Strip till continues to gain traction among corn growers, but one question keeps coming up: how much fertilizer can you safely apply within the strip without risking crop injury?
On this RealAgriculture Corn School episode, University of Guelph graduate student Jonathan Sawicki joins host Bernard Tobin to share a preliminary look at what his research is revealing about safe fertilizer rates and placement strategies in strip till systems. He'll present full recommendations later this year.
Current guidance for strip till fertilizer rates is sparse, leaving many farmers to experiment on their own. As Sawicki explains, too much fertilizer—particularly nitrogen and potassium—can lead to ammonia toxicity and salt injury, conditions that can stunt or kill seedlings. With this in mind, he and his team of research advisors set out to develop baseline guidelines farmers can trust as they adopt or refine strip till fertility programs.
The multi-year trial, conducted in-field from 2022 to 2025 at several Ontario locations with varying soil types, evaluated four common strip-till fertilizer placements. These included a shallow shank releasing fertilizer four to six inches deep, a deep shank placing nutrients six to eight inches below the surface, a double band applicator placing fertilizer on either side of the strip, and a mixing coulter that distributes fertilizer throughout the strip. Across these placements, Sawicki tested multiple fertilizers and blends—including N, PK, NPK, and fall-applied K, at six nutrient rates for each fertilizer.
Early trends from the research indicate that placement matters. Shallow shank and mixing coulter units showed yield declines and reduced plant emergence when urea-based N rates exceeded about 100 pounds per acre. In contrast, double band and deep shank placements maintained consistent yields across higher rates, suggesting they may pose less risk of fertilizer injury. For PK blends and fall-applied K, yields generally rose with increasing rates before plateauing, with little evidence of injury within the tested range.
Sawicki also shared soil profile work showing fertilizer “hot spots” under different placements, reinforcing why deeper placement can be safer.
In his preliminary assessment of the research, Sawicki says the data indicate that placing fertilizer at the 6–8 inch depth with a deep shank would be the safest strategy.
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Hi, I'm Berner Tobin. Welcome to the Corn School. Today we're going to dig into fertiliser rates for strip till. As we'll discover, very little research has been done to determine safe rates of fertiliser application in strip till. Many farmers are relying on trial and error to determine rates and placement within the strip to optimise yield while avoiding seed burn. But that will soon change when today's guest completes his research on the subject to talk about what he's learning about safe rates for strip till. I'm now joined by University of Guelph graduate student Jonathan Sowicki. Hi, Jonathan. Hey, great to have you on the Corn School.
Thanks for having me.
Now, hey, before we dive into your research, tell us what we currently know about fertiliser rates and placement of those nutrients in strip till.
Right. So, as you know, too much fertiliser can lead to ammonia toxicity and salt injury, again primarily in the N and K fertilisers. So fertiliser can severely damage and kind of ruin a crop. Right now, there is little to no research on safe rates in strip tillage. So farmers are currently relying on trial and error on their own farms, come up with what rates work best for them. So our goal as research is to kind of come up with a baseline or a guideline for farmers to say, hey, I'm starting strip healing or I'm changing my programme. How much fertiliser can I put down with my placement?
Tell me about your research team. You have a great group of advisors.
Yep. So I'm working with Dr. John Lauzon from the School of Environmental Science at Guelph. He's my primary advisor. Ben Rosser, the corn specialist at OMAFA, is a special advisor and Dr. Josh Nasaleski from the top department of Plant Agwealth is the other co advisor.
So what does the research plan look like, Jonathan? Locations, replications. You probably want to look at different soil textures as well, for sure.
So the trial took place from 2022 to 2025 growing seasons, again utilising common stripto practises, Ontario completing four reps per blend. And we also wanted to look at the effects soil texture had on fertiliser injury and safe rates, because we know that fertiliser or soil texture affects the rate at which fertilisers mineralize immobilise in the soil, kind of through water holding capacity, cation, exchange capacity and Organic matter. So the trial was held at Elora Research Station. Loam soil, listable with the heavier clay soil and then Paris with the lighter, sandier soil.
Now, what about different fertiliser placements? Will you look at different methods and locations within the strip?
Yep, for sure. So we're looking at four different placements and I kind of utilise them throughout Ontario. So the first unit is a shallow shank unit which tills at 6 inches and releases the fertiliser at the 4 to 6 inch mark at the base of the strip. And the next unit is a double banded row unit which places fertiliser at 4 inches on either side of the centre of the strip and roughly 2 inches below the soil surface. The third row unit is a deep shank unit which tills at 8 inches, releases fertiliser at the 6 to 8 inch mark, and the final placement is a mixing coulter row unit, again, that just mixes the fertiliser so throughout the strip with coulters.
Now, what about fertiliser rates and blends? What are you looking at, Jonathan? I'm assuming NP and K. Yep.
Again, so we're looking at four fertiliser blends, including spring N, NPK and a PK blend. And then we're looking as well as out of fall applied K. So all N fertilisers are urea, all K fertilisers are potash and then mono, mono and phosphates. Phosphate was used for pea. We're looking at six different rates for each blend from the control of 0 to 250 pounds of N for urea, 0 to 300 pounds per acre of N plus K2O for PK and NPK and then 0 to 450 pounds per acre of K2O for fall applied K. Again, just stating all rates are nutrient values, not product rates.
Now, you're already collecting data. You mentioned, obviously this trial is pretty much, you know, in the field, pretty much wrapped up. Emergence timing, collar counts, grain yields. Let's look at what you learned so far. And again, these are not recommendations, but some trends that are emerging. What are you learning about urea?
