Know your soil type
Soil texture is defined as the percentage of sand, silt, or clay particles. Understanding the differences between these three overarching aggregates and how water behaves with these particles is the first step to understanding how soil-applied herbicides work.
Among other applications, knowledge of soil texture can be important when diagnosing in-field issues such as drought stress, compaction and crop diseases.
Soil texture can be determined in several ways, from manually performing an analysis (e.g. using the ‘soil ribbon’ method), referring to Canada Land Inventory maps or taking soil cores for particle size analysis by a reputable soil lab.
How water moves and interacts with different soil textures
Three different forces dictate how water moves through porous materials like soils:
Water can move by gravity alone (saturated flow), by a combination of gravity and capillary action (unsaturated flow), or as vapour in dry soils.
Water itself has two forces at play. Adhesion, which is the attraction between water molecules and solids, and cohesion, the attraction between water molecules themselves. Both forces are why water droplets visually appear to cling together and onto the surfaces of solid objects.
Since the amount of surface area varies between soil types, the behaviour of water also varies.
Making soil-applied herbicides work
Product rate, soil pH, organic matter levels, as well as soil moisture and texture all influence how well herbicides work in soil.
As rain washes soil-applied herbicides (mainly focusing on Groups 13, 14, 15 characteristics) from crop stubble into the soil, an active layer forms in the upper soil profile. This herbicide solution binds to soil and organic matter particles. That means soils with higher clay or organic matter content have greater binding potential compared to sand soils, thus herbicide is more readily available.
What happens in sand?
The larger particles characteristic of sand soils means there is less surface area, or fewer binding sites, which means the herbicide’s active ingredient is more readily available for plant uptake. A lower rate can be used as a result. If the soils dry completely, however, that will not be unavailable (adsorbed to soil) for plant uptake until rain puts it back into solution – assuming the active has not fully degraded. In extremely wet conditions, the active is readily available and not binding to the coarse soil particles. This gives it greater mobility to move further in the soil profile. If it moves into the root zone of germinating crop seedlings, temporary crop sensitivity can result.
What happens in clay?
Smaller clay particles result in more adsorption or product tie up. With more of the active ingredient being tied-up, higher rates need to be used. Since clays also retain more water, however, it is possible for active ingredients to stay within the soil water solution for longer dry periods. There is also less downward movement in overly saturated conditions.
Considering a pre-seed herbicide application? Ask yourself these four questions first:
What affects the availability of the chemistry you are using? Soil-applied herbicides can vary in how soil parameters may affect them.
The difficulty of in-crop weed control, ongoing resistance issues, and a variety of other factors make soil-applied pre-seed herbicides a practical and powerful choice for western growers. Understanding how these products, soil texture, and water interact with each other helps ensure the right rate is achieves maximum effect.
Want to know hear more from the experts? Watch Rachel Evans & Nolan Kowalchuk, technical sales managers with FMC, highlight the ins-and-outs of pre-seed herbicide management.
As soon as harvest is done, winter annual weeds start their growth cycle all over again and perennials move nutrients to the roots to build up reserves for the following season. The right approach to fall weed control can set growers up for success next spring, so let’s go back to school to learn how fall weeds can impact your fields! Watch this webinar for a product-agnostic approach to the value of weed management in the fall.
Growing lentils isn’t often much like caring for Holsteins but both cash crop and dairy farms thrive under a long-term plan.
“Take care of your cows and they’ll take care of you,” Kevin Krahn’s dad used to say when Kevin and his wife Sherry took over the family’s purebred dairy operation in 1988. Now they grow peas, lentils, durum, some barley and canola. The wisdom from Kevin’s dad transferred into cash cropping after they sold the cows.
“I think the same thing applies to the land,” says Krahn from his farm near Swift Current. “We try to make decisions based on the long-term health of each field just like we did with the cows.”
Krahn, Sherry and hired man work on the operation. They do the majority of scouting themselves, although they hire an agronomist for advice on fertilizer rates and on which weed control and fungicide products to use.
