Strip-tillers growing corn, soybeans and sunflowers should consider using a pre-emergent grass herbicide like Dual, followed by a post-emergence herbicide.

That's the conclusion of USDA Agricultural Research Service scientists Frank Forcella, Don Reicosky and Kurt Spokas, who conducted a study a few years ago in Morris, Minn.

The study compared results with shallow and deep strip-tillage, no-till, chisel plow and moldboard plow. Average crop stands were 25,000 plants per acre for corn, 98,000 per acre for soybeans and 30,000 per acre for sunflowers.

Reduced tillage causes delays in weed emergence, which reduces crop-weed competition, the USDA says. The short-duration of weed emergence makes weed control easier, but more difficult if it is prolonged. Because the emergence of foxtail in strip-till is prolonged, control is more of a problem, the agency says

Strip-tilling delays and prolongs the emergence of foxtail, while it delays and shortens the emergence of lambsquarters. The scientists say strip-till eliminates mustard.

They recommend strip-tillers use pre-emergence grass herbicides like Dual and Harness/Surpass, followed by post-emergence herbicides, even in Roundup-Ready corn and soybeans.

Crop Emergence

Strip-till -- especially deep strip-till -- never differs from best treatment. No-till causes delays in emergence of all crops.

The differences for soybean probably aren't important but may be for other crops, the scientists say.

Foxtail is an all-purpose weed that handles all tillage systems well, but prefers rows in reduced-tillage systems. Lambsquarters clearly prefers plowed soils, but can also be abundant in reduced tillage. Wild mustard is restricted to plowed soils.

Basically, good crop varieties don't care much about tillage, the scientists say, but corn is the exception. Corn stands can be reduced in no-till, and a possible solution is to plant 10% to 20% more seeds when no-tilling corn, the scientists suggest.