Whenever soils are subject to anoxic conditions, denitrification is the primary nitrogen cycle that is undertaken where nitrous oxide is a product (Hu et al, 2015). As conditions become more oxygenated, the rate of nitrous oxide production proportionally declines (Hu et al., 2015). Nitrous oxide has 300 times greater of a warming potential than carbon dioxide. As we emit more greenhouse gasses, the heat penetrating onto the earth's surface is being trapped and radiated back into the atmosphere where this heat energy. This increase in temperature is predicted to bring about a wide range of negative implications, where we'll take a closer look into increased precipitation rates. Based on climate change models, it's predicted that certain areas such as Ireland will bring around higher flood frequencies.
What this flooding might do is waterlog the soils where they prevent the passage of oxygen across soil aggregates spaces. This then as one might suspect, creates pockets of anoxic soils. Other ways this can be done is when the soil is compacted where intense trampling from the likes of livestock, heavy machinery will essentially squeeze the aggregates together where the porosity of the soil is reduced and they'll inherently be less oxygen passing through the soil. In essence, the increase in climate change will bring about further increases in average global temperatures.
Agriculture is also a major contributor along with climate change to have increased the rates of nitrous oxide from soils. Agriculture requires the use of heavy machinery such as tractors, combine harvesters, sprayer, grain carts etc for the maintenance of their farms. This use of heavy machinery will compact the soil particles that prevent the amount of oxygen passing through as it has less porosity which will create anoxic conditions down the soil column and so as mentioned earlier will increase the amount of nitrous oxide gasses that will be emitted. As one might suspect, use of mineral fertilizers also provide sufficient substrate that will promote the production of the potent greenhouse gas Nitrous oxide where the Nitrogen present in the fertilizer will be used as part of the gaseous compound. For every 100kg of fertiliser applied into the soil, approximately 1-5kg of it is released in the form of Nitrous Oxide (N2O).
To overcome this issue where soils act as a source rather than a sink, greenhouse gas emissions must be reduced in order to slow down the temperature increase that is currently being observed so that flooding intensity and frequency is less common than what would be expected if society continues to follow the RCP 8.5 (worst case scenario climate projection). As farmlands are the predominant habitats associted with Nitrous Oxide (N2O) production and so controlling this emmision of Nitrous Oxide (N2O) must be focused in the context of these farmlands. Initially, one must consider trying to avoid heavy machinary where appropriate and creating corridors allowing for the passage of the heavy machinary. These corridors should be carefully chosen based on areas least vulnerable to compaction ie. waterlogged, degraded soils. Constant monitoring of the soils should be undertaken to acknowledge when the soils making up the corridor needs a recovery period.
The most effective method that will aid in reducing the amount of nitrous oxide emmited from the soils is to simply reduce the amount of artificial fertiliser that is applied into the soils. Moving down this avenue will offer good benefits from a variety of environmental factors including run off into freshwater, reducing an over reliance of organic matter from external sources. To do this, one would like to enhance the solubilisation of non-bio available organic compounds ie. Phosphorous, nitrogen, carbon etc (Battini et al, 2017). A method to promote this is to plant more trees onto the farmlands that traditionally had trees occupying the land (Finn et al, 2017: Moyes et al, 2016). Metagenomic studies have found that conversion of wooded areas into croplands had displayed a decrease in traits associated with breakdown of recalcitrant (difficult to break down) carbon compounds and an increase in traits associated with breaking down easily biodegradable compounds (Finn et al, 2017).
References
Battini F., Grønlund M., Agnolucci M., Giovannetti M., Jakobsen I. (2017). Facilitation of phosphorus uptake in maize plants by mycorrhizosphere bacteria. Sci. Rep. 7:4686. 10.1038/s41598-017-04959-0
Finn, D. Kopittke, P. Dennis, P. Dalal, R. (2017) Microbial energy and matter transformation in agricultural soils. Soil and Biology Chemistry.
Hu, C. Qin, W. Onema, O (2015) Soil mulching significantly enhances yields and water and nitrogen use efficiencies of maize and wheat: a meta-analysis. Scientific Reports.
Laghari, M., Naidu, R., Xiao, B., Hu, Z., Mirjat, M.S., Hu, M., (2016) Recent Developments in Biochar as an Effective Tool for Agricultural Soil Management A Review. Journal of the Science of Food and Agriculture, 96, 4840-4849
Moyes, A. Kueppers, L. Pett-Ridge, J. (2016) Evidence for foliar endophytic nitrogen fixation in a widely distributed subalpine conifer.
