Last updated on
May 31, 2012
Soybean Plant Arrangement - Dimensions of planting
Plant soybeans as early as possible after April 25 as soil conditions permit;
if possible, complete planting by May 20.
- planting date
- row spacing
- plant density
- seeding depth
- Soybean response to planting date is important not only in years when planting is
delayed by inclement weather, but also when weather does not disrupt the normal
- Early season freezes, hail storms, flooding, and other situations can reduce crop
stands to a point where late planting is necessary.
The Photoperiod Effect
The concept of planting shorter season corn hybrids as planting date is delayed
is a proven practice in most management systems. However, this concept needs modifying
when applied to soybeans.
Soybean varieties respond much differently to delayed planting than corn hybrids.
- This is because soybean flowering is more closely related to photoperiod (the length
of the daily light and dark periods) than corn.
- The shift from the vegetative to the flowering stage in soybeans is caused mostly
by changes in the length of darkness.
- Adapted varieties flower soon after the dark period begins to lengthen in late
Soybean flowering is also influenced to some extent by temperature.
- High temperatures hasten flowering. Given a very warm vegetative period, flowering
can start before the dark period begins to lengthen.
- Since flowering response of corn is more temperature dependent than that of soybeans,
accumulated growing degree days are reliable for estimating corn growth stages but
not for estimating soybean growth stages.
Planting Date Considerations
Soil temperature is an important aspect.
- The optimum temperature for soybean germination is 86Â°F.
- Seed planted into soil that is 50Â°F germinates slowly, and emergence will probably
- Planting into seedbeds that are in the low fifties is not advisable unless soil
temperatures are rising rapidly.
Sixty degrees Fahrenheit is a good target at which to begin planting.
Soybeans have a unique ability to yield well when planted over an extended time
period. This permits them to complement other crops in cropping systems.
Soybeans planted in May are the most productive. Yields were considerably lower
- Plant heights were greatest from mid-May to mid-June and are shorter with
earlier and later planting dates. Podding height dropped off considerably in July.
- Earlier planting may reduce stands because of the inability of emerged beans
to tolerate freezing temperatures. If you intend to plant soybeans after mid-June,
your best variety choice is an early to mid-season, adapted variety. Non-adapted
varieties do not have the yield potential given a later than average freeze date,
and later varieties might not fully mature.
- Indeterminate varieties are much more suited to the stressful conditions associated
with late plantings and have greater yield potentials than determinate varieties
for late plantings. These recommendations apply to double crop situations as
Late-April to early-May planting dates are more beneficial to corn than to soybeans.
Planting soybeans in mid-May after corn provides the best results.
Late Planting Cultural Practices
When soybeans are planted later than mid-June, vegetative growth is reduced.
- Without changes in planting patterns a large portion of the available light energy
is lost, evaporative water losses are greater, and weeds are more competitive.
- Row widths less than 20 inches, combined with plant populations 20 to 25 percent
higher than normal will provide a more rapid canopy closure and will maximize yields.
- Late-planted soybeans are shorter and sometimes have lower podding heights. Narrow
rows and slightly higher planting rates provide a better chance of maximizing yields.
Reduction of row spacing to between 7 to 15 inches will increase yields and reduce
competition due to weeds.
Skip row soybeans
- narrow row concept with cultivation.
- spaces are left during planting for tractor tires 15 inch row width and 30 inch
- primary advantage is weed control by both cultivation and chemicals.
- provides flexibility for controlling other pests without damaging plants.
- have yield advantage of narrow rows while having tracks to work fields.
- skip row soybeans may yield slightly less than solid seeded soybeans if chemical
weed control in solid seeded soybeans is successful.
Soybeans do not have a large yield response to a wide range in seeding rates because
soybeans can compensate by branching.
- For this reason, most soybeans in the Midwest are seeded at a rate of 50 to 70 lbs
of seed per acre.
- An adequate seeding rate, rather than a high seeding rate, reduces the possibility
of lodging and makes more efficient use of the seed that is planted.
- Because soybean varieties differ substantially in seed size, many growers determine
seeding rate in number of seeds/acre or number of seeds/foot of row. This number
can be converted to pounds of seed/acre for calibrating the planter.
- Increase seeding rates on light colored soils and decrease seeding rates on dark
colored soils. For rows wider than 20 inches, use tall, bushy soybean varieties.
Regardless of planting date and row spacing, select varieties with good tolerance
and/or resistance to Phytophthora root rot. Research indicates seed treatments aid
in Phytophthora control and are highly economical.
A commonly recommended rate in the Midwest is 150,000 plants/acre
- 40 inch rows = 10 to 11 seeds/foot of row
- 30 inch rows = 8 to 9 seeds/foot of row
- 20 inch rows = 5 to 6 seeds/foot of row
The following equations can be used to calculate seeding rate in pounds/acre:
- 43,560 sq ft/acre times plants/ft of row = seeds/acre divided by row width in feet
times % germination
- Seeds/acre = seeding rate in pounds/acre divided by seeds/pound
- Example: suppose that Hardin soybeans will be planted in 30 inch rows at 150,000
seeds/acre. Letâ€™s say that Hardin has 80% germination and has 2870 seeds/pound.
What is the seeding rate in pounds/acre?
- 43,560 X (8.5 / ((30/12) X 0.80)) = 187,308 seeds/acre
- 187,308 / 2870 = 65.3 pounds/acre
Seeding rate adjustments
- Use 175,000 plants/acre as a base if planting in 10 inch row width or less.
- Add 10% if planting very early or very late.
- Add 10% if planting short, narrow canopy varieties or early maturing varieties.
- Add 10% if planting in a poor seedbed.
- Subtract 10% if planting in deep, fertile soils where lodging is a likely problem.
- Subtract 10% if planting in ideal conditions for the area (planting date, seedbed,
soil moisture and temperature).
Depth is more critical than with wheat and corn.
- Depth should be about 1 inch.