The good news is you will have plenty of nitrogen. Unfortunately alfalfa has an extremely deep and powerful root system that make it difficult to eradicate by mechanical means. Growing up on a dairy, I plowed 5 yr. old alfalfa on sandy soil that had roots at least 2 ft. deep. In California alfalfa roots have reached 49 ft. deep!
I'm not sure what part of the country you're in but your weed
control strategy will depend on whether you're in the arid West or
the sometimes very wet East. Also porosity of soil. Go towards
lower herbicide rates on sandy or gravely soil. Since your trees
are non bearing, PHI will not be a factor. You just need to avoid
stunting or killing them. Safe preemergent choices would probably
be Solicam, Surflan, or Prowl, again, depending on your climate,
rainfall patterns, and prevailing weeds. I like Solicam for grass
prevention. I have clay soil, my climate varies from jungle to
desert (sometimes in a single season), and I take the maximum rate
and apply half of it in spring and the other half in the fall,
which is a common practice in the southeast. Application under
drip is no problem. In fact, the wet strip is where weeds will
first appear. You do need rainfall within x number of days
after application in order for these products to work.
In the west there are ongoing trials of alfalfa cover crops in
apples. I think the biggest negatives have been delayed fruit
maturity and rodent burrowing. If you're in a dry climate with
easy to work soils you might do well with removal by tillage,
maybe with a weed badger. If not, then consider plan B: while
glyphosate is generally not recommended around young trees, I have
successfully used it around newly planted trees using tree guards
and a hand wand at very low pressure under relatively windless
conditions. Become very familiar with drift potential from your
equipment before doing so. On 5 acres of trees this might not be
feasible, but then again, depending on your method of mechanical
removal, it might.
For application by tractor, I generally prefer gramoxone for
young trees, but have applied glyphosate to 1st yr. plantings with
a mid mount orchard boom, 30 psi with air induction nozzles. I use
an old school boom with a cable and pulley going into the cab to
quickly and precisely vary the angle of the boom to eliminate
trunk contact above the guard. Just make sure you don't spray any
suckers. If you do, go back and cut them off. You can also spray
to within 4-6" of the tree and clean up the unsprayed strip later.
This application would best be applied soon rather than later in the summer; you can come back later with gramoxone or another burn down herbicide and burn off alfalfa regrowth. The only reason I suggest doing this during the current season is the fact that you will have more root suckers next year, and you will probably have to use glyphosate at some point if you want to truly eradicate the alfalfa.
Clopyralid (Stinger) is very good for reducing clover (and should
work for alfalfa) for an entire summer, but trees have to be in
the ground for 1 year, and trunk contact is not allowed even for
older trees. It could be helpful next season.
You can also burn down multiple times this summer, and start with systemic means next season. Upon completion, you will have a nice mat of dry legume releasing nitrogen, choking out weeds, and eliminating erosion. So in my opinion, the end result will be worth the extra caution with the sprayer.
I use cheap, reusable guards that are .35 USD each:
Beech Creek Orchards LLC
2011 Georgia Highway 120
Tallapoosa, Georgia, 30176
On 6/13/2017 9:50 AM, Doug Nelson wrote:
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