The History of Soil Science
“The eternal genetical relationships that exist between the forces of the environment and physical matter, living and nonliving domains, plants and animals and man, his habits, and even his psychology – these relationships comprise the very nucleus of natural science.”
Humans have had a strong connection to soils since the first hunters and gathers settled down to farm, but that doesn’t mean we have been scientific about our relationship. We are keen observers of our environment. We have attempted throughout history to determine which human impacts were beneficial and which were detrimental but not always with success. Our relationship with Soil has primarily had an economic base. Humans have used whatever tools available for the purpose of using soils to gain the highest yield on labor and inputs.
Ancient Soil Science
Among the first soil scientists were the Greek Theophrastus (371 BC-287 BC) who wrote “On the Causes of Plants”, and the Chinese Fan Shengzhi (1st century BC) who wrote on many agricultural topics including “Field Usage, Plowing, Irrigation, Harvesting,” and other crop specific topics. Their works were based on observation so, in the modern world, they are not considered “scientists.” They were excellent observers and were very knowledgeable about soils and crops but they didn’t conduct experiments to test theories.
Soil science then, as now, was serving both basic research and soil and crop productivity. As early as the Yao dynasty (2357 – 2261 BC) in China the productivity of the soil was used to determine amount of taxes paid.
The soil knowledge of scholars in Ancient Greece, Ancient China, the Americas, and Europe had periods of intense learning and periods of knowledge repression based on societal norms. But what we call “Soil Science” today is based on their observations.
Still Not a Distinct Science but Scientific Investigation of Soils Was Starting
As early as the 16th century in Europe Renaissance scholars began looking at the world in a new way. All aspects of the world were subjects for study. The concepts of biological and chemical laws were seen as both being influenced by humans and influencing. The beginnings of soil science started with an exploration of soil biota and their processes. Before long the tools we know of today for soil study were invented.
One that changed how we looked at the world the most was the microscope, invented in 1590 by Zacharias and Hans Janssen. Suddenly microorganisms were visible and the world became an entirely different place.
Reproduction of first compound microscope made by Hans and Zacharias Janssen, circa 1590. From the National Museum of Health and Medicine, Washington, D.C. (Image credit: Public domain.)
Many famous scholars worked on soils issues. Francis Bacon, Robert Boyle, and Leonardo da Vinci all had theories on how plants grew, the relationships with soil, and the importance of water. They all used the experimental method but were limited by lingering societal religious beliefs and lack of tools for accurate measurement.
Soil Science Takes Off in the 19th Century
The father of soil science, Vasily Dokuchaev (1846-1903), was a Russian geologist. He conceived of soil as a living system and saw soil as a biological science. Up until then scientists had seen soil as merely a medium for holding plants upright so that nutrients could be furnished by water and manures. Soil was seen as small pieces of rock and literally dead.
“Dokuchaev introduced the idea that geographical variations in soil type could be explained in relation not only to geologic factors (parent material), but also to climatic, biological, and topographical factors, and the time available for pedogenesis to operate.”(FAO, Resources)
Genetic soil science, as Dokuchaev named it, created the underpinnings for soil science to become a distinct science. In Russia a soil museum named after Dokuchaev was established in 1904 and contains soil samples and monoliths from his soil expeditions.
The biochemistry of soil became an area of study as early as the 18th century. The word “humus” was used by Johan Gottschalk Wallerius in 1753 to refer to the organic surface horizon relative to decomposing organic matter. And Albrecht Thaer differentiated peat (formed under limited O2) from humus (formed under adequate O2), each having very different qualities. Thaer has been called the father of sustainable agriculture. He wrote in the late 19th century:
“Latterly the practice of sowing white clover with the last crop has become very general; only a few apathetic and indolent agriculturalists or men who are firmly wedded to old opinion and customs, neglect this practice.”
The Humus Theory of plant nutrition was formulated by Thaer. Other soil scientists found that cultivated soils contained less humus than virgin ones. They studied the impacts and values of crop rotations. These studies point to some of the same questions today about soil C and climate change.
