Growth and metabolic responses of maize roots to straw biochar application at different rates

Biochar application in soil has been increasingly suggested as an option to improve soil ecosystem functions and optimize agricultural systems. The main goal of the present work was to explore the effects of straw biochar application at different dosages on the growth and metabolic processes of maize plants, especially roots. Field and pot experiments were conducted independently, in which maize plants were grown in soil amended with straw-biochar at dosages of 0%, 1%, 3%, 5%, 15% and 30% (w/w). Metabolic profiling in both leaves and roots were analyzed by nuclear magnetic resonance. Biochar application at rates from 1% to 5% caused growth and physiological changes of maize plants including increases in plant height and stem diameter, and improvements of chlorophyll content and net photosynthetic rate, which led to an increase in grain and straw yield. The root growth in maize seedlings was stimulated at a BC dose of 5% and was inhibited up to a dose of 30%, which was characterized by changes in root elongation, root thickening, lateral root branching and root cell viability. A wide range of metabolic responses, including changes in metabolomic profile, and metabolism of sugars and amino acids, may also contribute to the observed stimulation of plant growth following BC application at an optimum dosage of 5%. The present results provided a better understanding of the mechanism underlying the enhanced plant productivity and its relationship with biochar application rates.