Top Crop Manager

Top Crop Manager
Canola crop rotations could condition northern soils

Canola crop rotations could condition northern soils

Not that long ago, farmers didn’t know planting bacteria with soybean seed produces better crops.

Inputs for sustainable crop management

Inputs for sustainable crop management

Optimum crop production depends on inputs of commercial fertilizer, livestock manure, herbicides, fungicides and insecticides.

Spraying into a mature crop canopy?

Spraying into a mature crop canopy?

A new project to discover the most effective ways to spray fungicides into mature crop canopies is already generating some interesting preliminary results.

Giant ragweed in southwestern Manitoba?

Giant ragweed in southwestern Manitoba?

Giant ragweed is more common to warmer climates in the United States and a few places in southern Ontario and Quebec.

UAVs: Where dreams meet dust

UAVs: Where dreams meet dust

The dream of using Unmanned Aerial Vehicles (UAVs) for precision agriculture took off faster than many developers could realistically keep up with, but researchers at the University of Guelph are hoping to close some critical technical gaps.

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Honey Bee AirFLEX...
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North American Manure Expo comes to Canada...
For the first time ever, the North American Manure Expo is being hosted within a Canadian province. The annual show is being held August 20 and 21, 2013, at the University of Guelph’s Arkell Research Station, located near Guelph, Ontario. So, what's a Manure Expo and why should you attend? This video will provide all the dirt.
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Expert Dr. Susan Watkins discusses Water Sanitatio...
Expert Dr. Susan Watkins discusses Water Sanitation
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The population explosion...
With the world's population increasing exponentially and farmland staying the same, BASF took to the streets to ask consumers if this trend is sustainable.

Seed/Chemical

Thiamethoxam, a broad-spectrum neonicotinoid insecticide contributes to better seedling vigour compared (as compared to no treatment) says Clarence Swanton at the University of Guelph.  When applied to seed, he and his team saw increased germination rates, faster root growth, greater seedling heights and more biomass accumulation. Additional benefits of neonics

