Invasive Aquatic Plant Biochar Increases Soil Organic Carbon Stocks and Maize Productivity in Tropical Climate

ABSTRACT Studies on the influence of invasive aquatic plant (IAP) biochar and its co‐compost on persistent soil organic carbon pool and crop productivity in tropical climates are scanty. Consequently, a three‐season field experiment was conducted in Ghana, West Africa to fill this gap. Maize was cultivated under nine treatments using recommended full mineral fertiliser rate (M) (90–60–60 kg ha −1 N:P 2 O 5 : K 2 O), biochar at 2.5 t ha −1 (B2.5) and 5 t ha −1 (B5), co‐composted biochar at 2 t ha −1 (C2) and 4 t ha −1 (C4), a co‐application of biochar and co‐composted biochar (B2.5 + C2), co‐application of mineral fertiliser with biochar (M50% + B2.5) and co‐composted biochar (M50% + C2), and a control. Our results showed that the application of IAP biochar or its co‐compost increased the persistent soil organic carbon pool by 36%–50% through greater accumulation of mineral‐associated organic carbon (MAOC). The largest bulk soil organic carbon stock of 25.52 t ha −1 was observed in C4 at 0–15 cm depth. The greatest proportion of bulk soil carbon was stabilised in the MAOC under M50% + C2, further showing the benefits of integrated soil fertility management with IAP. The B5 treatment increased particulate organic carbon (POC) and soil microbial biomass carbon concentrations by up to 300%, highlighting the potential role of IAP in increasing tropical soil health. In all three seasons of cropping, amendments particularly C4, C2, and B2.5 + C2 significantly ( p < 0.05) enhanced leaf chlorophyll content, NPK uptake, and grain yield. The most profitable soil amendments were C4, C2, and B2.5 + C2 reflected by higher value‐cost ratios (VCR > 2). We suggest that biochar from IAP serves as a climate‐smart technology and offers the potential to increase crop productivity and contribute to the “recarbonizing global soils” initiative for sustainable agro‐ecosystems.