Alfalfa Stand
Establishment
An estimated 60 percent of
all spring alfalfa seedings are made with a small-grain companion crop.
The companion crop is planted largely to reduce soil erosion risks and
assist in weed suppression. However, it’s important to remember that
the faster-growing, lower value companion crop competes with young alfalfa
seedlings for light, moisture and nutrients, thus raising the risk of
higher alfalfa seedling mortality and a poorer final alfalfa stand.
Seeding the companion crop
at an excessive planting rate, or even a delay in harvesting the crop,
is usually enough to cause trouble. Planting oats at 1 bu/A, for example,
is more than adequate to stop soil erosion. And while a higher planting
rate may provide marginally improved weed control, the higher rate also
more effectively chokes out the alfalfa seedlings.
In similar fashion, delaying
harvest of the small-grain companion crop until dough stage or even later
may add to the yield and nutritional value of the companion crop. But
extending the length of time the companion crop shades the alfalfa also
slows its establishment, reduces final stand and decreases first-year
alfalfa yield.
To eliminate the competitive
effect of a companion crop, many growers have adopted the practice of
clear seeding new alfalfa stands. Herbicides are applied before seeding
to control weeds, then alfalfa seeds are planted alone. The risk of soil
erosion increases, however, so this option is best for land with minimal
slope.
On land with greater erosion
risk, chemical control of the companion crop may be a more viable option.
Under this system, the lower-value companion crop is sacrificed with the
aid of chemicals once alfalfa seedlings have sufficiently rooted and begun
to grow. This system provides the needed early erosion protection while
eliminating much of the negative competition presented by the companion
crop. Under this system, grassy weeds will also be controlled. If broadleaves
are bad, additional herbicide treatment will be required.
No matter which system you
choose, remember that a careful balance is needed to achieve needed erosion
protection while optimizing the environment for the best possible alfalfa
stand.
|
