An Interview with Dr. Dan Quinn of Purdue University
Dr. Dan Quinn grew up in central Michigan in a small town between Grand Rapids and Lansing and has been surrounded by Ag his whole life. This led him to two degrees at Michigan State university. A bachelors and masters in crop and soil science. From there Dan pursued a Ph.D in agronomy at the University of Kentucky where he worked heavily in applied research. Dan has a background in applied crop management, soil fertility, and extension work. He has worked with numerous growers in several crops and currently works for Purdue University where he is the resident corn specialist. The following article is an interview Cultivace conducted regarding Tar spot and corn nutrition with Dr. Quinn.
When did Tar spot first appear?
Dr Quinn: it was first found in 2015 in the U.S. I think it was in northern Michigan, in northwest Indiana and also in north central Illinois. It's really been around for quite a long time, primarily in Mexico and Central America. In 2015 it was found in low levels. 2018 was the first year tar spot exploded especially in the northern parts of Indiana, and Michigan. Irrigated acres were especially affected.
Tar spot originates from Mexico. How does it get up here? Is it carried by the wind?
Dr Quinn: So it's originally from Mexico and Central America. Researchers still don't know how it was brought into the US. You think of a disease like southern rust as something that blows up from the south every year. Well tar spot is a little different. Once you have it, you have it. There is still a lot that is unknown about it since it is so new.
There's a comorbidity with tar spot, a second fungal disease that you can get. It's common in Mexico. Have we seen that in the U.S. currently?
No, we haven’t. It causes halos in corn but as far as I know, it hasn't been found in the U.S. yet.
Are healthier plants Or certain hybrids less susceptible to tar spot ?
Dr Quinn: What we're finding now is that there are hybrid differences. The seed companies are really scrambling to understand what those differences are between their hybrids so that information can be available to the farmers. I know farmers are noticing differences as well. At this point we are recommending growers take notes, walk in your field at this time of year to understand how this hybrid is performing compared to others. With the research at Purdue combined with that of the seed companies, information should be more reliable next year.
If you end up with Tar Spot, what could you expect in terms of yield loss?
Dr Quinn: It depends on what growth stage your field is affected. I'm hearing reports of 40, 50, 60 bushel losses. Depending on whether they had a fungicide out there or not. Also at what stage of development the crop was affected. Tar Spot kind can show up and overtake your plants, it can move pretty rapidly and you can lose a significant amount of yield. Trying to pinpoint exactly how much yield loss you get is really difficult because it depends on when it comes in. It can also depend on your hybrid, depend on your location, your severity, your incidence, all of these different things. It can be pretty significant.
Are there any management practices that you would recommend that can help mitigate Tar Spot?
Dr Quinn: The big one is fungicide applications, but the difficulty with that is what we're starting to find applying those fungicides might be a moving target every year. Previous research indicated that you should apply a fungicide at R1. But now, maybe this year it needs to be the V10 stage. We are trying to get farmers and agronomists to make sure that they are walking these fields all the time. The pathologist here at Purdue, Darcy Telenko, and the pathologists around the Midwest do a really good job of tracking this disease. You know what the county's tar spot is and when. Farmers can kind of get an idea of, ok , it's in my county I need to start watching for it. If you see, get a fungicide on and control it. As I said before, hybrid selection is going to be big. So choosing hybrids as we get more and more information will be a large part of management. Also understanding where you've had tar spot in the past will play into management. Tar spot is interesting in that, once you have it, you have it. Understanding which fields have had really bad pressure in the past can help pinpoint exactly where tar spot is going to reappear. There's an app that was developed called Tar Spotter that can help predict if you're going to get tar spot or not. Overall, listen to the pathologists and their reports, understand where it is, find it. Then, get those fungicides out there and in the future using the correct hybrids.
Does corn nutrition go beyond NPK?
Dr Quinn: It does. Sure. NPK are by far the most important, but you think about the one that's creeping up in importance is sulfur. Sulfur responses we’ve found in Indiana can be inconsistent, but they're also increasing. This year we've gotten 20 bushel responses from sulfur in some of our trials but others we’ve seen five bushels and some trials with no response. So it's really kind of difficult for us to understand where corn needs sulfur. We're getting more and more data and sulfur responses are increasing. We saw sulfur deficiency even in our prairie soils in West Lafayette, which you wouldn't fully expect to see sulfur deficiency. The air is a lot cleaner. Fertilizers are a lot cleaner as well. So you don't get that free sulfur anymore. You get a little bit of that free sulfur, but not as much. Some of the micronutrients are important to apply externally. Most of the soils, especially in the Midwest supply most micronutrients. However, there are certain instances where you need micronutrients. Manganese is a big one in certain muck soils. One of our farms in northwest Indiana we do track manganese deficiency pretty regularly and we actually do apply manganese pretty regularly on that farm. In certain soils in certain situations you might need different nutrients. zinc is another, especially in high phosphorus soils. Zinc can be important. It comes back to make sure you're taking your soil samples, assess your tissues, test taking them together and really try to track what your nutrient levels are both in the plant and soil.
What would you say is the most common nutrient deficiency that growers ask you about or you see yourself in the field?
Dr Quinn: You know, I think from a year to year basis you typically always see nitrogen deficiency, but I’d say sulfur. Even in my short time at Purdue as well as my time at Kentucky and Michigan I saw increasing sulfur deficiencies. That is what's kind of a stand out to us and why we have so many trials. Bob Nielsen, who is the retiring agronomist, and Jim Camberato, our soil fertility specialists have been looking at this in trials for a long time. We have 10 to 12 locations every year across the entire state, both on farm, and using large scale field trials. So sulfur is something that we're watching very closely, something that we get a lot of calls about.
