 In 2013, the USDA Natural Resources Conservation Service entered into a cooperative agreement with the South Dakota No-Till Association and IGRO, SDSU Extension, for delivering the latest soil health and productivity technology to South Dakota farmers and ranchers. A series of two local events were held in South Dakota, in Lemon and Fort Penn. So I'm a captive audience in South Dakota and how many of you have ever been to Gear One, two, three, four. Well, you know, that's kind of like me. I've only been to Lemon three times. So we live in the same state and we don't know each other. And I think that speaks to the diversity in our state. And I just love it. Our state has so much to offer and experience. And so, yeah, I was asked to come and talk about interpreting soil tests and so forth. The last question I asked Dr. Lehman and Dwayne chimed in on that. It's kind of a serious issue because these soil test recommendations are going to, I'm going to show you, tell you should put on phosphorus at different soil test levels. And what I'm hearing is if we're in a long-term no-till situation and we have soil microbiology and fungi in the soil, we can tend to keep those soil test levels lower. And so that suggests that there's a set of different calibrations for no-till and we don't have that. And so what I'm going to do is go through and discuss what we do have and we'll call it that. But it's a very intriguing thought, these long-term no-till soils. So what are the reasons for soil sampling? There's several of them. Obviously to determine the current nutrient status of the soil helps you determine more accurate nutrient application rates, keeps you from losing yield, from having under-application of nutrients or soil test levels, prevents over-application, saves you money, provides the ability to track soil nutrient trends over time. I'm going to show you a graph about that from my farm. Soil cost testing is minimal compared to the cost of fertilizer, isn't it? It's just the time and finding someone to go out and get it done is kind of the hard part there. It's a tool used in site-specific soil management, grid sampling, zone sampling, diagnosing problems. That's the next one there, number eight. If you have an area in the field that's got a plant health problem, it could be nutrient-related and soil testing and plant tissue testing help you to do that. And then the last one on the list, we do have to realize that we live in a world with other folks. And we call everyone a stakeholder. Everyone has input and is concerned about our environment and our planet. And so protecting the environment using soil testing to do that is an excellent way to help do that. So the soil nutrient trend part, here's my farm. Soil test phosphorus over a lengthy period of time, way back to 93. It's an average of all fields that were tested for each one of those years. And you can see that, well, this is a big drop, but I only soil test half of my fields every year. So this half had a little bit higher test than that half. So this half here is again appearing here and then it's appearing here and here. But the overall trend is what? It's up. Soil testing is not perfect. You have field variability. When you take a sample one year and you go back and sample it, again, the next year there's variability. Where do those cores come from? So you have that variability. And then you have laboratory variability, too. Labs aren't perfect. Each test has a variability that they know. Some tests have less variability in the lab than others. For instance, the sulfur test has huge variability. It's really not a very good test, but we still can use it as a tool. The zinc test is really accurate in the lab. You can repeat those numbers over and over. So when you take into account the variability, seeing trends like this doesn't surprise me. And maybe it does surprise you, but that happens. And so the importance of tracking over time where you're headed is a really good tool to do. And I'm going to discuss phosphorus later, but we really want to manage our fields in that medium range, 10 to 12. And I'll discuss the probabilities of a response to phosphorus application so you understand that. But just kind of keep that in your mind, that 10, 12, maybe 14 part per million range. There are two types of soil tests. There's ones that provide absolute values and ones that are related to an index. Ones that are absolute values are nitrate, nitrogen, sulfur, and chloride, where we measure the amount of nutrient at the time of sampling. And that can change with water movement through the soil, microbial activity releasing more nitrogen and sulfur and things like that. So those are the mobile nutrients that are reported in absolute values. You have so many pounds per acre. The ones that are related to indexes are basically the non-mobile nutrients. Those used to be reported in pounds per acre, but that was changed always back, 15, 20, 25 years ago. As it was confusing, a grower would say, I have 15 pounds of phosphorus in my soil. Well, you really don't, but that's the way the test was reported. And so it was switched back to a concentration report in part per million. And that concentration is related to an index where the soil fertility researchers went out to a number of fields, sampled the soil, measured the phosphorus, and then applied rates of phosphorus, and looked at where the responses were coming. And so that response is related back to an index, and I'll talk about that in a little bit. First of all, I want to