2021 Nebraska Cover Crop and Soil Health Conference - Jerry Hatfield

Deloris Pittman Author

03/29/2021 Added

36 Plays

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Pathway Toward a Healthy and Resilient Soil to Achieve Optimum Productivity and Environmental Quality: Cover Crops are Key! - Jerry Hatfield, Retired Director, National Laboratory for Agriculture and the Environment

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[00:00:00.060][music].
[00:00:21.980]Our next speaker is, Jerry Hatfield.
[00:00:25.610]Jerry is the retired director of the national laboratory for agriculture and the
[00:00:30.050]environment. Jerry, back in the day when spent some time in Ames,
[00:00:34.370]it was the soil till flap. So that probably dates my,
[00:00:39.260]dates my time back in Ames. but anyway, the,
[00:00:42.420]the title of Jerry's talk today is pathway toward a healthy and resilient soil
[00:00:47.120]to achieve optimum productivity and environmental quality cover crops
[00:00:52.040]are key. And Jerry, go ahead.
[00:00:55.250]All right, let me get,
[00:01:02.420]get my slides up here.
[00:01:09.290]Alrighty.
[00:01:11.390]Yeah. thanks Daren. And, yeah,
[00:01:14.510]that dates both of us because when I first became the director of the national
[00:01:18.290]lab for, agony environment, it was what's that,
[00:01:31.100]But today we're going to talk about,
[00:01:33.620]this pathway towards a healthy and resilient soil.
[00:01:36.680]And that over the past 10 years,
[00:01:39.560]I've spent a lot of time looking at how do we, um,
[00:01:42.500]really think about the resilience out of our soils and how do we look at that
[00:01:47.300]from not only, balancing productivity,
[00:01:50.330]but environmental quality and cover crops are a key component of all of
[00:01:54.980]this. And so I think you begin to see these dynamics,
[00:01:58.160]but I want to start with just, three different definitions,
[00:02:02.180]from this standpoint. And when we talk about resilience,
[00:02:05.360]that's kind of become a new buzzword in all of this. And we,
[00:02:09.440]we think about resilience and it's really this ability to recover from stress.
[00:02:13.310]And one of the major stresses that we have in our soils is,
[00:02:18.140]related to water availability. we see a lot of impacts from water stress.
[00:02:23.630]The other piece of this is the optimum productivity,
[00:02:27.110]and it really is a production that effectively utilizes the resources available
[00:02:32.000]from, water and light and nutrients,
[00:02:35.090]and thinking about how those have coming together.
[00:02:38.420]And then there's increasing attention, on environmental quality,
[00:02:42.680]both the state of our water and soil resource and air resources out there and
[00:02:47.390]what we can do to protect those.
[00:02:48.860]And we're going to see more emphasis on the role of agriculture and
[00:02:52.910]environmental quality and all of these different pieces.
[00:02:55.430]So when we think about these things,
[00:02:58.340]it's really important to understand what we're talking about from that
[00:03:01.900]standpoint.
[00:03:03.660]right. Why don't.
[00:03:11.110]And I have a framework that I've been working on that, um,
[00:03:14.880]that kind of puts this into perspective,
[00:03:17.670]genetics by environment by management.
[00:03:20.280]we spent a lot of time looking at water nutrient and light use efficiency of
[00:03:24.210]crops, and then linking that to soil health.
[00:03:27.360]So we're really looking at how do all these pieces fit together,
[00:03:31.980]from a different perspective than what we've been doing. So, uh.
[00:03:40.650]Why am I a slides one advance? Okay.
[00:03:45.000]Um,
[00:03:45.810]if we think about this GBE by him and in reality,
[00:03:50.010]it's the think about it from this perspective?
[00:03:51.960]One is that management is what producers oversee because of the
[00:03:56.910]options that we make in there.
[00:03:59.070]But what we're really trying to do is overcome our environment, either,
[00:04:03.060]whether, problem, solve variation problem. And,
[00:04:07.290]but the ultimate goal is that we want to optimize our genetics.
[00:04:11.460]we want to be able to optimize that for maximum yield.
[00:04:15.000]You look at all these different pieces that are going on out there.
[00:04:17.820]And so when we're talking about all of this is really is how do we bring these
[00:04:22.530]pieces together? And so we've looked at this framework of being able to,
[00:04:26.660]to bring this together.
