Top Crop Manager

Top Crop Manager
Triticale: Poised for the future

Triticale: Poised for the future

With the wrap up of the Canadian Triticale Biorefinery Initiative (CTBI), growers and industry are investigating innovative ways to move triticale forward.

Compromising borders

Compromising borders

Insect invaders and windborne diseases are common foes of the average farmer but invasive weeds usually don’t take centre stage. Expect that to change.

Dicamba-tolerant soybean moving forward

Dicamba-tolerant soybean moving forward

Soybean growers will have to wait another year or two before they have the option of using a soybean cultivar that is resistant to both glyphosate and dicamba.

Genetics of nitrogen use efficiency

Genetics of nitrogen use efficiency

Developing corn hybrids with improved nitrogen use efficiency – whether they have higher yields under normal nitrogen levels or maintain their yields despite low nitrogen levels – is a significant challenge.

Australia’s fight against herbicide resistance

Australia’s fight against herbicide resistance

In Australia, the development of multiple herbicide resistance has been the catalyst for the development of new agronomic practices.

video
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.
video
Expert Dr. Susan Watkins discusses Water Sanitatio...
Expert Dr. Susan Watkins discusses Water Sanitation
video
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.
video
Lily Tamburic...
Lily Tamburic

Seed/Chemical

Liquid or granular, the type of P fertilizer applied does not affect plant availability of P. All phosphate fertilizer forms perform the same

Monoammonium phosphate (MAP), ammonium polyphosphate (APF) and orthophosphate (OP).  These commonly used inorganic phosphate fertilizers are used to meet nutrient demand for crop growth, but are there differences in soil solubility and plant availability? Not according to research from the University of Manitoba (U of M). “In the experiment, what we saw was that within a few days, differences in solubility and plant available P became insignificant,” says soil scientist Rigas Karamanos at Calgary who collaborated on the research with Tee Boon Goh with the department of soil science at the U of M, and John Lee with Agvise Laboratories at Northwood, N.D. Phosphorus (P) is absorbed by plants largely as the primary and secondary orthophosphate ions, H2PO4- and HPO42-, which are present in soil solution. The orthophosphate forms are soluble in the pH range found in agricultural soils from pH 5.0 to pH 9. The concentration of these ions in soil solution, and the ongoing concentration in soil solution are of the greatest importance for plant uptake of P. Granular phosphate fertilizer dissolves slowly in soil solution and converts to orthophosphate forms, but the latter react quickly in soils to form secondary phosphate compounds with calcium (Ca), iron (Fe) and aluminum (Al), becoming insoluble over time. Liquid P fertilizer formulations that combine sparingly soluble orthophosphates and more soluble phosphates such as P2O74-, were theorized to be more available because they do not require dissolving in soil solution. However, P2O74- must still convert to orthophosphate for plant uptake. To address this theory, the researchers investigated the impact of fertilizer formulation on short-term solubility and plant availability. Three soils, four fertilizers and one unfertilized controlThree soils of similar texture, organic matter and “available” P level were selected for use in the greenhouse trial. One was acidic and two were alkaline (one non-calcareous and one calcareous).  Four fertilizer formulations were applied; a MAP (11-52-0), an ammonium polyphosphate (10-34-0) and two ammonium orthophosphates (6-24-6 and 9-18-9), at a rate of 100 ppm. All treatments were replicated four times. The fertilizer was physically injected into the soils. The soil water was kept at nearly field capacity throughout the experiment. Samples were assayed for water soluble (orthophosphate) and “available” P (Olsen method) immediately after application (zero days) and at one, two, four, eight, 16 and 32 days after application. No differences after two to four daysKaramanos says that the trends for all three soils were similar. Water soluble and available P levels were significantly different immediately following application of the fertilizer products. However, the differences were not significant after two to four days. Specifically, the three liquid fertilizers had significantly higher (P<0.05) water solubility than the granular 11-52-0 fertilizer in the acid soil until day 2; the 9-19-9 liquid fertilizer had significantly higher water solubility than all the other fertilizers until day 2. In alkaline soils, Karamanos explains that the P converted to less soluble Ca and Mg compounds producing the same trends, except that the 9-18-9 maintained higher water soluble P values until day 4 in the non-calcareous soils. Looking at plant available P using the bicarbonate extractable P method, the trends were the same, with higher plant available P from the liquid fertilizers in the first two to four days, and then non-significant differences after that. Differences in the first few days were widest in the non-calcareous soils and narrower for the slightly acidic soil, reflecting the limitation of the bicarbonate extractable P method in acidic soils. When phosphate fertilizer is applied at time of seeding, either side-banded or seed-placed, the differences in short term P availability observed by the researchers would not make a difference to P uptake by a crop. Plants would not start to take up P from the soil until well after the two to four day period after planting when the fertilizer formulations differences become insignificant. Time of emergence after seeding depends on the crop and soil temperatures. Generally, research in Western Canada has shown that even under optimum conditions, the earliest a crop typically emerges is in four days, but for most crops under cool soil conditions, emergence is typically more in the six- to 10-day range. Additionally, research has shown that P uptake by plant roots does not start until approximately 10 days after seeding. Other research in Western Canada has confirmed that P uptake and accumulation in cereals happens at the tillering to stem elongation stage between approximately 22 and 36 days after seeding. In canola, Karamanos did a study monitoring nutrient uptake in hybrid canola and found that measurable biomass and nutrient accumulation did not start until the third week after seeding. He says the biomass accumulation in the third week averaged one pound per acre per day, and the P uptake was 0.0 to 0.1 pounds P per acre per day. “What the research is telling us is that the type of phosphate fertilizer formulation applied does not have any impact on long term solubility or plant availability and uptake of P. The soil-P interactions control P uptake and not the formulation of fertilizer applied,” says Karamanos. Further, Karamanos cautions that no matter the formulation applied, phosphate fertilizer needs to be applied at rates that will ensure the long-term sustainability of P fertility in the soil. Cutting P fertilizer rates because a fertilizer is thought to have better solubility and plant availability will lead to nutrient deficiencies over the long term. “Soil test using a recognized and calibrated soil test for your area, and apply adequate amounts of phosphate to maintain soil fertility,” he advises.      

