DOES BIOCHAR IMPROVE DISTURBED, SANDY SOILS?

We studied whether adding biochar to sandy, carbon-poor soil impacts plant growth. Biochar is an organic compound composed mainly of black carbon and made by pyrolysis of organic matter. Biochar is of interest as a possible soil amendment to alleviate stresses on agricultural production due to its high water and nutrient retention capabilities, high cation exchange capacity, high porosity that increases mycorrhizal growth, and ability to sequester carbon dioxide.

We examined the growth of three different plant types, Avena sativa (common oat), Vigna radiata (mung bean), and Raphanus sativus (cherry belle radish), in greenhouse and garden plot experiments. In the greenhouse we used five different treatments of soil from a demolition site: soil alone and soil mixed with 2%, 5%, 10%, and 20% biochar by mass. All biochar was washed to remove ash and inoculated with compost tea before mixing. Four replicates of each species were planted in individual pots of each of the five soil types for a total of 60 plants. Plants were grown for 5 weeks and watered every other day. At the end of the growth period, A. sativa and V. radiata plants were cut off at the soil surface and entire R. sativus plants were removed from soil, then dried in a plant press before weighing. All 60 replicates produced plants, with no statistically significant differences in oat and mung bean above ground biomass or radish whole mass for any treatment.

In the garden experiment at a grassed-over former building site, we planted 10 seeds of each plant in each of 5 plots: soil only, 3% compost by mass, 3% biochar by mass, and 3% and 5% biochar inoculated with compost tea. Oats had 100% germination in all plots, while radishes yielded 8, 7, 5, 9, and 7 plants respectively. For mung bean the control and compost plots yielded only 2 and 4 plants while the biochar treatments yielded 7, 3, and 9 plants. Whereas all soil treatments grew plants under controlled greenhouse conditions, the garden experiment, which is ongoing, suggests that under more natural conditions biochar may influence germination and survival.