Subsurface Application Enhances Benefits of Manure Redistribution

Abstract

E nvironmental sustainability requires improved manure manage-ment in animal agriculture, by both efficiently using valuable nutrient resources and minimizing nonpoint-source pollution impacts (Maguire et al., 2011). In the Chesapeake Bay Watershed, which occupies an area of 166,000 km 2 in the eastern United States, 36 million Mg of manure is produced per year, and brokering programs have been established to promote the redis-tribution of manure from areas of concentrated animal production to areas of nutrient deficit (Kleinman et al., 2012). Such programs most commonly result in redistribution of dry poultry litter because it is more economically and con-veniently transported than liquid or semisolid manure (Aillery et al., 2005). Ideally, imported manure contributes to farm nutrient needs without adversely affecting local air and water quality (Kleinman et al., 2012), while simultane-ously reducing excess nutrients from its source location. Immediate incorporation of manure into soil can reduce the potential for manure phosphorus (P) losses in runoff (McLeod and Hegg, 1984; Johnson et al., 2011) and ammonia (NH 3) volatilization (Malgeryd, 1998; Dell et al., 2012), both by as high as 90%. Nonetheless, surface application of manure remains the dominant application method in the Chesapeake Bay Watershed, where more than 60% of the agricultural land is in reduced tillage or perennial grass cover. Thus, low soil disturbance technologies are crucial for successful adop-tion of manure incorporation (Maguire et al., 2011). The USDA-ARS Subsurfer is a mechanical applicator that places dry poul-try litter below the soil surface using no-till planter components with mini-mal disturbance (Pote et al., 2011, 2012). The Subsurfer has reduced nutrient losses to the environment in areas of concentrated poultry production, such as Maryland's eastern shore (Feyereisen et al., 2010; Kibet et al., 2011), where farmland area is small relative to the manure nutrients produced. Recent Subsurfer trials on poultry litter application in Pennsylvania's south-central poultry production region confirmed soil nitrogen (N) increase with incorpo-ration but significant yield increase in only one of the six fields. Abstract: Sustainable nutrient management requires redistribution of livestock manure from nutrient-excess areas to nutrient-deficit areas. Field experiments were conducted to assess agronomic (i.e., corn yield) and environmental (i.e., ammonia volatilization and surface nutrient loss) effects of different poultry litter application methods (surface vs. subsurface) and timings (fall vs. spring) in a potential manure-importing region in the Chesapeake Bay Watershed in the United States. All four litter treatments (205 kg nitrogen ha