2017 ASHS Annual Conference

Sixteen mixes with biochar (BC; 20, 40, 60, 80%, vol.) and vermicompost (VC; 5, 10, 15, 20%, vol.) were evaluated as container substrate on container-grown basil (Ocimum basilicum) and tomato (Solanum lycopersicum ‘Roma’) plants, and compared to 100% commercial peat-based substrate. The commercial substrate made up the rest of the volume when the BC and VC did not add up to 100%. The physical properties of these different substrates were tested which showed adding up to 80% BC to the substrates significantly decreased the container capacity and increased air space. Plant growth index, SPAD, substrate pH and electrical conductivity (EC) were also measured at 0, 4, 6, 8 and 11 weeks after transplanting (WAT), and plants were harvested to measure dry weight (DW) of shoot and root and additionally combined fruit and flower dry weight for tomato plants. As the percentage of biochar increased, substrate pH increased. At 11 WAT, none of the SPAD readings of basil was lower than the control, while the SPAD readings of tomato plants in the 60% and 80% BC mixes were all lower than the control. After 8 WAT, EC of substrate leachates of basil in all BC and VC mixes were lower than the control, except for 5%VC with 20% BC, and for tomato plants EC of 80% BC with 5%, 15% and 20% VC mixes was lower than control. Growth index, shoot dry weight DW, total DW of basil and tomato plants and root DW of basil grown in mixes with BC and VC were similar to or even higher than the ones in commercial substrates at 11 WAT. No tomato plants in mixes with BC and VC had higher root DW than control. Tomato plants in 60% BC+ 20% VC and 20% BC+10%VC had higher combined DW of fruit and flower than the control and the other treatments are not different from control. In summary, the biochar and vermicompost mixes had the potential as replacements for commercial peat-based substrates for container-grown plants.