Mike Howell (00:08):
The Dirt with me, Mike Howell, an eKonomics podcast where I present the down-and-dirty agronomic science to help grow crops and bottom lines. Inspired by eKonomics.com, farming’s go-to informational resource, I’m here to break down the latest crop nutrition research, news, and issues, helping farmers make better business decisions through actionable insights. Let’s dig in.
(00:32)
Well, hello again, everyone, and welcome back to The Dirt. I’ve got a guest back with us today. We’ve got Dr. Karl Wyant, the new director of agronomy with Nutrien. Welcome back to The Dirt, Dr. Wyant.
Dr. Karl Wyant (00:49):
Hi, thanks for having me. I appreciate it.
Mike Howell (00:51):
This week on The Dirt, we’re going to talk about drought, and I was looking at the US Drought Monitor a few days ago, and it looks like about half of the United States is covered with some form of drought. And then, when you go from Texas across to Oregon, it looks like that’s pretty exceptional drought. I haven’t had the chance to go out to that part of the country this summer, but looks like a lot of drought going on out that way, and it’s starting to pick up a little more drought in the eastern part of the US.
Dr. Karl Wyant (01:17):
Yeah, that’s right, Mike. There’s a lot of dry conditions out there, spotty patches of drought in the southeast US, the Great Lakes area, and up the Eastern Seaboard. As you make your way west into the Central Plains and Southern Plains, those drought conditions get even worse. And then, out towards California, across the Rocky Mountain West, it’s pretty nasty, and it’s about half the country as of late June here. And some areas are starting to see some relief from the drought, some areas not so much.
Mike Howell (01:44):
Yeah, it’s getting pretty bad. We had Eric Snodgrass on several weeks ago talking about the weather and what we could expect this summer, and that was one of the things he was warning us about is the potential for drought, the way things were shaping up. Looks like he’s got it right on for now. We hope we can see some relief to this coming soon. Right now, we’re in this situation, and try to learn how to deal with it and prepare for it next time it comes.
(02:06)
So we were talking about doing this episode on drought, and I got to thinking. Exactly what is a drought? We hear that term thrown around, and a lot of people in my part of the world say we’re only a week away from a drought. We’ve got these sandy soils through the Delta, and they can dry out pretty quick. I know out in your part of the world it never seems to rain at all. So how do we define a drought and the difference between where I’m at and where you’re at? And I mean, we get 50 inches of rain annually over here, and y’all may get what, four or five inches maximum?
Dr. Karl Wyant (02:35):
That’s right. I live out in Arizona, right smack dab in the Sonoran Desert, where some parts get three four inches of rain a year, and on the wet end, some of the cities out here get eight inches of rain, nine inches of rain. So pretty different conditions from where Mike lives and from where I live, but this drought piece is all sort of adjusted relative to your area. And the National Weather Service calls a drought, “A deficiency of moisture that results in adverse impacts on people, animals, or vegetation over a sizeable area.” So it’s that relative absence of precipitation, then you can adjust from an average rainfall, you can standardize their regions and standardize what you’re calling a drought based on those different climates.
Mike Howell (03:15):
Okay, so we hear about drought all the time, and we know that droughts are a lack of rainfall or a lack of precipitation. But what causes these droughts? What do we know meteorologically that’s going to cause these drought situations to develop?
Dr. Karl Wyant (03:28):
Droughts are generally what’s called a creeping phenomenon, where it’s not like a hurricane that comes in and then goes. It’s not like a forest fire season out west where there’s a defined period generally when those events occur. These droughts are generally, think of someone just turning a volume knob up slowly over time. And of course you have some of your quicker droughts, but really it’s that creeping phenomenon, and that’s because drought is complex.
(03:52)
Drought is caused by this complex interplay between global weather patterns. El Niño, La Niña, depending on where you live, could help cause drought conditions. There’s changes in wind patterns and jet streams, that all of a sudden those jet streams change, and you bring in a whole lot of hot air or pressure that doesn’t let moisture in for a while, and that could set up drought. You’ve got some geography that’s important, and they have these mountains that block rain, and on the other side in the rain shadow, you can have extended droughts just from all the rain falling on the rain side of the mountain, the wet side of the mountain. And then, you have very locally some of these conditions where you can have poor soil moisture storage on your field, and you can induce a drought, where your rainfall or snow melt isn’t going into the soil and going into where the crop could use it later. It’s running off and not being stored in your field.
(04:40)
And so, a lot of complexity here. The main really driver of a lot of drought, when you kind of take away the global weather patterns and then down to that local field storage, is that lower than normal rain or snowfall, really that lack of the input and then lack of storage locally in your field.
