Biochar Rates and Bio-Nematicide Effects on Tomato (<i>Solanum lycopersicum</i> L.) Growth, Yield and Root-Knot Nematodes (<i>Meloidogyne</i> spp.) Suppression in Northern Ghana

Abstract

Root-knot nematodes (Meloidogyne spp.) are among the most destructive pests limiting tomato production, particularly in tropical regions. Two experiments (pot and field trials) were conducted at the University for Development Studies, Nyankpala, Ghana, to evaluate the effects of different biochar amendment rates on the efficacy of a peptide-based bionematicide (Nemanol) in suppressing root-knot nematodes and improving tomato yield. The pot experiment comprised five (5) treatments; 0, 1, 3, and 5% biochar (w/w), applied with or without 5mL of peptide solution. Treatments were arranged in a completely randomized design with four (4) replications. The field experiment evaluated biochar application rates of 0, 2, 4, and 6 t/ha combined with 20 mL of peptide solution per plant, using a randomized complete block design with three (3) replications. In both experiments, treatments significantly (p<0.05) affected most measured growth, yield and nematode infestation indices. Low biochar application rates (1–3% in the pot experiment and
2 t/ha in the field experiment) significantly enhanced plant growth, canopy spread, flowering, and fruit yield compared with the control and higher biochar rates (5% in pots and 6 t/ha in the field). The combined application of 1% biochar and peptide increased plant height by 28.9%, while 2 t/ha biochar combined with peptide reduced root galling severity by 58.3% relative to untreated soil. Biochar amendment also reduced soil pH to a range more favourable for tomato growth. Overall, the combination application of moderate biochar rates and a peptide-based bionematicide effectively suppressed root-knot nematode populations and improved tomato growth and yield. These findings suggest that applying 2 t/ha of rice husk biochar together with 20mL per plant of peptide-based bionematicide can be recommended as an effective management strategy for root-knot nematodes control in tomato production in the study area.