Agricultural crop residues such as corncobs, rice husks, and cassava stems are generated in massive quantities across farming regions in Thailand. When farmers burn these leftovers before the upcoming planting season, large volumes of greenhouse gases and harmful air pollutants enter the atmosphere. Processing agricultural leftovers into carbon-rich biochar through oxygen-limited heating presents a sustainable alternative for waste management while simultaneously sequestering carbon and improving soil fertility.

Coffee plants, specifically Arabica coffee seedlings, remain highly sensitive to environmental factors and soil nutrient availability during early growth stages. Producing strong, healthy seedlings in nursery environments ensures higher survival rates and better growth once plants move to open field conditions. Integrating corncob biochar alongside plant growth-promoting bacteria like Bacillus megaterium can optimize soil structure, enhance nutrient retention, and encourage robust root and stem development. Evaluating different application rates reveals that higher proportions of biochar yield distinct chemical improvements in nursery soils. Applying biochar at rates of two percent and three percent by dry soil weight produced significant increases in soil pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More, organic matter, total carbon, exchangeable potassium, and cation exchange capacity. The porous physical structure of corncob biochar provides physical protection and micro-habitats where beneficial bacteria can thrive and expand their populations over time.

Soil carbon dynamics and microbial respiration respond differently depending on the concentration of biochar introduced into the soil environment. A lower application rate of one percent biochar combined with beneficial bacteria generated the highest initial respiration rates, dissolved organic carbon, and microbial biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More carbon. This indicates that lower biochar concentrations provide a temporary balance that favors early carbon availability and rapid microbial activity during initial incubation periods. Coffee seedling physical traits show noticeable improvements under combined soil treatment conditions over 180 days. Plants grown in soil containing two percent biochar paired with beneficial bacteria achieved the highest overall stem dry biomass. Leaves from coffee seedlings treated with higher biochar amounts accumulated greater concentrations of chlorophyll pigments, proline, and total soluble sugars, which contribute to improved plant energy production and cellular function.

Physiological measurements further confirm that amended soil environments enhance seedling vitality and leaf water balance. Seedlings receiving two percent or three percent biochar combinations maintained significantly higher relative water content in their leaves compared to untreated control plants. Additionally, these plants exhibited lower levels of hydrogen peroxide accumulation and reduced cellular membrane damage, indicating overall healthier cell structures and stable internal redox status during nursery growth. Strong statistical associations link positive soil chemical adjustments directly to improved coffee seedling health parameters. Cation exchange capacity and exchangeable potassium levels correlated strongly with leaf chlorophyll amounts, proline content, and total aboveground biomass. Conversely, lower levels of leaf cell damage and hydrogen peroxide coincided with higher availability of soil potassium and magnesium. These findings confirm that combining corncob biochar with beneficial soil bacteria at appropriate rates optimizes seedling establishment for coffee cultivation.

Source: Kullachonphuri, S., Sriwichaikaew, T., Demyan, M. S., Ninlaphong, P., Chromkaew, Y., Iamsaard, K., Hemrattrakun, P., Wang, B., & Khongdee, N. (2026). Efficiency of corncob-derived biochar and plant growth-promoting rhizobacteria as growth promoters for Coffea arabica L. seedlings. Scientific Reports, 16, Article 66239.