Weed blasting offers new control method for organic farmers

Weeds are a major scourge for organic growers, who often must invest in multiple control methods to protect crop yields. A relatively new weed control method known as abrasive weeding, or "weed", could give organic growers another tool. The method, recently field-tested at the University of Illinois, is surprisingly effective.

In conjunction with plastic mulch, abrasive weeding reduced final weed biomass by 69 to 97 percent compared to non-weeded control plots, said U of I agroecologist Samuel Wortman.

Abrasive weeding involves blasting weed seedlings with tiny fragments of organic grit, using an air compressor. For the current study, grit was applied through a hand-held siphon-fed sand-blasting unit connected to a gas-powered air compressor, which was hauled down crop rows with a walk-behind tractor. The study looked at a number of grit sources: walnut shells, granulated maize cob, greensand, and soybean meal. If applied at the right plant growth stage, the force of the abrasive grit severely damages stems and leaves of weed seedlings.

Wortman found no significant differences between the grit types in terms of efficacy. "When it leaves the nozzle, it's at least Mach 1 [767 mph]," Wortman noted. "The stuff comes out so fast, it doesn't really matter what the shape of the particle is." Because ricocheting particles can pose a risk to the applicator, Wortman advises using protective eyewear.

Blasted grit does not discriminate between weed and crop seedlings, which makes it important to use this method in transplanted crops that are substantially larger than weed seedlings at the time of grit application. Although some visible damage occurred on stems and leaves of both tomato and pepper crops, the damage did not affect marketable fruit yield. Studies are ongoing to determine whether abrasions on crop tissues could result in increased susceptibility to disease, but early results show little effect.

Importantly, plots with plastic mulch and one or more blasting treatment achieved the same fruit yields seen in hand-weeded plots, and 33 to 44 percent greater yields than in non-weeded control plots.

An additional benefit of weed blasting is the potential for growers to use organic fertilizers, such as soybean meal, as blasting material. "We expect that abrasive weeding could contribute between 35 and 105 kg nitrogen per hectare [31 - 94 lbs per acre] to soil fertility." The idea that a grower could both fertilize and kill weeds in a single pass is appealing, but it is still unknown whether the fertilizer would be available for plant uptake within critical windows.

According to Wortman's research, weed blasting does affect some weeds more than others. Essentially, the smaller the seedling, the better. Also, seedlings whose growing points are aboveground (annual broadleaf species) are more susceptible to blasting than seedlings whose growing tips are located belowground (grasses and broadleaf perennials). Finally, Wortman noted that the presence of plastic mulch seemed to factor strongly into the equation. Weed blasting alone "is not a silver bullet, but it is an improvement," he said.

The method is now being tested in different horticultural crops, including broccoli and kale, with and without additional weed control methods. Early results suggest that the presence of polyethylene mulch or biodegradable plastic mulch strongly enhances the success of weed blasting, as compared with straw mulch and bare soil. Wortman and his collaborators have also developed a mechanized grit applicator, which they are currently testing.

The paper, "Air-propelled abrasive grits reduce weed abundance and increase yields in organic vegetable production," was published in Crop Protection. Funding was provided by the National Institute of Food and Agriculture's Organic Agriculture Research and Extension Initiative.

http://www.sciencedirect.com/science/article/pii/S0261219415300788.





Food industry can help lower cardiovascular diseases by adding little seaweed to products

Adding seaweed to processed foods such as frozen pizzas, hot dogs and dried pasta will reduce cardiovascular diseases, concludes a new scientific article. One suggestion is to replace 5% of the flour in pizza dough with dried and granulated seaweed.

According to the World Health Organization (WHO) cardiovascular diseases are the number one cause of premature death globally. Ironically, many of the pathologies leading to premature death from cardiovascular diseases are not only widespread, but they are preventable.

One way to prevent cardiovascular diseases is to avoid obesity and eat healthy, leaving the responsibility with the individual consumer.

But the responsibility should also be shared by society, argues University of Southern Denmark professor of biophysics, Ole G. Mouritsen, who has authored several books on seaweed as food.

Professor Mouritsen is the co-author of an article in the journal Phycologia reviewing existing knowledge on the health effects of 35 different seaweed species.

In the article the authors offer suggestions to how both individual consumers and the food industry can use seaweed to make our everyday meals healthier.

"Certain substances in seaweed may be important for reducing cardiovascular diseases. We think this knowledge should be available for society and also be put to use," says Mouritsen.

Seaweed salt is healthier salt

Many seaweed species have a variety of health benefits. They contain, among other things, beneficial proteins, antioxidants, minerals, trace elements, dietary fiber and polyunsaturated fatty acids.

Seaweed's content of potassium salts does not led to high blood pressure -- unlike the sodium salts, typically encountered in the processed food.
An important feature is also that the seaweed has umami -- the fifth basic taste, which is known to promote satiety and hence regulate food intake in addition to reduce the craving for salt, sugar and fat.

"It is difficult to determine how much seaweed a person should consume to benefit from its good qualities. 5-10 grams of dried seaweed per day is my estimate," says Professor Mouritsen.

He and the co-authors suggest that seaweed should be added fast food, thus making this type of food healthier. It can even enhance the flavor of the food, they argue. For example, dried and granulated seaweed can replace some of the flour when producing dry pasta, bread, pizza, snack bars, etc.

Seaweed is also good in meat products

It is also possible to add seaweed to meat products and thereby provide the consumer with an increased intake of dietary fiber and antioxidants -- or maybe the aim is lower cholesterol levels.

In the article Professor Mouritsen and his co-authors describe a study in which a group of overweight but otherwise healthy men were asked to taste bread with added dried seaweed from the species Ascophyllum nosodum. The men's reaction was that the bread tasted acceptable as long as the seaweed content was kept under 4%.

By eating bread containing 4% of dried seaweed the overweight men ingested more dietary fiber (4.5 g more fiber per. 100 g) than when they ate the control whole-meal bread. Another effect was that they consumed 16.4% less energy in the 24 hour period after eating the seaweed enriched bread.

"We know that many people have difficulty distinguishing between healthy and unhealthy food. By adding seaweed to processed foods we can make food healthier. In many cases we also get tastier food, and it may also help reduce the risk of cardiovascular diseases," the authors believe.

http://www.sdu.dk/en/Om_SDU/Fakulteterne/Naturvidenskab/Nyheder_2015/2015_11_20_junktang