Characterization of Ammonium Sorption by Beef Cattle Feed yard Manure

摘要

Ammonia (NH_3) emissions from beef cattle feedyards represent a loss of agronomically important N and can potentially affect the environment. Sorption of ammonium [NH_(4~+)]and NH3 by mineral and organic solids decreases the proportion of free, aqueous ammoniacal N, which reduces volatilization potential. In the U.S., the High Plains region of Texasis subject to arid conditions with widely fluctuating temperatures. Furthermore, feedyard manure contains little soil and has high dry matter (DM) content; therefore, it is unclear if sorption parameters determined for soils or liquid manure systems arevalid for feedyards. Our objectives were to use batch equilibration experiments to characterizeNH_(4~+) sorption by two feedyard manures. Kinetic and isotherm studies with (NH_4)_2SO_4/0.01 M CaCl2 solutions revealed that feedyard manures could sorb up to 227 cmolkg~(-1) NH_(4~+)-N and that sorption was rapid and linearly related to NH_(4~+) concentration. The Freundlich partitioning coefficient (K_p) for NH_(4~+) sorption averaged 13.3 L kg~(-1). From 58% to 96%> of the sorbed NH_(4~+) was readily desorbable wit