Manganese Management of Soybeans On Chronically Mn Deficient Soils.

Soybeans are produced on significant calcareous lakebed and organic muck landbases in Michigan.  The high pH of these soils, and for muck soils, high organic matter concentrations, decreases Mn availability, making management of this nutrient a particular challenge.  Producers have articulated a need for Mn fertilizer recommendations that fit within the unique management systems on these soils.   Research initiated at two muck soil sites in 2009 sought to evaluate the effect of several fertilizer products and application timing with glyphosate to correct Mn deficiency.  The scope of this research was broadened in 2010 to include evaluations of additional fertilizer products and rates, as well as applicability of including adjuvants with fertilizer products.  In 2009, separating Mn and glyphosate applications tended to increase soybean yield compared to tank-mixes of the two products.  This effect was not observed in 2010, though Mn deficiency pressure was low at both sites.  In adjacent studies in 2010 exhibiting greater Mn deficiency pressure, yield and trifoliate Mn concentrations differences were observed between fertilizer products and rates.  Studies have been continued in 2011.