September 7, 2012

This year's drought may cause you to consider whether it's time to rotate your alfalfa, especially from dryland fields.

The most obvious indicator is when it gets is when the stand gets too thin. Older, dryland fields should have 25 or more shoots coming from two or more plants per square foot. Irrigated fields need 40 shoots from three or more plants. If your stand is thinner than these guidelines, look for somewhere to start a new field next spring.

Another indicator is  weed density. Are your fields getting weedier each year? Are many of the problems perennial plants like bluegrass, dock, or dandelions? If so, your alfalfa stand may lack the vigor or density needed to compete. A new field should be considered.

A third factor to consider may be especially important this year. Just because your stand is thick and weeds aren’t a problem doesn’t mean you should keep the field another year.

This is especially true for many dryland fields following drought. Once dryland fields exhaust all available subsoil moisture, yields drop even though stands may remain thick. In these fields, yield is limited to only what annual rainfall can support. Many dryland fields now have reached this stage. Rotating to a new field can provide a fresh source of deep subsoil moisture.

It will also provide the crop following alfalfa with some free nitrogen as well as a rotation-based yield boost. Rotating alfalfa through your fields just a little more frequently will give you this boost more often.

Bruce Anderson
Extension Forage Specialist