Skip to main content
SLU publication database (SLUpub)

Doctoral thesis2017Open access

Greenhouse gas emissions from cultivated organic soils : effect of cropping system, soil type and drainage

Norberg, Lisbet

Abstract

Pristine peatlands are accumulators of organic material and large stores of carbon. During the past two centuries, large peatland areas in Sweden have been drained for agricultural purposes. Drainage of peatlands leads to an increase in soil carbon and nitrogen turnover rate, accompanied by release of the greenhouse gases (GHG), carbon dioxide (CO2) and nitrous oxide (N2O). Fluxes of methane (CH4) also change following drainage. Therefore, on-farm management and mitigation strategies are important. This thesis investigated whether choice of cropping system (grassland, cereals or row crops) can be used as a mitigation option for GHG emissions, whether differences in soil properties can explain emissions of GHG, how changes in drainage intensity influence CO2 emissions and whether different peat soil types respond differently to drainage. Effects of different cropping systems were studied by on-site measurements of GHG emissions from soil under two different crops grown adjacent to each other, and hence with the same soil type, drainage intensity and environmental conditions. The study was performed on 11 different sites representing different types of organic soils. The influence of drainage and chemical and physical soil properties was investigated in a laboratory study where 13 different organic soils were drained to different soil water suctions (near water-saturated to 1.5 m water column) and emissions of CO2 were measured at each suction step. The results show that no specific cropping system can be recommended as a better option for limiting GHG emissions from cultivated organic soils. The cropping system did not influence the fluxes of N2O and CH4, while the differences regarding carbon dioxide emissions were not conclusive. The laboratory soil samples represented a wide range of soil properties, but none of the measured properties was correlated with CO2 emissions. When peat soils were drained to 0.5 m water column, CO2 production was already at its highest level, so increasing the drainage intensity (to 0.75 or 1 m water column) did not result in higher CO2 emissions. The variations in GHG emissions were large between sites, within sites and over time. Soil properties, e.g. pH and carbon content, varied widely between soils. The peat soils studied responded differently to drainage, as was evident from the shape of the emissions-drainage curves.

Keywords

carbon dioxide, peat, greenhouse gas, cropping system, drainage, nitrous oxide, marl

Published in

Acta Universitatis Agriculturae Sueciae
2017, number: 2017:30ISBN: 978-91-576-8833-0, eISBN: 978-91-576-8834-7
Publisher: Department of Soil and Environment, Swedish University of Agricultural Sciences