Mike Howell (04:57):
Okay. So Dr. Wyant, in preparation for this, I was doing a little digging and found out that there’s actually different types of drought. Can you talk a little bit about the different types of drought and differences between those?
Dr. Karl Wyant (05:08):
Sure. So a lot of the droughts are classified by what they impact. This is an agricultural podcast, so we have agricultural drought, and that’s when these crops become impacted by these low moisture conditions, conditions that reduce water availability to the crop, and that water availability starts to decrease those farms’ or ranch capacity to produce the products that we’ve all come to expect and to buy from our local growers and ranchers.
(05:35)
So that’s agricultural drought, but there’s other stages of drought here. We have meteorological drought, that’s dry weather patterns that may or may not impact the ag areas. A hydrological drought, that’s a water supply problem, so if you’re irrigating, you might have a hydrological drought if that water supply gets too low to run your pivots and your drip systems and whatnot. And then, you have socioeconomic droughts, things that impact people. So parts of the world last summer were running out of water. Local cities were running out of water. Their reservoirs got too low, so that has a lot of impacts on the people that live in those places and their day-to-day activities. And then, you have ecological drought when these natural ecosystems, lakes, mountains, national parks, when they get impacted by a drought. So lots of different definitions, but really that lack of moisture is that common thread weaved through all those different ways to think about how drought impacts our lives.
Mike Howell (06:30):
Dr. Wyant, we always think of drought as hot, dry conditions. That temperature seems to always be a factor in my part of the world anyway, but maybe that’s just the way I’m thinking about it because most of our crops are growing during the summertime, and it gets hot. And here this week, it’s been upper nineties. We even hit a hundred for a couple of days here in June, and we never see that. We’re not going to talk about how hot it is in Phoenix, but I know the temperature gets a little warmer out that way. But is drought always associated with hot conditions, or can we have drought when it’s not so hot?
Dr. Karl Wyant (07:00):
Yeah, so that hot drought, that’s what I call it, it’s exactly what you’re talking about, the classic viewpoint of drought. I was looking at the temperature and precipitation outlook map for the southeast US just a moment ago, and you’re setting up for low precipitation and excessive heat warnings across the region. So that is those two factors that are being manipulated not in your favor to cause a hot drought, and that’s what a lot of folks think of when they think of drought, high temperature, low moisture, and your crops in the ground during the summer when you’re trying to get some work done out in the field.
(07:30)
And there’s this opposite called cold drought, and that’s related a lot to these snow conditions, these regions that rely on snowpack in the winter to feed their water needs in the summer when the snow melts. So that’s a cold drought, where you have just lack of snowfall, a lack of water storage through the reservoir system. And this is something that the Rocky Mountain West and California and Arizona are going through right now is this impact of a lot of cold droughts, lack of snowpack in the wintertime, exacerbating water supply conditions during the spring, summer months.
Mike Howell (08:02):
Okay. Well, let’s move on into the field and talk a little bit about how these droughts are going to impact the crops and the plants that are growing in this field. What can we look for in the field, and what are the plants going through?
Dr. Karl Wyant (08:13):
Yeah, so we’ll go back to that agricultural drought definition, that definition of drought that really impacts our day-to-day. It’s impacting the crop, and that’s an active area of study right now is this drought impact on crops. And we know something happens, but detailing how we get to the eventual symptoms, that’s been an active area of research for several years now. And we know that the hotter it is and the drier it is, that’s going to draw intensive vapour transpiration demands through that crop. So the hotter and drier it is, the more water that plant’s going to need, depending on its crop life stage, to satisfy that water demand, that moisture demand just to keep itself alive. And so, you kind of accelerate your moisture needs as you move into a drought, and that’s why you can quickly deplete soil moisture once these drought conditions set in.
(09:01)
There’s a lot of stress that happens to your crop and to you, but we’ll keep it on the crop here as we talk about drought. Because you have that high temperature, low moisture, your plant has to deal with that, so it starts to take some of that photosynthetic energy, some of that energy it’s using formerly to make yield and to make leaves and to make roots. It’s taking some of that energy, and now it’s spending it on pathways that help reduce stress. So it’s spending it on these materials and molecules and compounds that help to keep the ion balance right in the root zone, and it helps to deal with this salt accumulation in the leaves that can happen in the high temperatures. So all of a sudden, your plant goes from spending its biological currency on yield and growth, now it’s got to spend it on something completely different when it’s dealing with those drought conditions. A lot of interesting pathways below ground on that drought stress in a very active realm of research, and a lot of cool stuff going on there.
