Mapping soybean sudden death syndrome as related to yield and soil/site properties

Soybean sudden death syndrome (SDS) appears as a mid to late season foliar disease. Presently, little on-farm research has been conducted to study soil and site factors as related to the SDS disease. The objectives of this study were to study the influence of SDS disease on soybean yield and to compare soil and site factors with the SDS disease incidence and severity so that the factors that influence the disease could be identified. This was a 2-year study conducted on a farm near Desoto, IL, USA. Various site and soil parameters were collected, mapped and analyzed statistically to correlate with the SDS foliar index, DX (= disease incidence × severity/9). Soybean yield declined 7% for every 10% increase in DX. Statistically, no significant relationship was found between DX and organic matter content in soils. However, DX was positively related to soil pH, bulk density and moisture content at field capacity, but inversely related to available potassium, and macro-porosity. Both rooting depth and topography of the field had mixed relationships with the SDS index.