air this out, the soil testing labs. We have two in South Dakota right now. There's one that just started in artesian called AgVision. I don't know, maybe some of you know his name. He retired from SDSU and he's managing that lab. AgLab Express in Sioux Falls is the one I helped start for a couple years when I had my midlife crisis. I left the university and helped them do that, which was a good experience. Then there's AgVise Labs, we're in Benson, Minnesota, Northwood, North Dakota, War Labs in Kearney, Nebraska, and Midwest Labs in Omaha. And there's a whole bunch more. But these are the ones I think that I wanted to mention because they're really close to us in South Dakota. So given that, I'm going to show you a soil test report form. And I tried to hide the name up here, but you can see what it is. But anyway, that's why I showed you the slide of all the labs. I don't want to be biased and say one lab is better than another. I just want to make that clear. So you get back a soil test report form from the lab and you look at that and all that fine print, you know, what does all this mean? And you know, it's really difficult to understand for some folks. But basically a soil test report form is I've divided into five areas. And the first area is just the general soil information, you know, who took the sample, for who, when it was taken, what field it is, all that type of stuff. They even give you a map if you want to draw a map. Then you have the laboratory results section and interpretation. You have the other soil test results, organic matter, electrical conductivity, soil pH. For those that like looking at base saturations, that's in that area too. You have the recommendation section. And then you have statements. That's that fine print at the bottom. And you should read those. There's a lot being said there. So I'm going to try to go through each one of those sections. And obviously I've done this one here. No secrets, just a lot of information. And this is the stuff you have to fill out on the form when you submit your sample. So if you don't put some things on your form when you submit your sample, you're not going to see it back. And so if you haven't kept track of what samples are what, you might be confused a little bit. So do a good job of filling out those forms for the lab. That next section is the lab, the nutrient analysis and the interpretation. And I've just kind of highlighted it here out. And so we have nitrate nitrogen here and phosphorus, potassium, chloride, sulfur, boron, zinc, and the rest. And so you see the analysis here. There's about 48 pounds of nitrate nitrogen in that top two feet. And then they give you an interpretation. They call that low. I honestly don't know where interpretations for nitrate nitrogen come from. But they've kind of just did that. The important thing is the interpretation for the rest. I think it just fills in their table here and it makes it look good. But the interpretations for phosphorus and potassium really mean something. That's that index. So you can see that phosphorus is in medium here and I'll talk about that in a little bit in the future here. But I wanted to talk a little bit about the nitrogen part. In South Dakota we use a rate calculator. It's the yield goal, which is very important. You have to do everything in this calculator the way we recommend or that calculator falls apart. So the yield goal is very important. Take your field, look at the last 5 to 10 years, throw out highs and lows. Take the average times 1.10, 110% or 115%. Because yields are going up, aren't they? We're getting better at managing our fields, more technology. That's how you come up with a decent yield goal. You don't say I want 250 bushel corn every year. And I think that's where this has been used the wrong way. The yield goal is past history times an improvement factor. Then we have an end coefficient. These are the coefficients that we currently have, 1.2 on corn, 2.5 on wheat and so forth. The reason soybeans and alfalfa are on this list, we know that we don't need to fertilize those crops with nitrogen. But if you're a large animal feeding operation and you have a lot of manure to get rid of, you can apply nitrogen to those two crops and get rid of your nitrogen if that's what you want to do. It's not probably a good economic choice, but it's being done. And then we subtract soil test nitrogen. That's what we just seen right here, the 48 pounds per acre. And we subtract other credits, like a legume credit. I'll show you the table for that. And then we have current recommendations say we add 30 pounds back for no-till. Well, there's a lot of questions with that one. How long have you been no-tilling? We really don't know when that should go away. We're working on that a little bit and I have a graph to kind of point in the direction. But the reason for adding that nitrogen back is that when you switch to no-till, you're really immediately building carbon back in the soil. And that carbon and nitrogen ratio in the soil wants to settle on a ratio. And so it's requiring some nitrogen as well. So at some point that carbon and nitrogen ratio will even out if you will. And this 30 pounds extra for no-till should go away. It shouldn't be needed anymore. But then if you start pushing cover crops again, you're going to push your carbon again. And so that balance is really hard to get at. But we've got some data that kind of shows that. Here's the legume credits. Soybeans is 40, alfalfa here depending upon the stand really dictates