Sustainable Agriculture Literature Review - Boulder County

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Summary
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5. Soil Health
There are 23 main soil combinations in Boulder County that sustain a variety crops,
livestock, native grasslands, shrublands, wetlands, and forests, serving important
functions for both plants and animals. The quality, yield, and viability of agricultural
crops are directly dependent upon a healthy and fertile soil. Improving soil quality is
considered to be a key element of a sustainable agriculture production system. Much
of the early research on soil health focused primarily on soil’s capacity for crop
production, while other factors, such as structure, carbon sequestration, and
biodiversity, were either not considered or were accorded secondary importance.
Recently, awareness has been increasing about how environmental factors interact and
impact economic sustainability.
Reduction of soil quality is a growing concern, particularly since anthropogenic soil
degradation has been reported on almost 40 percent of the world’s agricultural lands.
Reasons for this soil degradation include increased erosion, atmospheric pollution,
extensive soil cultivation, over-grazing, land clearing, salinization, and desertification.
The primary agricultural practices identified in the literature that strongly affect soil
health positively or negatively include tillage method, soil amendments, soil
conservation, grazing practices, and crop rotation. One of the most important aspects of
healthy soils is the organic matter content, which is heavily influenced by these farm
practices. Most soils in Colorado have low amounts of organic matter, containing less
than 1.5 percent. Methods such as cover crops and green manures can serve as
organic material sources for agricultural systems, helping to decrease the potential for
soil erosion, while improving soil tilth, water-holding capacity, stability, and structure.
The use of cover crops and green manures needs to be evaluated on both
environmental and economic conditions, as a number of factors can affect their financial
viability.
Conservation tillage methods were identified as one of the most important factors for
building healthy and fertile soil. Methods of conservation tillage were strongly
associated with increasing the amount of soil organic matter, nutrient availability, and
erosion resistance. While there were many benefits associated with conservation
tillage, two main concerns were raised regarding economic viability and the increased
use of synthetic nitrogen fertilizers. A study conducted in the Fort Collins area
concluded that a conservation tillage system required more nitrogen fertilizer than
conventional tillage to produce equal yields, but less irrigation and machinery were
necessary. A similar study found comparable results and showed that on irrigated
continuous corn, no-till was actually more profitable than conventional-till because of
lower machinery and labor costs as well as a decrease in fossil fuel use.
These results highlighted that conservation tillage methods are crucial for improving
and maintaining soil health and can be done at a profit. In multiple studies it was noted,
however, that ultimately, farmers and landowners should be the ones to decide which
soil management practices should be implemented because soil type is specific to each
location.
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