In your research, have you ever done anything regarding foliar fertilizers and do you see that as a viable option for nutrition?
I've done some work with foliar fertilizers and I actually am working on getting a trial going currently. We're hoping to gather information across a couple of states next year where we'll start looking at some of those foliar, especially micronutrient, applications. One nutrient that we typically use foliar application with is manganese. We put manganese foliar fertilizer down when we need it. If you do have manganese deficiency in certain soils such as muck soils that we see in some areas of northwest Indiana, we will apply manganese as a foliar. The difficulty with applying foliar fertilizers is a lot of time we just can't get enough of the nutrient out there. I think that's one of the most difficult parts to using a foliar. I think some of the industries will push foliar fertilizers based on tissue levels. But tissue levels can be highly variable. They can depend on the time of day you pull them, the weather conditions that you pull in, and the growth stages of the crop. When you pull a sample that test might say a nutrient is low, but is it really low and do you really need it? So I think that makes it tricky but there are certain instances when you are seeing nutrient deficiencies on your soil and tissue tests below a critical level a foliar can help.
When I heard you speak at the West Lafayette Field Day, You mentioned trial plots with late stage nitrogen applications. Can you go into some detail about these plots?
Dr Quinn: We’re starting to look at late season nitrogen particularly split application of nitrogen. We are trying to pinpoint when to put nitrogen down when that corn plant needs it. A lot of farmers now have high clearance equipment, so they can do a lot of these late season nitrogen applications. We are trying to improve the efficiency of how we apply that nitrogen. Newer corn hybrids as compared to older corn hybrids use nitrogen a lot later and actually move a lot of nitrogen in the plant a lot later. There's been a lot of work here at Purdue that see some benefit from late season nitrogen applications. I've also done work where we haven't seen the benefit from later applications as well. We are working to pinpoint when exactly another application would benefit that crop. Starting next year, we're going to have quite a few trials across the state where we look at five nitrogen applications versus V5 plus V10 application or V10 with no V5 application. The overall goal is to increase nitrogen use efficiency and limit loss.
Are the corn nutrient utilization charts put out by the universities and extensions a good guide for timing nutrient applications?
Dr Quinn: Yeah, I think it is a good guide, but it too comes down to the equipment availability for some farmers. Sometimes they just can't get the nutrients out when they need them. We're pretty big on side dressing applications, especially when it comes to nitrogen. If you put all your nitrogen up front at planting that corn plant is not using much nitrogen at all at that time. In that scenario you are losing a lot of nitrogen. If you split that nitrogen application, moving it to V6 or V7, while having a little bit in the starter to get that corn plant through that period, where it might only need 20 or 30 pounds of nitrogen then you're timing that nutrient, right when that peak uptake is happening. Trying to pinpoint exactly when that plant is reaching peak uptake can be tricky but I think that it's really beneficial, especially for the more mobile nutrients. Nitrogen doesn't hang around in the soil, compared to potassium or phosphorus which don't move as much as nitrogen. It is common to apply P and K in the fall or in the spring and you are usually fine. But those more mobile nutrients, nitrogen even more so than with sulfur, putting that on inside your house, more so that planting you can help, but those more mobile nutrients are trying to pinpoint. Can we put it down right at peak uptake, just so we're not losing so much?
Do you see an advantage to using pop up fertilizers at planting?
Dr Quinn: I like starter fertilizer. Whether it be a pop up, in furrow, or 2x2. I'm more kind of prone to 2x2 just because you can get more down without risking injury to the seed. The difficulty with pop up a lot of times is that you just can't get as much down there because you run the risk of harming that seed if you have too much nutrient there. So the 2x2 is what we've seen is really beneficial. It just comes back to that efficient fertilizer. I like having it when that corn plant is young and it's going through, I would say the awkward middle school stage of life as it moves from autotrophic to heterotrophic stage and uses up its kernel reserves. It needs something right there to help it get it through to that rapid growth phase. Anytime you can get nutrients right next to that root or even in the furrow it is beneficial. Phosphorus is especially beneficial because it can fix really easily .That phosphorus can fix really easily and it doesn't move. When soils are wet and really cool early on in the season, you can actually see some phosphorus deficiency. If we can get those nutrients close to that root system. It just helps it get through that early period. I'd rather have that corn plant have a good start. In regard to nitrogen you're going to put on say 200 pounds of nitrogen regardless, you might as well put on a little bit as pop up to help that plant get through that earlier period then come back and apply more later on.
Is there a difference between ortho and polyphosphates?
Dr Quinn: You typically think about orthophosphates being more available, and that polyphosphates have to go through hydrolysis or go through a biological change, but research wise, I just haven't seen any difference at all between ortho phosphate or polyphosphate. I think because polyphosphate change happens very quickly. I researched this at Michigan State, the difference between the products, and I know other universities have looked at it and they just haven't really seen any difference between yield differences between an orthophosphate or polyphosphate. It seems because that changes so rapidly that it ends up being available and there really isn't much difference between those two products.
This interview has been a part of a series of interviews CultivAce seeks to organize in the coming weeks. If you have suggestions for relevant interview topics or interview subjects please send an email to info@cultivacegrowth.com or brock@cultivacegrowth.com. To learn more about research Dr. Quinn is working on at Purdue University visit his website https://thekernel.info