Analysis of the effect of air temperature on ammonia emission from band application of slurry

Arbuscular mycorrhizal fungi offset NH3 emissions in temperate meadow soil under simulated warming and nitrogen deposition

Most soil ammonia (NH3) emissions originate from soil nitrogen (N) that has been in the form of exchangeable ammonium. Emitted NH3 not only induces nutrient loss but also has adverse effects on the cycling of N and accelerates global warming. There is evidence that arbuscular mycorrhizal (AM) fungi can alleviate N loss by reducing N2O emissions in N-limited ecosystems, however, some studies have also found that global changes, such as warming and N deposition, can affect the growth and development of AM fungi and alter their functionality. Up to now, the impact of AM fungi on NH3 emissions, and whether global changes reduce the AM fungi's contribution to NH3 emissions reduction, has remained unclear. In this study, we examined how warming, N addition, and AM fungi alter NH3 emissions from high pH saline soils typical of a temperate meadow through a controlled microscopic experiment. The results showed that warming significantly increased soil NH3 emissions, but N addition and combined warming plus N addition had no impact. Inoculations with AM fungi strongly reduced NH3 emissions both under warming and N addition, but AM fungi effects were more pronounced under warming than following N addition. Inoculation with AM fungi reduced soil NH4+-N content and soil pH, and increased plant N content and soil net N mineralization rate while increasing the abundance of ammonia-oxidizing bacterial (AOB) gene. Structural equation modeling (SEM) shows that the regulation of NH3 emissions by AM fungi may be related to soil NH4+-N content and soil pH. These findings highlight that AM fungi can reduce N loss in the form of NH3 by increasing N turnover and uptake under global changes; thus, AM fungi play a vital role in alleviating the aggravation of N loss caused by global changes and in mitigating environmental pollution in the future.

A review of mitigation technologies and management strategies for greenhouse gas and air pollutant emissions in livestock production

One of the key issues in manure management of livestock production is to reduce greenhouse gas (GHG) and air pollutant emissions, which lead to significant environmental footprint and human/animal health threats. This study provides a review of potentially efficacious technologies and management strategies that reduce GHG and air pollutant emissions during the three key stages of manure management in livestock production, i.e., animal housing, manure storage and treatment, and manure application. Several effective mitigation technologies and practices for each manure management stage are identified and analyzed in detail, including feeding formulation adjustment, frequent manure removal and air scrubber during animal housing stage; solid-liquid separation, manure covers for storage, acidification, anaerobic digestion and composting during manure storage and treatment stage; land application techniques at appropriate timing during manure application stage. The results indicated several promising approaches to reduce multiple gas emissions from the entire manure management. Removing manure 2-3 times per week or every day during animal housing stage is an effective and simple way to reduce GHG and air pollutant emissions. Acidification during manure storage and treatment stage can reduce ammonia and methane emissions by 33%-93% and 67%-87%, respectively and proper acid, such as lactic acid can also reduce nitrous oxide emission by about 90%. Shallow injection of manure for field application has the best performance in reducing ammonia emission by 62%-70% but increase nitrous oxide emission. The possible trade-off brings insight to the prioritization of targeted gas emissions for the researchers, stakeholders and policymakers, and also highlights the importance of assessing the mitigation technologies across the entire manure management chain. Implementing a combination of the management strategies needs comprehensive considerations about mitigation efficiency, technical feasibility, local regulations, climate condition, scalability and cost-effectiveness.

Effect of anaerobic digestion on odor and ammonia emission from land-applied cattle manure

High ammonia (NH₃) and odor emission can occur after land application of liquid animal manure. This study was aimed at evaluating NH₃ loss and odor nuisance after field application of cattle manure and how it is affected by two anaerobic digestion strategies: i) digestion of cattle manure alone and ii) digestion with catch crops and dilution by water. A system of dynamic chambers with online measurements of NH₃ and odorous compounds (summarized as odor activity value, OAV) was used. Two experiments were conducted under different temperature conditions. The results demonstrated that anaerobic digestion did not affect NH₃ loss but did decrease OAV. Addition of catch crops and water to the digestion process reduced both NH₃ loss and OAV. Cool temperature in one of the experiments had a large effect on both NH₃ and odor emissions, and at high temperature the differences between treatments increased.

Effect of storage and field acidification on emissions of NH3, NMVOC, and odour from field applied slurry in winter conditions

Land spreading of liquid animal manure (slurry) is a major source of atmospheric emissions. Ammonia (NH₃) emission is of concern, as it is one of the main contributors to ambient air pollution and nitrogen deposition. Storage and field acidification of the slurry prior to application is used to mitigate NH₃ emission, but the effect of acidification on emissions of odorous non-methane volatile organic compounds (NMVOC) has not been investigated, and there is a scarcity of data investigating the effect of field acidification. Four field experiments, two with cattle slurry and two with pig slurry, were performed. Ammonia and NMVOC emissions were measured simultaneously in a system of dynamic chambers and online measurements by cavity ring-down spectroscopy (CRDS) and proton-transfer-reaction mass spectrometry (PTR-MS). The system allowed for a high time resolution and low variation. All four experiments were performed under cold conditions (<10°C average temperature). Storage and field acidification significantly lowered the NH₃ emission by 79 ± 18% and 30 ± 6% on average, respectively. The NMVOC cumulative emission increased by 202 ± 133% and 17 ± 16% on average after storage and field acidification, respectively, even if the increase was only significant for storage acidification. Storage acidification significantly increased the emissions of odour at most measuring times. The increases of cumulative NMVOC emissions and odour was primarily caused by higher emissions of volatile fatty acids.