NEWS for North Dakotans
Agriculture Communication, North Dakota State
University
7 Morrill Hall, Fargo, ND 58105-5665
May 7, 1998
Profitable soybeans begin with good quality seed and correct seeding rates.
"Seed quality is extremely important to ensure uniform emergence and good stands," says Duane Berglund, extension agronomist at North Dakota State University. "That's why I'm a strong believer in using quality certified seed. If soybean seed is more than two years old it can lose its germination ability and seedling vigor, particularly if storage temperatures have been extremely warm. So if growers use binrun seed they should make sure it's tested for germination—look for a germination rate of at least 85 percent—and that it has size uniformity. Also, they should remove all splits and cracked seed, if possible."
He says that when purchasing seed a grower should ascertain the number of seeds per pound and the germination percentage, then adjust the seeding rate accordingly. Most varieties range between 2,800 to 3,200 viable seeds per pound.
"When solidseeding soybean in 6 to 12inch row spacing," he says, "growers should raise the rate to 65 to 70 pounds of seed per acre, for a plant population of 200,000 per acre. This will lead to better ground cover and fewer crusting problems."
Berglund prefers 12inch over 6-inch row spacings in solidseeded soybean. Tighter bean plant spacings within rows 12 inches apart mean seedlings will emerge better and pods will set higher, which will result in reduced harvest losses. Also, spraying is done more easily when driving down 12inch row spacings.
"The disadvantage of 12inch row spacings," he says, "is that you don't get ground cover quite as rapidly as with 6-inch rows: it takes five to seven days longer to get a full plant canopy. So far as yield is concerned, there's not much difference between 12 and 6inch row spacings."
Growers may want to increase their seeding rate also in the following cases:
*In early June plantings. If a grower gets a late planting start or has to replant soybean in June, plant a shortseason variety and increase the seeding rate at least another 10 pounds per acre from the standard seeding rate.
*In notill systems or cold growing temperatures. The seeding rate should be increased in these cases to compensate for colder germination conditions.
*When using a harrow or rotary hoe in the seedbed after planting. Both tools can be effective for controlling emerging weeds or breaking soil crust after planting, but these implements will take out a few beans. Consider upping the seeding rate five to seven pounds to compensate. Damage will be minimal if the hoeing or harrowing is done three to four days after planting, with the seedling 3/4 to 1 inch below the soil surface.
"Soybeans have proven to be an excellent choice to include in a corn or spring wheat rotation in eastern North Dakota," says Berglund. "In eight years of crop rotation field trials conducted at Fargo, average yield of continuouscropped spring wheat was 31 bushels per acre over the eightyear period, while wheat following barley yielded 35 bushels an acre, wheat following sunflower yielded 40 bushels per acre, and wheat following sugar beet yielded 42 bushels per acre. But wheat following soybean yielded 45 bushels per acre.
"In short, wheat in rotation with soybean yielded 14 bushels better than continuouscropped wheat, and better than all the other combinations."
Berglund suggests three reasons why wheat does well following soy beans. First, planting wheat after soybeans helps prevent head scab and certain foliar diseases. Second, weed problems in wheat tend to be lessened when soybean is in the rotation. Third, soybeans use less soil moisture than other deeprooted row crops, and leave behind fixed residual nitrogen that benefits wheat.
"I would think that in many areas of eastern North Dakota and northwest Minnesota, soybean ground will be as good for wheat yields as fallow ground," says Berglund.
###
Source: Duane Berglund (701) 231-8135
Editor: Barry Brissman (701) 231-7866