Synergistic effects of engineered biochar and organic fertilizers on the plant growth, yield, and fruit quality of bell pepper and tomato in a tropical laterite soil

The synergistic effects of engineered biochar (EB) and organic fertilizers on plant growth, yield, and fruit quality of bell pepper (Capsicum annuum) and tomato (Solanum lycopersicum) were assessed through a field study in tropical laterite soil in West Bengal, India. EBs were synthesized via slow co-pyrolysis of Eucalyptus biomass with waste plastics (polystyrene and low-density polyethylene) under optimized process conditions. The experimental design consisted of 40 treatments, incorporating three EB application rates (5, 10, and 15 t ha⁻¹) with or without fixed quantities (20 t ha⁻¹) of organic fertilizers—manure, vermicompost, and their 1:1 (w/w) mixture—alongside negative and positive controls. Co-application of EB and manure significantly enhanced plant growth and fruit yield, achieving increases of 112% (bell pepper) and 84% (tomato) compared to manure alone. Relative to the control, fruit yield improvements reached 238% for bell pepper and 198% for tomato. Notable enhancements in fruit quality parameters and mineral content were observed under combined EB and organic fertilizer treatments. While EB application rates and organic fertilizer types exhibited significant effects, the type of biochar showed minimal influence on outcomes. Unlike the rapid nutrient release dynamics characteristic of organic fertilizer-soil mixtures, co-application of EB and organic fertilizers facilitated higher nutrient retention and gradual release dynamics. The study identified 10 t ha⁻¹ EB combined with manure as the optimal treatment for maximizing bell pepper and tomato productivity in tropical laterite soils.