has been used here in looking for deposits of boron, nickel, cobalt, iron, chromium and molybdenum.

The use of indicator plants is the simplest botanical prospecting method. No chemical analysis is necessary. Nor a detailed knowledge is needed of how various minerals affect the size or form of plants. Where indicator plants are present, a prospector needs only make a map of their distribution to find possible mineral-rich areas.

Since the time when Helen Cannon's horse died from eating selenium containing grass the United States govern ment, too, has begun botanical prospecting studies. Scientists are beginning to understand that this technique can open up to prospectors large areas of the world now hidden² in forests or tropical jungles.

Notes and Commentary

¹ solution - розчин

² hidden - прихований

GREEN FACTORIES

Every green plant is a "factory". It's a sugar "factory". It works from early day to dark every day, even on Sunday.

The plant must have two things for making sugar: water and carbon dioxide. Carbon dioxide comes from the air. It is one of the gases the air is made of. Water comes from the ground.

As soon as water from the ground gets to a leaf it goes all over the leaf. Water and carbon dioxide are put together to make sugar. Most factories run on electricity. The green factories run on sunshine.

After the plant has made sugar, it makes the other kinds of food it needs.

Without green plants there wouldn't be any sugar or any other food for men and animals. Green plants are the world's most important "factories".

 

DO YOU KNOW THAT...

... The sunflower came from Central America? As Incas were sunworshippers they reproduced this flower everywhere. They made different decorations in the form of a sunflower and even their flags were in the form of a sunflower.It was a very popular flower at one time, but by the end of the 17th century, had rather gone out of fashion.

Most people when they first see a sunflower, however, are amazed at its size. Not only is it very tall, but its actual flowers are very large, compared with the flowers of other plants. One in the Royal Gardens at Madrid was supposed to have reached a height of 24 ft,, and one in Padua, Italy, a height of 40 ft.

Sunflowers are very useful plants. Their petals produce a yellow dye. The leaves make excellent food for livestock. The most valuable parts of sunflowers, however, are the seeds. As many as 2,362 seeds have been once in a single head. They are rich in protein and calcium and are used for making edible oil for margarine and also artists colours.

... Primula is the name of one genus of the Primulaceae family sometimes known as the primrose family. There are three wild species which grow in Great Britain and these are the primrose, the cowslip and the oxslip.

The primrose is supposed to have been the favourite flower of Benjamin Disraeli, who was Britain's Prime Minister in the 19th century, and it is said that Queen Victoria often gave him these beautiful yellow flowers. When he died, in April 1881, the Queen sent primroses to his funeral. Later Primrose Day was set up. This was celebrated on April 19th, the day of his death. On that day primroses were laid on his statue in Parliament Square.

The generic word "primula" is a corruption of the French "primeverole" and the Italian "primeverola". Both these words came from the Latin "prima vera" and mean "the first flower of spring".

CEREAL CROPS

Cereal crops, and wheat in particular, are grown on a large territory in Ukraine.Ukrainian selectionists have made real efforts to raise new, hardy strains of wheat, the best of which are Besosta-1, Saratovska-29, and Myronivska-808. This is hard-grained wheat which has great germinating force¹ and high yields – 40–50 centners per hectare. Now, the scientists have developed new, even more productive varieties of wheat – the Avrora, Kavkaz and Myronivska-Yuvileina. The winter strain of the Myronivska-Yuvileina wheat yielded 100,3 centners per hectare.

Rye is also grown on vast areas. Groat cereals and leguminous plants² occupy vast tracts – mostly in the Crimea. As to rice, it needs a lot of moisture. Plans are afoot³ for the costruction of large irrigation systems to supply water to rice fields.

Maize is popular in Ukraine as well. New varieties of hybrid maize have been adapted to various climatic and soil conditions.

The crop-producing power⁴ of grain, especially wheat, is being investigated at various research institutes and at a great number of strain testing stations⁵, and farms.

Notes and Commentary

¹ germinating force - схожість

² groat cereals and leguminous plants - круп'яні і бобові культури

³ plans are afoot - розробляються плани

⁴ the crop-producing power - врожайність зерна

⁵ strain testing station - сортовипробувальна станція

WHEAT IN THE USA

Most of wheat in the United States is produced in the Great Plains area¹. A considerable amount of it is grown in other areas of the country. In fact, wheat is grown in every state of the country except in the deep South. Kansas, the leading state, produces approximately 18 per cent of the total wheat grown in the USA.

Wheat will grow on a wide range of soil types, but well-drained, medium- and fine-textured soils are generally considered to be best adapted for wheat production. Deep sandy soils usually do not produce satisfactory yields of high-quality wheat. These soils are better adapted to rye and some other crops.

To improve the soil for wheat one should apply both manure and commercial fertilizers when needed.

On dark-coloured soils containing a sufficient amount of nitrogen to produce a good growth of straw, superphosphate can be used to increase the yield of wheat when moisture is not a limiting factor in plant development. The rate of application may vary from 100 to 200 pounds per acre, depending upon the fertility of the soil. On light-coloured soils which are low in organic matter, a mixed fertilizer containing nitrogen will increase the rate of plant growth which may be important when the crop is to be used for winter or early-spring pasture.

The yield of wheat is greatly affected by the amount of moisture in the soil at the time the crop is seeded. In the wheat area of the USA the amount of rain that falls during the growing season is often not sufficient to produce a good yield of grain. It is essential, therefore, under such conditions that the soil be well supplied with moisture at the time the crop is seeded.

Fall plowing as soon after harvest as possible is generally recommended for both winter and spring wheat varieties. The fall-plowed land for spring wheat is usually left rough during the winter season to accumulate snow.

Depth of plowing seems to be less important than time of plowing. The depth necessary to obtain best results will vary with soil and climatic conditions but will usually be not more than 6 or 7 inches.

Since young spring wheat plants can withstand cold or freezing weather there is no danger from low temperatures when seeding is done early. Both wheats do best, having been sown early.

The best rate of seeding for the Eastern part of the Great Plains area is 60 to 90 pounds per acre for either spring or winter wheat. However, farther to the West, as moisture becomes a limiting factor, only about 30 to 45 pounds should be used. Where the land is irrigated, in the Western states, for example, 50 to 80 pounds are considered to be the best rate. These rates should be increased a little when wheat is seeded late because late seeding usually results in poor tillering².

Better results are known to be obtained by seeding wheat with the drill³. Broadcasting is no longer used in most countries. The drill provides a uniform distribution of seed. It also places the seed at a uniform depth and covers it with the soil.

Wheat may be harvested with the binder, the header, or the combine harvester. At present wheat is combined almost everywhere in the Plains area.

The moisture content of the grain should be not more than 14 per cent at the time of harvesting. If the grain is stored at a higher moisture content, it can be damaged by heat.

Wheat straw is usually used for bedding⁴. If the straw is not needed for this purpose, it should be returned to the land to increase the organic content of soil.

Notes and Commentary

¹ Great Plains area – район Великих Рівнин

² tillering – кущіння

³ drill – рядова сіялка

⁴ bedding – підстилка