Alternative Cropping Systems for Improved Manure Management: The Grass Ley

Most dairy farms in the North central and Northeastern U.S.A. continue to grow most of their feed and recycle the manure nutrients on the farm. However, to remain economically viable, many dairy farms are increasing herd size and importing more feed nutrients onto the farm. The trend in Wisconsin and throughout the upper Midwest is an increasing number of cows per farm. By 2005, farms with more than 200 animals housed 32% of the state herd and accounted for 34% of the milk production (USDA-NASS, 2006a). It has been found that these larger farms have higher stocking rates (Saam et al., 2005), exacerbating the problems of nutrient management.

Most manure is applied to the corn-alfalfa rotation on dairy farms. However, this rotation leaves the farmer with few spreading windows and nitrogen-efficient opportunities for manure application (Sutton et al., 1979). Even moderate application rates of manure on legumes are not recommended because of salt toxicity and/or crown damage that can occur with slurry and the heavy tanker traffic (Kelling and Schmitt, 2003). The most practical window to apply manure in this rotation is just prior to corn or a new seeding of alfalfa. WICST data shows however, that fall nitrate levels were excessively high and most at risk for leaching in corn following manured alfalfa (WICST 10th Technical Report, p. 31). These findings have been confirmed by other authors. (Beiebly et al., 1973; Sanford et al., 2008). Furthermore, because spreading is limited to primarily the fall and spring in the corn-alfalfa rotation, many dairymen are required to invest in large concrete holding pits to store manure, often for 6 or12 months.

In this project we propose an alternative approach–promoting the use of grass leys on dairy farms to improve nutrient cycling, facilitate manure management, and reduce nutrient leaching and run-off. The term grass ley is European and refers to land that is planted to grass for a few years then followed by annual crops. The grass may be grown for pasture, hay, silage, or green chop. The addition of a nitrogen-demanding grass crop to the rotation would have several advantages while providing feed for the herd. It would permit manure application on a growing sod crop that would minimize the risks of surface runoff and groundwater contamination (Heathwaite et al. 1998; Simmelsgaard, 1998; Schmitt et al., 1999; Webster et al., 1999, Kanneganti and Klausner, 1994). Because of their shallow fibrous root system, grasses are known for their high nutrient absorption levels, especially N. For example, in Great Britain, researchers added 200 lb N/a as liquid slurry in spring and measured only 10 lb N/a leached and by increasing the applications to four times per year (800 lb N/a), nitrate losses were only 15-30 lb N/a. In addition to improved nutrient management, grass sod has practical advantages such as being available earlier for spreading when other ground may be too wet for traffic. An unknown effect of frequent slurry applications however, is cattle acceptance/rejection level of the forage. This issue was examined in a concurrent feeding trial and will be reported on in another paper in this technical report (‘Effects of Land Applying Dairy Slurry on the Subsequent Voluntary Intake of Orchardgrass Hays by Growing Dairy Heifers’).

Authors: Janet Hedtcke, Josh Posner, Rick Walgenbach, John Hall, and Gregg Sanford