Vermi – biochar as alternative to peat as growing substrate for greenhouse vegetables

| Type artikkel: Månedens masterMasteravhandling
Biochar is a novel soil amendment technique with a potential of sequestering atmospheric carbon into soil with an increase in certain soil quality parameters essential for crop production. Intense use of peat as growing media, especially in horticulture, has led to a huge exploitation of stable carbon from wetland mosses into the atmosphere accelerating climate change.
Certainly, there is a need for sustainable alternatives. Series of research on using coconut fiber or other composts have been conducted for testing peat alternatives. The results, however have not always been positive, mainly due to water and nutrient mobility and stability issues. My study examined biochar prepared from a mixed woodstock of ash (Fraxinus excelsior L.), beech (Fagus sylvatica L.) and oak (Quercus robur L.) prepared at 500 - 550 °C in a slow pyrolysis reactor on a vegetable farm in Åsgårdstrand, Vestfold. An initial experiment was made to examine the effect of biochar on germination and in this trial onion (Allium cepa L.) was selected due to its sensitivity at an early stage. These initial results showed that biochar, if diluted, would not harm the crop establishment. A new experiment was then conducted to test if biochar mixed with vermicompost (vermibiochar) in a 1 : 2 ration (w/w) could replace, at least some of the peat used in greenhouse production of vegetables. This vermibiochar was then mixed with a commercial peat soil in different volumetric ratios 40 : 60, 60 : 40, 70 : 30, 80 : 20, 100 : 0 respectively, and with 100 % of the commercial peat soil as a control. Vermibiochar has a slightly alkaline nature and contains high levels of macro-and micro-nutrients. Red Cherriette radish (Raphanus sativus L. var. sativus) was selected for the experiment, as this was a priority crop for the collaborating farmer. Germination rate, radish root and shoot weight, number of marketable leaves and total biomass production were examined. The results showed that vermibiochar rates from 40 to 70 % in the peat mix, led to a significant increase in radish root weight and total biomass production compared to peat soil alone. As there was no significant differences in root weight and total biomass production between a growth substrate based on vermibiochar and substrate based on peat, one could argue that vermibiochar could replace 100 % of the peat used in greenhouse production of radish. Most likely, the same will be true for other crops raised in peat-based soils. Further research is needed to verify if this would also be the case for other peat-based horticultural productions.   Se masteroppgaven under "relevante dokumenter".