[00:04:28.410]And if we think about water or nutrient use efficiency
[00:04:33.300]and, and it really gets down to the question of what assumptions we make,
[00:04:36.750]and that is water used, or nitrogen applied, for example, you know,
[00:04:41.400]how much grain do we get out? How much total biomass,
[00:04:44.190]if we're producing a forage crop.
[00:04:46.350]And so it becomes a really important metric to say is my cropping system
[00:04:51.930]being able to supply what we want out of it and be able to use the
[00:04:56.520]resources that we've put into it.
[00:04:58.980]And that really brings us to soil health as a cornerstone because
[00:05:03.930]soil health is a cornerstone of production. You think about the,
[00:05:07.270]the functions of soil and being able to supply water, supply nutrients,
[00:05:12.600]all those different things that are going on. But if we look at soil health,
[00:05:16.950]it is this kind of intersection between production and environmental
[00:05:21.660]quality economic return. You can see the impact of,
[00:05:25.590]of soil health and the visible attributes of the soil.
[00:05:30.000]the little diagram on the left, the soil aggregation climb.
[00:05:33.900]When you talk about building soils up and improving soil health,
[00:05:37.430]the first step on that is,
[00:05:39.210]is getting biological activity restored in the soil.
[00:05:43.050]You see the invisible and the dynamic processes going on.
[00:05:46.950]We see a lot of organic matter turnover,
[00:05:49.530]improve nutrient cycling and the visible things that we see in there.
[00:05:53.220]As we see improve soil structure, we see improved water visibility.
[00:05:58.040]we've been see improved, um, crop, nutrient uptake. And you,
[00:06:02.510]you look at the, all this and this handful of soil. We,
[00:06:05.500]we see those aggregates out there. We see that change in the soil profile,
[00:06:10.700]increasing the organic matter near the surface and all these different dynamics
[00:06:15.080]that are going on. So we,
[00:06:16.280]we actually have visible indicators of soil health and,
[00:06:20.000]and you look at all these different pieces,
[00:06:22.190]but we really get back to this.
[00:06:26.960]w we'll talk,
[00:06:27.710]we'll talk about this through the rest of this is Saul degradation.
[00:06:32.600]You know, how do we degrade soils? so we'll have processes where to,
[00:06:36.950]cover crops and nutrient management even fit into that.
[00:06:40.340]And then the implications for improve crop production efficiency. Um,
[00:06:44.660]cause the end of the day,
[00:06:45.770]what we really want is to make sure that our crops are, are doing what we want.
[00:06:49.730]We want that genetic potential to be realized.
[00:06:53.120]So we think about soil degradation and put it into this spiral component is that
[00:06:58.580]and all that everybody put in their own mind what they think poor land
[00:07:02.750]management is.
[00:07:03.650]But when we begin to subject the soil and our management systems
[00:07:08.420]to poor land management,
[00:07:10.460]the first thing that begins to change is our aggregates.
[00:07:13.430]We begin to destroy the aggregates because we're no longer supplying that
[00:07:18.110]glue that holds that sand, silt and clay together.
[00:07:20.630]And so we see that change and right away,
[00:07:23.810]we can begin to see compaction in that soil because it no longer has a
[00:07:27.560]structure.
[00:07:28.760]we can see crusting at the surface because those aggregates are no longer
[00:07:32.420]stable. once we have compaction and crusting,
[00:07:37.370]we end up with a lot of water and wind erosion because we're not able to either,
[00:07:41.900]infiltrate water. we are lose soil near the surface.
[00:07:46.280]So we see a lot of wind erosion as we erode that topsoil out,
[00:07:50.180]we see plant growth begin to diminish.
[00:07:53.780]Once we see the plant growth, we're no longer supplying,
[00:07:58.310]the biological component. We're no longer feeding that sole biology,
[00:08:02.420]yield begins to disappear.
[00:08:04.400]And then all of a sudden we have reduced soil productivity.
[00:08:06.680]And so this is a spiral that just works down,
[00:08:11.090]all of this and it it's,
[00:08:12.740]it's occurs sometimes so slow that we don't recognize that this is what's
[00:08:16.640]happening,
[00:08:17.090]but you can look at all these different attributes occurring across the
[00:08:21.230]landscape. All the soil variation that,
[00:08:24.830]Kristen talked about was in Arizona.
[00:08:26.800]A lot of it is result of the degradation of different parts of the field.
[00:08:32.360]And one of the things that we discovered,
[00:08:35.450]from a lot of our studies is that in measuring
[00:08:40.250]corn and soybean systems, that, that then here's with any correlation equipment,
[00:08:45.020]looking at the CO2 exchange between the surface and the atmosphere,
[00:08:50.150]you know, and, and these basically measure the amount of,
[00:08:54.110]of carbon that's exchanged as well as water being exchanged.
