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Natural Weed Control

There are many ways for growers to implement non-toxic weed control methods on their farms. The most obvious is to take the chemical farming approach and find an organically-approved material to do the killing. Very strong vinegar has been the most marketed material. The important factor in vinegar formulas is to include a surfactant to strip away any waxy protective coating on the plant surface to allow the desiccation (drying out) of the plant. Salt provides the same mode of action and may be included in the formula.

Natural weed control

The primary condition that promotes broadleaf weeds is the ratio of available phosphorus to available potassium, as shown by a LaMotte soil test. The further you deviate from a 1:1 ratio, the stronger the broadleaf pressure.

Other modern mechanical approaches to weed control include flaming, cultivating, and smothering. Cultivators are a modern version of hoeing or hand pulling. Rotary hoes or spiked harrows are special adaptations of the cultivation approach. Using plastic films, whether biodegradable or not, is a form of smothering that is similar to mulching with any material. The cover denies sunlight to prevent growth.

Repeated cuttings of a perennial weed in a fallow field may weaken a plant over time by using up its stored energy. Farmers should also make every attempt to prevent the reseeding of an offending species. Treating isolated patches is worth the effort to keep them from spreading. If a field is overwhelmed to a point of not having an economic crop worth harvesting, be sure to take the whole field down before the weeds go to seed. Keep in mind that there are seeds in your fields that may have been there for years. Just lime or activate the calcium in your soil and watch clover appear in uncultivated ground, even if you haven’t seeded it since you bought the farm.

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Flame Weeding: Turn up the Heat to Fight Weeds

Flame weeding (also referred to as flaming) has been an apt option for or­ganically ridding row crops and fields of uninvited weeds while also replenishing the soil with nutrients from the result­ing carbon. Wedding the proficiency of flame with the compressed liquid power of propane has served many farmers and food producers well over the past cen­tury. According to the Northwest Coalition for Alternatives to Pesticide, the first agricultural flame weeder was patented in 1852.

flame weeding with propane

Flaming with propane attacks weeds with no repercussions on crops or fields.

Flame weeding is done by generat­ing intense heat through a chosen de­vice — whether it is a handheld torch or tractor-mounted — that sears the leaves of the weeds, which causes the cell sap to expand, thusly damaging the cell walls. “You’re watching for the color change, depending on the weed and its maturity,” said Charles House of Earth & Sky Solutions. Leaves wilt and dehydrate the plant, leaving the invaders no other option than to die, sometimes up to three days later.

“The key to successful flame weeding is the maturity of the plant you’re trying to eradicate. The smaller, the better,” he explains. The best time is when they’re immature and in the cotyledon stage.

Flame Weeding Background

Flaming gained popularity in the first third of the 20th century and continued through the 1960s until pesticides re­placed industry attentions. Though its use waned over the following 20 years, flame weeding resurfaced and regained popularity in the early 1990s, and con­tinues to be used today. So continues flame weeding’s renaissance. Continue Reading →

Organic Weed Control: Cultural and Mechanical Methods

Organic weed control methods are often debated and dismissed by large chemical sprayers. But organic weed control methods do work, and work better for your field’s health.

Organic weed control

Weeds happen. Knowing how to work with them can save you a lot of time and effort.

Weeds happen. That is a fact of life for organic farmers, and therefore many of our field operations are designed to make sure that the health and quality of our crops are not jeopardized by the inevitable weed pressure.

Planning an effective weed-control program involves many different aspects of organic crop production. As farmers begin to explore organic possibilities, the first two questions invariably seem to be: “What materials do I buy for soil fertility?” and “What machinery do I buy to control weeds?” We asked these questions when we started organic farming, but we rapidly realized that this is not the best way to understand successful organic farm management.

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Smart Sowing for Natural Weed Control

weedy-wheatNew research results from the University of Copenhagen’s Department of Plant and Environmental Sciences report that weeds would have a tough time competing against crops such as corn, grains and beans if farmers were to alter their sowing patterns.

“Our results demonstrate that weed control in fields is aided by abandoning traditional seed sowing techniques. Farmers around the world generally sow their crops in rows. Our studies with wheat and corn show that tighter sowing in grid patterns suppresses weed growth. This provides increased crop yields in fields prone to heavy amounts of weeds,” said Professor Jacob Weiner, a University of Copenhagen plant ecologist.

Research studies performed in Danish wheat fields, together with recent studies in Colombian cornfields, demonstrate that modified sowing patterns and the nearer spacing of crops results in a reduction of total weed biomass. The amount of weeds was heavily reduced — by up to 72 percent — while grain yields increased by more than 45 percent in heavily weed-infested fields. The trick is to increase crop-weed competition and utilize the crop’s head start, so that it gains a large competitive advantage over the neighboring weeds. The research results from Colombia have been published in Weed Research. This encapsulation of the research is from the March 2015 issue of Acres U.S.A.

Fighting Weeds with Microbes

Ragweed

We read many, many studies involving manipulation of DNA with as of yet uncalculated risks. It was quite refreshing to read new research employing DNA-based tools in tandem with common sense for the good of all forms of agriculture and the health of the soil.

Using high-powered DNA-based tools, a recent study at the University of Illinois published in Microbial Biology identified soil microbes that negatively affect ragweed and provided a new understanding of the complex relationships going on beneath the soil surface between plants and microorganisms.

“Plant scientists have been studying plant-soil feedback for decades,” said U of I microbial ecologist Tony Yannarell. “Some microbes are famous for their ability to change the soil, such as the microbes that are associated with legumes — we knew about those bacteria. But now we have the ability to use high-power DNA fingerprinting tools to look at all of the microbes in the soil, beyond just the ones we’ve known about. We were able to look at an entire microbial community and identify those microbes that both preferred ragweed and affected its growth.”

Researchers believe an effective strategy to suppress weeds might be to use plants that are known to attract the microbes that are bad for ragweed, and in so doing, encourage the growth of a microbial community that will kill it.

“We used the same soil continuously so it had a chance to be changed,” Yannarell said. “We let the plants do the manipulation.”

This encapsulation of the research is from the June 2014 issue of Acres U.S.A.

Fungus May Offer Natural Weed Control

Weed control AmaranthA naturally occurring fungus may prove useful in the weed control fight against Palmer amaranth, an aggressive southern weed that can grow at the rate of 2 inches a day and out-compete corn, cotton, soybean and other crops for resources, potentially reducing their yields.

Weed Control Important to Avoid Glyphosate Resistance

To make matters worse, some biotypes of the weed have become resistant to weed control using glyphostate herbicides. As a possible alternative, USDA scientists are exploring ways to formulate Myrothecium verrucaria, a fungus which attacks Palmer amaranth’s leaf and stem tissues, causing wilt, necrotic lesions, loss of chlorophyll and other disease symptoms that can kill young plants and weaken older ones. Studies at the Jamie Whitten Delta States Research Center operated by USDA’s Agricultural Research Service in Stoneville, indicate Myrothecium can wreak similar havoc on biotypes of Palmer amaranth that resist glyphosate and other herbicides such as triazines. Learn more about this possible weed control in the February 2014 issue of Acres U.S.A.