Soil Science and Microbiology
The period from 1890 - 1910 has been called the Golden Age of Soil Microbiology. Some forms of fungi could be seen with the naked eye and treatises on fungi, their fruiting bodies, and the reproductive aspects of spores were written by numerous scientists. Microscopes were continually being improved and scientists kept seeing smaller and smaller organisms.
A.B. Franck hypothesized that fungi, and he coined the term “mycorrhizal”, create a mutualistic relationship with host plants, especially trees. He hypothesized that the fungus extracted nutrients from soil minerals and translocated those nutrients to its host. The host in turn, nourished the fungus. He also identified the differences between endo and ecto mycorrhiza. Differences that are applicable today.
The development of the microscope had unintended consequences. It divided the soil science community into 2 camps: agro-chemists, who extracted microorganisms from the soil and studied them in labs, and agro-geologists, who saw that field experiments were necessary for replication to account for all the factors (known and unknown) in soils.
The agro-geologist scientists acknowledged the heterogeneity of soils, agro-chemist scientists often came to the conclusion “…if an organism did not grow on a gelatin or agar plate it could not be important and thus not worth studying.”(van Baren, Hans, et al, 75 Years The International Society of Soil Science)
This dichotomy still exists in 21st century agriculture. It is the basis of genetically modified crop varieties that can stand intense chemical spraying and genetic lab breeding versus open pollinated varieties suited to regenerative agriculture practices and traditional field plant breeding.
Soil science has only begun to explain the complexity of soil. The multitudes of organisms and the multitude of roles is staggering.
Soil biota have both direct and indirect affects on the ecosystem. They are responsible for carbon and nutrient cycles, soil structure modifications, food web interactions, and the yield of your crops.
The Importance of Soil Mapping and Soil Science
Soil science has always had one foot in research and the other in food production. Many soil scientists such as Dokuchaiev, Curtis F. Marbut, and Hans Jenny contributed to our understanding of soil formation. That information helps to answer some of the practical questions of
- How to select soils most responsive to agriculture
- How to avoid waste of effort and inputs in managing the soil
- What were the soils in given areas
These questions could be answered by the two camps coming together and sharing their information. According to Dr. Eric Brevik, “…soil science did not evolve into an independent scientific field of study until the 1880s.”
The critical question for soil scientists in the 20th century was whether “soil science” had the ability to stand alone, apart from microbiology, geology, or any of the other natural science disciplines made possible by new technology. This dilemma of soil scientists was solved when the two camps of agro-chemists and agro-geologists came together in 1924 and established the International Society of Soil Sciences, now the International Union of Soil Sciences.
Their main interests were in establishing standardized methods of soil analysis and soil classifications. They partnered with the FAO and UNESCO to create a world soil map. It is comprehensive but a lot of work still needs to be done to make it applicable to farmers and ranchers.
Soil information for most purposes is in the form of dozens of national soil classification systems. A more standardized soil mapping system at the agricultural level would benefit farmers as we go into the 21st century. Local soil maps, with the aid of new technologies such as GPS sensing and on-site geophysical instrumentation, are constantly being updated. Agricultural land becomes subdivisions, deserts become larger, climate change creates land/water boundary changes.
Soil scientists have many different job titles. Some work for government agencies, at the local county, state, or national level. Some soil scientists only do research. Many teach at universities while doing research. With the interest in sustainable and regenerative agriculture many soil scientists have become consultants, helping farmers transition from conventional to sustainable agricultural practices.
All their work is aimed at helping the farmer grow a higher yielding crop while retaining, or increasing, the fertility of the soil. There is a great deal of debate about the best way to accomplish that goal.
Since the 19th century there have been debates over a number of agricultural issues; most not resolved to this day.
Till or no-till, net profits vs gross yields, soil biology vs soil chemistry, yield per acre vs yield per unit of labor, rotation costs vs input costs.
What are the debates you have with your farming neighbors? Are they some of the same discussions that have led to research and experimentation in the relatively new “soil science?”