[00:08:57.480]But in typical corn soybean production systems,
[00:09:01.800]we're losing about a thousand pounds of carbon per acre per year.
[00:09:06.810]and this, this conventional system is,
[00:09:11.010]deep rip in the fall field conservation in the spring.
[00:09:14.610]There's really no residue removal. What's all staying there.
[00:09:16.950]The only thing that's going off is a green.
[00:09:19.410]you can see that if we look at the total season, you know,
[00:09:23.850]you'd see those negative components,
[00:09:26.130]during the growing season is still slightly,
[00:09:29.700]positive in terms of net ecosystem productivity.
[00:09:33.600]And then in the off season, which is that lower graph,
[00:09:36.690]you can see the soybeans are really, I have a lot of carbon loss,
[00:09:39.930]good rapid degradation. corn is not too far behind.
[00:09:44.390]and then the Prairie system is in the middle.
[00:09:47.130]So actually compared our corn soybean system to a native Prairie,
[00:09:51.390]to look at these different dynamics. So the question is,
[00:09:56.160]is that that thousand pounds of carbon per acre per year, and you form,
[00:10:00.450]or you farm 40 years, you know, that's 20 tons of carbon,
[00:10:04.830]out of that soil. And so you begin to see these different dynamics.
[00:10:08.760]And we see this, when we look at a lot of these different pieces,
[00:10:12.720]but the question is, everybody says, well, you know,
[00:10:14.700]you've got these Eddy correlation systems that are measuring this well,
[00:10:18.510]what really happened in the soil? And,
[00:10:21.090]and what we've done is that we've actually measured,
[00:10:26.040]within the footprint of that Edie correlation tower on different fields,
[00:10:30.570]to be able to look, look at the same footprint.
[00:10:34.820]And we find that what we get and soil measurements over that
[00:10:39.410]this is a 16 year experiment.
[00:10:42.140]That's all measurement is the same time or same magnitude as their
[00:10:46.580]anticorrelation equipment. So we see this. Um,
[00:10:50.300]and so this intensive tillage,
[00:10:53.000]Don Rakowski has as shown this,
[00:10:56.270]that we've seen that we reduce our soil carbon in the upper surface.
[00:11:01.250]he sells a lot of puffs of CO2 that rapidly go in there because we,
[00:11:06.050]we stir that Sol biology.
[00:11:08.930]it leads the instability of the aggregates at the soil surface,
[00:11:13.010]begin to reduce our infiltration rate.
[00:11:15.620]It limits the infiltration and precipitation because once we begin
[00:11:20.360]to make those aggregates less stable and then raindrops begin to
[00:11:25.220]hit them, they puddle off a surface.
[00:11:28.940]And then we end up with a runoff.
[00:11:31.220]and what we find in a lot of Midwestern soils is that our infiltration rate is
[00:11:36.560]actually less than a half inch per hour.
[00:11:39.560]and a lot of our rainstorms are occurring in this two to four inch rain per
[00:11:43.490]hour. So we,
[00:11:45.800]by changing aggregates near the surface,
[00:11:49.040]we have a tremendous impact on our ability to infiltrate water,
[00:11:53.980]because if we can infiltrate water, we can store water,
[00:11:57.130]but if we're running it off, then we have a problem. And you know,
[00:12:01.540]that everybody has seen this graph over time. It's,
[00:12:04.360]it's an old one from Keith posthuman.
[00:12:07.480]They just analyze the Sanborn plots and the moral plots showing that
[00:12:12.340]as we went from years of cultivation,
[00:12:15.040]and those long-term experiments is that we continue to degrade your organic
[00:12:19.240]matter. and you, you look at across the,
[00:12:22.960]all the different systems,
[00:12:24.310]but they're still showing the same thing that we are losing organic matter out
[00:12:28.600]of our soils. We see all those different pieces going on from there.
[00:12:32.070]So we've been changing our soils ever since we started cultivating them.
[00:12:36.940]and you know,
[00:12:37.570]it really has put us into a situation where we end up seeing scenes
[00:12:42.520]like this. this is a soybean production field.
[00:12:46.870]it's just West of Ames. It is,
[00:12:51.970]two different scenes in there. One is early August.
[00:12:54.790]It was about the 2nd of August, on the left,
[00:12:59.350]that imagery in there,
[00:13:00.730]you can see that there's very little variation across that field.