Do certain seed treatments go beyond protecting young plants from insect pests? That’s an important question, especially if the seed treatment is a neonicotinoid insecticide. Neonics are currently under intense scrutiny by government agencies in many countries and their use is being restricted in some jurisdictions. It’s clear that at least one neonic seed treatment seems to provide more than insect pest protection in corn, but just what protection it provides and how it does so hasn’t been completely clear. “Thiamethoxam is a broad-spectrum neonicotinoid insecticide that, in seed treatment form, contributes to better seedling vigour compared to no treatment,” Clarence Swanton, a professor in the department of plant agriculture at the University of Guelph (U of G), says. Thiamethoxam controls a wide variety of commercially important crop pests, and is used as a foliar spray or soil treatment (Actara), or as a seed treatment (contained within Cruiser). “When thiamethoxam is applied to seed, we see increased germination rates, faster root growth, greater seedling heights and more biomass accumulation, but the physiological mechanisms by which these enhancements occur is not well known,” Swanton explains. “Other researchers have measured the ability of thiamethoxam to do things such as increase the antioxidant capacity of a certain molecule found in corn seedlings, called salicylic acid, which is an antioxidant that plays an important role in the defence against plant pathogens. It is also able to improve plant response to abiotic and biotic stresses, including those caused by the presence of weeds.” However, thiamethoxam seed treatment may be helping seedlings perform better because it reduces the amount of hydrogen peroxide (H202), a free radical that can accumulate in a seedling due to the stress of having weeds nearby. (Free radicals cause damage in plant and animal cells through a process called oxidation.) “Thiamethoxam may be elevating the expression of genes involved in natural scavenging and destroying of H202, in addition to genes involved in other metabolic pathways. This is what we wanted to find out more about,” Swanton says. Swanton and his colleagues have investigated how much better corn seedlings perform with weed pressure, with and without thiamethoxam as a seed treatment. They conducted measurement and analysis at the plant (macro) level, as well as at the molecular level. In addition to Swanton, the team included Maha Afifi, Elizabeth Lee and Lewis Lukens, a research team at the department of plant agriculture at the U of G. In a laboratory environment, thiamethoxam-treated seeds were planted, with some of the resulting seedlings growing up in the presence of neighbouring weeds (a perennial ryegrass). The researchers harvested seedlings at the fourth-leaf-tip stage, washed the roots, and counted and measured crown roots. Shoots and the entire root system were then bagged separately and dried to determine total shoot and root biomass. Other seedlings were harvested for physiological and molecular analysis. “At the macro level, we found the treated corn seedlings showed enhanced root development and seedling vigour, with none of the shade avoidance characteristics that typically develop when there are neighbouring weeds present,” Swanton explains. “We believe this was a result of morphological, physiological and molecular processes. This is the first report to identify the mode of action of thiamethoxam within the physiological mechanisms of early crop and weed competition. “In short, our results suggest thiamethoxam enables corn seedlings to maintain their antioxidant protective system to avoid damage caused by oxidative stress from neighbouring weeds,” Swanton says. Swanton, Afifi, Lee and Lukens found thiamethoxam reduced H202 accumulation, as well as the subsequent damage caused to cells by its accumulation. “It seems to accomplish this through boosting the capacity of genes involved in scavenging this free radical,” Swanton says. “Preventing the accumulation of H202 and enhancing the entire antioxidant system means the plant experiences less cellular damage caused by abiotic and biotic stresses, such as lower light levels caused by neighbouring weeds. The plants from treated seed don’t have to expend as much energy for cellular repair and the energy can therefore be used for growth and maintenance of plant tissues. So, these results suggest plants from thiamethoxam-treated seeds may be better adapted for survival under harsh environmental conditions.” Swanton believes these results have several other implications for the role of seed treatments in agriculture. “Normally, seed treatments are thought of only in terms of insect and disease control, but the results of this study suggest it may be very worthwhile to explore entirely new chemistries and new modes of action in novel seed treatments to enhance free radical scavenging and activate genes involved in the antioxidant defence system,” he says. “It’s clear from our study and the work of other researchers that some seed treatments have this capacity, and that may be critical in the development of crop hybrids and cultivars that are more stress tolerant to weed competition.” The researchers are now investigating whether soybean seedlings grown from thiamethoxam-treated seed will demonstrate the same responses to weed pressure as those of corn seedlings. 

Agronomy

Researchers grow sunflower in a greenhouse to study how the plant and soil interact to affect plant growth. Plant-soil interaction linked to weed control

