Dr. Dave Mengel

(Jim) Welcome to That’s My Farm. I’m Jim Shroyer your host. We’re on the Agronomy Farm, here on the campus at K-State in Manhattan. And behind me you can see some soybeans. And you know, a lot of times we don’t think about soybeans needing a whole lot of fertilizer and nutrition and that sort of thing. But we’re gonna be talking with Dr. Dave Mengel, our Fertility Specialist about soybean nutrition and fertility. So, get your cup of coffee. Come on back and we can start the show.Closed Captioning Brought to you by the Kansas Soybean Commission. The Soybean Checkoff, Progress Powered by Kansas Farmers.

(Jim) Good morning folks, welcome to That’s My Farm. I’m Jim Shroyer, your host and we’re in luck because we’re in Manhattan, Kansas, on the Agronomy Farm on the K-State campus. And with us today we have Dr. Dave Mengel. Dr. Dave has been a former department head here in the department and he is now the fertility specialist. So, Dave I recently heard you give a presentation on soybean fertility. And you know a lot of times people think, you know soybeans, they build the soil. They’re a soil-building type of crop. But that’s kind of…that’s not quite right. (Dave) Not quite right, you’re right. They’re actually a very extractive crop. (Jim) That’s right. (Dave) They remove more nutrients than any other crop we grow. (Jim) Yea, I guess thinking about that-the phosphorus and potassium. (Dave) Yea, yea, I really do. (Jim) OK, so I heard you give this presentation the other day and you had four or five topics. And we’re gonna delve into those topics right now. And let’s talk about the importance of pH first. (Dave) OK. Well, I like to couple pH with soil testing cause that’s the way we want to manage it. (Jim) Right, OK. (Dave) Because one of the key…here’s two really big factors. One is soybeans are legumes. They require the rhizobia bacteria to get the nodulation, for nitrogen fixation. And that’s the weak link. The bacteria are not very…hearty. (Jim) Tough. (Dave) They’re not very hearty, they don’t survive well particularly in acid soils. (Jim) Right. (Dave) So… (Jim) And we have plenty of acid soils. (Dave) We have plenty of acid soils in particularly the eastern half, but they’re showing up everywhere because of nitrogen applications. (Jim) Right. (Dave) So we need to get the soil pH’s adjusted and for soybeans we probably need to adjust a little bit higher, than we normally we do. The standard recommendation for wheat, corn, milo, is lime to a pH of 6. But realistically for soybeans 6.2 to 6.4 is probably a little bit better and will get a little bit higher yield. So, that’s something to think about along the way. So, the big thing is pH, look at variability in the soils, because it does vary across the fields substantially based on the soil color and clay content. And so if we could soil test by soil type or grid sample or some other system to look at the variability that’s out there and make some variable rate adjustments, we can do a much better job of managing pH. (Jim) So you’re saying that… not pulling into the gate there, walk out 50 feet and take a couple samples and walk back in and mix ’em up. We’re talking about intensive. (Dave) We’re talking about intensive sampling and management. And it will pay. Because it would not be unusual to see a five bushel differential due to soil pH variability across the field. Well five bushel at today’s nine dollar soybean price will pay for some lime. (Jim) Yea, that’s a little more than chump change. (Dave) Yea, it is. And so it’s important, it’s worthwhile to do this. So, the pH is really the big thing. (Jim) OK. So, what about the other end? (Dave) OK, that’s a good point. The other end- high pH’s. High pH’s normally are not a major problem, except in some of our soils we run into iron chlorosis problems with soybeans. That’s one we can’t really change or adjust. We have to be aware of. And we want to make sure we don’t over lime to create those problems also. (Jim) Right, right. (Dave) But the biggest way we can manage that, the best way we can manage that, is with variety selection. Most of the seed companies have done screening for iron chlorosis and they have chlorosis resistant varieties. And that’s a pretty effective management tool. (Jim) Right, right. Dave, we’ve got to take a break now, so don’t go away we’ll be right back. And you folks at home, now is a good time to get a cup of coffee and rush right back because we’ll be back after these words from our sponsors.

