February 12,2007

Especially with corn prices up

Planting new fields of alfalfa is expensive so many of us put off tearing up old fields and planting new ones; however, this may not be the best long-term economic strategy.

Alfalfa stands usually reach peak production by year two or three. Thereafter, yields tend to decline each year. By year four or five, yields of many dryland fields are much lower than their peak years because subsurface moisture available in the earlier years is now gone. This is most noticeable during drought years when regrowth is almost zero after the first or second cut.

Yield decline in irrigated fields is slower but usually is a ton or more lower by year five or six.

When you try to squeeze another year out of your alfalfa stand, you can lose two ways. First, and most obvious, is the lower yield of your old field compared to yields from a younger field. Second is the reduced benefit for crops like corn that follow alfalfa in rotation. Not only will alfalfa reduce your nitrogen fertilizer needs by 100-150 lbs over the next couple years, research has shown that corn after alfalfa often yields 10-20 bushels more per acre than it will even with extra fertilizer.

This rotation effect could be especially valuable this year if corn prices stay high.

If you have alfalfa fields that are past their prime or showing winter damage, this might be an excellent time to rotate those fields to a different crop and plant some new, higher yielding acres to alfalfa.

Bruce Anderson
Extension Forage Specialist