Читать книгу Soil Health Analysis, Set - Группа авторов - Страница 33

As noted previously, soil physical and chemical aspects of soil management dominated post‐World War II activities for most soil and crop scientists. We suggest this reflected our limited understanding of soil biological properties and processes as well as the lack of instrumentation and analytical tools that are now available. None‐the‐less several well recognized soil microbiologists such as Allison (1968, 1973), James P. Martin (1939, 1940, 1971), Eldor Paul (Mathur and Paul, 1967; Paul and Voroney, 1980; Paul, 2014), and Martin Alexander (Alexander, 1961, 1980; Acea et al., 1988) contributed insights that expanded the foundation upon which soil health has evolved. There was also an increasing awareness that decreased use of crop rotations, increased size and weight of farm tractors and implements, as well as increased use of conservation tillage practices, were having measurable soil tilth effects in the northern Corn Belt (Voorhees, 1979). Soil compaction, caused by those factors, was recognized as being important for several reasons, including its effect on annual freezing and thawing processes (Voorhees et al., 1978; Voorhees, 1983; Voorhees and Lindstrom, 1984). Coupled with increasing concern regarding soil degradation, Pierce et al. (1983, 1984) conducted several erosion – productivity studies and Dormaar et al. (1988) intentionally eroded a Dark Brown Chernozemic soil (Mollisol) to demonstrate that applying commercial fertilizer or manure could restore soil productivity. However, during a subsequent drought, only the sites that received manure maintained yields and furthermore, after five years those treatments showed increased SOM content and improved water‐stable aggregation.

Warkentin and Fletcher (1977) introduced the concept of soil quality, which in many ways became the foundation for current soil health activities. The transition to soil quality emphasized the multiple ecosystem services (i.e., food and fiber production, recreation, and recycling or assimilation of wastes or other by‐products) that soils must provide (Carter et al., 1997). A focus on soil quality required recognition that: (1) soil resources are constantly being evaluated for many different uses; (2) multiple stakeholder groups are concerned about soil resources; (3) society’s priorities and demands on soil resources are changing; and (4) soil resource and land use decisions are made in a human or institutional context (Warkentin and Fletcher, 1977). They also stated that because of inherent differences among soils, there is no single measurement that will always be useful for evaluating soil quality (Karlen et al., 2003a).

Another 1980s soil and crop management challenge influencing SOM, erosion, and crop productivity was the suggested harvest of crop residues for off‐site bioenergy generation (Paul et al. 1980; Blevins et al. 1983; Elliot and Papendick, 1986). This was spurred by the 1970s energy crisis, and although a portion of the crop residue remaining after grain harvest had traditionally been harvested and used for animal feed or bedding, off‐site transport of the crop residues was the critical issue being questioned (Karlen et al., 1984). On‐farm use resulted in recycling of nutrients and organic matter via manure disposal, but off‐site transport would likely prevent closing field‐specific carbon cycles.