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Dietary Crude Protein and Tannin Impact Dairy Manure Chemistry and Ammonia Emissions from Incubated Soils
Author(s) -
Powell J. M.,
Aguerre M. J.,
Wattiaux M. A.
Publication year - 2011
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2011.0085
Subject(s) - slurry , tannin , loam , manure , soil water , chemistry , ammonia , zoology , agronomy , environmental chemistry , food science , environmental science , environmental engineering , biology , ecology , biochemistry
Excess crude protein (CP) in dairy cow diets is excreted mostly as urea nitrogen (N), which increases ammonia (NH 3 ) emissions from dairy farms and heightens human health and environmental concerns. Feeding less CP and more tannin to dairy cows may enhance feed N use and milk production, abate NH 3 emissions, and conserve the fertilizer N value of manure. Lab‐scale ventilated chambers were used to evaluate the impacts of CP and tannin feeding on slurry chemistry, NH 3 emissions, and soil inorganic N levels after slurry application to a sandy loam soil and a silt loam soil. Slurry from lactating Holstein dairy cows ( Bos taurus ) fed two levels of dietary CP (low CP [LCP], 155 g kg −1 ; high CP [HCP], 168 g kg −1 ) each fed at four levels of dietary tannin extract, a mixture from red quebracho ( Schinopsis lorentzii ) and chestnut ( Castanea sativa ) trees (0 tannin [0T]; low tannin [LT], 4.5 g kg −1 ; medium tannin [MT], 9.0 g kg −1 ; and high tannin [HT], 18.0 g kg −1 ) were applied to soil‐containing lab‐scale chambers, and NH 3 emissions were measured 1, 3, 6, 12, 24, 36, and 48 h after slurry application. Emissions from the HCP slurry were 1.53 to 2.57 times greater ( P < 0.05) than from the LCP slurry. At trial's end (48 h), concentrations of inorganic N in soils were greater ( P < 0.05) in HCP slurry–amended soils than in LCP slurry–amended soils. Emissions from HT slurry were 28 to 49% lower ( P < 0.05) than emissions from 0T slurry, yet these differences did not affect soil inorganic N levels. Emissions from the sandy loam soil were 1.07 to 1.15 times greater ( P < 0.05) than from silt loam soil, a result that decreased soil inorganic N in the sandy loam compared with the silt loam soil. Larger‐scale and longer‐term field trails are needed to ascertain the effectiveness of feeding tannin extracts to dairy cows in abating NH 3 loss from land‐applied slurry and the impact of tannin‐containing slurry on soil N cycles.