Soil pH and Carbonates Effects on Soybean Cyst Nematode Population Densities.
Natalia Rogovska1, Alfred Blackmer1, and Greg Tylka2. (1) Iowa State University, 2211 Agronomy Hall, Ames, IA 50011, (2) Department of Plant Pathology, Iowa State University, 351 Bessey Hall, Ames, IA 50011
Soybean Cyst Nematode (SCN) infestations pose a serious problem in the Midwest, where soils often range from slightly acid to highly calcareous within fields. Recent evidence suggests that SCN population densities tend to increase with increase in soil pH, but the effects of soil carbonate content on SCN densities have not been reported. Studies were conducted to learn how soil pH and calcium carbonate equivalent (CCE, %) affect population densities of SCN. Remote sensing of soybean canopy was used to select sampling points within each of 30 fields showing wide range in plant growth. Soil samples were collected and analyzed for pH, CCE, and SCN. Regression analysis was used to identify the effects of soil pH and CCE on population densities of SCN. The results confirmed that higher soil pH resulted in higher population densities of SCN in soils having little or no carbonates. In soils having carbonates, however, SCN densities decreased with increasing CCE. The highest population density, therefore, occurred in soils having high pH and low CCE. The results suggest that carbonate content might be as important as pH when studying SCN densities and that both must be measured.