Abstract
Increasing costs and environmental issues regarding excessive use of peat moss is impacting the horticultural industry. Biochar is a valuable substrate additive that has the potential to reduce the use of peatmoss in greenhouse production. However, its varying effects on ornamentals requires that individual species and cultivars of crops must be evaluated to determine the threshold for benefits. Viola cornuta is a high value ornamental crop; however, information on how different rates of biochar rates affect productivity and physiology of Viola cultivars in container production is not known. To determine if biochar rates could increase the productivity of Viola, we mixed a peat-based substrate with 10, 25, and 50% (w:w) hardwood biochar in two studies on four cultivars. Without fertilizers, 10 and 25% biochar improved plant biomass, growth, root length, and flowering, but 50% biochar was found to have negative effects on plant growth and flowering. Cultivars varied in their response to biochar rates. When fertilizer was applied in the second experiment, biochar rates did not impact growth parameters or flowering. These results suggest that up to 25% biochar can be used in Viola production without detrimental impacts. However, 50% biochar can be used with the addition of fertilizer without negatively affecting plant growth. Biochar can have a short-term impact on the growth characteristics of Viola plants in container production, but fertilization and growing period of Viola may influence these effects. These results indicate that biochar could be the suitable replacement for peat moss, with up to 50% biochar rate in Viola production reducing the environmental and economic burden for peat moss.
Highlights
Peat moss is one of the main components of soilless potting mixes used in container production in commercial greenhouse industries
The objective of this study was to determine the threshold rates at which hardwood biochar can be added to potting soil in container production of Violas without having detrimental effects
The differences in nutrient content in the two experiments is likely due to fertilizer application, nutrient leaching by biochar, plant age, and the length of time plants were grown (5 weeks for experiment 1 and 13 weeks for experiment 2). These results show that biochar may have had some effect on nutrient availability and uptake in container grown plants and further research is needed to determine the effect of biochar on macro- and micronutrients of container grown plants
Summary
Peat moss is one of the main components of soilless potting mixes used in container production in commercial greenhouse industries. Horticultural crops use around 11 million kilograms of peat moss annually [1]. Due to adverse environmental pressure and high rates of peat extraction, alternatives for peat moss are needed [2]. Most of the peat is extracted in Canada and transported to the US, increasing the shipping and handling cost [3,4]. Different organic and inorganic soil additives are being substituted for portions of this growing media [5,6]. Biochar is being increasingly explored in production due to its many beneficial properties [5,7]
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