Application of Invasive Weed Biochar as Soil Amendment Improves Soil Organic Carbon Fractions and Yield of Fodder Oat in a Semi-Arid Region

The use of biochar has been widely recommended to improve crop productivity, carbon (C) sequestration, and soil quality in a variety of agro-ecosystems. However, the impacts of biochar and chemical fertilizers on soil organic carbon (SOC) fractions in fodder production systems are inadequately investigated. We evaluated the effects of combining reduced recommended dose of fertilizers (RDF) with invasive weeds biochar as soil amendment on SOC fractions, oat (Avena sativa L.) yield and carbon management index (CMI). To compare the effects of biochar on SOC fractions, fodder production, and CMI, ten treatments (Control, 100% RDF, 75% RDF, and three dosages (2.5, 5.0, and 10 tha^-1) of Parthenium hysterophorus L. biochar (PB) and Lantana camara L. biochar (LB), and 10 tha^-1 PB/LB alone) were used. Application of biochar 10 tha^-1 with 75% RDF significantly improved TOC (~ 34–44%), WBOC (~ 21–23%), POC (~ 40–44%), SMBC (~ 4.89–4.98%) and mean SI (~ 40–54%), CMI (~ 17–28%), and ultimately C build up (~ 43–56%) as compared to RDF, whereas HWSC and KMnO₄-C were significantly higher in LB and PB at 5 tha^-1 with 75% RDF, respectively. Green and dry fodder yields of oat were also remarkably improved with biochar application, but at par with RDF. The application of PB and LB as soil amendment with 75% RDF provides novel avenues for C sequestration, counteracting climate change, and improving soil quality via increasing TOC and its fractions, resulting in higher productivity. At the same time, it also provides an economical feasible approach to invasive weed control.