(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer, we’re in Manhattan, Kansas, at the Agronomy Farm and with us we have Dr. Dave Mengel. And Dave is our Fertility Specialist and we’re talking about soybean fertility. And we talked just a moment ago about pH and the importance of pH. And now Dave I think phosphorus comes to mind. So, I know you’ve got some new things going on phosphorus with soybeans, so kinda… (Dave) We’ve been doing quite a bit of research the last four or five years, on both phosphorus and potassium. But the big thing with phosphorus is Kansas is somewhat unique. We make two types of recommendations for fertilizers. We make a build and maintain recommendation, which basically is we build our soil test up to the level that will meet the needs of the crop and then just try to maintain it. Versus the traditional of trying to apply fertilizer as needed at a particular soil testing, keeping the test lower. (Jim) OK. (Dave) One of the interesting things with soybeans and one of the things that prompted some of this, is that soybeans historically, people have had the feeling that they respond more to fertility soil test level, than they do to actual fertilization. And that was one of our objectives, was really to look at that and what we found is that there is some validity to that. Unless the soil tests are really, really low soybeans don’t utilize fertilizers very effectively. (Jim) And phosphorus is not a very efficient…you know of the 100 pounds you put on that first year what 25 or 35… (Dave) Normally that’s true because you’ve got this big pool of phosphorus available in the soil that…and the plants are really good at extracting it. The other aspect of it is that we use a general critical level or desired soil test level of 20 parts per million. (Jim) Right. (Dave) Soybeans don’t need that. What we’re finding is they do perfectly fine at 12 parts per million. (Jim) OK. (Dave) So, what that basically means is that farmers need to think about maintaining some minimum fertility levels if they’re gonna grow soybeans. And then the phosphorus fertilizer that they want to apply, let’s put that on our more responsive crops, like wheat for example. (Jim) Or corn or grain sorghum. (Dave) Or corn. Corn or wheat in particular are the real responsive ones. So, it’s a little different mindset. It’s actually what a lot of farmers do automatically. But we need to make sure that we maintain that soil test level. Now, the other aspect about it is that we traditionally always said, if we have low soil test levels, we need a starter fertilizer on all of our crops. But if you think about a soybean, it’s a pretty good size seed. (Jim) Right. (Dave) And it has a very high phosphorus content. (Jim) To begin with. (Dave) To begin with. And so consequently we’re not seeing responses. We had 23 experiments over the last four years in Kansas, many of which did respond to a little phosphorus at very low soil test. Never did we see a response to starter fertilizer. (Jim) Now what about time of season and that. We’ve always thought about…well with corn, if we plant it early we use a starter to get it out of the ground, pop up so to speak. (Dave) Right. (Jim) And when the soils are a little bit cooler. But with soybeans we’re not planting quite as early so how does that play into soil temperature? (Dave) That probably does play into it a great deal. But most Kansas farmers don’t push soybean planting very hard. (Jim) Right. (Dave) They wait for the soils to get warm, cause they’ve had issues with poor stands under crusted soils and cold soils, wet soils. So, they wait for soils to warm up there…into May at least or generally mid-May. And so consequently you don’t have those conditions that would be as conducive. But with all that phosphorus in the seed, it’s not as likely to respond. (Jim) Interesting. Dave, we’ve got to take a break here. And don’t run off. Folks, you too, don’t run off, we’ll be right back after these words from our sponsors.

