Impact of rice straw biochar in association with inorganic fertilizers and Trichoderma harzianum on charcoal rot (Macrophomina phaseolina) of maize

Phytosanitary regulations concerning pesticide residues are among the most important problems faced by today's agricultural environment. Therefore, the purpose of this study was to produce and characterize indigenously produced biochar from raw material based on rice straw. The biochar synthesized at 480°C, was used as amendment at different volumetric concentrations (3 and 6%), along with in-organic fertilizers for restricting the development of charcoal rot (Macrophomina phaseolina), in maize (Zea mays L.) The scanning electron microscopy (SEM) analysis of rice straw biochar showed micro-cracks, rough texture, and intricately formed pores, thus showcasing the complex and porous nature of the rice straw biochar resulting from the pyrolysis process. The energy dispersive X-ray spectroscopy (EDX) analysis confirmed its carbonaceous composition (approximately 54%), with the presence of functional groups like hydroxyl and carboxyl, as well as trace amounts of potassium, calcium, and silicon. Maize grown in soil amended with 6% biochar showed significant reduction in shoot and root weights (51.72 and 74.11%, respectively) when compared to 3% biochar amended soil in the presence of M. phaseolina. Our results revealed that 3% rice straw biochar and Trichoderma harzianum proved most effective for the management of charcoal rot as indicated by lowest disease incidence and disease severity (40%, each). Maize showed variable degrees of defense mechanisms activation in response to soil biochar amendments. Biochar application rate of 6% did generally not improve the maize dry biomass production and tolerance to charcoal rot. These findings will surely help us understand biochar-induced changes in physiology of maize and possible activation of defense response against M. phaseolina