Manganese (Mn) deficiency in crops has occasionally been noted in Wisconsin and is most common on soils with high pH (>7.0) and/or high organic matter (>6.0 %). Soils that meet these criteria are typically, but not exclusively, found in Eastern Wisconsin. Soybean has a relatively high requirement for Mn. Current University of Wisconsin nutrient application guidelines (Laboski et al., 2006) for Mn are based on research conducted in the early 1970s (Randall et al., 1975) when soybean was gaining popularity as a crop in Wisconsin. These guidelines indicate that for soils with OM ≤ 6.0% a soil test for Mn coupled with the relative crop need for Mn should be considered to determine fertilizer Mn needs. For crops with a high relative need for Mn, like soybean, grown on soils with OM > 6.0%, starter fertilizer containing Mn or foliar Mn application is recommended.
Soil Science Extension
University of Wisconsin Madison