Soil Health Analysis, Set. Группа авторов
to help raise public awareness of soil erosion problems occurring within the United States and globally. The second is Hillel (1991) who in his book “Out of the Earth: Civilization and the Life of the Soil” included a treatise in which Plato has Critias deliver a proclamation comparing degraded land and soil resources to an abandoned, emaciated person.
Science‐based principles influencing or even controlling overall soil health and the critical functions healthy soils provide for humankind can be traced to Aristotle or van Helmont, who provided some of the first insight and understanding of how plants obtain their nutrients from soils. Carter et al. (1997) quoted Columella, a prominent writer about agriculture within the Roman Empire, to illustrate his early (~40 to 60 BCE) guidance on how soil resources differ, the impact of terrain or landscape position, and how to manage them using virtues of good soil husbandry [management], such as optimizing soil moisture status, incorporating plant residues and/or manure to restore (“grow fat”) the soil. Bennett (1950) in his report on American Land emphasized that “we can’t keep our present standard of living if we lose much more [soil].” He continued stating that “more waste of good land would amount to a national crime on the part of those who are responsible – meaning ourselves.”
Another soil science pioneer, Hans Jenny (1980) stressed interrelationships between soil type and soil properties, while in the 1990s Warkentin (1995) emphasized how tillage energy as well as irrigation, drainage, and fertilizer inputs are all factors affecting the quality of soil for crop production. Carter et al. (1997) have also provided many details regarding the history and evolution of the soil quality concept, which we consider to closely parallel those of soil health and thus use the terms interchangeably throughout these two volumes. Carter et al. (1997) does, however, provide excellent insight regarding subtle differences between the two terms. The soil quality concept emerged as efforts were made to place a value on soil resources for providing specific functions, serving a specific purpose, or supporting a specific use. But, in contrast to water and air quality for which their functions can be directly related to human or animal consumption, soil functions are generally more diverse and usually cannot be directly linked to human health. One of the few situations that do closely link soil and human health is the function of filtering and buffering, especially if the heavy metals, radionuclotides, and/or toxic organic compounds can enter surface and groundwater resources or the food chain. This issue, specifically with regard to lead (Pb) is addressed in Chapter 7 of this volume.
More recently, Jared Diamond (2005) and David Montgomery (2007) inspired public awareness of the fragility of soil resources in their books entitled “Collapse: How Societies Choose to Fail or Succeed” and “Dirt: The Erosion of Civilizations”, respectively. Building on the foundations laid by those writers and numeerous agricultural scientists and engineers, our objective for this chapter is to briefly summarize and acknowledge the insight, passion, and selected contributions that have contributed to soil health evolution during the two decades since publication of the soil quality books edited by Doran et al (1994) and Doran and Jones (1996).
Pre‐20th Century Soil Awareness
Soil health is built upon a solid foundation reflecting numerous agronomic and soil science publications and advancements in knowledge. We would be remise not to mention classic scientists, like Darwin and Dukochaev, that spearheaded not only the modern scientific revolution but also our understanding of soil development and biology (e.g., Brevik and Hartemik, 2010; Johnson and Schaetzl, 2015; Ghilarov, 1983). Likewise, it’s imparitive to acknowledge the indigenous ecological knowledge on soil health acquired by non‐colonial cultures over thousands of years (Pawluk, 1992; Raji, 2006). Those roots of soil health are critical, but beyond the focus of this chapter. Therefore, we start with the late 20th Century and in the United States, where the concept of tilth (Warkentin 2008; Karlen 1990) is considered a key driver for what is now recognized as soil health. One example, provided in a review of past, present, and future soil tilth issues (Karlen et al. 1990) is a 1523 book by Fitzherbert, entitled “Boke of Husbandry.” Therein, Fitzherbert wrote that to grow peas (Pisum sativum L.) or beans (Phaseolus vulgaris L.) the soil was not ready to be planted “if it synge or crye, or make any noise under thy fete” whereas “if it make no noyse and wyll beare they horses, thane sowe in the name of God” (Keen, 1931). A similar quote from Fream (1890) described “good” soil as being “open, free‐working, mellow or in good heart” and “non‐productive” soil as “hungry, stubborn, still, cold, or unkind.” For some, these descriptions of “good” and “non‐productive” soils cause them to recall the Biblical connection between soil and life described by Hillel (1991) or even the New Testament parable wherein Jesus describes people and their actions as being similar to one for the four soil categories.
From 1900 to 1970
Examples of influential publications include one by Yoder (1937), who concluded poor soil structure was a major factor limiting various soil functions because of its influence on processes including granulation (aggregation); wetting, drying, freezing and thawing cycles; organic matter accumulation and decomposition rates; biological activities, plant root development, as well as tillage and crop rotation response. This remains relevant because the work led to development of the “Yoder” water‐stable aggregate method that is currently being used for many soil health assessment projects. Another is Waksman and Starkey (1924) who measured CO2 emissions as an indicator of the “decomposing power of soils” – using procedures similar to those associated with the Haney test (Haney et al., 2006).
Wilson and Browning (1945) emphasized soil aggregation and documented significant differences for a corn (Zea mays L.) – oat (Avena sativa L.) ‐ meadow rotation versus continuous corn. They also reported that after only four years of continuous corn aggregation levels created by either alfalfa (Medicago sativa L.) or bluegrass (Poa pratensis L.) was decreased to levels below that found for the corn‐oat‐meadow rotation. Conversely, implementing the corn‐oat‐meadow rotation after 11 years of continuous corn increased aggregation. Another pioneer was Selma Waksman, who is more famous for the discovery of streptomycin, conducted early work on understanding the nature of soil organic matter (SOM), including the decomposition of plant components by soil microorganisms and preservation of nitrogen (N) in the SOM (Waksman and Hutchings, 1935). Waksman and colleagues also focused on the formation of soil aggregates during the microbial decomposition process (Martin and Waksman, 1939, 1941). In another review, Whiteside and Smith (1941) documented the importance of measuring SOM and total N, two factors important for soil health. They concluded that since the origin of agriculture per se soil productivity had gradually been depleted due to crop production. Similarly, Van Bavel and Schaller (1950) showed that both cropping systems and soil erosion influenced SOM content. They reported that 11 years of continuous alfalfa increased SOM, but 11 years of bluegrass did not. They also found that although a corn‐oat‐meadow rotation did not maintain SOM levels, although the decrease was “small and probably not significant.”
Post‐World War II soil management studies gradually began to focus more on soil physical and chemical manipulation than biology, primarily because equipment manufacturing and fertilizer development technologies advanced rapidly, while biological theories (e.g., discovery of deoxyribonucleic acid [DNA]), methods of analysis, and modern instrumentation took additional decades to evolve. The importance of soil biology was not overlooked, as confirmed by Lyon et al (1950) who concluded plowing and cultivation should be used to loosen the soil with a minimum of soil aggregate destruction. Similarly, Browning and Norton (1947) found that crop yield associated with moldboard plowing was generally better than yields associated with other forms of tillage. They attributed this response to the moldboard plow design, which was intended to accentuate granulation by lifting, twisting, and shearing the soil, while at the same time, inverting organic residues on or at the soil surface for subsequent decomposition. During this same era, advances in chemical weed control were also made, but the use of tillage was still favored despite writings such as “Plowman’s Folly” by Faulkner (1943).
Tillage