Determining Eastern Red Cedar Biochar Soilless-Media Supplementation Rates for Potted Geranium and Petunia Production

Abstract

The use of biochar in soilless media is becoming more common in greenhouse production. This study was conducted to evaluate Eastern red cedar biochar as a soilless-media supplement for the growth of geranium (Pelargonium graveolens L.) and petunia (Petunia sp. J.) as potted plants in greenhousese. Eastern red cedar biomass was produced at three different temperature ranges 300–350 °C, 400–450 °C, and 500–550 °C and applied at 15%, 30%, 45%, and 60% v/v to a soilless media plus a control. Additionally, Eastern red cedar (ERC) bark was also applied at 15%, 30%, 45%, and 60% v/v to a soilless media. The growth characteristics of the plants along with the physical and nutrient properties of the growth media were recorded. For physical properties, 100% soilless media had the greatest bulk density, 60% biochar at 400–450 °C showed the greatest total porosity, and 60% ERC bark showed the greatest air porosity. For geranium, 15% biochar at 500–550 °C showed the greatest height, water use efficiency, and shoot dry weight, while 15% biochar at 300–350 °C showed the greatest width. The greatest number of flowers was at 45% biochar at 500–550 °C. For petunia, 15% biochar at 300–350 °C showed the greatest height, and 15% biochar at 500–550 °C showed the greatest width. The greatest number of flowers and flower diameter was achieved with 100% soilless media. The 15% biochar at 500–550 °C had the greatest shoot dry weight and water use efficiency, and 60% biochar at 400–450 °C had the greatest root dry weight. Biochar treatment outperforms the ERC bark treatment for both species. Within biochar treatment, 15% biochar outperforms dry biomass, while for flowering, 100% soilless media performs best for petunia, and biochar performs best at less than 45% for geranium.