The variability in weather patterns will always be the hardest component to manage in farming. The last two springs have been drier on Krahn’s farm. “We had some rain that came just in time this past year,” he says. “In 2018 we were very dry, in 2017 we were a little dry and in 2016 we were extremely wet.”
Through all the years – wet, dry and “normal” – his attitude has stayed the same. Krahn says he will continue to do what’s best for each piece of land. He might seed a little more spring wheat or seed a new pulse crop as an experiment but otherwise he sticks to the long-term plan.
“I’m kind of set in my ways,” Krahn says with a chuckle. “I do what’s best for the dirt, not what’s a fad. That’s not going to change. I could give you the rotation on 80 per cent of our farm for the next three years.”
The one area that Krahn is willing to experiment is in technology. They recently upgraded their sprayer and he tested out a new combine with significantly more automated features than his current combine.
For Krahn, taking care of the land means sticking with his crop and chemical rotation. “We don’t really ever plant according to where we feel the markets are going,” he says. “We stick to the plan. It’s not just for the sake of managing pests but also to keep a diverse chemical rotation as well.”
Some tougher, less predictable weather years make it tempting to drop lentils from the rotation. And weed control options are limited when growing large green conventional lentils, says Krahn. He says their main weed pressures are wild oats, kochia, wild buckwheat and narrow-leaved hawk’s beard.
Four years ago, Krahn started using Focus® herbicide from FMC.
“It’s more reliable in different weather patterns,” he says. “But the main reason we like Focus is its ability to control weeds.”
“Lentils are a poor competitor when it comes to weeds,” says Rachel Evans, technical sales manager at FMC. “There needs to be a whole farm weed management strategy if lentils are in the rotation.”
For instance, part of the weed control strategy could include increasing seeding rates. Research by Dr. Steve Shirtliffe at the University of Saskatchewan showed that higher seeding rates up to 240 plants per square metre reduced weed populations and increased yield.
“Increasing seeding rates means you’ll have a more competitive crop and have more plants competing with weeds for resources,” says Evans. “And, you’ll also get better performance out of your herbicide.”
Resistant weeds, such as Group 1- and Group 2-resistant wild oats, are limiting the number of effective weed control products in a grower’s rotation. Evans says that Focus herbicide, made up of Groups 14 and 15, provides alternative modes of action to hit those problematic weeds.
Jesse Entz is from the B Creek Farming colony near Swift Current. Kochia is one of the biggest problem weeds the colony faces in lentils. They use Focus herbicide to suppress wild oats, which are becoming a problem as Group 1 resistance grows. “But the biggest reason we use it is for kochia,” he says. “There wasn’t much we could do for kochia in lentils before Focus.”
“The first year we put some down early on about 500 acres,” says Entz. They usually grow in the neighbourhood of 3,400 acres of lentils. “It was ready and activated when we needed the control in the spring.”
The colony had a lot of lentils flooded out in 2019. But even with the rain they still saw good weed control. Part of keeping a long-term plan involves spreading out weed control risk.
For instance, an early application allows Entz to sleep at night knowing his herbicide is already down even before seeding. He can concentrate on seeding and count on Focus herbicide and the protective layer it forms to protect his crop.
Managing weeds early also means more effective in-crop control, helping to avoid harvest challenges.
Research at the University of Saskatchewan found that lentils have a long critical weed-free period. The critical weed-free period is described as the stage of crop development where a yield loss of more than five per cent would occur if the crop were not weed free. In lentils, the crop needs to be weed free from the five-node stage right through to the 10-node stage.
“It’s quite a length of time, which shows you how uncompetitive lentils are,” says Evans. “It’s important to keep that critical weed-free period in mind as growers consider the timing of their herbicide applications and as they consider extended weed control products.”
Once again, planning and an eye on the long-term is key to growing a clean crop of lentils.
