Biochar as a way to increase environmental friendliness for potted plants production and disease suppression

Abstract

Greenhouse production uses large amount of peat moss, which causes environmental and economic concerns. Using biochar (BC), a by-product of pyrolysis, to replace peat moss for greenhouse production could potentially address peat moss' environmental and economic concerns. Five experiments were conducted to test the potential of two types of BCs (the sugarcane bagasse biochar (SBB) and mixed hardwood biochar (HB)) as replacement of commercial substrates (CS) at different rates (by vol.) for tomato and basil seedling and plants production; the effects of the BCs, composts (vermicompost (VC), chicken manure (CM)), and mycorrhizae on fertilizer use reduction; and the effects of the BCs and Trichoderma spp. on Phytophthora capsici (pepper) and Pythium aphanidermatum (poinsettia) suppression. Plants grown in the CS were used as the control. Plants growth parameters such as soil-plant analyses development (SPAD) values, growth index (GI), total dry weight (TDW) were measured and disease parameters including disease severity (DS), disease incidence (DI), and area under disease progress curve (AUDPC) were measured. The results showed that tomato and basil seedlings from all the BC mixes (except SBB30) had similar SPAD and GI to the control. Tomato and basil plants grown in the BC mixes had a similar GI, SPAD, and yield to the control. Tomato and pepper plants grown in the HB-VC mixes had similar SPAD, GI, and TDW to the control. Pepper plants grown in 30%, 50%, and 70% HB and poinsettia plants in 20% HB had significantly lower DS, DI, and AUDPC for P. capsici and P. aphanidermatum, respectively. In conclusion, the HB70 mix can be successfully used for tomato and basil seedling production without negative effects on plant biomass; the HB can replace CS at 50% and the SBB at 70% for both tomato and basil plant growth without negative effects; the HB (≤ 70%) amended with VC mixes can reduce fertilizer use in tomato and pepper production without negatively affecting plant growth; HB30, HB50, and HB70 mixes can reduce pepper blight disease caused by P. capsici and HB20 can reduce poinsettia root rot disease caused by P. aphanidermatum.