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Story Posted: March 09, 2011 Canola Watch: Fertilizer rates, Seeding rates, Budget for disease In This Issue: Increase fertilizer rates to match yield potential, Larger seed requires higher seeding rate, 90% germ guaranteed for No.1 certified seed, Budget for disease management, Blackleg and tight rotations, Broadcast seeding in April, Coming events, Questions and contacts. Quick hitters What is your risk for glyphosate-resistant weeds? Glyphosate resistant weeds have been found in the U.S. and Ontario, so we know it can happen. Take the quick test at www.weedtool.com to see if your practices put you at risk. Peace growers, consider a soil test. Dry conditions the past few years could mean high levels of residual fertilizer in some soils in the Peace River region. If more "normal" moisture conditions return for 2011, growers in the Peace could have the opportunity to generate a high-yielding canola crop without having to apply high rates of fertilizer. However, making this assumption without a soil test could lead to under-fertilizing, limiting yields in a year of good canola pricing opportunities. Soil testing in winter. If you haven’t tested your soil, but would like to get a test done ahead of seeding, sampling in winter is an option. Click here for tips from last month’s Canola Watch. Soil temperature and seeding date. While growers may be able seed in mid April in some years and in some locations, seeding that early increases the spring frost risk and usually results in a much wider germination window. This multi-stage and patchy crop presents challenges for weed control, disease management and harvest. For fast and more uniform emergence, which helps a crop mature earlier and more evenly, temperatures in the seed zone should average at least 4-5°C when measured over a 3-day period. Increase fertilizer rates to match yield potential This may not be enough for high yielding canola. Canola that yields 35 bu./ac. removes 61-74 lb./ac. of nitrogen, 33-40 of phosphate, 16-20 of K2O, and 10-12 of sulphur. Average fertilizer rates are probably keeping up with removal for canola at that yield. But many growers harvested higher canola yields the past couple years. A 50 bu./ac. canola crop removes 87-105 lb./ac. of nitrogen, 47-57 of phosphate, 23-29 of K2O and 14-17 of sulphur. If that 50 bu./ac. crop was produced from the average application rates above, the deficit would have come from available nutrient in the soil. When canola achieves higher yields than targeted with a fertilizer application, it may be depleting soil nutrient reserves. Growers should evaluate the nutrient balance for preceding crops on each field to determine if this is the case. If so, soil testing may reveal lower than expected residual nutrient levels, and producers may need to increase fertilizer rates for 2011 if they want to maintain this higher yield potential. Larger seed requires higher seeding rate
The ideal target is 10 plants per square foot, which provides some buffer for mortality. Seeding large seed at 4 lb./ac. will not achieve desired plant stands. Higher seeding rates are required. Studies have shown that larger seeds will have better germination, especially in cooler soils, but once seeds get above 4-5 grams per 1,000, this seed size benefit may plateau. Seed weighing 5.5 grams may not have an advantage over seed weighing 5 grams, for example. Stands below 5 plants per square foot can still produce reasonable yields under ideal conditions, but are much more vulnerable to later stresses that limit the ability of the plants to compensate through increased branching and pod production. There is no buffer against further plant losses due to weather, diseases and insects. Also, canola that branches out to compensate for a thin stand will mature later, which increases the risk of yield loss and high green counts due to fall frost. 90% germ guaranteed for No.1 certified seed Growers are advised to keep a sample of all seed lots. Put a minimum 500 ml (2 cups) from each seed lot into a seed lab bag. Record seeding date and rate, keep the blue seed tag, and store samples in a cool, dry place in a rodent proof container. For more on seed quality, Alberta Canola Producers Commission will host a webinar this Thursday, March 10, at 8:30 a.m. MST with Sarah Foster of 20/20 Seed Labs. Click here to register. Budget for disease management Hopefully growers will be in a position to need this fungicide when the time comes. Why? Because crops that warrant a fungicide spray are the same crops that have the stand and the moisture for high yield potential. Blackleg and tight rotations For example, available evidence does not support that a crop sequence of canola-canola-wheat-wheat is better than canola-wheat-canola-wheat. Latest research indicates that blackleg severity tends to be highest for canola on canola stubble, then lower with one year between canola crops, and lower still with two and three years between canola crops. We know based on crop insurance records and a recent Agriculture and Agri-Food Canada study that canola on canola yields lower than canola on any other stubble. When growing canola on a one in two year rotation, consider rotating varieties on those fields. Many genes are responsible for blackleg resistance in canola and at least 16 described virulent blackleg races are currently found on the Prairies. Growers don’t know which varieties have which resistance genes, but rotating varieties will likely bring a mix of resistance genes to the field over time. This reduces the risk of selecting for blackleg races that can overcome the specific genetic resistance in any one variety. Click here for more blackleg management tips. Broadcast seeding in April Expect a poor and uneven stand. Canola can start to germinate at temperatures as low as 1°C. Seed broadcast in early April could start to germinate within a week if weather turns warm. It could germinate before the ground thaws, which will almost certainly lead to seedling death. A high seeding rate may compensate for higher than average seed and seedling mortality. Those seeds that do take root and grow will likely do so at a broad range of days and in a patchy formation, producing a highly variable stand. Careful mixing seed and fertilizer. The ideal is to use a floater with two tanks, one for seed and another for fertilizer. If growers do not have a broadcast applicator with two tanks, blend seed and fertilizer in the tank just before application so their time together is limited to a few hours or less. Fertilizer, especially any kind of nitrogen fertilizer, can start to reduce canola seed germination rates within a couple hours of blending. Larger canola seed has more surface area and in some cases a thinner seed hull, which means less protection from fertilizer toxicity and salt effect. Consistent seeding rate is an added benefit of having two tanks. With a separate tank for canola seed, the floater is more likely to apply the same seeding rate across the whole field. With canola seed blended with larger fertilizer prills, the seed and fertilizer may not maintain a consistent ratio throughout the tank. Crop insurance depends on establishment. Broadcast canola does not automatically quality for crop insurance. The established stand must be inspected and meet crop stand standards before it can be insured. If the crop does not grow and the ground is too wet to seed, the grower could be eligible to receive an unseeded acreage benefit. Rules for unseeded acreage benefits vary by province. In Alberta, for example, growers qualify only if 10% or more of acres in the area remain unseeded. Farm saved seed is illegal for most varieties. Any canola seed with a herbicide tolerance (HT) system is protected under contract. Growers cannot legally use farm saved seed from these varieties and hybrids. Coming events Seed quality webinar. Alberta Canola Producers Commission hosts a webinar this Thursday, March 10, at 8:30 a.m. MST with Sarah Foster of 20/20 Seed Labs. Click here to register.
Questions and contacts If you have questions on regional issues, contact one of the following Canola Council of Canada regional agronomists or provincial oilseed specialists:
This report is supported by each of the provincial canola grower associations. For more information on some of their activities, check out the following links:
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