Corralling Versus Broadcasting Dairy Manure: Volatilization, Leaching, and Mineralizable N.

Because they lack sufficient manure storage, a majority of dairy farmers in the northern USA spread livestock manure as frequent broadcast applications. Corralling livestock in the fields could achieve desired application rates, while reducing N losses and labor. We conducted two field experiments on clay loam soils in southern Wisconsin, USA, to compare the effects of corralling versus broadcasting on the fate of manure N. Once per month year round, groups of dairy heifers were moved to 6-m by 6-m corrals (plots) for 2 or 4 d. Other plots received manure collected after 2 or 4 d from heifers kept in a barn on straw bedding. Ammonia losses during the first 3 to 4 wk were quantified using a micrometeorological mass balance technique. Manure application phases were ‘fall through winter’ (Oct. to Mar.) and ‘spring through summer’ (Apr. to Sept.). Once each phase was complete, appropriate crop rotations were initiated, beginning with winter wheat (Triticum aestivum L.) in Sept. or corn (Zea mays L.) in April. We measured inorganic N in soil cores taken after the first cropping phase and again at the end of the experiment, nitrate leaching in enclosed lysimeters, and topsoil mineralizable N under aerobic conditions in the lab. Ammonia volatilization losses were less with 2 d of corralling than with the other treatments. In two subsequent measurement periods on a subset of plots, volatilization continued at greater rates in the broadcast than corralling treatments. Soil nitrate amounts were higher under corralling than broadcast application, but leaching losses were small and did not differ. Manure treatments generally produced similar net mineralizable N, but the high manure rate with corralling sometimes maintained higher rates of N mineralization. On fine textured soils, corralling may improve N retention compared to broadcast manure applications.