Epsilon Archive for Student Projects

Abstract

In a column experiment the effect of three different biochars on nitrous gas emissions, nitrogen
retention and water filled pore space (WFPS) were studied in a Swedish sandy soil, classified as a
Cryopsamment. Ammonium retention was positively correlated, while KCl-extractable ammonium
was negatively correlated, with the specific area of the biochars. The question was raised whether the
negative correlation between extractable ammonium and biochar specific area reflects the amount of
ammonium present in the soil or its extractability from the biochar, and whether methods for
extracting soil mineral nitrogen, like KCl-extractions, have to be modified for application on biochar
amended soils. There was a tendency of increased nitrate retention and KCl-extractable nitrate with
biochar and KCl-extractable nitrate was positively correlated with the specific area of the biochar. pH
was higher for all biochars compared with control, although the differences were not significant, and
WFPS was lowered by biochar addition, significantly in one case. Nitrous oxide emissions were
generelly lower from biochar amended columns, although emissions from one of the biochars was
higher than control in the beginning of the measurements. The effect on nitrous oxide emissions
seem, in part, to be mediated by the increase in pH from the biochar addition. Among other factors,
nitrous oxide emissions was also negatively correlated with the specific area of the biochar.

I ett kolonnförsök studerades effekten av tre sorters biokol på lustgasavgång, kväveretention och
andel vattenfyllda porer (WFPS) i en svensk sandjord (klassificerad som Cryopsamment).
Ammoniumretentionen var positivt korrelerad med kolets specifika yta, medan KCl-extraherbart
ammonium var negativt korrelerad med kolets specifika yta. Det diskuterades huruvida den negativa
korrelationen med kolets specifika yta berodde på mängden ammonium i jorden eller dess
extraherbarhet och om metoder för att mäta markkväve behöver modifieras för att ge en rättvisande
bild på biokolberikade jordar. Det fanns en tendens till ökad nitratretention och mängd KClextraherbart
nitrat med biokol och KCl-extraherbart nitrat var positivt korrelerat med den specifika
ytan på kolet. pH var högre med alla kolsorter jämfört med kontrollbehandlingen, även om
skillnaderna inte var signifikanta, och WFPS minskades av tillsatt biokol, signifikant i ett av fallen.
Lustgasavgången var generellt sett lägre från de biokolberikade kolonnerna, men från en av
kolsorterna var avgången högre i början av lustgasmätningarna. Effekten på lustgasavgången verkar
delvis orsakas av biokolets pH-höjande effekt. Bland andra faktorer korrelerade med lustgasavgången
fanns kolets specifika yta som var negativt korrelerad med lustgasavgången.