Introduction to Soil Chemistry

Analysis and Instrumentation

Alfred R. Conklin, Mark F. Vitha

• Publisher: Wiley
• Year: 2013
• ISBN:
  9781118773314
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Industrial & Technical Chemistry

Provides the tools needed to explore the incredible complexities of the earth's soils

Now in its Second Edition, this highly acclaimed text fully equips readers with the skills and knowledge needed to analyze soil and correctly interpret the results. Due to the highly complex nature of soil, the author carefully explains why unusual results are routinely obtained during soil analyses, including the occurrence of methane in soil under oxidative conditions. The text also assists readers in developing their own analytical techniques in order to analyze particular samples or test for particular compounds or properties.

The Second Edition of Introduction to Soil Chemistry features four new chapters. Moreover, the entire text has been thoroughly updated and revised. It begins with a review of the history of soil chemistry, introducing fundamental concepts that apply to all soils. Next, the text explores:

• Basic soil characteristics, horizonation, texture, clay, air, water, solids, organic matter, organisms, and fundamental chemical concepts essential to soil chemistry
• Tested and proven sampling techniques for soil analysis that provide reliable analytical results
• Basic soil measurement techniques and extraction procedures
• Instrumentation to isolate and identify soil chemicals, including plant nutrients and contaminants

Detailed examples and figures throughout the text help readers successfully perform soil sampling and analytical methods as well as better understand soil's chemical characteristics. At the end of each chapter, a bibliography and list of references lead to additional resources to explore individual topics in greater depth. Each chapter also offers problem sets, encouraging readers to put their newfound skills into practice.

Reflecting the latest research findings and best practices, the Second Edition of Introduction to Soil Chemistry is ideal for both students and soil chemists who want to explore the incredible complexities of the earth's soils.

CHAPTER 1

Summary of the History of Soil Chemistry

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1.1 The 19th Century

1.2 The End of the 19th and the Beginning of the 20th Century

1.3 The 20th Century

1.4 The End of the 20th and the Beginning of the 21st Century

1.5 Conclusion

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Soil is essential to life. All life supporting ingredients derive, either directly or indirectly, from soil. Plants growing in soil are directly used for food or are fed to animals, which are then used for food. These same plants take in carbon dioxide produced by animals and give off oxygen. Soil and the plants it supports moderate the amount of liquid and gaseous water in the environment by serving as a reservoir controlling its movement. Elements essential to life, even life in water, are released from soil solids and are recycled by soil chemical and biologically mediated reactions. Thus, an understanding of soil characteristics, the chemistry occurring in soil, and the chemical and instrumental methods used to study soil is important.

As the field of chemistry developed, so did the interest in the chemistry of soil. This was natural because the early chemists extracted elements from geological sources and, in the broadest sense, from soil itself. In fact, the development of the periodic table required the extraction, isolation, and identification of all of the elements, many of which are found abundantly in soil.

The total elemental composition of different soils was studied for some time. This involved a great deal of work on the part of chemists because methods for separating and identifying the elements were long and complicated. As knowledge accumulated, the relationship between the elements found in plants and those found in soil became of greater interest. This was sparked by an interest in increasing agricultural productivity.

At the end of the 19th and beginning of the 20th century, much of the theoretical work and discoveries that would be necessary for the further development of soil chemistry were in place. This included the fundamental scientific basis for various types of instrumentation that would be necessary to elucidate more fully the basic characteristics and chemistry of soil.

Toward the end of the 20th and into the 21st century, basic knowledge of soil chemistry was well developed, although much was and still is not understood. Instrumentation had matured and had been married to computers providing even more powerful tools for the investigation of chemistry in general and soil chemistry in particular. Instruments were being combined sequentially to allow for both separation and identification of components of samples at the same time. Instrumentation that could be used in the field was developed and applied.

