The advice comes from Matt Cutull, assistant professor of plant weed science at the Clemson Coastal Research and Education Center. Cutulle and other agricultural researchers presented “integrated weed management” techniques at a recent workshop at the Clemson Madron Convention Center and Student Organic Farm.
Weeds compete with crops for soil nutrients, causing $32 billion in crop losses annually, Cutulle said. Effective weed control begins when growers notice a weed-free period, a critical time in the growing season when weeds cause the most crop loss, he says.
“This period can vary greatly depending on the crop, how it is grown (seeded or transplanted), and the types of weeds present,” Cutulle said. “The conservative weed-free key period will be six weeks, but again, this can vary depending on the crop and weeds present.”
The Critical Weed Free Period is a point in the growing season when keeping a crop free of weeds is critical for growers to maximize yield potential. After this critical period, growers should focus on preventing weed seeding. Farmers can do this by letting the seeds germinate and then killing them, or they can prevent germination and wait for the seeds to die or be eaten by seed-eating animals.
One method is soil solarization, which involves using the heat generated by the sun to control soil-borne pests. This is achieved by covering the soil with a clear plastic tarp during the hotter seasons when the soil will be exposed to direct sunlight for up to six weeks. The plastic tarp heats the top layer of soil 12 to 18 inches thick and kills a variety of pests including weeds, plant pathogens, nematodes and insects.
Soil insolation can also improve soil health by accelerating the decomposition of organic matter and increasing the availability of nitrogen and other nutrients to growing plants, as well as by beneficially altering soil microbial communities (bacteria and fungi that affect soil health and ultimately on plant health).
Anaerobic soil disinsection is a non-chemical alternative to the use of fumigants and can be used to control a wide range of soil-borne pathogens and nematodes. This is a three-step process that involves adding a carbon source to the soil that provides nutrients to beneficial soil microbes. The soil is then irrigated to saturation and covered with plastic mulch for several weeks. During deworming, oxygen in the soil is depleted and toxic by-products kill soil-borne pathogens.
Using cover crops early in the season to suppress weeds can be helpful, but killing is key, says Jeff Zender, Clemson’s program director for sustainable agriculture.
“Vegetable growers generally don’t plant cover crops due to management issues, including when is the best time to plant cover crops for the most efficient biomass,” Zender said. “If you don’t plant at the right time, you may not have enough biomass, so when you roll it, it won’t be as effective at suppressing weeds. Time is of the essence.”
The most successful cover crops include crimson clover, winter rye, winter barley, spring barley, spring oats, buckwheat, millet, hemp, black oats, vetch, peas and winter wheat.
There are many weed suppression mulches on the market today. For information on weed control by planting and mulching, see Clemson Home and Garden Information Center 1253 and/or HGIC 1604.
Cutulle and others at Clemson Coastal REC, along with researchers at Clemson’s student organic farm, are exploring other weed control strategies, including using liquid nitrogen to freeze open weeds before killing them and rolling cover crops with a roller. Organized low-temperature weed control.
“Farmers need to understand weeds — identification, biology, etc. — so they can manage their farms and avoid weed problems in their crops,” he said.
Farmers and gardeners can identify weeds using the Clemson Weed ID and Biology website created by Coastal REC lab assistant Marcellus Washington.
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Post time: Apr-16-2023