Having a long-term crop rotation plan and a strategy that incorporates tank-mixes and herbicide layering is a great way to manage herbicide resistance.
Hitting the same weeds at the same time using the same modes of action creates a pressure that can result in a change in weed population (where the population shifts to a majority of resistant individuals), or a change within weeds where they adapt and become resistant. Either way you’re training weeds to win.
Herbicide layering is the practice of using multiple herbicide groups and active ingredients at different application timings to control the same resistance-prone weeds. Using products with different modes of action is good and hitting weeds at different timings is even better.
For example, a pre-emergent product like Focus herbicide brings two modes of action – Group 14 and 15 to manage kochia. When combined with glyphosate, the Group 14 and Group 9 give you activity on any emerged, resistant kochia. Then, since kochia is a flushing weed, the group 15 portion provides activity on resistant kochia that’s germinating or about to emerge.
“[In herbicide layering], you are incorporating products at different timings that work on different weeds to achieve an overall higher level of weed control,” says Evans.
With limited in-crop options available for lentil growers, a burnoff herbicide application with extended weed control can be a game changer – providing flexibility during the growing season, as well as at harvest. At the FMC Swift Current lentil plots, researchers compared treatments of burnoff plus extended weed control to burnoff alone.
Here’s what they found out…
Burnoff + extended weed control:
Check out the video to see the trial:
When it comes to resistance management, what’s the number one thing we’ve been told to do over the past several years? Rotate your herbicide groups.
Then from there, we’ve moved to adding multiple modes of action into the same tank mix.
However, researchers have found herbicide layering may offer you the best chance at reducing your overall resistance risk.
The idea behind layering is to use multiple herbicide groups and actives at different application timings to control the same resistance-prone weeds in the same fields.
Unlike straight tank-mixing, herbicide layering doesn’t require you to spray all your active ingredients within the same tank load. Instead, it’s different application timings. You may start with a pre-seed application of multiple herbicide groups before following up in-crop with a completely different set of groups.
Nolan Kowalchuk, Technical Sales Manager at FMC of Canada, recommends growers start their herbicide layering program by applying an extended control, pre-emergent herbicide – such as Focus® (Group 14 and 15) – at pre-seed timing.
Once activated by rain or moisture, pre-emergent herbicides create a protective “barrier” within the top layer of soil that controls weeds as they germinate. This herbicide barrier can help cut back resistant weed populations right out of the gate.
“Just as an example – if you’re dealing with Group 2, 4 or 9-resistant kochia, applying a pre-emergent product like Focus® herbicide with glyphosate gives you Group 14 activity on any emerged, resistant kochia and Group 15 activity on resistant kochia that’s germinating or about to emerge,” explains Kowalchuk.
He adds that the pre-emergent herbicide does a lot of the heavy lifting up-front, which allows your in-crop herbicide to be more effective and reduces the chance of more resistance issues cropping up.
Traditional Group 2 products can still fit in other areas of a grower’s herbicide program, as they control perennial weeds, like narrow-leaved hawk’s-beard and dandelions, where there are few herbicide options.
But in addition to perennial weeds, growers may have resistant wild oats, kochia or cleavers in their fields. This is where layering in pre-emergent herbicides can help provide a valuable first line of defense on those resistant weeds.
“Ideally, you’ve got newer modes of action in your pre-emergent herbicides controlling the resistant weeds and the traditional Group 2s working on weeds like hawk’s-beard and dandelion,” he says. “And by layering in pre-emergent products for your resistant weed populations, you’re covering parts of your weed spectrum that other modes of action can’t manage as effectively.
Picture this: It’s mid-April. You’ve had a cool, droughty spring and you’d be hard-pressed to find a single weed in any of the fields you’re about to seed.
So, you start thinking, “if there aren’t any weeds out there, do I really need to spend the time and resources putting down a pre-emergent herbicide?”
Getting a head-start on seeding seems like the smart move – especially when there haven’t been any heavy rains to keep you out of the field.