the credit. And if you're no-tilling, we cut those credits in half because you're not oxidizing the soil. You're not mineralizing nitrogen out of the organic matter. You're building it up so we take less of a credit when we're no-tilling. And hence the second year we also cut that in half too from the time we take the first credit. So here are the two studies we did on no-till, where we had tilled systems side by side, randomized side by side with nitrogen rates applied, randomized across that. That's a very difficult study to do. But we had a couple of sites that we could use. Here are the yield response curves given the different nitrogen rate across the bottom. And you could see that the no-till curve is coming to its peak there at a little bit later time than the conventional till. And by golly, we had two of these studies that were going for six, seven, eight years. And the difference is about 30 pounds. And so that's where that 30 pounds came from. At this time, we did this. We thought, well, boy, this has been a no-till quite a while. Really, that wasn't true. We've got no-tillers now 20 to 25 years. So this is a really short-term no-till. So the question is, when can we stop adding that 30 pounds? Well, we found a graduate student and we have a site at the Southeast Farm that's been in it about 24 years. And she's working on that. And this last year, they had an early and late-season hybrid planted. And then the two-tillage systems in the two-year rotation, they also have a three-year. I'm kind of lucky to get this data, I feel privileged. But anyway, there's four response curves there. The yellow and the green are the no-till. And the red and the blue are black are the conventional till. First thing that you can see is the response curves for the no-till are more steep, aren't they? So we're getting greater efficiency to nitrogen application in the no-till with those lower rates. Because we're not doing that tillage and we're not mining that soil organic matter with the tillage. But what's really interesting is where they're peeking out at, they appear to be at the same place. So maybe when she gets done with her study and analyzing this data, maybe we can come up with a recommendation that for longer-term no-till, that adding 30 pounds goes away. And so I think this data really shows that that... We kind of thought that's the way it was. You know, the science would say that, but really we need to have the data. And I think that's what this is saying. So the end coefficient history in South Dakota has been this. In 75, it was 1.4 for corn, 82, 1.3, 91, 1.2. We missed 2001. And so coming to 2015, we've done some work. And I'm going to show you a little bit of those results. And I think it probably can change again. But I do talk in other parts of the state and the rest of the North Central region is using a price-racial approach. And I try to sell the fact that our calculator gives you more flexibility. There's more inputs to put in it. It's more farm-specific, if you will, field-specific. Where the price-racial approach is they take all the studies, combine them together, and then you change the price of corn and the price of fertilizer, and it gives you a rate. The point I was trying to make is the difference when you change those prices isn't a lot. We're talking less than 10 pounds. And so hence that our calculator really gives you more flexibility. It's more input. You have to do a lot more work than just going to a table on the internet and filling in your numbers. But our calculator, I think, gives you more flexibility. So in 2013 and 2014, we had these sites for corn in South Dakota, red being no-till, yellow being conventional-till. These are the response curves for 2013, which look really messy. That's the way nitrogen data looks. Some respond, some don't. And that's part of how nitrogen dynamics work. But what we're looking for is an optimal N-rate at each one of those sites. And so this is a site from Brown County. This is the yield response curve. You can see here at no nitrogen, we got 126 bushels. And up here at 120 pounds, we got 177 bushels. So a nice response. What we do is we do a linear plateau calculation where essentially these yields up here are not different from each other. There's a different number there, but when you do statistics comparing the replicated data, they're not different. So we draw a linear function here on the responsive part of the curve. And then we draw the plateau where those two meet. We come up with about 98 pounds of N was the optimal N-rate at that site in that year. Then we do our calculations. And so the coefficient was just over one. So we did that with all of those sites in 2013 and 2014. And in 2013, our coefficient averaged one. You can see the great variability there. And then that's just the way it is. Certain factors would play into that. You really need N-rate studies on your farm every year. And we can't do that. Some farmers probably can figure that out, but we try to get as many sites out there to get this coefficient as strong as possible. 