Effect of nitrogen content and additional straw on changes in chemical composition, volatile losses, and ammonia emissions from dairy manure during long-term storage

Abstract

Twelve 200-L barrels were used to determine the effects of N content and straw addition on changes in chemical composition and volatile losses measured by mass balance of dairy manure during a 136-d storage period. In addition, on d 0, 3, 6, 12, 28, 56, and 136, rate of NH₃-N emission was measured, and core samples were collected to characterize fermentation pattern. High N (3.06% N, HN) and low N (2.75% N, LN) manures were obtained from cows fed diets with 17.2 and 15.2% crude protein (dry matter basis), respectively. On d 0, manure scraped from a freestall barn floor was diluted with water to 10% dry matter and loaded in barrels with (+S) or without (-S) mixing 22g of chopped wheat straw per kilogram of undiluted manure. Data were analyzed as a randomized complete block with a 2×2 factorial arrangement of treatments and 3 replications. We observed no interaction between treatments for the reported measurements, but several day-of-storage by treatment interactions were found. Throughout storage, total NH₃-N (TAN, NH₃-N + NH₄⁺-N; 71.9 vs. 104.3 mg/dL), pH (6.40 vs. 6.74), and total volatile fatty acids (TVFA, starting on d 12) were lower for LN relative to HN manure. In the presence of straw, crust formation occurred between d 12 and 28, and pH became lower and TVFA became higher starting on d 56, compared with no straw. Treatments did not influence loss of organic matter, organic N, organic C, or N, which averaged 31, 29, 26, and 20%, respectively. However, neutral detergent fiber loss was 44% higher for +S relative to -S manure. Consistent reductions in the C:N ratio indicated proportionally higher volatile C loss than volatile N loss during storage. Overall rate of NH₃-N emission was 36% lower for LN than for HN manure. In the presence of straw, rate of NH₃-N emission did not differ until after crust formation, but was 67% lower on d 56 and 95% lower on d 136, when it was barely detectable, compared with manure with no straw. Manure pH was highly correlated with TVFA:TAN ratio (r=-0.78), and rate of NH₃-N emission was correlated with pH, TVFA:TAN, TVFA, and TAN (r=0.47, -0.44, -0.23, and 0.28, respectively). In this trial, both microbial fermentation and crust formation influenced NH₃-N emission rate and other measured responses, highlighting the importance of long-term sampling to evaluate treatment effects in manure storage studies.

Addition of Straw or Sawdust to Mitigate Greenhouse Gas Emissions from Slurry Produced by Housed Cattle: A Field Incubation Study

“…This may have reduced the air flow across the surface of the treatments, thereby affecting the rate of crust formation. Reduced NH 3 losses from slurry due to straw addition have been observed by others (Külling et al, 2001; Chadwick et al, 2005; Aguerre et al, 2012). Aguerre et al (2012) added chopped straw at 22 g per kg dairy cattle manure and observed a 70% reduction in cumulative NH 3 emissions after 136 d of storage.…”

“…Reduced NH 3 losses from slurry due to straw addition have been observed by others (Külling et al, 2001; Chadwick et al, 2005; Aguerre et al, 2012). Aguerre et al (2012) added chopped straw at 22 g per kg dairy cattle manure and observed a 70% reduction in cumulative NH 3 emissions after 136 d of storage. Külling et al (2001) added straw to slurry (dung and urine mixture) at 11.8 kg straw per cow‐day and observed that straw addition reduced NH 3 emissions by 25% when measured over a 7‐wk period.…”

Impact of manure storage conditions and time on decomposition and losses from liquid dairy manure stored in a temperate climate

“…Considering the relatively low and stable pH, likely drivers of volatilized NH 3 are initial urea concentration (Webb and Misselbrook 2004), particularly near surface, as pointed out by Kirchmann and Witter (1989). Further longer term NH 3 losses are probably through mineralization of organically bound N that subsequently may be volatilized and depleted under the oxygenated zone at shallower depth while accumulating as TAN at depth (Aguerre et al 2012). Presence of a naturally forming crust, not noteworthy in this study, was found to reduce NH 3 losses (Smith et al 2007;Sommer 1997) but crust may also lead to increased N 2 O emissions (Aguerre et al 2012), offsetting the NH 3 loss reduction.…”

“…Further longer term NH 3 losses are probably through mineralization of organically bound N that subsequently may be volatilized and depleted under the oxygenated zone at shallower depth while accumulating as TAN at depth (Aguerre et al 2012). Presence of a naturally forming crust, not noteworthy in this study, was found to reduce NH 3 losses (Smith et al 2007;Sommer 1997) but crust may also lead to increased N 2 O emissions (Aguerre et al 2012), offsetting the NH 3 loss reduction. More effective NH 3 volatilization mitigation strategy for open manure storages, albeit more expensive, are synthetic surface covers (Hou et al 2015;VanderZaag et al 2008).…”

Manure leachate production and change in manure weight during the storage depending on the amount of bedding

“…Increasing proportions of bedding and correspondingly boosting amounts of oxygen in the manure support microbial processes occurring in the manure during storage as well the overall amount of gas emissions (Jeppsson 1999;Misselbrook, Powell 2005;Aguerre et al 2012).…”