Fast forward a couple weeks: you get the whole crop in without too many hiccups, but then the rain finally comes. Suddenly, there’s an explosion of cleavers clogging up that clean, weed-free field. Worse yet, the weeds are now out-competing your crop right as it’s emerging.
Here’s the harsh truth: you’ve always had weeds – and you always will. They just may have taken a while to wake up and start causing you grief. Weed seeds are notoriously resilient and will lie dormant in your soil for years – decades, even – just waiting for the right conditions to germinate and flourish.
As a result, growers can get caught out by big flushes of weeds after a cool, dry spring gives way to rain.
“When you get those heavy flushes of weeds, we know they’re actively competing with your crop for moisture and robbing valuable nutrients from your fertility program,” says Paul Allen, Product Manager with FMC of Canada. “So, it all comes back to being as proactive as possible by protecting that early-season stand establishment and getting your crop off to a weed-free start.”
He adds that putting down a PRE herbicide prior to seeding – even when you don’t see weeds – sets up a layer of control by forming a protective barrier at or near the soil surface.
Once your PRE herbicide is in place, it offers long-lasting extended control of weeds before – or shortly after – they emerge. Some PRE herbicides will sit on the soil surface until they are activated by moisture. That way, when you do get that shot of spring rain, the PRE gets right to work – ideally at the same time as weeds are germinating.
“With a preventive product, you’re knocking out a significant portion of the weed population and seriously injuring anything that comes up afterwards,” explains Scott Knox, account manager with FMC. “When you do get that weed flush – and it will happen – the PRE you’ve applied is going to take out those first weeds very quickly.”
Another major factor to consider is resistant weed management. PRE herbicides provide alternative modes of action (which tend to come from Groups 3, 8, 13, 14 and 15 to name a few) that target Group 1, 2 and 9 resistant weed populations and reduce the overall resistant weed seed bank in your field.
Then, as you get into the season, far less pressure is placed on in-crop herbicides to clean up your fields.
“I always tell my growers that you’ll never ever regret having sprayed a pre-emergent herbicide,” says Knox. “Especially when you’ve got resistant weeds, PREs allow you to be far more proactive in your decision making and take action right out of the gate with alternate modes of action so that your in-crop isn’t doing all the heavy lifting.”
Some years back, farmers in Western Canada were under pressure on several different fronts. With the rising threat of weed resistance, many growers found their in-crop application was becoming less effective year by year. Glyphosate – an essential weed control tool – had resistance concerns of its own. Meanwhile, with farm sizes increasing, more growers were needing to cover more acres and managing various farm operations.
Farmers needed to find a way around these constraints, and pre-emergent herbicides have provided it.
The arrival of a strong PRE product portfolio, led by FMC, has given growers a new set of tools to control weeds, achieve higher yields, manage resistance and save time.
The agronomic insight behind PREs is one that growers know from personal experience, but it’s now firmly backed by science. Research over the years show that crop yield potential is largely determined early in the season. One way to maximize yields is to keep crops weed-free up to the 3-leaf stage. Weeds emerging later might be visually bothersome, but they won’t hurt yields much.
“Early weed removal is proven to give the crop the advantage,” notes Sonia Matichuk, Technical Sales Manager with FMC of Canada. “When weeds are removed early, the crop – not the weeds — uses the moisture and nutrition. With PRE herbicides, you’ve got a more competitive, healthier crop that’s in a better position to face any environmental stresses later on in the season.”
Alongside early weed removal and higher crop yields, PREs are a powerfully, sustainable answer to the threat of herbicide resistance. The key resistance issues in Western Canada relate to herbicide Groups 1, 2 and 9 (glyphosate). PREs generally belong to Groups 3, 8, 13, 14 and 15.
Even so, not all early-season herbicides are created equal. Soil-incorporated herbicides – heavily used twenty plus years ago that have staged a comeback as resistance concerns grow – require specialized and costly equipment and disturb the soil in a way most of today’s growers want to avoid. FMC PREs come in convenient liquid formulations and don’t require incorporation.
