Although valuable in it’s useful N-fixing / high protein forage phase, alfalfa growers often acquire a dislike for it’s sequential weedy-nature as a so-called “volunteer” upon return to annual cropping. Perhaps it stems from the fact that conventional herbicides, designed to impede development of new roots and shoots or injure the exposed growth of flushing weeds and common volunteer plants, seem to carry little clout on the well-developed alfalfa root system and/or its fast growing foliage.

The best approach to remove established alfalfa in rotation requires timely pre-harvest application of correct herbicide rates in adequate spray volumes.

Normally, intensive tillage (bare-fallow) destroys an alfalfa stand sufficiently to avoid root regrowth, however for reduced tillage reasons, sod seeding is the preferred method. Sod seeding implies that an unwanted alfalfa stand was previously terminated by herbicide (glyphosate). There is very little information and few herbicides registered for in-crop control of volunteer alfalfa because it is normally referred to as a crop, not a weed!

Depending on rotation, control of volunteer alfalfa after sod seeding requires planning.

Keeping in mind all the benefits of a reduced tillage cropping system, the following presents some points for direct seeders to consider when faced with the challenge of removing volunteer alfalfa in sod-seeded crops.

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Through a persistent pursuit of no-till methods, direct seeders have succeeded in making it an efficient cropping practice for growing annual crops. Farmers are now refining their ability to make reduced tillage work as well for perennial forage rotations in continuous cropping systems. Done right, direct seeding is working to establish most forages, but the main challenge arises when these same perennial forage fields are rotationally terminated[1] back into annual crops, as has been occurring in many regions since wheat prices surpassed $8/bu. and cattle of all size and age fell below $100cwt.

 

Timely herbicide treatment appears to profitably trump most time-wasting tillage approaches, however one of the toughest perennials to confront in this manner (spraying) is the leguminous alfalfa plant. Although valuable in it’s useful N-fixing / high protein forage phase, alfalfa growers often acquire a dislike for it’s sequential weedy-nature as a so-called “volunteer” upon return to annual cropping. Perhaps it stems from the fact that conventional herbicides, designed to impede development of new roots and shoots or injure the exposed growth of flushing weeds and common volunteer plants, seem to carry little clout on the well-developed alfalfa root system and/or its fast growing foliage.

 

There is however some control techniques, in common with the innovative weed control strategies which emerged from no-till annual cropping, that can be adapted to controlling unwanted alfalfa. The indispensable practice of a pre-seed burnoff [2] is one. Proper pre-harvest [3]timing is another. Also, there is always the hope for new-age [4] herbicide chemistry to control tough perennials without re-cropping restrictions. Let’s take a look at these methods and how they can reduce the problem of volunteer alfalfa, or not.

1. Pre-seed burnoff alone seldom controls volunteer alfalfa (think perennial weed such as dandelion). It will almost always be at the wrong growth stage for these reasons:

Aside from unacceptable consequences in tillage-based cropping systems, using traditional forage plowdown[7] methods can result in sufficient alfalfa control. Indeed, as farmers adopt sodseeding[8] in quest of no-till economics other new perennial “weed” scenarios may arise. To assess risk and avoid the dismay of uncontrolled (volunteer) alfalfa, growers will need to consider the following herbicide related questions:

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