Doctoral dissertation: No-till farming benefits the environment, but climate impact remain small
No-till farming reduces soil erosion and promotes soil biological activity, but its climate benefits appear to be minor under Finnish conditions. This is demonstrated in the doctoral dissertation of MSc Henri Honkanen, a researcher at the Natural Resources Institute Finland (Luke), who examined the impact of no-till cultivation on carbon cycling and greenhouse gas emissions in mineral and peat soils.
The no-till method, which has become more common in Finland, is known for reducing workload decreasing nutrient leaching and improving soil structure. However, its climate effects remain unclear in boreal conditions, particularly on peat soils.
In his study, Honkanen measured greenhouse gas emissions, carbon dioxide (CO₂), nitrous oxide (N₂O) and methane (CH₄), as well as the soil carbon balance in spring cereal cultivation on both no till and ploughed fields. Measurements were conducted over two years on clay soil and over three years on peat soil. In addition, on the clay soil, subsurface and surface runoff and grain yields were monitored on clay soil for ten years, after which the soil properties were studied.
Several environmental benefits
“No-till improved soil structure and clearly increased the earthworm abundance compared with ploughing. This indicates better soil biodiversity and reduced erosion,” Honkanen says.
On clay soil, total erosion caused by subsurface and surface runoff was reduced by more than half, but grain yields were on average 16 per cent lower compared with ploughing.
“In contrast, changes in both the carbon balance and greenhouse gas emissions of clay and peat soils were small. The climate benefit was therefore not clearly visible, at least in the short term,” Honkanen notes.
Although the amount of carbon lost through erosion decreased significantly under no-till farming, its contribution was small compared with the carbon loss, which was mainly due to soil respiration. Especially on peat soil, soil respiration accounted for a large share of carbon loss.
Weather conditions affect the results
The study found that nitrous oxide emissions varied considerably between years. In one year, no-till reduced emissions on both clay and peat soils, while in another year, the effect was the opposite compared with ploughing
During the measurement period, the global warming potential of greenhouse gas emissions from peat soil was on average about 13 per cent lower under no-till than under ploughing. However, the results include uncertainties, and the short monitoring period does not yet reveal long-term effects.
Honkanen emphasises that weather conditions can greatly influence the effect of no-till on greenhouse gas emissions from fields compared with ploughing. For example, the measurement period, included a dry early summer, which may have benefitted no-till compared to ploughing. To assess long-term effects, measurements are needed over many years and under different weather conditions.
“The results show that changes in emissions are not self-evident: the reduction in erosion under no-till is consistent from year to year, whereas changes in greenhouse gas emissions are smaller and more variable,” Honkanen concludes.
Doctoral dissertation on 7 November 2025
MSc Henri Honkanen will defend his doctoral dissertation “Effect of no-till on carbon balance and greenhouse gas emissions in boreal mineral and peat soils” on 7 November 2025 at 13:00 in the Faculty of Agriculture and Forestry of the University of Helsinki.
The opponent will be Professor Marja Maljanen from the University of Eastern Finland, and the custos will be Professor Laura Alakukku from the University of Helsinki.
The public defence will take place in Lecture Room 1041, Biocenter 2, Viikinkaari 5, Helsinki. The event will also be accessible online.
