02.5 Zone Soil Sampling: Making Fertilizer Dollars Go Farther

In this episode, Sarah and Jodi dig into why zone soil sampling pays off when fertilizer prices are high and every pound has to earn its keep. We explain why composite soil sampling can hide field extremes and how better sampling leads to smarter variable rate fertility prescriptions. 

We talk:
• high fertilizer prices driving interest in variable rate fertilizer and better prescriptions 
• composite soil samples providing an average while hiding extremes like low pH pockets 
• pH variability on sandy ridges and why missing it increases yield and input risk 
• sampling every zone at least once to build a dependable baseline 
• sampling high and low productivity zones to capture the true spread 
• low productivity areas often holding excess phosphorus and potassium from years of flat-rate applications 
• using soil test data to cut back safely in poor zones and reallocate dollars to higher return acres 

Tune in next time for a Tiny Byte of Knowledge from GK Technology, where we have a map and an app for that.

https://gktechinc.com/

Transcript

Fertilizer Prices And The Real Problem

Sarah 0:00

And now it's time for a Tiny Bite of knowledge. Well, Jodi, should we start this podcast by stating what the current fertilizer prices are?

Jodi 0:20

Are you sure you want to do that, Sarah? I don't want everybody to get really sad before we start talking about today's topic.

Sarah 0:27

I agree with you. I think if we actually state the current fertilizer prices, everyone will just turn us off and they won't listen. So we don't want that. So we'll just start talking about what is the topic for today, Jodi.

Why Zone Maps Need Soil Tests

Jodi 0:42

So we're going to talk about how we can maximize the use of our zone soil sampling maps so that we can make the best possible fertility prescriptions given the high prices of fertilizer. Because who doesn't want to maximize their inputs when things are this expensive?

Sarah 1:00

I agree. And, you know, going into this spring, there's been a lot of new interest in variable rate technology and especially as it pertains to fertilizers because of the current state of the input prices and our commodity markets. That's just how this spring went. And that's that's great. But there's a lot of people that kind of came into this and they didn't do any soil sampling last fall, or maybe they could have done some soil sampling things better. And so we really want to kind of hammer home on that just a little bit so that we can make your prescriptions just a little bit better, make your fertilizer dollar go just a little bit farther. So um one of the things that we really need to advocate is if you're a grid sampler or a zone sampler, and this is especially true for zones, uh, because I feel like we see this more with the zones, the zone guys, but people that are like, we're just gonna variable rate based on the zones, but they don't have a soil test at all, or they've only got a composite soil test. And that is sometimes challenging to make really good soil fertility recommendations.

Composite Averages Hide pH Risk

Jodi 2:14

Absolutely. And I just want to I'll just point out some examples of why this is so important. So I'll use my always example of soil pH. And so say if we're if you're looking to figure out where you can cut back or like where you can reallocate your fertilizer resources to maximize your return on investment, you need to know exactly where in the field that those that fertilizer needs to be applied and where it needs to be cut back and put higher. And you you can't always guess that. And the point I want to make is that, like, say, um, doing composite soil sampling, it can give you a good average, right? Um, but it can also be missing some things. And a great example of this is soil pH, especially in western North Dakota, and also here in eastern North Dakota as well, where we've got sandier ridges. If we're just doing a composite sample, we very well could be missing those areas that have pHs that are in the fours and the fives. And I've seen that on my own fields back home, just doing composites, it was missing that we had serious issues where our pH was as low as 5.5. So, yes, a composite will get a good average, but if you're looking to really maximize your inputs, you got to get out there and do soil samples um in your zones and not just a composite. Right.

Sarah 3:36

Again, not to say the same thing over and over again, but to hammer it home. When you composite sample, you are getting an average. That is the point of that soil test, and you are getting an average. You will not understand the extremes of what's going on in your field. We have the ability to address those extremes, but we need the information to help make the decisions. So make sure that you're doing your zone sampling and actually pulling good soil samples in the zones. Absolutely.

