Impacts of Fall Manure Application Method and Timing on Nitrogen Conservation for Winter Annual and Subsequent Corn Crops.

Manure storage limitations often require farmers to apply manure in the spring and fall, but there are risks of nutrient pollution with fall applications. Applying manure to winter annual crops can reduce nutrient losses provide additional forage. Further we hypothesized that more manure nitrogen would be conserved for the winter annual and subsequent corn (Zea mays L.) when manure is: i) injected versus broadcasted and ii) applied later (Nov.) versus earlier (Sept.) in the fall. In 2013-2014, three different management strategies were evaluated in a 3-way factorial field experiment where a fall sown winter rye (Secale cereal L.) was followed by corn. Nitrogen conservation and availability for corn silage was estimated based on ammonia volatilization at manure application, rye nitrogen uptake, and rye and corn silage biomass. In 2014, corn silage yields differed significantly between winter crop management treatments. Corn silage yields following a rye cover crop were higher than after rye silage (23%); after manure was injected versus broadcasted (19%); and when applied later versus earlier (16%). Corn silage yields following rye managed as silage were 22% higher after manure was injected versus broadcasted. Total dry matter of combined rye and corn biomass was higher when rye was managed as silage versus a cover crop (9%); manure was injected versus broadcasted (20%); and when manure was applied in November versus September (8%). Higher corn silage yields after a rye cover crop and late injected manure suggest greater nitrogen conservation and availability. Similarly, total rye and corn biomass were significantly greater when manure was injected late versus broadcasted or applied early in the fall. Increased biomass of rye and corn after rye silage can provide farmers additional flexibility in management and result in wider adoption of practices.