Progressive producers don't let tech fees and other costs prevent them from making sure plant populations are high enough to generate a good stand.
John Cooper rotates soybeans and rice in northeastern Arkansas. And since planting soybeans in early April can leave them vulnerable to cold, wet spring weather, obtaining a solid stand is essential.
“I like to plant a little heavy,” says Cooper. “That helps assure we get a good stand. I'd rather have too many plants than not enough. When you cut back on seeding rates, every plant has to come up.”
Alan Blaine, Mississippi State University soybean specialist, says southern growers typically plant 45-50 lbs. of seed per acre. That should translate to between 7-8 seeds/row ft. for 38-40 in. rows. For 30-in. rows, about 6 seeds/row ft. are ideal.
Those numbers are reduced for narrow row soybeans. For 20-in. rows, Blaine says an ideal planting rate is 5 seeds/row ft. That goes down to 3.75 seeds for 15-in. rows. Drilled soybeans in 7-in. rows should see a 2.25 seed rate.
“Soybean plant populations can vary considerably without affecting final yield,” says Blaine. “It's best to plant enough seed to insure an optimum final stand, but not to overplant.”
Blaine says the 7-8 seeds/ft. or row rate translates to a cost of $23-27/acre. That compares to $29-30/acre or more in the upper soybean belt.
Purdue University agronomist Ellsworth Christmas says optimum planting numbers are similar for Indiana and much of the Midwest.
For 36-in. rows, he recommends 7 seeds/row ft. That drops to six for 30-in. rows and five for 20-in. rows. Planting rates for 15-in. rows are 3.7/row ft. For drilled beans it's 2.2.
Christmas notes that for determinate varieties, growers may need to increase plant populations to realize full yield potential. “An extreme example is the determinate variety, Hobbit 87, which is recommended for solid seeding (6-, 7-, or 8-in. rows) at populations of 200,000-250,000 plants/acre, or about three plants per foot of row,” he says. That's 50% greater than the standard recommendations.”
Cooper plants on 19-in. centers using a 32-ft.-wide planter modified from a Case unit. His rate of 7-8 seeds/row ft. is a little higher than average. But that rate still provides him protection against thin stands.
“Along with a good stand, we also obtain a quick canopy to help prevent weed problems (not controlled by glyphosate over-the-top herbicide applications),” says Cooper. “We also usually count on having to replant up to 30% of our soybeans, depending on weather situations in the early spring. We make sure early planted seed is treated against potential disease problems.”
Agronomists warn that seed weights may vary from year to year. So even though 7-8 seeds/row ft. on 38-in. rows may normally translate to 40 lbs. of seed, it may not in some years.
That's why rates should be based on seeds per foot of row and not pounds, says Mississippi State's Blaine. “Adjusting planters to plant a specific number of seeds per foot of row is the key to obtaining a proper stand,” he says. “Use weed pressure, soil type, seedbed condition and the history of stalk size to help determine the proper seeding rate.”
He adds, “In narrow rows, a slight shift in the number of plants per foot of row can have a major effect on per acre population. Excessive seeding rates are the norm for most plantings, but can be even higher in narrow rows unless you pay close attention to planter settings.”
Purdue's Christmas notes that for no-till soybeans, growers shouldn't worry about increasing seeding rates if a properly weighted and adjusted drill or planter is used and soil conditions are acceptable.
“Special care should be taken to assure correct planting depth, good slot closure and soil firming around the seed,” he says. “Most problems occur when trying to plant when the soil is either too wet or too dry. If too wet, it's difficult to obtain good slot closure and soil firming because of ‘slabbing out’ of soil by the no-till coulters. If too dry, it's difficult to obtain adequate coulter penetration and seed placement at the correct depth.”
Don't Skimp On Cotton Seeding Rates
While some soybean producers don't mind planting more seed than is usually needed, some cotton producers consider cutting back on seeding rates to save on seed costs. However, seeding rates required to make a sound crop today haven't changed from rates from 40 years ago, says Tom Barber, Mississippi State cotton specialist.
Despite the higher costs, population studies of the most common varieties indicate that optimum plant populations have been the same from the 1960s to today.
“A stand of 40,000-55,000 cotton plants per acre has consistently produced the highest yields for the last 40 years,” says Barber. “It may be false economy. For growers who plant the very minimum amount of seed, if anything adverse happens in the field they could face replanting. Planting one extra seed per foot of row is cheap insurance.”
Cottonseed prices have gone from $1,000-2,000 to as much as $10,000/ton the last 20 years, depending on variety and associated traits.
Barber says that depending on the technology, fees to cover the research and development can account for two-thirds of the total cost of seed, or as much as a few hundred dollars per bag of cottonseed.
“You're no longer simply buying a seed,” he says. “You're buying a planting unit. The embryonic cotton plant now may have superior yield potential and include the ability to resist certain herbicides and cotton insect pests.”
Barber encourages growers to request the standard germination and vigor data for the seed lots they purchase from seed companies.
“Plant the highest germination, highest vigor seeds first in the cooler soils,” he says. “On standard 38- to 40-in. rows, growers should have three or four living plants per foot. Producers must drop four or five seeds per foot to ensure that survival rate.”