Jodi 4:06

A quote unquote traditional zone map might include five zones. So you go from like your really good zones to your really bad zones. Sometimes a mod area might be included in that, whether that is a low spot that is salty compared to a hilltop in a field, you might split that out, and instead of just traditional five zones, you might have six, you may have eight. However, many zones you have, that's totally fine. Zones are meant to bin variability so that they can be treated differently in the field. The point I want to make on that is that you know, the first year that you're going out and collecting that zone soil fertility information or sampling four zones, it's a really good idea to go out and sample as many of those zones as you can. So, for example, on my own farm, the first years that I was out soil sampling, I went out and I did go out and sample every single zone. And now when I've got a shorter time to get samples done and I kind of know how my intermediate zones work, so like my zones two and four, I do just do zones one, three, and five. And I still think that gets me a pretty clear picture because I know you know what those zones two and four tend to look like based on previous soil test information. So

Sample Every Zone At Least Once

Jodi 5:18

point is it's a good idea to get out there and soil sample every single zone at least once.

Sarah 5:24

Absolutely. And absolutely, Jody, but you bring up a really good point too, because I have worked with some customers that have generally only soil sampled their more productive areas, and they have not been soil sampling their lower productivity areas in the field. And if I hear you correctly, it sounds like you're talking about soil sampling, your highest productivity, your medium productivity, and your lowest productivity. So we're really getting those extremes. So we really understand what's going on in that area. That's such a good practice, you know. So often when we think back to those low productivity areas, those are the areas where we have applied the same amount of fertilizer in those spots as we have the rest of the field forever, but they're low productivity. So you're only harvesting um very little yield off of it. And all of those nutrients, especially when you're talking about something like phosphorus and potassium, they're left behind and they've accumulated. So many times in those spots, once I have that soil test and I understand where exactly those values are or how high those the soil testing values are in those spots, when you couple though that increase in nutrients in those areas along with the decreased potential uh yield potential in those areas, uh sometimes it doesn't require any additional fertilizer. But we can't make that decision if we don't have those soil testing data for that area. So even though you're gonna be depending upon the higher productivity zones for most of your yield, make sure that you're still soil sampling those lower productivity areas so we can understand how the best way to manage that cost into that lower productivity area is.

Jodi 7:20

Absolutely. I mean, if your goal is to maybe you say, Oh, I want to cut back on fertilizer, well, that's probably a good place to cut back on, is those areas that have been flat rate applied and haven't been getting yield. Like that's a that's such a no-brainer. But it sounds kind of counterintuitive to be spending that money in those poor zones with a soil sample and a soil test, but you really should be because you're gonna get that money back pretty quick if it has those high for soil fertility levels. And most of the time, these low productivity areas have a lot of fertility that doesn't need to be there.

Sarah 7:58

So the takeaways

Low Zones Can Hold Extra P And K

Sarah 8:00

from this whole thing, first of all, if you're trying to do variable rate fertilizer and you aren't already, make sure you soil sample. And if you're soil sampling and I go to gonna go to all that work, don't just composite soil sample and get an average. Make sure that you sample across your zones. Um, most of the grid sampling people out there are just grid sampling. So now don't worry about you guys too much. But hey, zone people, get out there and get your zone soil samples done. Okay. And when you are doing your soil sampling, make sure that you are sampling the extremes of your field so that you have that data when it's time to make the decisions. Soil sample the highest productivity and the lowest productivity, maybe one zone in the middle.

Jodi 8:46

Yeah, when inputs are as high as they are and crop prices are as low as they are, the last thing you want to question is whether or not you're applying too much or too little in areas of your field. And the best way that you can reduce any sort of risk in that is getting out there and getting a soil sample and a soil test. So don't guess soil test, and maybe not always composite, do some zone sampling. Oh my gosh, I love that.

Sarah 9:14

I'm so gonna use that. Don't guess, soil test, don't guess, soil test. But I like it. Don't guess, soil test. There's a cheer in there, but instead of pom-poms, we can have soil probes. That sounds really heavy and dangerous. We could use them like batons, it'd be great.

Jodi 9:33

So don't guess. Soil test and make sure to sample your zones.

Sarah 9:41

Sample your zones.

Jodi 9:42

Tune in next time for a Tiny Byte of knowledge from GK Technology, where we have a map and an app for that.