[00:13:03.700]You see the couple pieces out there. Those are waterways that are,
[00:13:07.960]that are grass in there. Everything else is pretty uniform.
[00:13:11.390]And then in late August, this is roughly three weeks later,
[00:13:15.430]that field has dramatically changed. you see the yellow spots,
[00:13:19.720]you see the light spots in there. You see the stilts, some dark spots in there.
[00:13:23.800]What happened over that three week period is it didn't rain.
[00:13:27.820]and we see this, in there,
[00:13:30.220]the fi the bushels or the yield out of that light colored spots,
[00:13:35.140]25 bushels, and now the dark card spots were 65 bushels.
[00:13:40.150]you know, we could lost 40 bushels,
[00:13:42.070]the acre because it didn't rain for three weeks in August.
[00:13:46.000]So our yield variability in field often comes from that.
[00:13:49.900]Soil is inability to supply water during the grain filling period.
[00:13:53.980]And we see this, across the Midwest. we,
[00:13:58.900]our yield variation,
[00:14:00.850]really begins to show up in that grain filling period because
[00:14:06.070]we don't have the capacity to store that water and make it available back to
[00:14:10.750]that.
[00:14:11.020]So water is going to become one of our major challenges as
[00:14:15.910]we go forward in terms of looking at our agricultural systems.
[00:14:21.820]Hudson showed this in 1994,
[00:14:25.060]that there's a direct relationship between organic matter.
[00:14:28.060]And so a water holding capacity,
[00:14:30.520]that the more organic matter we put in there, we improved our, our soil,
[00:14:35.200]water-holding capacity. And if you look at this, you know,
[00:14:39.250]you move from that two to 4% organic matter on a,
[00:14:43.480]on a silty loam soil is roughly five more days of available water.
[00:14:49.000]and so this is probably one of the number one questions I get is how much does
[00:14:53.750]so organic matter influence water availability or enhance it.
[00:14:57.650]And you just think about this. The upper six inches of soil has got a massive,
[00:15:02.630]roughly 22 million pounds,
[00:15:06.320]organic matter holds about 10 times its weight in water.
[00:15:09.110]So a 1% change in organic matter is,
[00:15:11.900]is about 23,000 gallons and a corn
[00:15:16.730]crop during grain filling uses about 4,000 gallons a day.
[00:15:20.540]So that extra 1% organic matter is five more days of
[00:15:25.310]available water for optimum productivity. and if you look at,
[00:15:29.540]at just rainfall statistics,
[00:15:31.610]the probability of getting a rain within a five day period in the Midwest is
[00:15:36.410]still pretty high.
[00:15:37.310]And so we can alleviate a lot of our stresses by
[00:15:42.380]improving our soil,
[00:15:43.460]water availability and improving the infiltration rates that go through there.
[00:15:47.570]So it really becomes a dynamic that we need to understand and
[00:15:52.460]realize how this all fits together.
[00:15:55.850]here's some data that we,
[00:15:58.010]analyzed across the three different States, in the Midwest.
[00:16:03.440]we related County average,
[00:16:07.610]soybean yields in this case,
[00:16:10.130]each one of those data points on there represents the average of 40 years of,
[00:16:14.390]of data that's collected out of the County level,
[00:16:18.050]through the NASA dataset.
[00:16:20.180]We related that back to the national crop commodity productivity index,
[00:16:24.800]an index that NRCS has in their database.
[00:16:29.360]And you find out that in this NCCP,
[00:16:33.500]I index of zero is basically a parking lot.
[00:16:37.400]One is really high quality soil. So the,
[00:16:39.510]the values of this index of a go from zero to one,
[00:16:44.120]and if you look at, Kentucky, they're on, they have degraded soils.
[00:16:48.800]we end up with a lot of really low yields in there. I will,
[00:16:53.810]is much higher yields. And then there's Nebraska.
[00:16:57.200]That's not showing any relationship and people often ask why,
[00:17:01.310]and that's because we took only irrigated counties out in
[00:17:05.720]Nebraska. So if you can control the water,
[00:17:09.650]the quality of the soil doesn't mean much to you in terms of productivity,
[00:17:15.020]but if you're relying on rain fed conditions,
[00:17:17.660]the quality of that soil is absolutely critical in terms of how do we look at
[00:17:22.460]this? So climate resilience is derived from good soils and rain fed systems.
[00:17:27.140]And we see this with, with corn. We've seen it with wheat,
[00:17:30.770]we've seen it with soy beans.