Getting more of the year’s weed control done early in the spring also takes the pressure off in-crop applications and give growers more flexibility in timing their summer workload on the farm.
By delivering effective early weed removal, helping to maximize crop yields, managing resistance and freeing up the grower’s time, PRE herbicides provide what crop producers are looking for in 2019.
Imagine a grower from the future showed up and told you what’ll happen with the resistant weeds on your farm if they’re not managed properly.
Sounds like something ripped from a bad movie, right?
Thing is, if you really do want a clearer idea of how the spread of resistant weeds could impact farming over the next 20 or 30 years, all you have to do is talk to an Australian grower.
Josh Lade first came to Canada back in 2009 and originally hails from a smaller, mixed operation where he and his family farmed livestock, grains and potatoes. Today, he farms part of a 15,000-acre operation just north of Saskatoon, SK. For Lade, weed resistance was a reality of day-to-day farming life in Australia.
“Down there, weed resistance has been happening since the 80s – but farmers didn’t really know any different or realize what was going on,” he says. “As soon as one herbicide group wasn’t effective, they’d move on to the next and the next one after that.”
Fast-forward to the present-day, and growing cash crops has become a tough, expensive prospect. Lade says that Australian growers will change up their crop rotations based on the dominant weed pressures in their fields, rather than grow the most profitable crops year over year.
Australian growers are also using mechanical options, like seed destructor equipment to pulverize resistant weed seeds, or going in with a moldboard plow, inverting the top foot of soil and burying weed seeds so they can’t germinate.
And when it comes to herbicide programs, Australian growers are forced to use higher rates and multiple modes of action on every acre.
“In a lot of cases, farmers now are layering up with $40 worth of herbicide per acre or more and still having weeds present at harvest – which is costing them even more,” Lade explains. “So, when you think of weed resistance in Canada, we’re at a point where we can either put our heads in the sand, try save a few bucks and end up in the same situation five or 10 years down the road, or we can be proactive now.”
He adds that skipping a pre-seed burn-off and relying solely on in-crop herbicides isn’t going to cut it long-term if growers want to stay ahead of weed resistance.
Lade stresses the importance of making an up-front investment in a pre-emergent herbicide – especially after discovering Group 1 and 2-resistant wild oats on his own farm a few seasons ago.
“It was really scary the first time I saw that weed pressure. There were almost more wild oats than canola in one of our fields. Now, a good 90 per cent of our acres get a pre-emergent application and we haven’t had a massive weed escape since,” he says. “Even though you’re spending an extra 10 to 15 bucks an acre up front, I always say that’s our insurance, so we’re hopefully buying ourselves more time by getting an extra mode of action on those wild oats.”
With the latest generation of pre-emergent herbicides, there’s never been an easier way to get powerful, extended weed control in place before seeding so your crop gets off to a clean start.
One feature to keep in mind with some pre-emergent herbicides is that they need to be activated by rain or moisture. For example, Command® 360 ME herbicide from FMC needs a minimum of ¼ inch of rain for activation at once, while Focus® herbicide requires a minimum of ½ inch of rain at once.
There are 2 application timing options to consider when using a pre-emergent weed control product.
Let’s talk about spring timing first and how moisture plays a role in weed control.
After your FMC pre-emergent herbicide is applied, it sits on the soil surface waiting for that early spring rain. The moisture allows the herbicide to form a powerful protective barrier that stops or slows down the growth of germinating weeds.
Ideally, you should try to time your pre-emergent herbicide applications early in the spring, ahead of a forecasted rainfall event. Another strategy is, the earlier you apply, the more likely you are to catch a spring shower and achieve activation prior to the weed seeds germinating.
But of course, nothing’s guaranteed when it comes to weather on the Prairies, and it can feel like a gamble applying a pre-emergent herbicide – or any other herbicide for that matter – if dry, windy weather is on the horizon.
