With the assumption that profitability must always be positive, let's discuss three threats to sustainability. Soil Erosion Erosion is a threat to sustainability because it threatens both soil productivity and environmental integrity. Erosion directly decreases productivity by reducing soil depth and preferentially removing topsoil, which contain much of the soil organic matter, Indirectly, the loss of soil organic matter and topsoil lowers water holding capacity, reduces infiltration, adversely affects soil tilth and decreases soil fertility. This research is summarized in Chapter 1 of the PAW Conservation Tillage Handbook, available through county extension offices. Erosion has many off-site impacts that adversely affect the environment.
Water erosion carries soil to streams, lakes and other water bodies.
Eroded soil contributes to siltation and sedimentation problems and also contains attached nutrients and possibly pesticides, These diminish water quality and pose a risk to aquatic plants, fish and aquatic life. Soil lost by wind erosion decreases air quality and can be a health risk. A trend that has generally been observed on most cultivated soils is the decline of soil organic matter with increasing time of cultivation. By 1930, organic matter had declined to approximately 2,0 percent in the top foot of soil. The plots at Pendleton are on less than 4 percent slope, therefore water erosion has been negligible and the decline is almost entirely due to oxidation.