Groundwater, climate change and air pollution impacts from manure amendment to agricultural soils

Johannes Christoph Haas1, Sajeev Erangu Purath Mohankumar2
1 Institut für Erdwissenschaften, NAWI Graz Geocenter; FWF-DK Climate Change, Karl Franzens Universität Graz
2 Institut für Systemwissenschaften, Innovations- und Nachhaltigkeitsforschung (ISIS); FWF-DK Climate Change, Karl Franzens Universität Graz, Österreich

P 13.1 in Nitrate and the importance of denitrification for water supply

The addition of manure to agricultural soils is a widely used fertilization technique. However, addition of manure is     associated with detrimental effects to groundwater, particularly nitrate loading of groundwater. Increased nitrate concentration in groundwater and subsequently drinking water, can lead to various well known negative impacts which are widely covered in academic literature and the general media.

Manure addition to agricultural soils is not only limited to groundwater contamination. It also leads to emissions of nitrous oxide (N2O) and ammonia (NH3). N2O is a greenhouse gas and causes climate change leading to issues such as sea level rise, increase in extreme weather events and losses in food production. NH3 on the other hand, is an air pollutant causing harm to human health and biodiversity. Application of manure to agricultural soils contributes to 10% NH3 and 9% N2O of the total emissions from agricultural sector in the EU-28. Hence addressing issues related to groundwater contamination, climate change and air pollution impacts from addition of manure to agricultural soils are imperative.

There are two main methods of manure addition to soils, namely – injection and surface spreading. From an emissions standpoint, preliminary estimates show that while injection of manure reduces NH3 emissions by 71 ± 25% relative to surface spreading, it leads to an increase in N2O emissions by 259 ± 416% [1]. Hence there are trade-offs between manure application methods with respect to air pollution and climate change. The impact of manure application methods on nitrate loading of groundwater seems to be rarely discussed in literature. A review of available sources indicates mixed results. While some studies suggest that the manure application method might not impact nitrate leaching [2] others point out that injection of manure could lead to higher leaching of nitrate into groundwater relative to surface spreading [3].

The objective of this study is to investigate the extent and quantify the trade-offs related to groundwater contamination, air pollution and climate change with the addition of manure to agricultural soils. Such an analysis which brings together these diverse aspects is virtually non-existent in literature. The results and analysis presented in this study would be a preliminary step forward in initiating a dialogue between the water and air emissions community.

[1] Sajeev, E.P.M., W. Winiwarter, and B. Amon, Greenhouse Gas and Ammonia Emissions from Different Stages of Liquid Manure Management Chains: Abatement Options and Emission Interactions. J ENVIRON QUAL (Revised, Under Review), 2017.
[2] Kayser, M., et al., Nitrate leaching is not controlled by the slurry application technique in productive grassland on organic–sandy soil. AGRON SUSTAIN DEV, 2015. 35(1): p. 213-223.
[3] McGechan, M. and L. Wu, Environmental and economic implications of some slurry management options J AGR ENG RES, 1998. 71(3): p. 273-283.