Does the Potential for Variable Rate Fungicide Application In Soybean Exist?.

Field-scale fungicide applications were made in 2007 and 2010 to soybean fields in eastern Oklahoma to evaluate the effect of fungicide application. Replicated strips were applied the length of the field to soybean plants that were in early reproductive growth stages. Applications were made at labeled rates with a sprayer or applied aerially. Yield comparisons were made the length of the application strips (no fungicide vs fungicide) using yield monitor data. In general, soybean seed yield was increased in lower yielding areas (less than field average) of the field of both irrigated and rainfed soybean fields. No response was observed in higher yielding areas (above field average). The cause of yield increase is not fully understood but the observed consistency of increasing soybean seed yield in lower yielding areas of the field may provide potential for variable rate fungicide application in soybean based on yield potential.