(09:56)
A couple other pieces just with that plant. Plants are looking for fertilizer, and they’re looking for nutrients, and water has a big part of how your plants get nutrients. So you can first start with thinking about a fertilizer, and we’ll just talk about dry fertilizers for a second. Granular fertilizers, they’re typically applied as a salt, a cation, which is positively charged, and then you have your anion which is negatively charged. So if you think of potash, that’s potassium chloride, the cation and the ion respectively. And so, for your plant to pull in that potassium, you first have to dissolve that fertilizer in water. Your plant can’t just pull in the full granule. I don’t know if that’s a little too big for a root to handle, but you have to have the moisture in the soil for that ion to come apart and for that positively charged potassium to become available, then the plant can grab it.
(10:47)
So you’ve got to have enough moisture to dissolve the fertilizer, and then you have to have enough moisture in the soil to help drive those fertilizers and those cations or anions, those separate ions, into the root zone itself through a mechanism called mass flow. And so, there can be challenges here, getting nitrogen, getting potassium, getting magnesium phosphate to your plants because they’re not disassociating the low ground in the solution. And then, they’re not actually moving towards the roots themselves because there’s not enough moisture to carry them.
Mike Howell (11:17):
Right. Dr. Wyant, you mentioned soil moisture, and I want to touch on that just a little bit more. A lot of people think of soil moisture and right up in that top two or three inches for germinating the seed and then down maybe as deep as a foot when you talk about a growing crop. When we get into a bad drought, we can see that soil moisture depleted several feet down into the ground.
(11:36)
And I guess I first realized how deep that dryness could go probably 10 or 12 years ago. I took a group of four ranchers out to Oklahoma City for the National Land Judging Contest, and what they do is dig a pit that’s about six feet deep, and they’ll get down in there and analyze various parts of the soil and figure out what the best use for that soil is. One thing we always had to do was moisten that soil to see if we could get it to ribbon out, to determine our texture and permeability and things like that, and it was so dry that we actually had to get a cup and soak the soil in that cup for several minutes to let it soak up the water.
(12:11)
And we think about a drought and well, we’ll get a two-inch rain, and that’ll get moisture back in the soil. Well, probably not. We get a big heavy thunderstorm, and a little bit will go in an inch or two deep, and the rest of it’s going to run off. So we’ve got to have some slow soaking rains to fill that soil profile back with water and get out of that drought situation. One single rain event isn’t going to end this situation and get our crops back where they need to be.
Dr. Karl Wyant (12:34):
Mike, that’s a great point. I like to use a term called the drought hangover, and we’re experiencing that right now is because last year we had a drought as well across much of the Midwest in Central Plains and in parts of the Northern Plains, and we depleted a lot of that stored moisture with last year’s crop. And then, this year parts of those areas that I mentioned are just not getting the moisture to replenish the moisture at those depths. You mentioned that one to three foot range depending on your crop, what they can get access to. So it’s going to be quite challenging because those deep moisture reserves aren’t quite there like they usually are, and so plants are going to be searching for water and spending some of that energy on growing deeper roots and looking for it.
Mike Howell (13:14):
Right. Well, Dr. Wyant, we’ve already mentioned that a big part of the United States is under a drought right now, and we’ve talked about some of these drought maps. And who actually is monitoring the drought situation? Do we have some websites that listeners could go to see how bad it is in their area?
Dr. Karl Wyant (13:29):
Yeah, there’s a couple great federally run websites, and I’ll kind of split it into two. One is, “What’s the drought now,” and then, the predictive part, “Am I going to go into a drought,” so you can help prepare. And so, drought.gov is a great resource. Lots of information on current conditions, and you could really dial into the state level and see where drought’s happening and who’s getting impacted. Lots of great statistics on drought.gov. You also have the US Drought Monitor that’s run through the University of Nebraska Lincoln. Another great resource, lots of good maps, lots of ways to assess situations and see how things have changed over the last few weeks. You can even go back historically, look at 10 years ago if you want to see what your area was doing for drought.
(14:13)
And then, you have this other website which helps predict drought, and that’s the Climate Prediction Centre. That’s also a federal run website, and that has a lot of forward-looking data products, three-month drought outlooks, and things like that that can help you prepare and look at the three-month models and even longer to help you prepare for drought. So you know it’s coming, and you can get your fields in shape and get everything dialed in before the drought hits.
Mike Howell (14:38):
So you’re talking about preparing for the drought. If we think a drought’s coming, what can we do to prepare for that?
