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Soybeans grow best in soils with a pH of 6.5 or higher.
They make good use of carry over fertility from previous
crops and can perform well when P is deficient or tied
up by calcium or magnesium. Soybeans need high levels
of K to produce maximum yields and grow strong stems to
resist lodging.
When soybeans are grown on a field for the first time,
the seed must be inoculated with rhizobium. After
soybeans have been previously grown on a field, the soil
may contain enough rhizobium to insure nodulation on
soybean roots, but inoculant is very cheap compared to
the cost of not getting good nodulation. It may help to
‘double inoculate’ or even to use soybean inoculants
from two different sources to insure good inoculation.
Both protein and yield are greatly reduced when beans
are not properly inoculated. Inoculants must be stored
carefully until they are used. Excessive heat or
sunlight can kill rhizobium bacteria very quickly.
Expiration dates should be checked to be sure that the
inoculant is fresh. Seed should be kept out of direct
sunlight and planted the same day that it is inoculated,
and or it may need to be re-inoculated before it is
used. Always use soybean Rhizobium inoculant –
the other Rhizobium strains will not be effective.
Soybeans can be successfully planted in 30” rows, or in
narrower rows on organic farms. Corn planters generally
give the best seed placement and emergence but grain
drills can be used with very good results under certain
conditions. For early planting dates or when weed
pressure is expected to be heavy, it is safer to plant
in wide rows and plan to use both a weeder and a
cultivator to control weeds.
With light weed pressure and later planting it is
possible to drill beans with good results. If beans
are drilled, use a drills with press wheels and
adjustable depth control for the best results. When
planting very late, yield per plant is less and weed
pressure is much lower so increasing population and
drilling beans maintains yield potential. Drilled
soybeans should be blind cultivated with a weeder harrow
just before emergence and again a week or so later
before the canopy closes.
Soybeans should be planted 1” to 2” deep planted into
moisture. They come up very quickly when the soil is
warm, the seedbed is fine, the seed is placed correctly,
and soil moisture is good. Extra time spent preparing a
good seedbed and adjusting the planter pays off very
well in less time spent battling weeds. In very warm
weather, it is important to watch the crop carefully for
emergence.
Soybeans must be weeded before they emerge but that is
also when they are most vulnerable to damage from
weeders. Small soybeans are most tolerant to
cultivation and weeding in the hottest part of the day,
they are most sensitive to weeding and snap off easily
early in the morning. As the sun climbs higher and the
soil becomes hotter, the little seedlings become
‘rubbery’ and harder to damage. In a good stand of
beans, you can take out 2 or 3 plants per foot with the
weeder without hurting yield. A properly adjusted and
operated weeder will seldom do that much damage unless
it is operated at the wrong time or the soil conditions
are bad. It is far better to thin a stand than to let a
lot of weeds escape early.
Taller bushy-type soybeans generally perform best in
wide rows and lower populations. When white mold is a
concern, wide rows help reduce incidence and severity of
the disease. Large soybean varieties such as Vinton 81
and Boyd can be planted as thin as 125,000 seeds/acre or
7 per foot in 30” rows with good yields if the seed
spacing is uniform. Shorter non-branching varieties may
need to be planted in narrower rows at populations as
high as 225,000 seeds per acre to achieve maximum
yield. Keep in mind that seeding rates must be much
higher to compensate for uneven seed spacing.
The
number of seeds in a bag can be easily found by
multiplying the seeds per pound by the weight of the
bag. A 50# bag with 3200 beans per pound contains
160,000 beans. If the desired seeding rate is 150,000
seeds per acre, then you need to plant about 47# of seed
per acre. Large seeded beans like Vinton 81 need many
more pounds of seed per acre because of the very low
number of beans per pound. With beans that are 2000 per
pound, it takes 75# to get the same population as 47# of
seed when beans weigh 3200 per pound.
As
bean size gets smaller, most drills and planters plant
more pounds per acre at the same setting. This makes
checking your rate when you start planting a new lot of
soybeans very important. Filling the planter boxes and
planting until you run out of seed to see if the machine
is set correctly can be costly either because of wasted
seed or because of a too thin stand. |
