Management of Drought Stressed Alfalfa

Richard H. Leep

Department of Crop and Soil Sciences

Drought Stress Symptoms

Several factors occur when alfalfa is subjected to drought like conditions, which have prevailed over many areas of Michigan this summer.  The alfalfa plant responds morphologically to drought stress by decreasing stem number, stem elongation, and yield while increasing leaf: stem ratio.  Forage quality is usually higher in drought stressed alfalfa.  The physiological response of alfalfa to drought is characterized by the following: Photosynthesis is maintained during early phase of drought but slows as the drought continues and as the stomata close.  Nitrogen fixation and nodule formation is reduced but more nutrients accumulate in the roots as compared to the foliage.  In new seedings, root growth is affected more than shoot growth. 

Drought Management

Established alfalfa stands as well as new seedings experiencing drought symptoms should be harvested only if there is enough forage to economically justify harvesting.  If enough alfalfa is present to justify harvesting, the quality of harvested alfalfa should be excellent.  Alfalfa should be mowed or clipped after the drought is broken to stimulate regrowth.  This is particularly important if the alfalfa is blooming or near blooming as clipping at this growth stage will encourage new crown buds to send out new shoots for regrowth.  With recent rains throughout the state, clipping drought-stressed alfalfa should be a good idea.