It will be easy to control most weeds in alfalfa that is tolerant to Roundup herbicide. But just because it’s easy shouldn’t be your reason to buy these varieties. You may not need this trait.
For example, I encourage many of you cow-calf producers to plant grass-alfalfa mixtures in your hay fields. Since Roundup will kill the grass, conventional varieties are more appropriate in these situations. You must also realize that controlling weeds in alfalfa usually does not increase hay tonnage. After all, weeds can boost yield, and sometimes weeds also can be acceptable feed. So spending time and money to kill weeds in alfalfa isn’t always worthwhile.
Another example is planting oats with the alfalfa and later harvesting the oats for either hay or as grain and straw. Roundup can’t be used in this situation until after the oats has been harvested. If a good stand of alfalfa is present after oats has been harvested, further weed control with Roundup or any other herbicide may not be needed.
Not everyone has problems with weeds in alfalfa. This often is true if alfalfa fields usually are rotated to a different crop after four or five years of production. If a good stand can be established using other weed control options or herbicides, weeds often don’t become a big problem in alfalfa until stands get older and start to thin out.
Don’t forget — it will cost you $2.50 more per pound of seed to get this new trait. That’s $30 to $50 per acre at most common seeding rates. So make sure easier weed control is really worthwhile to you before you make this investment.
Bruce Anderson is forage specialist for Nebraska Extension.