California Agriculture

To learn whether soil properties important to production agriculture and environmental quality have changed significantly in the past half-century in California, we analyzed archival samples and samples collected in 2001 from the same locations. Comparisons of organic matter content, pH, electrical conductivity, total nitrogen, total carbon and plant- available phosphorus showed significant changes since the mid-1900s. Across the state we found increases at the 95% confidence level for plant-available phosphorus, total carbon, pH, and percent clay, and increases at the 90% confidence level for percent silt and total nitrogen. We measured significant decreases at the 95% confidence level for electrical conductivity and percent sand. Based on this sample of 125 soils, we believe that California’s soil chemical quality has not decreased significantly over the past 60 years. However, increased clay percen-tages may be interpreted as a sign of accelerated erosion, which is a sign of decreased soil quality.