FACTORS AFFECTING AMMONIA VOLATILIZATION FROM LAND-APPLIED CATTLE SLURRY INTHE MID-ATLANTIC REGION

Authors: Thompson, Richard; Meisinger, John

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2002
Publication Date: 6/12/2002
Citation: THOMPSON, R.E., MEISINGER, J.J. FACTORS AFFECTING AMMONIA VOLATILIZATION FROM LAND-APPLIED CATTLE SLURRY INTHE MID-ATLANTIC REGION. JOURNAL OF ENVIRONMENTAL QUALITY. 2002.

Interpretive Summary: Ammonia volatilization is a major nitrogen loss process for surface- applied cattle slurries. Information is needed on how management factors affect ammonia losses. A series of field studies, using a system of small wind tunnels, was conducted to examine the effect of several management factors on ammonia loss. Two studies compared losses from slurries applied to grass versus bare soil. Average total losses were 1.5 times greater from the grass than from bare soil. Two studies examined the effect of total solids content on ammonia loss. Total ammonia losses over four days was not affected by slurry total solid content for six slurries with total solids ranging from 5.4 to 13.4%. However, the time-course of ammonia loss was affected by total solids. The rate of ammonia loss was higher for high total solids slurries than for dilute slurries during the first 12-24 hours. But this effect was reversed beyond 24 hours, where the more dilute slurries lost the most ammonia. The changing effects of slurry total solids content was attributed to crust formation on the more viscus slurries after 12-24 hours which was encouraged by the hot summer conditions of the study. Three studies also compared the effect of tillage on ammonia losses. Losses from unincorporated slurry was 45% of applied ammonium nitrogen, which was reduced to negligible amounts by immediate incorporation with a moldboard plow. With a tandem-disk or a chisel plow, ammonia losses averaged 5% and 9%, respectively. Immediate incorporation was an effective method to reduce ammonia loss.

Technical Abstract: Large N losses by ammonia (NH3)volatilization occur following surface application of cattle slurry. Information on the effect of management factors is required to more accurately estimate and manage NH3 loss. A series of field studies, using a system of small wind tunnels, was conducted to examine the effect of several factors on NH3 loss. Two studies scompared NH3 loss from grass swards and bare soil. The average total NH3 loss was 1.5 times greater from a grass sward than from bare soil. Two studies examined the effect of slurry total solids (TS) content on NH3 loss under hot, summer conditions. From six slurries with TS contents between 54 and 134 g kg-1, total NH3 loss was not affected by TS content. However, the time-course of NH3 loss was affected by TS. The rate of NH3 loss was positively related to TS content during the first 18 h, and negatively related after 18 h. In the second study total NH3 loss was again not positively related to slurry TS content on either a loose or crusted soil. However, higher rates were measured from viscus slurries within 18 h of application while dilute slurries lost more after 24 h. Under the hot summer conditions, the more viscous slurries appeared to dry and crust more rapidly causing smaller rates of NH3 loss after 12B24 h, which offset earlier positive effects of TS content on NH3 loss. Three studies compared immediate incorporation with various tillage implements. Ammonia loss from unincorporated slurry was 45% of applied slurry NH4+BN, which was reduced t negligible amounts by immediate incorporation with a moldboard plow. With a tandem-disk harrow or chisel plow, NH3 losses were, respectively, 2B8 and 8B12% of slurry NH4+BN. Immediate incorporation with a moldboard plow or a disk harrow was very effective in reducing NH3 loss.