When it comes to controlling weeds in a no-till cropping system, some No-Till Farmer readers may think Randy Anderson has gone to extremes. That’s because the Agricultural Research Service agronomist has come up with a 9-year rotation that features no-till and plenty of crop diversity.

As reported recently in Successful Farming, Anderson’s goal is to utilize a number of cultural practices that have been used for years to try and outsmart the weeds.

Warm-Season, Cool-Season

Stationed at the USDA North Central Agricultural Research Laboratory in Brookings, S.D., Anderson says no-tilling both warm- and cool-season crops in the same rotation can eliminate many weed concerns. In addition, growers gain from the fact that most crops yield better when they show up less frequently in a no-till rotation.

As an example, studies in Anderson’s area have shown corn can yield 24% more when grown only once every 4 years rather than in a 2-year corn and soybean rotation. In addition, he says no-tillers can improve soil health by growing at least 3 years of a perennial forage, such as alfalfa, in their rotation. Plus, having 2 or 3 years of alfalfa will produce enough soil nitrogen to meet the fertility needs for up to 4 years for small grains with South Dakota conditions.

9 Years Of Crops

Anderson’s rotation starts with a cool-season seeding of alfalfa that lasts 3 years. This is followed by a year of corn and soybeans in a warm-season cropping program. Next an oat and pea mix is seeded followed by winter wheat. Then corn and soybeans are no-tilled before the 9-year rotation is completed and a new cycle is started once again with a 3-year stand of alfalfa.

To get effective weed management in the Great Plains, Anderson finds it’s important to no-till, develop effective long-cycle crop rotations, diversify with both warm- and cool-season crops and find ways to produce early season crop canopies that help control weeds.

Anderson says the key is developing rotations that disrupt and reduce weed populations. By doing so, he says some no-tillers have trimmed herbicide usage by as much as 50% due to a reduction in weed densities.

Reduce Weed Germination

Anderson says no-till offers the opportunity to keep weeds from getting started. By leaving residue on the soil surface and not turning under weed seeds, he says no-tillers can dramatically reduce weed germination concerns.

In studies where no-till was compared with minimum tillage, Anderson says there was a five-fold increase in weed density in the tilled plots. In a study with four crop rotations, weed density was 13 times higher with a two-crop rotation where the ground was tilled.

More details on Anderson’s highly diversified 9-year no-till rotation are available by contacting him at randy.anderson.@ars.usda.gov.