July 13, 2007

After several years of drought, some tough winters and this spring's freeze, some alfalfa plants that managed to survive finally are showing the accumulated effects of stress. This isn't unusual because harvesting alfalfa also causes stress. Add in any insect damage or leaf diseases and plants that were old or weak starting out this spring may simply have too much root disease and not enough healthy root to keep going.

Now is a good time to assess these fields and determine whether you need to reseed them this August or next spring. If weeds are becoming a problem, this suggests replacement. Also, older dryland fields with fewer than 25 shoots per square foot coming from two or three plants should be replaced. Very productive sites, such as irrigated and sub-irrigated fields, should have over 40 shoots per square foot from four to six plants.

Dig up the roots and check them. Healthy roots are solid and white, with a firm texture. A little browning in the top couple inches of the crown may not be much of a problem yet, but it could develop into a serious disease in another year or two. Roots that are discolored in one-third to one-half of the tissue might survive this coming winter, but plants will not yield well next year. If crowns and taproots show extensive brownish discoloration or are becoming mushy and partly rotted, these plants will not survive another winter.

Observe and anticipate declining alfalfa stands then replace them on your terms instead of Mother Nature's.

Bruce Anderson
Extension Forage Specialist