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Nitrification and denitrification activity in simulated beef cattle bedded manure packs

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  RRV15-056,  ASABE/CSBE North Central Intersectional Meeting. (doi: 10.13031/RRV15-056) @2015
Authors:   Ferouz Y. Ayadi, Erin L. Cortus, Mindy J. Spiehs, Daniel N. Miller
Keywords:   Bedpack, beef cattle manure, confined beef systems, DEA, denitrification, denitrification enzyme activity, depth, emission, greenhouse gas, layers, nitrogen, nitrification activity potential, nitrous oxide, zones.

Abstract. Besides significant nitrogen (N) losses through ammonia, N can also be lost as nitrous oxide (N2O) via microbial incomplete nitrification and denitrification in the manure. We conducted lab-scale experiments to determine N2O, denitrification enzyme activity (DEA) and nitrification activity potential (NAP) in simulated beef cattle bedded manure packs (BP) under different conditions. Thirty-six BP were stored in humidity-controlled chambers at 10°C or 40°C, contained either corn stover or soybean stubble as the bedding material, and were 0-3, 3-6 and 6-9 week old. The DEA and NAP were measured weekly before material addition. Samples were taken from varying depths based on BP age, and incubated at room temperature with different reagents and distilled water. For DEA, subsamples were analyzed for both nitrite N and combined nitrite-nitrate N consumption over 56 h of incubation. For NAP, samples were measured for nitrite production over 144 h. Results showed that NAP (1.22 nmol gbedpack-1 h-1, SE = 0.10) was much lower (1000 fold) than DEA (1.93 mmol gbedpack-1 h-1, SE = 0.14). The DEA was similar throughout BP depth, whereas NAP was higher in BP middle section. Nitrifiers are slow growing microorganisms which may explain low NAP in BP, whereas denitrifiers are fast growing communities that can survive in aerobic and anaerobic environments. Surface gas fluxes were measured with static flux chambers (n=2 per treatment). Nitrous oxide concentrations were on average 0.50 ppm (SE = 0.03) with peak concentrations occurring as high pulses right after material addition. Nitrous oxide production was most likely caused by incomplete denitrification from pulse nitrate concentrations available in the dried bedding material. However, future research using specific inhibitors or stable N isotopes should verify which process, nitrification or denitrification, is responsible for N2O production.

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