Legume-grass integration for mycorrhizal-mediated nutrient management in sandy soils

Overview

This research investigates how integrating legumes into grass pastures can improve nitrogen retention in soil through mycorrhizal networks (MNs), a community of fungi that connect plant roots underground. The study focuses on Florida sandy soils, which are prone to nutrient leaching, and uses rhizoma peanut (a legume) and bahiagrass as a model system. By understanding how MNs facilitate nutrient sharing and retention, the research aims to reduce dependence on nitrogen fertilizers and minimize environmental impacts from nutrient runoff.

Technical specifications

Research approach:

• Uses an H-shape rhizopipe bioassay system to grow bahiagrass alone versus a mix of bahiagrass and rhizoma peanut
• Employs soil collected from bahiagrass pastures to preserve the native keystone microbiome
• Applies arbuscular mycorrhizal fungal (AMF) spores collected from pastures as inoculum
• Uses 15N-labeled nitrogen gas to track biological nitrogen fixation and transfer pathways
• Uses 15N-enriched inorganic salts and urea to evaluate how nitrogen fertilizer affects mycorrhizal-mediated nutrient fluxes
• Profiles AMF structure and gene expression of whole microbiomes
• Quantifies 15N in roots and soil aggregates to map nutrient allocation

Key findings so far:

• Integrating legume into grass pastures enhanced net biomass and nitrogen content of forage
• Increased the amount of soil aggregates
• Both legume and grass roots contain approximately 5% arbuscular mycorrhizal fungal biomass
• Legume-grass integration reduced nitrogen fertilizer use and soil nitrogen leaching compared to grass monoculture

Technology readiness level

This research is in the experimental validation stage, with initial field observations already completed. The next phase involves controlled bioassay experiments to test three specific hypotheses about how mycorrhizal networks regulate nutrient movement between legume and grass species. The work generates fundamental knowledge about soil microbial ecology and nutrient management that could inform improved pasture management practices and fertilizer recommendations for sandy soil environments.