Abstract
Biochar has been proposed as an amendment that can improve soil conditions, increase harvest yield, and reduce N losses through NO3− leaching and N2O emissions. We conducted an experiment to test the hay biochar mitigation effect on N2O emissions depending on its production temperature. The pot experiment consisted of the soil amendment with three different production temperature biochars (300 °C, 550 °C, 850 °C) alone and in combination with three different organic fertilizers (cattle slurry, slurry digestate, vinasse), in growth chamber conditions. The effects of biochar and fertilizer were both significant, but the interaction biochar:fertilizer was not. The amendment with the three fertilizer types and with the highest production temperature biochar resulted in significantly higher cumulative N2O fluxes. Biochar did not show a mitigation effect on N2O emissions when applied with organic fertilizer. Cumulative emissions were higher with biochar addition, with increasing emissions for increasing biochar production temperature. Our results support the idea that biochar cannot be considered as a universal tool for the reduction of N2O emissions.
Highlights
The urge to reduce emissions of greenhouse trace gasses (GHG) is generally acknowledged [1], with special focus on nitrous oxide (N2 O) due to its high global warming potential [2], and for being the main ozone-depleting substance [3]
We studied N2 O emissions from a soil amended with pelletized hay biochar produced at three different temperatures (300 ◦ C, 550 ◦ C, and 850 ◦ C) and three organic fertilizers separately and in mixture
The ineffectiveness of the studied biochar in reducing N2 O emissions could be explained by its low C/N values (Table 2), as the C/N values of the studied biochars were much lower compared to those commonly reported in the literature [21], even for biochar produced from herbaceous residues [23]
Summary
The urge to reduce emissions of greenhouse trace gasses (GHG) is generally acknowledged [1], with special focus on nitrous oxide (N2 O) due to its high global warming potential [2], and for being the main ozone-depleting substance [3]. Anthropogenic sources of N2 O account for almost 40% of global emissions, of which, agriculture represents 67%–80% [4]. Nitrogen fertilization, both organic and inorganic, is the main factor explaining the contribution of agriculture to N2 O emissions [4,5]. N2 O emissions from the soil are the product of two main processes: nitrification and denitrification [6,7]. Organic fertilization is the main fate of manure slurry [8], a by-product of livestock farms rich in NH4 + , but it has been found to produce higher N2 O emissions than synthetic fertilizer for the same amount of applied nitrogen [9,10]. Slurry digestate is the by-product of anaerobic digestion of slurry, used for fertilization [11], and can have a higher NH4 + content than the original slurry [12]
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