[00:17:31.790]We've looked at all of these different pieces of the come together.
[00:17:34.580]And if you look at the NCPI, just across the corn belt States,
[00:17:40.340]you know, we've, we've got these dark areas, that,
[00:17:44.330]are really high quality soils. And then we, we move as we move into Missouri,
[00:17:49.140]we move into poor quality soils, all of this. So, you know, we've,
[00:17:53.400]we've looked at this and we moved. And even within counties,
[00:17:56.400]we can start seeing all the different variations that are going on,
[00:17:59.240]but as we change cropping distributions across the
[00:18:03.950]Midwest,
[00:18:05.090]we're going to be often moving them from good soils into poor soils.
[00:18:09.290]And we need to understand that relationship as well.
[00:18:12.890]And if you look across field, I mean,
[00:18:16.250]there's a couple of different fields that we've worked in.
[00:18:19.370]so a water holding capacity can go all the way from 150 to
[00:18:23.870]400, plus millimeters on that, five foot profile.
[00:18:29.180]so you see all these different variation and you go back to that graph that I
[00:18:34.010]showed you in looking at soybean yields,
[00:18:36.500]you can look at the yield monitor data across these fields.
[00:18:39.080]You see that same thing when we've got these low,
[00:18:42.710]water-holding areas of the field, in typical years,
[00:18:46.520]those are often are,
[00:18:47.870]are low yielding parts of it because they lack water during that very specific
[00:18:52.760]time of the year.
[00:18:54.920]So how all of this begins to fit together is what
[00:18:59.870]I'll put back is what I call the soil health pathway is how do we,
[00:19:03.470]how do we change soil health? If,
[00:19:05.710]if we really want to think about this and going back and expanding that diagram
[00:19:10.040]up a little bit is that we need to have a restored biological
[00:19:14.630]activity within that soil.
[00:19:16.580]And what that requires is a biology wants food.
[00:19:21.830]It wants water, it wants air, and it wants shelter,
[00:19:26.000]the same four basic things that you and I want,
[00:19:30.020]is what microbes and biological systems want within the soil. They want to be,
[00:19:36.020]they won't have a drink of water. They won't have,
[00:19:39.770]and they want to have a, basically an undisturbed environment.
[00:19:43.460]Once we supply those four things in that saw microclimate,
[00:19:48.470]then we see an explosion of biological activity.
[00:19:52.070]and we see that rapid organic matter turnover, we see improve nutrient cycling,
[00:19:56.930]and then we see the visible things of improving soil structure, um,
[00:20:01.250]and all these different things that go with that. But all of this,
[00:20:05.510]we need to realize that we're,
[00:20:09.100]we're working in a system that is not just a car
[00:20:13.880]carbon cycle, or it's not a water cycle, or it's not a nitrogen cycle,
[00:20:17.930]but it is the interaction between carbon water and
[00:20:22.610]nitrogen. And you've got the carbon processes in terms of food,
[00:20:25.940]census respiration, or organic matter decomposition,
[00:20:30.410]plant decomposition. you've got the water in terms of what we get in,
[00:20:35.020]in terms of precipitation, but what we,
[00:20:37.850]move back out in terms of evaporation or runoff,
[00:20:41.240]and then you've got nitrogen with either fixation, mineralization,
[00:20:44.750]denitrification,
[00:20:46.550]you got all these different things and these cycles interact over time and space
[00:20:50.830]at different rates. And so, and it's all driven by solar radiations.
[00:20:55.380]So our whole cropping system is really based on how we're
[00:21:00.220]utilizing sunlight
[00:21:03.180]in aspects of the carbon water nitrogen cycle.
[00:21:06.380]And then we get at other nutrients along with this,
[00:21:08.760]but you begin to understand that we deal in a complex system
[00:21:13.440]and that we need to understand these dynamics. Now,
[00:21:17.340]I want to talk about the role in which cover crops really begin to put into this
[00:21:20.760]overall aspect and has now there's a, there's a corn crop,
[00:21:24.390]but that's mature at the end of the season.
[00:21:26.460]And there's a very healthy cover crop, within that,
[00:21:30.810]within those rows in terms of looking at all this,
[00:21:34.530]and you can look at just this role of, of residue on the surface, um,
[00:21:39.930]this passive protective blanket,
[00:21:41.790]if we just leave corn or soybean or wheat residue out there on the
[00:21:46.380]surface, it's a passive protective blanket. it does modify the temperature.
