Conservation tillage promotes mycorrhizal colonization in older alfalfa stands

Mycorrhizal colonization such as mycorrhizal intensity and arbuscule abundance of alfalfa roots was assessed over two years and related to root biomass, plant density, average feet weight and soil properties, including available phosphorus. Our results revealed that five-year-old alfalfa stands showed the highest mycorrhizal colonization. Conservation tillage (i.e. Reduce Tillage, RT, and No-Tillage, NT) strongly enhanced mycorrhizal colonization compared with Conventional Tillage (CT). Under RT+NT, mycorrhizal intensity exceeded 35% and arbuscule abundance reached 10% in five-year stands, whereas CT fields remained low. Age-related differences were significant only under RT+NT, with 4 and 5-year stands performing better than 1-year stands. Correlations between mycorrhization parameters and agronomic traits revealed a negative relationship with plant density and a positive association with average feet weight across both tillage systems, suggesting enhanced individual plant performance rather than increased stand-level biomass. Soil available phosphorus was the main soil factor linked to mycorrhization, with colonization decreasing as P-Olsen increased, particularly in RT+NT fields. Our findings show that perennial stand duration and reduced tillage synergistically promote AMF establishment and functionality in alfalfa systems. These practices improve our understanding of AMF dynamics in perennial systems and offer valuable guidance for advancing ecological intensification in forage crops.

Contact : babacar.thioye@unilasalle.fr; pascal.thiebeau@inrae.fr