Agronomy

Comparison of clubroot-resistant (left) and clubroot-susceptible (right) cultivars at flowering stage in clubroot-infested field. More tools for your clubroot toolbox

Within a few years of clubroot’s discovery in a canola field near Edmonton in 2003, the disease became a serious problem for Alberta canola production. The emergence of this devastating disease on the Prairies has triggered intensive research, including investigation of possible tools for integrated management of clubroot. “Ideally for most diseases we want to use integrated management. That means integrating chemical controls, such as fungicides, and cultural controls, like planting practices and using resistant cultivars, and biological controls, like a microbe that kills a pathogen,” notes Dr. Sheau-Fang Hwang, a plant pathologist with Alberta Agriculture and Rural Development (AARD). Even though a single control measure may work well in the short term, integrated management is a better approach in the long run. “For example, if you rely on a fungicide too much, you might cause issues like fungicide resistance or environmental pollution,” explains Hwang. Clubroot is caused by Plasmodiophora brassicae, a soil-borne organism. The pathogen requires moist conditions to infect a plant, and it flourishes in warm soils around 25 C (temperatures below about 15 C inhibit its development). The pathogen attacks canola and other cruciferous plants, causing irregular swellings, or galls, to form on the roots. Those galls prevent water and nutrients from moving up into the rest of the plant, so the plant withers and dies. Fortunately, several clubroot-resistant canola cultivars are now available. They are the foundation of any clubroot management strategy. But resistant cultivars aren’t a magic bullet. Hwang’s research has shown that a small percentage of the plants from a resistant cultivar’s seed will develop galls when exposed to the pathogen. As well, the pathogen could potentially evolve to overcome the resistance genes if a resistant cultivar is grown in the same field year after year. To find ways to further strengthen the fight against clubroot, Hwang and her colleagues at AARD, the University of Alberta, and Agriculture and Agri-Food Canada (AAFC) conducted several trials to assess the effects of fungicides, seeding date and seedling age for suppressing clubroot. Fungicides to control seed-borne transmissionSome of the initial questions from producers about clubroot related to seed-borne transmission of the disease. “So the objective of one of our trials was to see whether or not a seed treatment might reduce the risk of clubroot if you have contaminated canola seed,” says Hwang. In this greenhouse trial, the researchers artificially infested seeds of a clubroot-susceptible canola cultivar, using infestation levels much higher than would occur in naturally infested seeds. Then they compared five fungicidal seed treatments: Helix Xtra, Dynasty 100 FS, Prosper FX, Nebijin 5SC, and Vitavax RS; for the control treatment, they applied water instead of a fungicide. The researchers planted the seeds in pots of clubroot-free growing materials, and allowed the seedlings to grow. Then they evaluated the disease level in the roots. All of the fungicides were able to significantly reduce the disease levels in the seedlings, in comparison to the control. So, this trial confirmed that contaminated seed can transmit the disease and that fungicidal seed treatments will likely prevent the problem. “Given the relatively low levels of clubroot infestation found in naturally infested seeds, any of the seed treatments used in this study would likely eliminate the risk of seed-borne transmission,” says Hwang. Fungicides for reducing disease in infested soilIn another trial, the researchers assessed the effects of fungicide seed treatments on a resistant and a susceptible