Right, Perfect. Yes. Again, these are just trends we've been seeing. So again, the average dry yield from urea here across all locations and years, excluding last year, because we haven't got that data in yet. This again, location will be done separately for the purposes of this. It's all just gathered together. So we see for the shallow shank and the mixing culture row unit that as rates exceed 100 pounds per acre of N, we kind of see a sharp decrease in yield. And then for the mixing of the sort of the double banded row unit, we see kind of yields are consistent across up to a point of 150 pounds per acre. And then we see start seeing the decline in yield. But as for the deep shank unit, we see kind of level yields across all rates tested, kind of indicating no issue with safe rates without your own unit.
Let's take a look at the PK blend.
So we see a positive yield response across all row units up to rates around 120 pounds per acre. And then they level off beyond all the way to 300 pounds per acre. They kind of just stay consistent, kind of again showing no drop off of yield from any of the rates we tested with the PK blend and indicating little to no safe rate issues with any of the rates we tested.
Now here's a slide fall applied K, what are you seeing here?
Yep. So for fall plot K, we see kind of the similar thing to the pk, which is a slight positive yield response for the lower rates as they increase and then a levelling off at all the rates tested again, further indicating that we're not seeing any detrimental or issues with safe rates at any of the rates we tested.
Now you also have some seedling emergence data. What can strip tillers learn here?
So what we wanted to look at here is just how much variance and how much and if at all, there's not any plants popping up or plants popping up. So we're expecting 31 plants in our plots and we wanted to see if they're all popping up in the first second day or if some of them weren't popping up at all. So we can see with the shallow shank and the mixing culture row unit, that is, rates kind of went beyond 100 pounds per acre. We saw a steep drop off in total plants emerge. As it can be seen in this kind of chart, we're expecting 31 plants again as rates get beyond 100 acres, 100 pounds per acre, we see a sharp decline in total plants emerged. As for the double banded and then the deep shank unit, we see kind of steady 31 plants across all rates tested.
Now another factor you're looking at is where does the fertiliser end up. Let's look at what you're seeing with a deep shank. Some amazing work here. Tell us about, tell us about what you had to do here.
Yeah, this was a lot of work. So we strip tilled in a clean field, high rate of K2O and then we broke the soil profile up into these 1 centimetre 1 inch cubes. As can be seen by this figure, each section is a 1 inch cube that was broken down into our profile. We did that a lot of times. It took a long time and it was a lot of work. But I think the results here kind of really show have a good result and show what we wanted to see. So again, for the deep shank unit, we clearly see that there's a hot spot of fertiliser at the 6 to 8 inch mark in the centre of the strip. Kind of indicating to us that kind of showing that maybe why this is the safest placement. Again, it's quite far from where the seed would be placed at the say 2 inch mark at the centre of the strip. And again indicating helping us visualise why this is a safe row unit.
Yeah. Now you also have some data here for the mixing coulter. This placement looks a little more risky.
Yeah. As can be seen from, from the results that we've seen there, this mixing coulter row unit definitely shows higher concentrations of fertiliser. Right where that particular the seed would be placed kind of right in that centre of the strip, you know, from the 1 to 2 inches below the soil surface. Kind of indicating again why we're probably seeing issues with rates of fertiliser at this placement.
Now, hey, just to wrap up, based on what you know so far, you know, what would you consider the safest placement for fertiliser in the strip?
Right. Definitely the safest placement would be the deep shank unit. So again, placing that fertiliser at 6 to 8 inches below the soil surface has shown no detrimental effect to safer to the crop safety. It's kind of shows no issue with it at all.
What about going that deep? I know you've had questions about starter fertiliser and whether going that deep you can pop a corn plant out really quickly. What do you say to that?
Definitely questions we have were questions we're looking at as with the yields with the urea. With the deep shank placement, we kind of saw a level across all rates tested. So we're not again sure necessarily if the fertiliser is reaching the getting to the planted time. But again we saw no drop off of yield. So I have to do some more kind of statistical analysis to determine if the yields kind of consistently going up as a rate so indicating that the plant is benefiting from the fertiliser in time.
So where do you go from here? Jonathan, what's your timelines and when you expect to have full recommendations for growers? I know you're finished in the field, correct?
Yep, finished in the field this, this fall. Just got to get all the data together and then get it analysed and get it written up. So right now, again, for what's next, something that we'd like to or somebody else will look at later would be dual placement. So we're putting starter fertiliser close to the seed and then simultaneously putting the remaining N and K deeper for safety, be the optimal result. So again, you get the starter fertiliser effect, but then you have the N and K bit deeper but ready for that plant when it needs it. And then what? Also looking at kind of starter fertilisers, placing bands with the planter kind of as typical, the two by two bands are doing some starter and then the rest of the fertiliser is placed with a deeper unit and with a strip tiller. So again, you could get that one pass system in, do all the tillage and fertilisation in one pass and then put the. And then just come back or come back over with the planter and putting a little bit of starter with the planter.
Yeah.
More on farm trials would be great. Again, just for every soil texture, every kind of farms, a bit different, just to kind of gather more. More information the better.
Yeah, lots to learn, lots to learn. And we're going to basically see, I guess, your results and your recommendations later in the year, is that right?
Right, sorry, yeah, we'll be finishing in mid April and then hopefully my thesis, thesis will be done and hopefully you're out. And then the information will be updated in the OMAFA Field Guide for Strip Tillage. There'll be a new section there on the safe rates of fertiliser with strip tillage.
Yeah. When you come back, I hope you come back and join us and share some more when you get everything wrapped up.
Oh, thank you. Thanks so much for having me. It was a great, great to have.
You on the corn school.