Dr. Karl Wyant (14:44):
If you have the ability, and you know a drought’s coming, you can plant drought-tolerant varieties. And either within the crop that you’re currently planting or planning to put in the ground, you can talk to your favorite seed rep or nurseryman and get that variety that can help withstand drought just a little bit better than some other varieties, and that could be a way to get around it. There’s also different crop choices. Wheat has a very different drought tolerance. It’s very drought tolerant relative to something like corn. Corn is not as drought tolerant as wheat, so if you know you’re going to be short on moisture, you could change your variety, and that gives you a little bit of leeway, or you can change the crop, and that could help really get you through the field and have a successful year.
(15:23)
Some other ways you can do locally to prepare your fields is really to look at your soil moisture storage. If you know that you’re coming into a drought condition, that could set up some goals for that field management to help trap as much water as you can, whether it’s from rain or whether it’s from snow, and that’s by deploying some of your tools. Things like soil surfactants, these are these products you can spray on the soil surface that help break that hydrophobic layer that can form during dry conditions and actually get water into the ground and store it for later, improving that reserve of moisture that we talked about earlier, relieving the hangover a little bit if you will.
(16:00)
Another way is by improving your soil health, and that’s by improving the soil structure, the aggregation. Well-aggregated soils can store more moisture. They can get down in the ground and store it actually around the particles and in the pore space itself. And there’s a variety of techniques you can use to do that. Cover cropping’s an example, reducing tillage is an example, really priming that microbial life in the soil because they’re the ones that glue your particles back together to make aggregates.
(16:25)
There’s several strategies depending on your situation that you can put together. I think that’s where talking to your crop advisor is so important to say, “We know this is coming. What can we do now? What fits within my field operations, my budget, and what can we deploy to help get through this drought conditions that we’re expecting?”
Mike Howell (16:43):
Right. Some good points there, Dr. Wyant. Another thing I wanted to mention was soil moisture sensors. They’re gaining prominence around the country. I think y’all have been using them out west for a good long while, and we’re just starting to see the benefits of them here in the southeast. But most of the time, we’re using these to trigger irrigation events, and they work great for that. But we have a really good webinar on those that you can find on our eKonomics website. That’s www.nutrien-ekonomics.com. Dr. Drew Goldstein, he’s the irrigation specialist at Mississippi State, did a webinar for us about a year ago talking about these soil moisture sensors and how we can use those to help determine how dry that soil actually is and help improve our irrigation efficiency. So I want to encourage our listeners to go check that out as well.
Dr. Karl Wyant (17:29):
Mike, that’s a great point. Those soil moisture sensors, and there’s tones of types you can choose from. Some that are, you leave in the ground for a long time, and some that you can kind of plug and play right out of the box and take them out at the end of the season. Lots to choose from, lots of different ways to interface with the data, and that’s probably the best question to ask your advisor. How do I get the data? And a lot of these soil moisture sensors now can send that data to your phone. You can look at the graphics. You can get text alerts when it goes below a certain moisture level, all kinds of fun stuff. These sensors have really advanced in the last 10 years and are becoming a lot more popular to use in the field, and you can even fund them through the NRCS EQIP program. There is a code for soil moisture sensors.
(18:13)
And take a look at your soil moisture because believe me, it’s hard to detect soil moisture at three feet every week unless you really like digging holes. A soil moisture sensor can give you that same data every 15 minutes and give you a lot more complete picture and help inform some of these decisions. These soil moisture sensors can also help you relate just how drought stressed are my crops, so you can relate some of these symptoms that you’re seeing back to the data you’re getting, and that can kind of form that feedback loop of, “I need to trigger an irrigation a little earlier, or maybe I can delay it depending on recent conditions.” Or you can work on overall field soil moisture storage, and you can watch those two and three foot soil moisture graft go back up as you deploy certain practices that we talked about earlier.
(18:54)
Mike, I wanted to talk about symptoms because that’s another piece. I know you’re sitting in the middle of an excessive heat warning, so you’re probably sitting around a lot of symptoms here. And I just wanted to talk through these stages of symptoms that we’re seeing when we do hit a drought, and we’ll just stick to the classic hot drought because that’s what agricultural drought is typically. We won’t talk about the cold drought, the snowpack-related droughts that impact the total water supply of some of our irrigated acres. We’ll stick to this hot drought.
(19:21)
And so, these symptoms, it first starts with this light drought stress, high temperatures, low moisture. And so, we’re just getting into these conditions, and this could be a D1 sort of drought that’s listed on some of these maps, that yellow color on the maps when you take a look at those resources we just mentioned on these websites and those government resources. But we have the early drought, and that’s when a lot of people start seeing leaves twisting up, slight wilts in the afternoon, and overall slight slowing down of that growth.
