materials such as mulch and compost, when they are left on the soil surface, provide a protective barrier between the soil and the destructive force of raindrops. They also moderate extremes in soil temperature and reduce evaporative losses from the soil. Soil cover can also be provided by leaves of growing plants. Keeping the soil covered throughout the year helps maintain soil aggregate integrity, protect habitat and provide food for soil organisms. Conservation practices that can be used to maximize cover include Conservation Cover (327), Cover Crop (340), Forage & Biomass Planting (512), Mulching (484), Prescribed Grazing (528) and Residue/Tillage Management (329/345).
Maximizing Biodiversity
It is well known that crop rotations are an important tool for managing plant pests (Altieri, 1991a, 1991b). What has been less appreciated until recently is that plants, primarily through their roots, affect the kinds and abundance of soil microorganisms, thus influencing soil biology and biological processes (Doran & Zeiss, 2000). Different plant species, and even cultivars, are typically associated with distinct soil microbial communities (Dick, 1997). In addition, since plant root architecture often differs among species, effects on soil function are also different (Brussaard et al., 2004). Above ground plant and animal diversity also encourages diversity in soil biology by increasing SOM levels, providing food and habitat for diverse soil communities, promoting greater aggregate stability, and helping alleviate compaction. Conservation practices that can be used to maximize biodiversity include Conservation Cover (327), Conservation Crop Rotation (328), Cover Crop (340), Forage & Biomass Planting (512), and Prescribed Grazing (528).
Maximizing the Presence of Living Roots
The area around plant roots is typically where the highest number and greatest diversity of soil microorganisms are found (Hornby & Bateman, 1997; Grayston et al., 1998; Ladygina & Hedlund, 2010; Singh et al., 2004). The rhizosphere is a very important ecological zone for SH improvement because living plant roots exude numerous carbon compounds as they grow and steadily slough dead cells from their surfaces. These contributions from roots add organic carbon to the ecosystem and help feed soil organisms. Plant roots are also involved in complex biochemical communication among soil microbes whereby beneficial organisms are “recruited” by plants while pathogenic organisms are often deterred. Plant roots also physically enmesh soil particles thus helping to create and preserve soil aggregates. Conservation practices that can be used to maximize the presence of living roots in the soil include Conservation Cover (327), Conservation Crop Rotation (328), Cover Crop (340), Forage & Biomass Planting (512), Mulching (484) and Prescribed Grazing (528). These selected practices are just some of the ways soil biological processes can be enhanced by SH management systems. Producers and those who work with them on establishing new management adaptations continue to innovate. The remaining chapters provide additional information and examples illustrating how continued implementation of known soil health promoting practices and new innovations can be assessed for their effects on critical soil functions by measuring appropriate SH indicators.
Summary and Conclusion
Efforts to build agricultural resilience through high functioning soil resources are still in their infancy, as documented by national adoption rates for soil health associated practices, and especially soil health management systems across entire human‐managed landscapes (Karlen & Rice, 2015; Wade et al., 2015). Fortunately, federal, state, NGO and private‐sector organizations and individuals are working diligently to advance awareness of soil health and the management practices that improve it. Through increased research, on farm implementation, and policy changes progress is inevitable. The focus in “Approaches to Soil Health Analysis” is to build standardized, basic capacity to better inform management decisions and quantify outcomes of soil health management system implementation.
Soil health developments during the past three decades have been progressive, provocative, and are thus still under debate. As such, this two‐volume contribution in no way is conceived as providing any final answers, but is envisioned as a step toward incorporating soil health into mainstream soil, water, and environmental science programs, and more importantly into every day agricultural management. Hopefully, they will also open new doors and stimulate additional study and education needed to encourage humankind to recognize the truth in Larson’s often quoted statement that soil is “the thin layer covering the planet that stands between us and starvation” (Karlen et al., 2014).
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