Effect of pine wood biochar mixed with two types of compost on growth of bell pepper (Capsicum annuum L.)

Abstract

The purpose of this study was to evaluate the biochar from fast pyrolysis of pine wood mixed with manure compost or vermicompost as a potential container substrate to replace peat moss. Seven biochar substrates were compared to the control (a commercial substrate; 0B) in container cultivation of bell pepper (Capsicum annuum L.): 100% biochar (100B), 90% biochar + 10% manure compost (90B10C; by volume), 80% biochar + 20% manure compost (80B20C), 70% biochar + 30% manure compost (70B30C), 90% biochar + 10% vermicompost (90B10V), 80% biochar + 20% vermicompost (80B20V), and 70% biochar + 30% vermicompost (70B30V). The physical characteristics of the container substrate (total porosity, container capacity, air space, and bulk density) were tested using NCSU porometers. The electrical conductivity (EC) and pH of container substrate leachates were measured according to the pour-through method on 34, 41, 62, and 83 days after planting (DAP). Growth index was measured on 34, 41, 48, 55, 62, 69, 76, and 83 DAP. Leaf SPAD value, net photosynthesis rate, total leaf area, and stem diameter were measured at week 11. Dry weight and yield were measured at the flowering (72 DAP) and harvesting (113 DAP) stages. The control showed the highest container capacity (59.2%) and the lowest air space (14.1%), with the opposite results observed on 100B. Control had pH values within 6.0–7.0 for optimum pepper growth, while container substrates with biochar resulted in a pH less than 6.0 from 41 to 83 DAP. EC in control at 34 DAP was approximately four times greater than values observed on the other substrates. EC of 70B30V slightly increased between 34 and 41 DAP, and the lowest EC was observed on 100B. SPAD value and net photosynthesis rate were the greatest on plants grown in control. The total leaf area, stem diameter, growth index, vegetative (stem + leaf) and flower dry weights, and yield were the highest in control, followed by 70B30V, 80B20V, and 90B10V, with the lowest in 100B.