Soil Health: What Does it Mean in North Carolina?
Soil health is defined as the capacity of soil to function as a vital living ecosystem (Doran and Zeiss 2000), where a healthy soil is believed to be highly productive, optimally functional, and naturally able to recover from disturbances (Doran and Parkin, 1994; Kibblewhite et al. 2008). Numerous research groups have developed or are trying to develop soil health tests (Rinot et al. 2018), but none is universally accepted.
To maintain soil health, USDA-NRCS prescribes a core set of practices (USDA-NRCS 2018):
- Keep the soil covered as much as possible.
- Disturb the soil as little as possible.
- Keep plants growing throughout the year to feed the soil.
- Diversify as much as possible by using crop rotation and cover crops.
Many North Carolina farmers already use these core practices. For example, a corn, wheat, soybean rotation with conservation tillage provides all four soil health practices. The ability to use these practices depends on the specifics of the cropping system, but in general, crop rotation and conservation tillage have been important management practices implemented throughout North Carolina for several decades.
Many farmers want to know the usefulness of soil health testing. The two most currently used tests in the United States are the Haney Soil Health Test (Haney) and the Cornell Comprehensive Assessment of Soil Health (Cornell). The Haney test measures carbon dioxide respiration from microbes in the soil as a soil health indicator in addition to nutrient testing (Haney et al. 2006). The test is provided by commercial labs for around $55 per sample. The Cornell test was developed by the Cornell University Soil Health Testing Laboratory and includes multiple physical, chemical, and biological indicators in its evaluation (Moebius et al. 2007). It costs $110 per sample. The Haney and Cornell soil health tests do analyze more soil properties than traditional soil tests. However, there is no confirmation that these assessments of soil health indicators will lead to recommendations to improve soil health for different soils.
North Carolina has three physiographic regions—coastal plain, piedmont, and mountains—and long-term agronomic trials have been conducted in each of these regions. The long-term coastal plain trial is in Goldsboro (20 years), the piedmont trial is in Reidsville (35 years), and the mountain trial is in Mills River (25 years) (Figure 1). Each trial has a unique management history, but two factors in particular were compared generally at Goldsboro (coastal plain) and Mills River (mountain). Those factors were tillage (no-till vs conventional tillage) and management (conventional vs organic management). At Reidsville (piedmont), researchers studied tillage intensity ranging from no-till to moldboard plowing (Table 1).