Planting new fields of alfalfa is expensive so many growers put off tearing up old fields and planting new ones, but this may not be the overall, smart decision.

Alfalfa stands usually reach peak production by year two or three, then 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 that plants were using during the early years is 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, by year five or six, is a ton or more lower.

Trying to squeeze another year out of your alfalfa stand can cost you in two ways. First, and most obvious, is the lower yield you’ll get from your old field compared to a younger field. A second loss occurs when you delay the nutrient benefit to the next crop in the rotation, such as corn. Not only will alfalfa reduce your nitrogen fertilizer needs by 100 lb to 150 lb over the next couple years. Research has shown that corn after alfalfa often yields 10 to 20 bushels more per acre than it will after another crop, even with extra fertilizer.

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

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

Both your alfalfa crop and the rotated crop could benefit.

Bruce Anderson
Extension Forage Specialist