Abstract
Ammonia (NH3) constitutes the single largest loss of manure nitrogen (N), making measures targeted at reducing its emissions meaningful for the environment and the overall efficiency of manure N use. In this study, the performance of two emission-reducing techniques, acidification and injection, were studied in a field experiment with grass ley over two growing seasons. Emissions of NH3, crop growth, and N use efficiency were determined from plots fertilized with cattle slurry either band spread, injected or band spread after acidification. The approximate cumulative NH3 losses from the plots with band-spread untreated slurry amounted to about 22 kg NH3-N ha−1 over the observation periods in 2017 and 10 kg NH3-N ha−1 in 2018. The injection and acidification reduced the estimated cumulative NH3 emissions by 43 and 95% respectively in 2018, and both by 97% in 2017. In 2017, the emission-reducing techniques had no impacts on crop growth, but in 2018, acidification increased dry matter yield by 29% and apparent N recovery by 65% compared with band-spread untreated slurry. According to the current results, acidification consistently produced the lowest NH3 emissions and a discernible positive yield effect. It can therefore be recommended instead of injection for reducing NH3 emissions in boreal grass cultivation.
Highlights
Despite decades of efforts to improve nitrogen (N) use efficiency in agriculture, a major reservoir of N excreted in livestock manures remains underutilized (Bouwman et al 2009; Leip et al 2011; Liu et al 2017)
The approximate cumulative NH3 losses from the band-spread untreated slurry (US) plots over the whole 28–54-h periods amounted to about 22 kg NH3-N ha−1 in 2017 (54 h) and 10 kg NH3-N ha−1 in 2018 (28 h) (Fig. 1), composing 31 and 12% of the NHþ4 -N initially applied in the slurry respectively
In 2018, the corresponding reductions were 43% for US inj. and 95% for Acidified slurry (AS), the estimated total emissions reaching about 5.7 kg NH3-N ha−1 (30 h) and 0.5 kg NH3-N ha−1 (29 h) respectively
Summary
Despite decades of efforts to improve nitrogen (N) use efficiency in agriculture, a major reservoir of N excreted in livestock manures remains underutilized (Bouwman et al 2009; Leip et al 2011; Liu et al 2017). Losses of manure N over storage and during and directly after soil application are dominated by NH3 volatilization (Webb et al 2013). According to the modeling of Oenema et al (2007), an average of 19% of the N excreted in animal housing volatilized as NH3 during storage, and another 19% following soil application. Due to the dominance of NH3 in N losses, measures targeted at reducing its emissions are meaningful in increasing the overall efficiency of manure N use
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