as productivity but also how the entire landscape is maintained (Schnepf and Cox, 2006). Although soil health approaches per se have become recognized research and technology transfer topics during the past two decades, to many readers the concept is not new but rather another term transferable to previous efforts defined as soil conservation, soil quality, soil condition, soil tilth, or simply soil management. For example, Table 3.1 lists four soil and plant management strategies often presented as 21st century soil health approaches that have been considered to be good soil management practices throughout not only the 20th century (King, 1911; Keen, 1931; Lowdermilk, 1953; Keen, 1931) but from the time of Plato and before (Fream, 1890; Hillel, 1991; Diamond, 2011; Montgomery, 2007). Without question, those four management practices are in no way comprehensive, but they do provide a general framework under which many soil health approaches can be listed. A common link between the practices is that they strive to improve soils by keeping them covered and protected by erosive forces of wind or water and they strive to keep soil biological and chemical cycles as active as possible (Table 3.2). Keeping soils covered with living plants minimizes runoff, encourages proliferation of roots, production of root exudates and recycling of senesced vegetation as food for soil microbes, and provides a biotic pump for moving water through the soil–plant–atmosphere continuum.
Table 3.1 Timeless generic strategies for improving soils.
| Management Practice | Year | ||
|---|---|---|---|
| 1937 a | 2017 b | 2097 c | |
| Keep soil covered | ✓ | ✓ | ✓ |
| Reduce soil disturbance | ✓ | ✓ | ✓ |
| Keep plants growing year round | ✓ | ✓ | ✓ |
| Diversify | ✓ | ✓ | ✓ |
a Adapted from Rule, 1937.
b Taken from guidelines presented by the USDA‐Natural Resources Conservation Service (NRCS), 2019b.
c Our projection of soil health approaches that will continue to be emphasized.
With regard to 21st century soil health approaches, two questions emerging from the generic guidelines in Table 3.1 are: (1) What methods can be used to implement practices that will effectively achieve the underlying management goals?, and (2) What magnitude of soil health benefit can be achieved by investing in these practices? To help address the first question, several USDA‐NRCS Conservation Practice Standards (Table 3.2) have been developed (Schnepf and Cox, 2006; USDA‐NRCS, 2019a). It is important to note, however, that each “practice standard” can apply to multiple conservation management options that have multiple interactions as illustrated in (Fig. 3.2). This uncertainty is also one reason soil health is considered useful by some and futile by others.
Table 3.2 Selected NRCS conservation practices identified as also having a soil health impact.
| Conservation Goal | Potential NRCS Approved Practices |
|---|---|
| Keep soil covered | Conservation cover (327a); Forage and biomass planting (512); Mulching (484) |
| Reduce soil disturbance | Contour farming (330); Controlled traffic farming (334); Residue and tillage management (329 and 345); Strip cropping (585); Windbreak (380) |
| Keep plants growing year round | Conservation crop rotation (328); Cover crop (340); Wildlife habitat management (645) |
| Diversify | Contour buffer strips (332); Filter strip (393); Grassed waterway (412); Riparian forest buffer (391) |
a Specific Conservation Practice Numbers associated with practices approved by USDA‐NRCS (2019a).
When considering the conservation practices listed in Table 3.2 or elsewhere as strategies to remediate or enhance soil health, it is very important to recognize that implementation will require producer dedication, more time, and perhaps greater financial investment than most business as usual operations. Producers may need to change several core components of their
Figure 3.2 Utilizing cover crops as a conservation practice to improve soil health can have many different effects and interactions.
Source: USDA‐NRCS (https://www.nrcs.usda.gov/wps/PA_NRCSConsumption/download?cid=stelprdb1270377&ext=pdf).
Operations, including planting date and rates, field equipment, traffic patterns, crop sequences, acreage distributions, harvest practices, storage requirement and ultimately market availability and potential economic returns, especially if new or non‐traditional crop rotations are introduced. Such changes are not trivial and can involve substantial time, effort, and financial costs, and may not be feasible or practical due to a range of climatic, social, or financial factors (Carter, 2019; Findlater et al., 2019; Giller et al., 2009; Janzen, 2001).
Recognizing these and other implementation challenges, it then becomes very important to consider the second question– how much of a soil health benefit can be achieved if those practices are implemented? The key phrase in that question is “how much!” Once again, there is no simple answer because every situation is site‐specific with regard to comparison groups, scale of production or implementation, cost and sensitivity of analytical methods, and the degree to which a biological, chemical, physical or overall soil health change is measurable. The latter must also consider whether the change is of statistical (i.e., p‐value) or practical value. We will now focus briefly on each of those concepts to explore how different decisions and actions will ultimately determine cost to benefit ratios for each of the potential soil health approaches.
Comparison groups
When documenting the specific benefit of a management practice, the potential magnitude of this change will depend on both inherent and dynamic soil properties (Fig. 3.3). For example,