A time line for discoveries, development of ideas, and instrumentation essential for our present-day understanding of soil chemistry is given in Table 1.1. It is interesting to note that, in some cases, it took several years to develop ideas and instrumentation for studying specific components of soil, such as ions and pH, and to apply them to soil chemistry. In other cases, such as visible and ultraviolet spectroscopy, application was almost immediate. Although tremendous strides have been made in the development of some instrumentation, such as nuclear magnetic resonance (NMR), it is still in its infancy with regard to application to soil chemistry.

TABLE 1.1. Time Line for the Development of Ideas and Instrumentation Essential to the Understanding of Soil Chemistry

19th Century
1800	Discovery of infrared light—Herschel
1835	Spectrum of volatilized metal—Wheatstone
1840	Chemistry and its application to agriculture—Liebig
1855	Principle of agricultural chemistry with special reference to the late researches made in England—Liebig
1852	On the power of soils to absorb manure—Way
1860	Spectroscope—Kirchoff and Bunsen
1863	The natural laws of husbandry—Liebig
End 19th Beginning 20th Century
1895	X-rays—Röntgen
1897	Existence of electron—Thomson
1907	Lectures describing ions—Arrhenius
1909	pH scale—Sörenson
1913	Mass spectrometry—Thompson
1933	Electron lens—Ruska
1934	pH meter—Beckman
20th Century
1940	Chromatography (described earlier but lay dormant until this time)—Tswett
1941	Column chromatography—Martin and Synge
1945	Spin of electron (leads to NMR spectroscopy)—Pauli
1959	Hyphenated instrumentation GC-MS

Sources:

Coetzee JF. A brief history of atomic emission spectrochemical analysis, 1666–1950. J. Chem. Edu. 2000; 77: 573–576.

http://www.nndb.com. Accessed June 3, 2013.

http://www.nobelprize.org/nobel_prizes/physics/laureates/1945/pauli-bio.html. Accessed May 28, 2013.

Gohlke RS. Time-of-flight mass spectrometry and gas-liquid partition chromatography. Anal. Chem. 1959; 31: 535–541.

1.1 The 19th Century

The 19th century is considered the century of the beginnings of the application of chemistry to the study of soil. However, foundations for these advances had been laid with the discoveries of the previous century. Antoine-Laurent de Lavoisier, Joseph Priestley, and John Dalton are well-known scientists whose discoveries paved the way for the developments in agricultural chemistry in the 19th century [1,2].

At the end of the 18th century and the beginning of the 19th, Joseph Fraunhofer invented spectroscopy. At that time, spectroscopy was largely used to investigate the spectra of stars [3]. William Herschel discovered infrared radiation that would later be used in infrared spectroscopy to investigate soil organic matter. Also in the early part of the 19th century, Sir Charles Wheatstone was actively investigating electricity. His most prominent work involved the development of the telegraph. But he also invented the Wheatstone bridge, which would become an important detector for chromatography. A lesser known observation was of the spectrum of electrical sparks, which he attributed to vaporized metal from the wires across which the spark jumped. These were important steps in the eventual development of spectrographic methods of studying metals, especially metals in soil [4].

The result of 19th century chemical analysis of soil was twofold. The soil was found to be largely made up of a few elements among which were silicon, aluminum, iron, oxygen, nitrogen, and hydrogen. The second result was that different soils largely had the same elemental composition. Along with this were the investigations of the elemental content of plants and the relationship between those elements found in soil and those found in plants [5]. As these investigations advanced, it became evident that the inorganic components in soil were essential to plant growth and that crop production could be increased by increasing certain mineral components in soil. It did not take too long to determine that ammonia, phosphorous, and potassium are three essentials that, when added to soil, increase plant productivity. At this early point, chemists were largely interested in studying changes in and the activities of nitrogen, phosphorus, and potassium in soil. Two things about these components were discovered. One was that they needed to be soluble to be used by plants, and the second was that not all forms were available to plants.

