The abundance of late summer-harvested corn silage in Wisconsin means that there are many

acres where manure can be applied between late summer and later fall. Current nutrient

management guidelines estimate manure N availability based on animal source, solids content,

and application method, but no adjustments are made regarding application timing. A Wisconsin

Fertilizer Research program-funded research project evaluated how fall grass cover crops affect

the amount of N in the fall applied manure will be available to a subsequent corn crop. Results of

this research have shown that cover crop biomass influences the amount of N in the manure that

will remain for the next corn crop. If there is greater than 2,000 lb/ac of dry matter biomass, the

cover crop will have used all the N from the manure, while if there is less than 1,000 lb/ac of dry

matter biomass, the effect on the manure N credit is minimal.