TY - JOUR AU - DeClerck, Fabrice AU - Singer, Michael J TI - Looking back 60 years, California soils maintain overall chemical quality JF - California Agriculture JO - Calif Agr Y1 - 2003/04/01 VL - 57 IS - 2 SP - 38 EP - 41 PB - University of California Agriculture and Nature Resources SN - 0008-0845 UR - http://dx.doi.org/10.3733/ca.v057n02p38 L3 - 10.3733/ca.v057n02p38 AB - 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 mid1900s. 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 percentages may be interpreted as a sign of accelerated erosion, which is a sign of decreased soil quality.