Greenhouse gas and ammonia emissions from soil: The effect of organic matter and fertilisation method

Abstract

Greenhouse gas emissions (GHGs) into the atmosphere derived from the use of fertilisers is a serious issue for the sustainability of agricultural systems, also considering that the growing global demand for food requires an increasingly productive agriculture. Emissions dynamics are very variable and are determined by many factors and their reciprocal interactions. Among driving factors, soil type (mineral, organic and microbiological composition), fertilisation method, climate, and the cropping system. In the present experiment, the combined effect of soil organic matter (SOM) and fertilisation method on the emissions of GHGs and ammonia (NH3) was investigated. Liquid fraction of digestate from pig slurries, compost from organic fraction of municipal solid wastes, and urea were applied on bare soil with two levels of organic matter (OM1: 1.3% and OM2: 4.3%). Emissions were directly monitored by a static chamber system and a portable gas analyser. Results show that soil organic matter as well as the composition of the fertilisers affect greenhouse gasses emissions. Emissions of methane (CH4) produced by digestate and compost during experimental period were higher in correspondence of lower organic matter content (0.58 – 0.49 kg CH4 C/ha/ day and 0.37 – 0.32 kg CH4 C/ha/day for digestate and compost respectively), contrary to what was observed for urea. For all fertilisers, carbon dioxide (CO2) and nitrous oxide (N2O) emissions were higher in correspondence of higher organic matter level. In particular, CO2 emissions were 11.05%, 67.48% and 82.84% higher in OM2 than OM1 for digestate, urea and compost respectively. Likewise, N2O emissions were 87.45%, 68.97% and 92.11% higher in OM2 than OM1 for digestate, urea and compost respectively. The obtained results show that the content of organic matter in soils plays a key role on the emissions of GHGs, generally enhancing the levels of gas emissions.

Greenhouse gas emissions in agricultural cultivated soils using animal waste-based digestates for crop fertilization

“…(2018b) where higher CO 2 emissions were observed in the digestates compared with mineral N possibly due to digestate composition and optimum soil moisture conditions which allowed the infiltration into the soil. The probable reason for the increased CO 2 emission was the enrichment of water content of soil combined with the mild air temperatures that occurred, which encouraged the proliferation of soil microorganisms and consequentially soil respiration (Verdi et al ., 2018b). Soil moisture positively correlated with CO 2 emission, which explained the slight increase in emissions observed 40 days after digestate application.…”

“…The most significant contributions to CH 4 emissions are enteric fermentation and manure management with minor contributions from rice paddies and agricultural burning (Johnson et al ., 2007). CH 4 emissions are related to the anaerobic conditions through the actions of methanogens resulting in most available data being focused on wetlands that represent the primary source of CH 4 from soils (Verdi et al ., 2018a).…”

The Potential of Digestate and the Liquid Fraction of Digestate as Chemical Fertiliser Substitutes under the RENURE Criteria

“…So, the resulting wide range of digestate properties combined with the further breakdown and release of its organically bound nutrients can result in unpredictable N dynamics in which the mineralised N exceeds crop demands, giving rise to N leaching [44,83]. Furthermore, the influence of soil texture (sandy, loamy, clayey) and SOM content was also shown to influence NH 3 volatilisation [84][85][86].…”

Evaluation of ammonia emissions from filtration of digestate used for fertigation

“…Ammonia deposition threatens ecosystem biodiversity, because it contributes to acidification and eutrophication processes (Petersen et al, 1998;Wagner et al, 2017;Truong et al, 2018;Zilio et al, 2020). Furthermore, NH3 can be transformed into nitrous oxide (which contributes significantly to the greenhouse gas effect), or into nitrate (which can leach into ground and surface waters, affecting aquatic biodiversity) (Verdi et al, 2018;EMEP/EEA, 2019). To progressively reduce the atmospheric emissions of five main air pollutants (including NH3), the EU has implemented the National Emissions Ceiling (NEC) Directive (European Environmental Agency, 2016).…”

“…To minimize these emissions, care and attention must be exerted when utilizing this product. The preferred application technique is by direct incorporation into the soil (Riva et al, 2016;Verdi et al, 2018). However, this approach limits the application of digestate to pre-sowing periods, which in turn reduces the nitrogen utilization efficiency; because nitrogen is applied long before crops will be able to uptake it, causing nitrogen leaching into the soil.…”