Submitted to: Progressive Forage Grower
Publication Type: Popular Publication
Publication Acceptance Date: 5/1/2015
Publication Date: 7/15/2015
Citation: Coblentz, W.K. 2015. Dairy slurry application effect on alfalfa silage fermentation. Progressive Forage Grower. 16 (7):28-30.
Technical Abstract: Many dairy farmers rely increasingly on corn silage to meet their forage needs. While the efficiencies associated with the production, harvest, and storage of corn silage are attractive, a less-desirable corollary of this management trend is the increased linkage of manure distribution with production of corn. Specifically, manure distribution is restricted to time intervals before spring planting, or after fall harvest. It is widely realized that both of these opportunities can be seriously affected by wet weather conditions throughout much of the US. The need for more diversified cropping systems that create additional hauling opportunities throughout the summer months has been widely recognized. Within that context, dairy producers periodically inquire about the potential risks of applying dairy slurry on alfalfa fields during summer months. An experiment was conducted in Wisconsin by USDA-ARS, University of Wisconsin, and University of Arkansas scientists to assess the risks of applying dairy slurry on the subsequent silage fermentation of alfalfa. Four application treatments were evaluated: i) no slurry (control); ii) slurry applied to alfalfa stubble immediately after the preceding harvest; iii) slurry applied after 1 week of alfalfa regrowth; or iv) slurry applied after 2 weeks of alfalfa regrowth. Alfalfa was ensiled in large-square bales wrapped in plastic stretch film, and stored on a concrete pad until the following spring, when silage samples were obtained for final analysis. Based on our results, risks of clostridial fermentations within alfalfa silages are greater whenever dairy slurry is applied; however, risks are reduced when the slurry is applied directly to stubble compared to delayed applications on growing plants. Other recommendations to avoid undesirable clostridial fermentations include: i) consider some additional field wilting (perhaps to a 55 to 60% moisture target) relative to traditional recommendations for precision-chopped silages (= 70%); ii) use a silage inoculant that supports production of lactic acid; and iii) apply dairy slurry only to stubble immediately after the preceding harvest. Any applications of dairy slurry to growing alfalfa should be viewed only as a last-management option. If delayed applications are absolutely necessary, select an old stand instead of risking damage to recently established plants.