In a three-year project, researchers at NIBIO have tested how biochar affects potato yields and soil quality under Norwegian conditions. The results show that biochar has little effect on yield, but that it may offer other benefits.
“We found no significant yield differences between fields with and without biochar in most of the trials,” says project leader and NIBIO Research Scientist Eldrid Lein Molteberg.
“The exception was one large-scale trial in Romedal (Innlandet County) in 2022, where biochar led to a moderate yield increase. Otherwise, the effects were small or uncertain – also in subsequent years with cereals.”
The researchers tested different amounts of biochar, both alone and in combination with organic and mineral fertilizers. Neither higher doses nor specially treated biochar enriched with clay minerals (bentonite) produced better results than standard biochar.
Soil quality and climate impact
Although the yield effect was limited, some measurements suggest that biochar may improve soil properties over time. Soil samples showed an increased level of active carbon – an important indicator of biological activity in the soil.
“Biochar appears to stabilize the soil,” says Lein Molteberg.
“It may contribute to better water retention and less erosion, especially in sandy soils.”
May contribute to lower emissions
Biochar may also have a climate benefit. The material is produced by heating organic matter without oxygen, binding carbon in the soil instead of releasing it as CO₂.
When used at scale, this can help reduce agriculture’s climate footprint.
Depends on soil and growing conditions
The researchers emphasize that the effect depends on where and how biochar is used.
In this project, the trials were carried out on fertile soil in good agricultural condition, where growing conditions were already favorable. The effect may be greater in poorer soils or under drier conditions.
“Our results are consistent with other Norwegian studies, which also do not find large yield gains,” says Lein Molteberg.
More knowledge needed
Even without a clear yield effect, the researchers believe biochar may be relevant for farmers who want to improve soil health or reduce emissions.
“We need more knowledge about long-term effects, and about how biochar affects different crops and soil types,” concludes Lein Molteberg.