2014 fewer sites, all of them no-till, same coefficient, about one. And then if you look at no-till and conventional till, the coefficients are the same. So I think we can go from 1.2 to 1. If we look at the phosphorus on the soil test recommendations, I mentioned that interpretation is kind of important. Dr. Malarino from Iowa State, the phosphorus and potassium leader, I think in the country, says we do a disservice by putting a number on the soil test report farm. But you paid for that and you want to see your results, don't you? It's really all about the interpretation. What level are you at? Are you at very low, low, medium, or high or very high? That's really what the recommendation is based upon. And so if you look at phosphorus and potassium interpretations, either for Olsen-P or Bray-P, a medium-test Olsen is the same as a medium-test Bray. When we get these arguments as you get closer to Minnesota and Iowa, some grow, or you got to do Bray, you got to do Bray, you got to do Bray. You get a higher number with Bray than you get with Olsen. But it's measuring the same thing. It's measuring that soil's ability to supply the plant with phosphorus is really what it's doing. And so if you're in the very low category, which is this range, 0 to 5 for Bray, 0 to 3 for Olsen, there's greater than an 80% chance you will get a yield response if you apply phosphorus. If you're in the low, it's about 60 to 80. The medium is 40 to 60, high 20 to 40. And if you're in the very high category, there's less than a 20% chance. So it's really about this index. It's related back to that. And if you think about the size of the response, this 80% chance of response, those responses are usually a lot larger than the ones you get if you're in the very high category. Okay, so now we have lower commodity prices. It doesn't seem like fertilizer prices are coming down to meet those levels, but they have a little bit. This really is important. It's important all the time. But it seems when there's more cash out there, we tend to buy more insurance. And so this is one thing that we can use to manage better. Here are those corn responses to that phosphorus index. 197 sites in South Dakota. I have added in a few from surrounding states for a total of 261 sites. If you're in that very low category, a number above 100 is a response to phosphorus application. There's that greater than 80% chance of response. You go to low, those dots aren't as high as they are, as high. So larger responses, still a lot of responses, but getting lower. You go to medium, a lot smaller responses, fewer responses. You go to high, hardly any deviation from that 100, which is a relative mark where the check plot and the plot you applied phosphorus to had relatively equal yield. And then you go to very high, and what do you see? Hardly any responses, and then the magnitude is really small. Okay, so that's where that index comes from. Very low, low, medium, high is all these tests that were done. And this is historic. This just isn't in the last few years. This is in the last 30, 40 years, maybe 50 years. Here's a study we did at the Northeast Farm long-term study started way back in the 90s, where we have plots where we put on all nutrients, NPK and zinc, plots we just hold off N, plots we just hold off P and so forth. And over time we've drawn down that soil test phosphorus level, it's at a one PPM Olsen. The yield is 114 bushels, where we had all the nutrients, it was 153 bushels. So a huge response, and the high probability. Here's the soybean response to the phosphorus index, basically the same as the corn. Basically the same thing. We had spring wheat plots at the Northeast Farm, same thing where we applied all the nutrients, hold off one in the presence of the others. Where phosphorus hasn't been applied for many, many years, the soil test is at five, and you can see the response. 78 bushels where we had phosphorus, 49 where we didn't. You can also see those other plots that had phosphorus, the variability in the soil test is real, the sampling and the testing, because they should all be about roughly the same, except for the no-n. Our yields on the no-n have been reduced too, so we're not as removing as much phosphorus so that test is higher. But you can kind of see the trend there for those other nutrients, there's no response. In the first part of this study there was tillage, but they've been no-till for the largest part of the study. And it's still going at the Northeast Farm, I'm fighting to keep it going, but we had it going last year. Okay, I'm going to go to the non-nutrient mineral soil test results section. I know it's small, sorry for the small screen today, but we have organic matter there which is an important test. Track that over time. Your salts, soluble salts here, and then pH. I'm going to discuss those as well. You can see that on my farm I don't look at the base saturation. It's just there because folks are driving the system and they want that test so the lab provides it. Here's a response of organic matter in an eroded landscape. When you're down around two, we're getting about 100 to 125 bushels and you get up at over four, it's about 175 bushels. So organic matter, very important. You can also use that organic matter, you know, some of our chemical labels have restrictions. And so you can use it for those decisions as well. Soil pH, long-term studies at Brookings, looking at crop response. This is corn to soil pH. We see here about 5.6, 5.7. The yield differences aren't that great above that point, but below they are. And so our recommendations, I hope that's the next one here, are related to a buffer index. And what a buffer soil test does is it really is stressing, I always say stressing, but it's really looking at the reserve alkalinity in the soil. Soils are constantly weathering. And so is that soil going to release more alkalinity and that pH go up? Or isn't there as much alkalinity there and that pH going to stay the same? Well, so that