Sustainable Cotton Project

Contamination from pesticide application to row crops is a major water quality issue in California. Cotton receives three to five times greater application of pesticide per acre than other row crops (USGS 2008). This Project included outreach, education, and technical support for growers to test alternatives to synthetic pesticides and inorganic fertilizers. In addition, water quality monitoring of cotton field runoff in the Central Valley of California was conducted during the 2007 and 2008 growing seasons.

The goal of the study was to evaluate differences in pesticide and nutrient loads to receiving water bodies comparing biological and conventional growing practices. The types and concentrations of pesticides in the sampled tail water were similar for biologically and conventionally grown cotton. Average pesticide concentrations in water and estimated loads for diuron, glyphosate, chlorpyrifos, and prometryn were not statistically significantly different with BMP implementations at the biological sites due to sample size limitations. However, there was a trend toward lower pesticide concentrations for diuron and prometryn at the biological sites.

Concentrations for most nutrient forms and loads were also generally similar within the two site types when compared to flow passing the site at the point of sampling. Nitrate and nitrite loads, however, were reduced at the biological fields by more than 70% compared to the conventional sites. Additionally, limited bioassessment samples showed slightly greater numbers of individuals and numbers of species collected at the biological sites.