Agriculture is of the utmost importance to human societies for its production of food and fiber (and increasingly fuel), but it is also a source of environmental harm as a producer of non-point-source pollution to the air and water. Nutrients, and nitrogen in particular, are vital to crop production but also create great environmental costs when they leave the farm and enter surrounding waterways or the atmosphere where they contribute to eutrophication and hypoxia (“dead zones”) and global climate change respectively.
Sociological research on the environment and agriculture tend to take a biophysical problem as the context of a study, with the biophysical problem as an abstract outcome of the human activities being studied, but do not often include biophysical problems or conditions as an influence on the human/social actions. This analysis takes a page from coupled human and natural systems, and social-ecological systems work by including biophysical variables along with social variables as predictors of county-level fertilizer use.
The goal of the analysis is to examine the effects of conservation tillage, no-till and cover crops on fertilizer use. These three practices have the potential to reduce the amount of nitrogen that a farmer needs to apply to get a good crop, but it is not clear to just what extent farmers actually do reduce their nitrogen use when using any of these practices. The assumption of reduced fertilizer use has important implications for water quality and farmers’ incentives to use or not use these practices.
A multilevel, random intercept, structural equation model with county-level and state-level data from the Census of Agriculture is used for a sample of 1,042 counties in the 12 states in the North Central region of the United States. Notably this analysis finds no reduction in fertilizer use as a result of conservation practice use, and in fact greater use of certain practices are associated with higher fertilizer use at the county-level. Because this is an analysis of county-level averages care should be taken not to extend these findings to the individual-level (an ecological fallacy). As such, while the result is a bit disappointing from a sustainable agriculture standpoint, it does not rule-out the practices having a fertilizer-reducing effect at the individual farm-level.