we do a buffer to kind of test that or stress that soil, I like to say. And so when we're above buffer index of 6.5, it's just a pH measurement, but we've added a buffer to the soil solution and just measured pH. So above 6.5, no lime wrecks, and if you go down or the buffer index goes down, then that lime wreck goes up. Electrical conductivity interpretation, you know, if you're farming where there's some salt in the landscape and, you know, all what we're talking about today, cover crops and everything really help to reduce that, use your water more efficiently. But we do have some areas and so that electrical conductivity is used to diagnose those. And exchangeable sodium percentage as well to see if those salts contain sodium. Then you got the recommendation part of the soil test report form. This lab provides three crop choices so you can play around a little bit, you know, put different crops in there or put the same crop with different yield goals. But if you've done a good job at determining your yield goal, you really shouldn't need different yield goals. You should go with the one you've determined, right? You can choose, some labs have what they call the university recommendations, and then some labs have their own. And you really got to understand, ask a lot of questions to those labs well, how are you developing your recommendations? You know, why would your lab recs be, this P and K maintenance is a good example, why would they be higher than the university ones? And they'll give you their answer. But I would go back to the fact that the university ones are based upon stuff like this. Lots of data, okay, based upon lots of data. So that's the recommendation portion, and you know, those labs have all these XYZ plus two minus three packages, and you have to figure out which ones to check. Do I need sulfur? Do I need zinc? Okay, and I'll point you in the right direction on some of that here. But they give you that rec in pounds per acre of that nutrient that's equivalent in that fertilizer. So reviewing these soil tests and nutrient recommendations is really important. So there's a difference, or there can be differences between university recs and someone else's recommendations. And I would point you to our EC 750 publication, our fertilizer recommendation guide. It's stored on the web right there, but basically if you Google SDSU soil fertility EC 750, it'll come up top of the list. You don't have to write all that down. If you can just remember that search and you can get it there. That guide needs to be updated really bad. I am not the soil fertility faculty person on campus. We don't currently have one. And so I think one of the duties for that new person will be to take a look at this, I hope. So how do you tell the difference between what a lab rec would be and what a university rec would be? Well, you go to EC 750. Here's the phosphorus table for wheat. Here's that index. Soil test levels there, very low to very high. We have a yield goal there, and you can see what the recommendation would be. Or if you want to hone in really tight, every table has an equation and you can put your numbers into that equation. So you can discern between a university rec and a lab rec. Sometimes they won't give you a lab or a university rec. So use that EC 750 for that. And then the statements portion on a soil test report form. Caution, seed place fertilizer can cause injury. Nitrogen credits granted here. They have crop removal information. They explain what their broadcast and maintenance guidelines do. So you don't necessarily have to ask this lab. They explain what they do. Well, I'm going to hone in on that seed place fertilizer statement there. Ron, Dr. Gelderman, I think is really one of the highlights of his career, 42 years at SDSU. He did a lot of work at evaluating different crops with different amounts and types of fertilizer placed in the furrow. Did a lot of work with that. And this is the results from that study. This is wheat. And so you can see three fertilizer materials here. Urea, potash, and DAP, Diimonium Phosphate, 1846O. I think that's what that is. And the rate of the fertilizer material and then its effect on relative stand. So where we didn't put any fertilizer with this seed, we got 100% stand or close to it. And then as we started applying DAP with the seed at higher rates, you can see what happened to stand. Well, different fertilizers have different effects on seed germination. Urea is really hard on it right here. Here's that curve. And potash and DAP being about the least. And there's all kinds of more information that Ron did in those studies. And you can get the spreadsheet to help you look at different materials and different crops at the soil fertility website. It's called the fertilizer seed decision aid. And so there's a spreadsheet there that you can get at to look at that. It's kind of interesting. So with that, I'm done. Am I early? Just a little bit. I had a bunch of slides. It's always hard to tell how many to throw in. And that's what I had today. So if there's any questions, I can try to answer them. If not, what do you got planned? Yes, that's a really good question. Because in EC 750, is there a place to know or check whether you need boron for your crop or zinc for your crop? And in the EC 750, if you go like to zinc, it'll discuss which crops you should be concerned about for zinc. It'll discuss boron. It'll discuss calcium and those things. So you can get that information out of EC 750. That's a good question. Sure.