More nitrogen to the crop! : to increase the nitrogen fertiliser value of cattle slurry and reduce its ammonia emissions

Sammanfattning

Nitrogen (N) is an essential nutrient in crop production. However, it is also a serious environmental pollutant. Therefore, maximising crop utilisation of applied fertiliser N, with minimal N losses to the environment, is crucial. The N fertiliser effect from cattle slurry, which accounts for 75 percent of all manure spread in Sweden, is generally low. Its high dry matter (DM) content leads to slow infiltration and this poses a risk of large ammonia losses after slurry application. A high DM content also means a high carbon/nitrogen (C/N) ratio, which reduces the plant availability of nitrogen. The focus of this PhD project was to study measures to increase the nitrogen fertiliser value of cattle slurry, through treatments that reduce the slurry’s C/N ratio and subsequently increase nitrogen availability to crops, combined with measures to reduce ammonia losses after slurry application. Crop utilisation of slurry N, expressed as Mineral Fertiliser Equivalents (MFE), was measured through harvest measurements in field trials and a pot experiment, and ammonia losses were measured in separate field experiments. Nitrogen availability depending on slurry and bedding material properties was investigated in two soil incubation experiments. Both solid-liquid separation and anaerobic digestion of cattle slurry, which reduces the slurry’s C/N ratio, increased slurry MFE. The relationship between slurry C/N ratio and nitrogen availability was also confirmed in the two incubation studies. Acidification of slurry with sulphuric acid effectively reduced ammonia losses from all slurry types. For untreated and digested slurry, this was also reflected in increased MFE values, but not for separated slurry. Slurry application with trailing shoes did in most cases not increase slurry MFE compared to trailing hoses. The study shows that there is potential to increase the N fertiliser value of cattle slurry, however, there are no simple solutions, and to achieve maximum effect, different measures must be combined.

Nyckelord

cattle slurry; slurry separation; biogas digestate; trailing hose; trailing shoe; acidification; ammonia emissions; nitrogen fertiliser value; C/N ratio

Publicerad i

Acta Universitatis Agriculturae Sueciae
2024, nummer: 2024:100
Utgivare: Swedish University of Agricultural Sciences

SLU författare

• Andersson, Karin

  • Institutionen för mark och miljö, Sveriges lantbruksuniversitet
    

UKÄ forskningsämne

Jordbruksvetenskap
Markvetenskap

Publikationens identifierare

• DOI: https://doi.org/10.54612/a.54eoldtk03
• ISBN: 978-91-8046-427-7
• eISBN: 978-91-8046-435-2

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/132431