That brings us to a key question: what happens to your pre-emergent herbicide if that activating rain is delayed by a few days or weeks? Will it dissolve and break down, wasting an application?
Not even close, says Sonia Matichuk, Technical Sales Manager at FMC of Canada.
“FMC pre-emergent herbicides are not going to degrade sitting there on the soil and it’s not going to get tied up in trash,” she explains. “The product is going to wait for moisture to come and wash it down into the soil, forming a barrier where the weeds are getting set to germinate as well.”
Matichuk adds that FMC pre-emergent herbicides are extremely photo-stable, meaning that they can withstand exposure to sunlight and won’t degrade or gas off.
“Even in a worst-case scenario where it doesn’t rain until two or three weeks after you’ve seeded, that pre-emergent herbicide is going to stop any weed seeds germinating from that point forward,” says Travis Goebel, Account Manager with FMC of Canada. “You may not have received the weed control initially but once it rains you will have product activation and weed control from that point forward.”
For example, once activated, Command® 360 ME herbicide will provide three to four weeks of extended weed control, while Authority® 480 herbicide and Focus® herbicide could provide up to 6-8 weeks of extended weed control, depending on soil parameters.”
Now, let’s talk fall application timing. Another option growers may want to consider, is applying their pre-emergent herbicides at post-harvest timing in late October or November.
“With a fall application, you don’t have to worry about getting rain at the right time in the spring and spraying those acres,” says Scott Knox, Account Manager with FMC of Canada. “This can give you the security in knowing your early weed control is in place – especially when you’re trying to get your crop in the ground, the following spring and treating your seed at the same time.”
Today, more and more growers are bringing additional herbicides into their spring weed control plans. They’ve seen how burnoff add-ins, like Aim® EC herbicide, Heat®, Express® herbicide, Blackhawk™ and/or extended weed control herbicides, like Authority® 480 herbicide and Avadex® – can get their fields cleaner than a glyphosate-only spring application.
Just a few years ago, many of these new pre-emergent users would’ve been reluctant to add another herbicide to glyphosate. Having used and trusted glyphosate for ages, they didn’t believe it needed any help.
That thinking is changing, with more growers embracing pre-emergent herbicides as essential to weed control today… and tomorrow. Here are two ways pre-emergent herbicides are making a difference.
“We started off with Group 2-resistant kochia – now we’ve got glyphosate-resistant kochia as well,” says Kowalchuk. “In the last little while there’s Group 4-resistant kochia. Now we have kochia that is resistant to all three of these herbicide groups. We’ve also got resistant cleavers out there, and wild oats that are Group 1 and Group 2 resistant. What’s next?”
Adding pre-emergent herbicides to the tank helps delay the development of resistant weeds. Adding Groups like 13 (Command® 360 ME herbicide, 14 (Authority® 480 or Heat®), and 15 (Dual II Magnum® or Focus®) brings another mode of action or two to the field so farmers can keep the traditional workhorses – Groups 1, 2, 4 and 9 – working into the future.
“With glyphosate alone, the efficacy on weeds like cleavers, kochia, stinkweed, flixweed, wild buckwheat and narrow-leaved hawk’s-beard isn’t always what you’d want,” says FMC’s Nolan Kowalchuk. “Growers know that early weed control is key and FMC’s pre-emergent herbicides deliver more complete control than glyphosate alone.”
For the folks at FMC, talking to growers about the benefits of pre-emergent herbicides is getting easier by the day. With urgent concern about weed resistance and the need for early weed removal, it’s become clear that glyphosate needs help. That’s progress, and FMC’s Scott Knox sees more to come.
“There are still many farmers who spray glyphosate alone in the spring and fall,” says Knox. “It might be as much as 50% of growers, even today. Given what’s at stake, we’ll continue to recommend that they add one of these pre-emergent herbicides to their glyphosate because if we ever lose glyphosate in Western Canada, it won’t be pretty.”