(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer and with us we have Dr. Dave Mengel and we’ve been talking about soybean fertility. And we’ve talked about pH, we’ve talked about phosphorus, and another big one for soybeans of course is potassium. So, Dave what can you tell us about potassium in soybeans? (Dave) Potassium is a real easy one to resolve, but one that’s often overlooked. Traditionally, we thought that Kansas soils are very high in potassium. (Jim) Disinherently in the parent material. (Dave) In the parent material. And in many part of the state that’s true. Even right around here, it’s normally true, except we’ve farmed now for 100 years, and we’ve removed a lot of K and our soil tests are going down. And we now have a lot of very low soil tests scattered around. (Jim) And southeast Kansas is more so. (Dave) Southeast is a real problem. South central is a problem. And just scattered everywhere we see these problems. So we need to first, soil test. Get a good idea of what you need. We need about roughly 130 parts per million soil test for potassium to have adequate amounts to meet the needs of the crop. And we really want to make sure we have that for dry years. (Jim) Right. (Dave) Because we get out biggest responses under dry weather. And so…the nice thing about K and the fact that it’s so easy is we just have to broadcast it. (Jim) Right. (Dave) There’s no real responses to banding or starter or anything like that. (Jim) Phosphorus. (Dave) Just test it and band it. Or test it and broadcast it and it will take care of it. So, it’s a fairly easy one to do. But we see some very nice yield responses, because we have soil tests we need 130. We’ve got soil tests down to 40 and 50 parts per million in many parts of the state where they grow a lot of intensive soybean production. (Jim) You’ll see some symptoms. (Dave) You’ll see actual visual symptoms. You’ll also see some really nice yield responses and again, it’s money in the bank for you. (Jim) I don’t want to…I guess I am interrupting you here, but about the symptoms…if a producer has been seeing some odd looking soybean leaves and the yields have been kind of suppressed, depressed a little bit, what’s a deficiency going to look like? (Dave) Generally what you see is along the edges of the leaf you’ll get a firing or burning that will move towards the midroot, or towards the veins themselves. And it generally occurs in the lower leaves, but not always. Sometimes you can get some weather induced problems, particularly with dry, hot weather, and they’ll be at the very top. But it will be sort of a golden color. And sort of a burning, and if it gets bad it will actually turn brown around the edges. The big thing with K is again, do your soil testing, and make sure you broadcast the appropriate amounts to get that soil test up for that crop. (Jim) A hundred thirty. (Dave) A hundred and thirty parts per million…(Jim) Is the baseline basically. (Dave) That’s the baseline. (Jim) OK. Dave, don’t go away. We’ve got more to talk about. And you folks at home, don’t go away either, we’ll be right back after these words.

(Jim) Welcome back to That’s My Farm. I’m Jim Shroyer, your host and we’re with Dr. Dave Mengel and Dave and I have been talking about soil fertility. Mainly Dave. And we’ve talked about pH, we’ve talked about phosphorus and potassium, let’s talk about nitrogen. You know, we don’t normally think about soybeans and nitrogen use and that sort of thing, but as you will say, soybeans use quite a bit of nitrogen. (Dave) They do. About half of it roughly, comes from the soil, like for any other crop. And the other half is fixed through the nitrogen fixation process as a legume, which takes a lot of energy. And because it takes so much energy, if nitrogen is available, the plant won’t do nitrogen fixation. So, that’s a key point. (Jim) Right. So yea, if you have high carryover or just inherently high nitrogen, it’s not gonna fix. (Dave) That’s right. (Jim) They may fix the nodules, you cut ’em open but they’re white, instead of that pink inside. (Dave) Exactly. (Jim) So, tell us…I know you’ve been working a lot on nitrogen applications on soybeans and when would that be appropriate? (Dave) Well normally there’s two places that you might want to make nitrogen applications to soybeans. We had a lot of expansion soybean acres and we moved into areas where we’ve not grown soybeans before and we do not have native populations of the rhizobia. We need to inoculate but for some reason it fails. Then we get a nitrogen efficient plant. There’s no nodules, it’s yellow… (Jim) It’s chlorotic. (Dave) Very chlorotic. And then the question becomes, well what can I do? You can fertilize with nitrogen. We did some studies in Saline County a couple of years ago, a few years ago and got great responses to applied nitrogen generally from flowering on. (Jim) Right. (Dave) And one location for example, we responded to 90 pounds of N and got a 25 bushel yield increase. Now, it would have been a lot better had the… (Jim) Bacteria… (Dave) …inoculation worked and we would have had the nitrogen fixation, but it still was very economic. The other situation that we can get into, is that of very high yielding situations… (Jim) High yield environments, right. (Dave) High yield environments, 60-70 bushel yield potential, irrigation is generally a piece of this, you get a situation where the nodules tend to shut off about the time the seed is really starting to fill and develop. (Jim) About R-5… (Dave) About R-5. (Jim) 5.5 to 6. (Dave) Yep exactly and so when they shut off then all of the nitrogen that’s present in the plant is translocated into the seed. But if you get a very, very good growing season and you get a potential for a lot bigger seed, you can fill more, you might get a response to additional nitrogen. And some people have successfully put on 20 to 40 pounds of N late in the growing season, R-3, 4, 5, somewhere along through there, and gotten a response. Ray Layman did some work here in Kansas back in the early 2000’s and he’s over in Shawnee County, got a response of about 5 percent yield increase two out of three years. And that sort of is the type of data we see on a regular basis with that approach. (Jim) Yea, you know like you were talking about R-3, starting pod and R-4, three quarters of an inch at the upper foremost nodes, hadn’t set seed yet, so you have time and you’ve got the water to get the nitrogen in. (Dave) Exactly. (Jim) In dryland that’s not necessarily the case. (Dave) That’s correct. If you were over in the eastern part of the corn belt where you had much more frequent rainfalls and cooler temperatures, they can make that work a little bit better under dryland, but with our environment it just doesn’t work very well. (Jim) Dave don’t go away, we’ve got to talk some more. Folks, now’s the time to get a cup of coffee and hurry back. So, listen to those commercials and we’ll continue the conversation with Dave here.

