An Alberta Agriculture research team has studied the agronomics and economics of direct seeding canola, peas, barley and wheat into sod.
“Results from these tests show that planning ahead is advisable,” says agronomist Eric Oosterhuis. “Better results will be obtained when the sod field is sprayed the year prior to seeding. A longer time interval between spraying and seeding gives more time for the sod to break down.
“Apply Roundup at a rate of two litres per acre in the fall or a split application of 1.5 litres per acre in the fall plus 0.5 litres per acre the next spring.
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“Forages must be sprayed when the grasses are at least eight inches tall and actively growing. The study included a mixture of 240 millilitres of 2,4-D in fall-applied Roundup.”
Forage restrictions
Caution should be used with 2,4-D because residual effects can harm later crop growth of field peas or canola. The forages should not be used for livestock feed if 2,4-D was applied before harvesting.
Seed size has a major effect on the success of crops direct seeded into sod. Small-seeded crops don’t appear well suited. Their shallow seeding depth requirements results in the seed being placed in the thatch layer, so there is poor seed to soil contact, poor moisture uptake by the seed and poor germination, emergence and yield.
“Barley, having an average size seed, is a very competitive crop and appears to be well suited for direct seeding into sod,” says Oosterhuis.
“Ensure a barley variety resistant to cereal leaf disease is selected as net blotch and scald can transfer from the decaying forage grass roots onto the new barley plant roots.”
Field peas with a large seed size are well suited for direct seeding into sod, he said. Peas are not subject to cereal leaf disease and because they are inoculated with nitrogen fixing bacteria, they may generate the best net return for producers.
Nitrogen fertilizer requirements for crops direct seeded into sod tend to be high, around 90 pounds per acre. The soil microbes that break down forage residues feed on nitrogen fertilizer so it is not available for crop growth until later.
The study also involved a comparison of two different types of direct seeding equipment, a zero-till machine using a John Deere 750 series drill equipped with disc type openers, and a low disturbance direct seeder using a Harmon air-drill and narrow hoe type openers.
Results showed the small amount of soil disturbance from the narrow hoe openers created better seed to soil contact for all crop types studied.