(19:49)
And a lot of that is due to the plant that’s going into water savings mode. It’s like, “Hey, I’m under some slight stress. I can wait this thing out. I hope that rain comes to help me out, but I can deploy some physiological mechanisms like closing the stomates that help with gas exchange.” If you close the stomate, you can help reduce water loss as well. So you see some of these twisted leaves on corn. Just remember that that’s that plant starting to respond to that slight stress, and usually things work out by the next morning. It’s untwisted, it’s gotten through that slight drought stress, and you’re good to go. Mike, any comments from you on what you’ve seen with some of that early drought stress symptoms?
Mike Howell (20:27):
Yeah, in the Mississippi Delta this year, we did see a lot of that. We actually had growers considering turning irrigation on prior to tasseling, and we usually don’t like to do that. We like to wait until we get to the tassel stage. But it was that slight twisting that you just described, and the next morning, the crop was recovered and ready to go again. When we started digging down into that soil profile, we did find that we had moisture maybe six or eight inches deep at that time. But we did have that moisture, and a lot of guys were able to hold off on that irrigation and get through that. And shortly after that, we started getting rains again, and we’re able to get to this tassel stage now.
(21:02)
And now, it’s starting to get dry again, and we’re going to have to start running some irrigation because this is a critical time for that corn to need water. When it starts the reproductive stage, that’s when it needs the most water, so we’re going to start irrigating that corn and making sure it’s got all the water it needs at this time. But the later you can initiate that irrigation, the better off you’re going to be. It gives those roots time to get deeper and get you a better root system so it can take up some of that deeper placed moisture in the latter part of the growing season.
Dr. Karl Wyant (21:29):
Yeah, that’s a great point, Mike. That’s that light stress. You’re seeing the plant actively manage its water demand so that it can get through those early stages of a drought. We’ll just keep turning up that dial here. We’ll go to medium drought stress, and that’s when you see some of that twisting and wilting in the afternoon. But you come back the next morning, and those crops haven’t recovered. They look a little flopped over. They look a little too twisted up, and that’s when that medium drought stress starts to kick in. That’s where alarm bells start to go off just slightly, where that plant’s ability to self-regulate the drought stress, it’s kind of overshooting that a little bit. And so, you start to have issues with things like turgor pressure, that pressure a plant can put on its cells to keep itself upright. It starts to lose some of that turgor pressure, and it starts to wilt and flop over.
(22:18)
If you go to severe drought stress, that’s when you have these nonrecoverable wilts, where the plants fall over, and you can’t bring them back. They’re eventually going to die, then you’re probably going to lose the crop. And that certainly happens in these dry land regions more so than in the irrigated parts of the world, but it’s something that happens. And unfortunately, nobody likes to see a grower get to that stage. It’s tough. It’s a little bit heartbreaking, but it’s all about that moisture demand and that creeping phenomenon of drought and the stress that comes with it.
Mike Howell (22:46):
Right. Well, Dr. Wyant, we sure appreciate you joining us today. Listeners, Dr. Wyant is actually going to be on the road next week. He is coming to Mississippi, so he’ll get to experience this heat along with the humidity that he doesn’t have out in Phoenix. So Dr. Wyant, if you haven’t started already, start the hydration process now. You’re going to need it next week.
Dr. Karl Wyant (23:05):
I sure will. That’s great advice, Mike. Thank you.
Mike Howell (23:07):
Is there anything else you want to touch on on drought before we wrap this up today?
Dr. Karl Wyant (23:11):
Just one more reminder of those resources, drought.gov and the US Drought Monitor. If you Google those, you’ll find lots of information about current conditions and for your local area as well. And then, that climate prediction center, if you type that into Google, you’ll find those tools you can use to look out into the future, see if drought’s coming, and to see if your area is likely to recover from drought so you can plan accordingly with your crop advisor and your local resources like the NRCS and USDA.
Mike Howell (23:35):
Okay. Dr. Wyant, we sure appreciate you joining us today.
Dr. Karl Wyant (23:40):
Thank you for having me. I appreciate it.
Mike Howell (23:42):
Listeners, thanks for joining in this week. We hope you’ve learned more about drought and the causes of drought and how it affects the crops. We know there’s nothing we can do about these droughts, but hopefully by understanding the mechanisms and what they’re doing in the plant, we can make some changes in our management systems that’ll help overcome a lot of these problems.
(24:00)
We’d like to invite you to join us again next week when we visit with Dr. Tom Allen, plant pathologist with Mississippi State University. Dr. Allen is going to talk to us about the relationship between crop fertility and disease occurrence and some things that we may can do to better manage diseases in these crops with crop fertility. Until next time, this has been Mike Howell with The Dirt.
