Overflatekompostering med tilsetning av urtefermentet Terra Biosa - Effekter på jordbiologi og nitrogen

Surface composting is an interesting method to end a cover crop without the use of glyphosate and ploughing. The purpose of the project was to investigate whether adding the herbal ferment Terra Biosa improves the effect of surface composting on soil fertility by stimulating faster and more controlled conversion of the organic material. We have investigated the effect on soil biology, the amount of mineral nitrogen in the soil and the plants' nutrient uptake and plant growth. The field trial will be carried out on the farm Ormo in Skjeberg in Sarpsborg municipality, hosted by Dag Molteberg. Conventional grain production with synthetic fertilizers has been carried out on the farm since the 1970s. Since 2020, the farm operation is run according to regenerative principles, i.e. all chemical-synthetic spraying is omitted, the use of synthetic fertilizers reduced, cover crops are used to avoid bare land and tillage is more gentle (surface composting with application of fermented herbs and microorganisms Terra Biosa). In the spring of 2021, spring wheat was sown with a cover crop mixture that grew throughout the autumn of 2021. The cover crop was relatively dense when it was surface composted on 1st of May 2022. The cover crop was shallowly mixed into the soil with a rotary tiller and the plant roots were cut off at a depth of about 3 cm. At the same time as rotary tilling, Terra Biosa (10 litres/day mixed with 30 litres/day of water) was sprayed on plots with Terra Biosa treatment. On 6th of May, the field was harrowed and seedbeds prepared. Six-row barley and a new cover crops were sown on 8th of May. The experimental field was not weeded. The experimental field was laid out as a block experiment with four replicates. Each route was 8.5 m wide and 25 m long. We expected that the addition of Terra Biosa would stimulate the content and activity of the soil microbiology and their metabolic processes. In our investigations, we cannot confirm that we have had a more controlled transformation of the plant material, but we found a significant effect of Terra Biosa on an increased content of fungi in the soil registered with microBIOMETER. At the first soil sampling on 5th of May, four days after surface composting with the addition of Terra Biosa, there was no significant effect on microbial carbon (fungi and bacteria), but the content of fungi increased throughout the season and after harvesting in September, significantly more fungi were measured with microBIOMETER. We found no significant effect of Terra Biosa on the concentration of nitrate and ammonium in the soil, soil respiration (Solvita CO2-C), microbial active carbon (POX-C), soil odor, microscopy according to the SoilFoodWeb methodology soil attachment ("root fur") on the barley roots. All these surveys were only done early in the season. Nutrient uptake was examined using leaf sap analyzes of the barley plants on 1st of June (2-3-leaf stage) and 15th of June (beginning stretch), but here too there was no difference between the treatments. We also found no effect of Terra Biosa on barley yield. Significant effect of Terra Biosa found late in the season suggests that beneficial processes may continue for a long time after application. Simultaneously, the 2022 season started dry and cool and may have reduced and delayed the effect of Terra Biosa. These facts may indicate that there are a greater effects of Terra Biosa than we could demonstrate in this survey. Therefore, more research is desirable to understand how Norwegian arable soil responds to the treatment of Terra Biosa during surface composting of cover crops and other organic material. More research is also needed on surface composting itself to find the best methods for different soil types and climates. Future investigations should therefore take place on several soil types, over a longer period of the growing season and perhaps over several seasons