(Jim) Welcome back to That’s My Farm. With us we have Dr. Dave Mengel. And we’ve talked about pH, we’ve talked about phosphorus, and potassium and nitrogen on soybeans. And in the last section here we want to talk about plant analysis. And Dave talk to us about plant analysis and how a farmer can use that. (Dave) Well, there’s two basic ways to use plant analysis. One is to diagnose a problem. It’s a very excellent tool to go in and try to figure out why you have that spot in the field. And we like to take comparison samples. The affected area, the bad area, versus the good area. (Jim) Now, you’re talking about the plants. (Dave) Plants, yes. Generally with soybeans we’re taking the top fully developed leaves on the plants. Very small plants we might take, say less than a foot tall, we would take the whole plants. (Jim) OK. (Dave) But anything bigger than that, the top fully developed leave on the plant. And the little petiole that attaches it to the stem. And we need about 30 sets to make a good sample. (Jim) Thirty, different… (Dave) Thirty sets of the leaflets to make a good sample. (Jim) Leaflets, right, OK. Well, how do you handle that? What do you do with the leaflets? (Jim) Take it in, air dry it a little bit. Stick it in a paper bag or a mailing envelope and get it to a soil testing laboratory for analysis. (Jim) Not plastic ziplock. (Dave) Please no plastic ziplock in August in Kansas. (Jim) I can just see the mold. (Dave) It will sorta pour out. (Jim) Oh, ya. (Dave) Now the other way, you use it is for quality control. (Jim ) What do you mean? (Dave) We invest all this time and money in lime and fertilizer. Did we do it right? Have we missed something? And a regular quality control program would include monitoring with plant analysis. (Jim) OK. (Dave) Basically would be when the plant is about that R-4, R-5 growth stage… (Jim) Well into podding. (Dave) Well into podding. You go in and pull the top fully developed leaves, again, about 30 sets. And we’ll look at those and look at about 10 nutrients within there. All the main nutrients that we’re likely to see a problem with in Kansas. (Jim) OK. (Dave) Now, what happens in many cases, there’s hidden hunger. Something that’s sort of there, but is not quite severe enough to cause a deficiency symptom. (Jim) But it’s nipping at the heels of the yield a little bit. (Dave) Yea, it’s cutting the top off the yield for ya. Or it’s potentially something that’s becoming a problem. And so it’s in that situation we can use that to sort of monitor our approach. We’re not going to use that data necessarily for that year’s crop. It’s too late. (Jim) Right. OK.(Dave) But what we are gonna do is try to use that data to make plans for the coming crops. (Jim) OK. (Dave) So that we can prevent any problems down the road. (Jim) Well, what nutrients are we talking about that would be nipping at the yields? Of course you do N, P, and K and probably sulfur. (Dave) Sulfur is one of the big ones because that’s something that over the last 7 or 8 years has become more of a problem in Kansas. It’s gradually spreading and so we’ll see, is that something that might be becoming a problem on my field? (Jim) I know in wheat we’re seeing a lot more problem with … (Dave) We’re beginning to see it on corn and soybeans also. (Jim) OK. What other nutrients are you thinking about? (Dave) Something like zinc, for example, manganese, iron. There’s a number of them that we can look at and there’s things that can be done if it does show to be a problem. (Jim) Well Dave, I tell you what, I really appreciate you taking time to talk to us. (Dave) My pleasure. (Jim) About soybean fertility and folks, I hope you’ve enjoyed this section on soybean fertility and don’t forget, next Friday we’ll be back with another show of That’s My Farm. See ya then.

Closed Captioning Brought to you by the Kansas Soybean Commission. The Soybean Checkoff, Progress Powered by Kansas Farmers.

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