canola cultivar grown in clubroot-infested soil. The sites for this field trial were at St. Albert and Leduc, Alta. The researchers applied various seed treatments: Helix Xtra (fungicide plus insecticide), Dynasty 100 FS (fungicide), Prosper FX (fungicide plus insecticide), and Sedaxane (fungicide). They applied Cruiser 5 FS, an insecticide seed treatment, as the control treatment. For the susceptible cultivar, none of the treatments reduced clubroot severity or improved seedling emergence or crop yield in comparison to the control. Similarly, for the resistant cultivar, none of the treatments improved emergence or yield compared to the control. “When you treat seeds with a fungicide, the protection lasts for perhaps two to four weeks, so the treatments work well for controlling seedling blights. But clubroot spores in the soil can affect the plant at any growth stage, as long as the moisture and temperature conditions are favourable,” explains Hwang. “None of the existing seed treatments can protect canola plants for the entire growing season. It may be a possibility for the future, but so far the chemical companies have not developed formulations that would allow the fungicide to slowly release into the soil, so it could protect against clubroot for the whole growing season.” Adjusting seeding date and seedling ageIn another field trial, the researchers evaluated the effect of seeding date on clubroot impacts. The field sites were at St. Albert and Leduc in 2008, and at Edmonton and Leduc in 2010. At each site, they planted several canola varieties at three seeding dates, ranging from mid-May to early or mid-June. With earlier seeding, clubroot severity tended to be lower and canola yield tended to be higher. “The results were no surprise to us,” notes Hwang. “Early seeding is always good for canola yields. In addition, early seeded crops usually are planted into cool soils, which clubroot does not like.” In a greenhouse experiment in 2009, the researchers examined the effect of inoculating canola seedlings at different ages with clubroot. At zero, one, two, three, or four weeks after seeding, they inoculated the plant’s potting mix with clubroot resting spores. When the plants reached maturity, the researchers evaluated the seed yields and the level of disease in the roots. For both the resistant and susceptible cultivars, the plants that were infected at the later growth stages did better – the disease was less severe and the plants had better seed yields. This finding supports the value of early seeding as part of a clubroot management strategy. Hwang says, “If you seed early, then the soil temperature is cooler so the resting spores germinate later. So the plant has a chance to grow bigger before infection occurs and when it is bigger it has a greater ability to defend itself from pathogen.” She adds, “In the future, perhaps we’ll have a chemical treatment or a biological agent that will delay the infection and reduce the impact on seed yield.” Practical implicationsThe results from these studies highlight two practices that help suppress clubroot: seeding early, and using disease-free seed. “It’s always a good idea to buy certified seed to make sure the seed is not externally contaminated. If you don’t buy certified seed, then you should use fungicide-treated seed to reduce the risk of getting clubroot,” says Hwang. However, she emphasizes the two seeding practices by themselves are not enough to manage clubroot. They must be part of an integrated strategy, with clubroot-resistant cultivars as the major weapon against the pathogen. “Resistant cultivars are the most economically feasible and environmentally friendly approach to clubroot management. And you need to do everything you can to stop the pathogen from breaking down the plant’s resistance. That includes rotating your crops and rotating your resistant cultivars.”