Farm Table says:
Biochar Decelerates Soil Organic Nitrogen Cycling but Stimulates Soil Nitrification in a Temperate Arable Field Trial
What is the problem?
Biochar (BC) is produced by pyrolysis (heating in absence of oxygen) and used as a form of carbon sequestration in carbon farming and as a soil amendment for crop and pasture production. The full effects of BC amendments to the soil are not understood but crop production increases have been recorded. This experiment by the University of Vienna focused on the effects of BC amendment in temperate arable fields, with analysis of probable cause and effects from the addition of biochar to the soil.
What did the research involve?
Biochar can impact soil processes by its porous structure and large surface area, in conjunction with its cation exchange capacity. This can change the bulk density, water holding capacity, pH and ion availability in the soil and in turn affect microbial activity, impacting available nutrients in the soil.
- BC for this experiment was made from beechwood ‘feedstock‘.
- The field trial in Austria tested 4 treatments (NPK fetilizer; NPK + 24t/ha BC; NPK + 72t/ha BC; and 72t/ha BC with no NPK)
- Isoptopic tools and molecular techniques were used to track nitrogen cycling, nitrification processes, and microbe populations
- Soil samples taken after 4 months and 18 months
What were the key findings?
Biochar amendment increased organic carbon and total nitrogen concentration in the soil. Although, the plant available nitrogen was dependent on the concentration of inorganic nitrogen fertilizer applied. This is because organic nitrogen cycling decreased while inorganic nitrification rates increased. This could lead to nitrate leeching if plant uptake does not match the increased nitrification rates.
It should also be noted that biochar from different sources could have different results.
Carbon sequestration is important for climate change reduction initiatives, with biochar showing promising aspects as a soil ameliorant as an additional benefit. Although BC addition does show an increase in nitrification rates, there would be minimal nitrification without the addition of nitrogen fertilizer.
This paper was summarised by Mia Courtney (Agricultural Sciences Student – La Trobe University) and reviewed by Nickala Best (PhD Student – La Trobe University). Learn more about Mia and Nickala here.