Impacts of Corn Hybrid and Nitrogen Fertilization on Plant Carbon Allocation and Belowground Carbon Dynamics: Exploring the “Surplus Plant Carbon Theory”

Intensive agriculture has depleted soil carbon stocks globally, necessitating a deeper understanding of soil organic carbon formation to develop effective management strategies to rebuild soil carbon losses. This study examines how corn hybrids (Bayer tall-statured and short-statured), soil types (sandy and loamy), and nitrogen fertilization rates (0, 90, 180, 270 kg N/ha) influence root exudation, belowground carbon inputs, and soil carbon pools in a greenhouse setting. By assessing carbon allocation between above- and belowground plant components, root exudation, and soil carbon pools (soil microbial biomass carbon and total soil carbon), we aim to optimize management practices for enhancing soil carbon storage. Results indicated that soil type and corn hybrid primarily drive root exudation and belowground carbon inputs, while nitrogen fertilization effects vary based on soil conditions. Additionally, short-statured corn contributed more to root development, and loamy soils exhibited a threshold where excessive nitrogen hindered belowground responses. These findings provide insights into managing mechanistic plant–soil–microbial interactions to enhance soil carbon accumulation and promote long-term agroecosystem sustainability.