AFIN Sustainable Forages Webinar Series - Effect of drought stress on plant growth in forage legumes

Effect of drought stress on plant growth, nitrogen fixation, soil nitrogen availability and soil microbial diversity in forage legumes presented by
Dr. Malinda Thilakarathna, Department of Agricultural, Food and Nutritional Science, University of Alberta

Drought stress poses a significant challenge to forage production, making it crucial to better understand how forage plants respond to this stress. Forage legumes engage in beneficial partnerships with specialized soil rhizobia bacteria, residing in root nodules and aiding in
atmospheric nitrogen fixation. However, legumes are vulnerable to drought stress, impacting nodulation and symbiotic nitrogen fixation. In our study, we assessed the effects of drought stress on nodulation, plant growth, physiological parameters, nitrogen fixation, soil nitrogen
levels, and soil microbial diversity in alfalfa and red clover using a greenhouse pot experiment.

Drought treatments, simulating severe, moderate, and well-watered conditions, were applied during the flowering stage. The results showed significant reductions in nodulation, root and shoot growth, and nitrogen fixation under drought conditions, particularly in severe drought.

Interestingly, severe drought led to increased soil available nitrogen, and the soil microbial community exhibited changes in the abundance of key bacterial groups. Overall results indicate that drought has deleterious effects on nitrogen fixation and plant growth, affecting soil nitrogen availability and soil microbial diversity.