Acidification Effects on In Situ Ammonia Emissions and Cereal Yields Depending on Slurry Type and Application Method

Abstract

Field application of organic slurries contributes considerably to emissions of ammonia (NH3) which causes sever environmental damage and can result in lower nitrogen (N) fertilizer efficiency. In recent years, field acidification systems have been introduced to reduce such NH3 emissions. However, combined field data on ammonia emissions and N use efficiency of acidified slurries, in particular by practical acidification systems, are scarce. Here, we present for the first time a simultaneous in situ assessment of the effects of acidification of five different organic slurries with a commercial acidifications system combined with different application techniques. The analysis was performed in randomized plot trials in winter wheat and spring barley after two applications to each crop (before tillering and after flag leave emergence) in year 2014 in Denmark. Slurry types included cattle slurry, mink slurry, pig slurry, anaerobic digestate, and the liquid phase of anaerobic digestate. Tested application techniques were trail hose application with and without slurry acidification in winter wheat and slurry injection and incorporation compared to trail hose application with and without acidification in spring barley. Slurries were applied on 9 m × 9 m plots separated by buffer areas of the same dimension. Ammonia emission was determined by a combination of semi-quantitative acid traps scaled by absolute emissions obtained from Draeger Tube Method dynamic chamber measurements. Experimental results were analysed by mixed effects models and HSD post hoc test (p < 0.05). Significant and almost quantitative NH3 emission reduction compared to trail hose application was observed in the barley trial by slurry incorporation of acidified slurry (89% reduction) and closed slot injection (96% reduction), while incorporation alone decreased emissions by 60%. In the two applications to winter wheat, compared to trail hose application of non-acidified slurry, acidification reduced NH3 emissions by 61% and 67% in cattle slurry, in anaerobic digestate by 45% and 57% and liquid phase of anaerobic digestate by 58%, respectively. Similar effects but on a lower emission level were observed in mink slurry, while acidification showed almost no effect in pig slurry. Acidifying animal manure with a commercial system was confirmed to consistently reduce NH3 emissions of most slurry types, and emission reductions were similar as from experimental acidification systems. However, failure to reduce ammonia emissions in pig slurry hint to technical limitations of such systems. Winter wheat and spring barley yields were only partly significantly increased by use of ammonia emission mitigation measures, while there were significant positive effects on apparent nitrogen use efficiency (+17–28%). The assessment of the agronomic effects of acidification requires further investigations.

Dairy Slurry Application to Stubble-Covered Soil: A Study on Sustainable Alternatives to Minimize Gaseous Emissions

“…Additionally, [29] reported reduced emissions from acidified pig slurry applied to crop residues, reinforcing the ability of acidification to mitigate NH 3 emissions under different field conditions. This ammonia abatement occurred because slurry acidification acts on NH 4 + /NH 3 balance, reducing NH 3 emissions [28,39]. The stubble cover on the slurry in US probably acted as a protective layer against abiotic factors that significantly influence ammonia volatilization (i.e., air flow and solar radiation), efficiently reducing NH 3 emissions, as described in [43].…”

“…Irrigation, when available, allows for slurry incorporation through rapid infiltration by water downwards into the soil when watering occurs immediately after slurry application [24]. Acidification is a technique, already used at field-scale [25], that can efficiently decrease NH 3 volatilization from animal slurry applied to soil [12,[26][27][28], although the slurry is applied on stubble-covered soil [29]. In-season slurry application (i.e., side-dressing application) may also contribute to decreasing N losses, as plants already emerged from the soil can uptake part of the available N [30].…”

Vallkonferens 2023

“…Med de mängder svavelsyra som krävdes för att sänka pH till önskad nivå blir svaveltillförseln (tabell 1) betydligt större än grödans behov (Jordbruksverket, 2021b). Danska försök med kommersiellt använd utrustning för spridning av surgjord gödsel har dock visat att man även med ungefär halva mängden tillsatt syra kan minska ammoniakförlusterna med ca 50-70 % (Wagner et al, 2021).…”

Perspectief van het aanzuren van mest in Nederland om methaan- en ammoniakemissie te reduceren

“…Nieuwe inzichten van onderzoekers in Denenmarken zijn dat er in de stal rond 12 kg zwavelzuur per ton varkensmest nodig is en rond 6 kg per ton melkveemest om een pH van 5,5 te bereiken (persoonlijke communicatie, september 2021). Uiteraard is de hoeveelheid zuur per eenheid mest afhankelijk van het type mest (zoals gehalte aan organische stof en carbonaat) en type zuur (Fangueiro et al, 2015;Seidel et al, 2017;Wagner et al, 2021) die worden gebruikt.…”

“…Dat is een stuk lager dan in Denemarken, waar gerekend wordt met een reductie van 49 % (Vera statement 2012) 6 . Recent onderzoek claimt in een vergelijking met het gebruik van sleepslangen door inmenging van aangezuurde drijfmest zelfs een reductie van de ammoniakemissie van 89% en 96% reductie bij aangezuurde drijfmest met gesloten slotinjectie, terwijl niet aangezuurde mest de uitstoot met 60% verminderde (Wagner et al, 2021).…”