Management Factors Affecting Ammonia Volatilization from Land-Applied Cattle Slurry in the Mid-Atlantic USA
2002
Ammonia (NH₃) volatilization commonly causes a substantial loss of crop-available N from surface-applied cattle slurry. Field studies were conducted with small wind tunnels to assess the effect of management factors on NH₃ volatilization. Two studies compared NH₃ volatilization from grass sward and bare soil. The average total NH₃ loss was 1.5 times greater from slurry applied to grass sward. Two studies examined the effect of slurry dry matter (DM) content on NH₃ loss under hot, summer conditions in Maryland, USA. Slurry DM contents were between 54 and 134 g kg⁻¹ Dry matter content did not affect total NH₃ loss, but did influence the time course of NH₃ loss. Higher DM content slurries had relatively higher rates of NH₃ volatilization during the first 12 to 24 h, but lower rates thereafter. Under the hot conditions, the higher DM content slurries appeared to dry and crust more rapidly causing smaller rates of NH₃ volatilization after 12 to 24 h, which offset the earlier positive effects of DM content on NH₃ volatilization. Three studies compared immediate incorporation with different tillage implements. Total NH₃ loss from unincorporated slurry was 45% of applied slurry NH⁺ ₄–N, while losses following immediate incorporation with a moldboard plow, tandem-disk harrow, or chisel plow were, respectively, 0 to 3, 2 to 8, and 8 to 12%. These ground cover and DM content data can be used to improve predictions of NH₃ loss under specific farming conditions. The immediate incorporation data demonstrate management practices that can reduce NH₃ volatilization, which can improve slurry N utilization in crop–forage production.
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