Although observations about agriculture in general and soils specifically had been made for centuries, it was the chemist Justus von Liebig who is generally credited with the beginnings of the application of chemistry to the systematic study of soils. That beginning is usually dated as 1840, when Liebig published his book titled Chemistry and Its Application to Agriculture. This was followed by Principles of Agricultural Chemistry with Special Reference to the Late Researches Made in England, published in 1855, and The Natural Laws of Husbandry, published in 1863.

Three ideas either developed by Liebig or popularized by him are the use of inorganic fertilizers, the law of the minimum, and the cycling of nutrients, which foreshowed the present-day concern for sustainability. One interesting aspect of this is the fact that Liebig is generally cited as being an organic chemist, while his work on soil chemistry, if not wholly inorganic, at least is largely based on or revolves around the characteristics and use of inorganic chemicals. Perhaps Liebig's involvement could be attributed to the fact that during this time, it was widely thought that organic matter was the most important constituent needed for plant growth, that is, that plants got their nutrients directly from the organic matter or humus in soil.

In the middle of the 19th century, Liebig espoused the idea that fields could be fertilized with inorganic compounds and salts, particularly those of phosphate [6]. In addition, other chemicals needed by plants and frequently mentioned by Liebig are sulfuric acid, phosphoric acid, silicic acid, potash, soda, lime, magnesia, iron, chloride of sodium, carbonic acid, and ammonia [7].

During this time, both organic and inorganic materials added to soil were called manure and exactly what was being added is sometimes confusing. Both organic manure from any source and inorganic compounds and salts added to the soil to increase yields were referred to as manures.

Today, manure refers to excretory products of animals and finds its most common usage in reference to farm animals. This organic material was and is used as fertilizer to provide necessary elements for plants. In the past, it was practically the only material readily available for increasing plant or crop production. The general idea, however, is to add something to soil that will improve plant production. Thus, it remains common in popular agriculture literature to find that material added to soil to improve crop production is called manure even if the material is not organic [8,9].

Organic materials were seen as a potential source of plant nutrients and of interest to agricultural chemist and the world at large. Sewage sludge, compost, and indeed any organic material became a potential source of nutrients for plants. There was little or no understanding of microorganism involvement in organic material in general or in manure in particular, and so there was no understanding of the possibility of spreading diseases by using untreated or uncomposted organic matter [10].

One excretory organic product of particular interest and importance, discovered on islands off the coast of Peru by Alexander von Humboldt in 1802, was guano. He studied this product, which became a widely exploited fertilizer material that was transported and sold around the world [11].

One of the important components of guano is ammonia and because of the observed beneficial effect of ammonia on plant growth, there was early interest in the ammonia content of the organic matter in general and its availability to plants. This led to an interest in understanding the composition of soil organic matter. Unfortunately, full understanding is yet to be had. Organic matter in soil can be extracted and classified in various ways on the basis of the extracti...

Table of contents

• Cover
• Series page
• Title page
• Copyright page
• Preface
• Instrumental Method Acronyms
• Common Hyphenated Instrumental Method Abbreviations
• Abbreviated Periodic Table of the Elements
• CHAPTER 1: Summary of the History of Soil Chemistry
• CHAPTER 2: Soil Basics Part I: Large Features
• CHAPTER 3: Soil Basics Part II: Microscopic to Atomic Orbital Description of Soil Chemical Characteristics
• CHAPTER 4: Soil Basics Part III: The Biological and Organic Components in Soil
• CHAPTER 5: Soil Basics Part IV: The Soil Air and Soil Solution
• CHAPTER 6: Speciation
• CHAPTER 7: Soil and Soil Solution Sampling, Sample Transport, and Storage
• CHAPTER 8: Direct and Indirect Measurement in Soil Analysis
• CHAPTER 9: Electrical Measurements
• CHAPTER 10: Titrimetric Measurements
• CHAPTER 11: Extraction of Inorganics
• CHAPTER 12: Extraction of Organics
• CHAPTER 13: Chromatography
• CHAPTER 14: Spectroscopy and Spectrometry
• CHAPTER 15: Hyphenated Methods in Soil Analysis
• Index