Researchers in the United States are looking at the relationship between plants and soil and how this relationship might be used for weed control. And they are solving the mystery like any good investigators would, using DNA fingerprinting. Tony Yannarell, assistant professor of microbial ecology with the Department of Natural Resources and Environmental Sciences at the University of Illinois (U of I), and grad student, Yi Lou, extracted the microbial DNA from soil collected for 10 home and away trials using two agricultural weeds – the common sunflower, Helianthus annuus L., and giant ragweed, Ambrosia trifida L. This gave them a pool of DNA from all of the micro-organisms in the soil and allowed them to create fingerprints of each soil community.The trials took place independently at agricultural research facilities in Michigan, Illinois, Kansas, South Dakota and Oregon using local soils gathered on site. Each trial used common seed stocks, with the sunflower seeds gathered in Manhattan, Kan. and the ragweed seeds gathered in Urbana, Ill. “Soil from Michigan and Montana have different organisms so we would get a different fingerprint,” Yannarell says. “When soils have similar micro-organisms, then we get similar fingerprints.”Yannarell became involved in the research after results from other trials examining plant-soil feedback loops ruled out nutrient depletion and soil chemistry as the causes of plant growth changes. “Plant-soil feedback research has been going on for 15 years or so,” Yannarell says. “When you have a particular plant growing, as it grows it interacts with the soil and what’s in the soil, and it changes the makeup of soil.” For this research they were looking at the feedback from the soil to the plant. If there is a positive plant-soil feedback, it will make the soil better for the plant. Alternatively, negative plant-soil feedback will be bad for the plant. The question was, how did these feedback impact generations of plants?“The idea is that weeds that have negative plant-soil feedback are good for us,” Yannarell says. “They can help farmers with weed control and potentially replace herbicides. We wondered if two weeds might have positive or negative plant-soil feedback, [and] did positive plant-soil feedback change as you go east to west. “Sunflower gives positive feedback in the west, negative in east. Maybe ragweed does the opposite?”In the trials, the researchers grew ragweed and sunflower plants in home and away soil to see how they interacted with the soil. They grew two generations of the plants in the same pots to give them the opportunity to do what it would do to soil, and then looked at the average growth of each in the away soil versus the home soil. If it does better in the away soil, it’s a negative plant-soil feedback; if it does better in the home soil, it’s a positive plant-soil feedback. “They expected the ragweed would show negative in the west but positive in east and that sunflower would have positive feedback west of the Mississippi and negative east,” Yannarell says. “That was not what they found at all. Ragweed showed negative feedback everywhere we did the experiment and sunflower showed positive feedback everywhere, although sometimes very slight.” They next looked to see if plants were making chemical toxins in the soil that might affect the plant, but found no evidence of this. “They started to think about micro-organisms and that’s where we got involved,” Yannarell notes, adding because the researchers froze the soil, they were able to study its microbial makeup. When they didn’t see similar organisms in the home and away soils, they realized ragweed was doing a good job picking out the bad-for-it micro-organisms wherever it grew. The search was on to find out just which micro-organisms might be bad for it. They developed a math equation to determine how good or bad each micro-organism is for ragweed or sunflowers. Scientists estimate a gram of soil contains over 10,000 species of bacteria. “If we drill down to the ones most responsible for soil health, on average less than seven per cent of the bacteria in soil could explain about 90 per cent of change in plant growth,” Yannarell says, adding while they can’t give a list of bacteria or fungi to use for weed control just yet, his department’s research does raise the possibility of identifying micro-organisms for weed control. “We can find plants we desire and plants we don’t want,” he says. “We are now looking at the use of cover crops to set up a soil environment that is good for plants but bad for weeds.” In Canada, Kari Dunfield, an associate professor and Canada research chair with Environmental Microbiology of Agro-Ecosystems at the University of Guelph’s School of Environmental Sciences, says they have been using similar molecular methods to examine pathogen communities associated with dog strangling vine, Vincetoxicum rossicum, a highly invasive plant in North America. “Dog-strangling vine is on Ontario’s Noxious Weeds list, and is not only an environmental concern, but a big problem for farmers and gardeners,” Dunfield says. “My graduate student, Nicola Day, and collaborator Pedro Antunes at Algoma University, have been looking across 100 years of natural invasion of dog-strangling vine in Ontario, and using high throughput genetic sequencing to identify the fungal communities associated with field-grown plants.  We have been looking for fungal communities to attempt to identify communities that may build up over long periods of time.” Along with genetic methods, Day has cultured fungal isolates from dog-strangling vine and is now testing them to see if they are pathogenic to this plant, and also to native plants, in order to get a better understanding of how dog-strangling vine becomes invasive. Dunfield explains that plants are associated with a diverse microbial community both surrounding their roots, in the rhizosphere, and within the roots, the endosphere. “Plants attract specific microbial groups through their pattern of root exudation,” she says. “By getting a better understanding of this relationship, it is possible we could either grow plants in rotation that attract beneficial microbial groups, or alternatively, attract weed specific pathogenic microbes.” She adds the value in research such as that being done at the U of I is its focus on targeting soils’ DNA. “Since less than one per cent of microbes are able to be grown in the lab, a critical component of this work is our ability to target DNA in the soil and identify microbial communities,” Dunfield says. “This metagenomics approach has allowed research groups to begin to move forward in these areas and ask these types of research questions.”

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