[00:21:51.360]It does modify the moisture conditions because it's protecting that soil
[00:21:54.990]surface, but cover crops are really a very active, protective blanket,
[00:22:00.000]from the rainfall perspective. both of those are the same.
[00:22:04.410]They intercept the raindrop energy allowed to move into that,
[00:22:08.190]that active protective blanket is continually putting,
[00:22:13.080]root material into that.
[00:22:14.850]looking at a lot of the different pieces that go with that and
[00:22:20.040]why this residue becomes important is that I don't think that
[00:22:24.870]we've really understood that a lot of times in our systems today,
[00:22:29.760]our typical conventional systems as that our soil surface temperatures,
[00:22:34.950]are off,
[00:22:36.250]near early part of the season are often above the li lethal limits for
[00:22:40.500]biological activity. and these,
[00:22:44.190]the graph on the left is just the number of hours above 40 degrees centigrade,
[00:22:48.540]or 104 degrees Fahrenheit. you can see in 2010,
[00:22:52.950]very dry in the spring, we had 120 hours that,
[00:22:56.460]that soil surface was exposed to conditions that were lethal
[00:23:01.350]to biological activity. So a lot of cases, what we're doing is we,
[00:23:05.040]we destroy the biological activity because we don't provide any shelter for it.
[00:23:10.020]And, and we see this dynamic going on.
[00:23:13.830]These temperature profiles within the soil become very important in terms of
[00:23:17.580]responding this. We put residue on the surface,
[00:23:21.180]we narrow that temperature profile, but if we've got a bare soil surface,
[00:23:25.500]they have very, very hot temperatures during the day.
[00:23:27.870]And they cooled down extremely to extreme levels at night,
[00:23:31.230]but they're also go from a wet condition to a dry condition very quickly.
[00:23:35.640]And so we take the water piece out of that as well.
[00:23:38.460]So we needed a stable microclimate for these microbes to work.
[00:23:43.590]So we've spent a lot of time at, at,
[00:23:46.880]how systems respond to it.
[00:23:48.980]We build a whole series of things within the laboratory. These are, um,
[00:23:54.650]controlled environment, chambers they're. So columns,
[00:23:58.430]they're roughly two feet in diameter by three and a half feet tall.
[00:24:03.230]we put the plexiglass dividers in there. We ran some initial experiments.
[00:24:08.180]there are six of these in each grow chamber.
[00:24:11.450]we hadn't enough variation among those six that we decided to further
[00:24:16.310]divide them into three. So we could put each treatment a,
[00:24:19.760]into a pie,
[00:24:21.710]within these columns and their instrumental was all moisture, soil,
[00:24:25.970]temperature, CO2, oxygen levels, this,
[00:24:30.680]picture on the right. we've done a lot of comparisons between,
[00:24:35.690]monoculture cover crops, no cover crops and a cover crop cocktail,
[00:24:40.460]from that standpoint.
[00:24:43.490]but what we've seen is that, they not only provide surface cover,
[00:24:48.050]but they enhance the soil biology. they changed the structure,
[00:24:52.040]they influenced production and all of this. So we've, we've grown,
[00:24:56.210]sorghum and wheat, in rotation, in these as well as soybeans,
[00:25:01.880]along with the cover crops to the look at these different dynamics and all of
[00:25:06.590]this. And it's just going to show you just a little bit of data on this.
[00:25:11.240]they saw CO2 levels. If you look at the,
[00:25:14.930]orange line on the top, that's from the cocktail,
[00:25:17.810]there's a lot of biological activity because of increased.
[00:25:20.780]Excavates going into that. then there's the,
[00:25:24.770]the next one is the oats.
[00:25:25.940]And then finally down at the bottom is when we don't have any,
[00:25:30.560]biological input into that, very low respiration rates,
[00:25:35.140]going on because, and there's low biologic activity,
[00:25:39.440]same thing in terms of oxygen, exchanges. and again,
[00:25:43.820]it's just result of the, the diversity of the exit date,
[00:25:47.750]going into that system. Um,
[00:25:50.180]and then we've looked at the changes in aggregate structure. you know,
[00:25:55.160]we see,
[00:25:56.780]that basically anything we do with the cover crop improves it over,
[00:26:01.580]the control in terms of looking at changes in aggregates. And,
[00:26:05.770]and this has changes after about 150 days of these experiments.
[00:26:10.730]and you see the same thing in terms of microbial biomass.
[00:26:14.690]anytime that we've added a cover crop,
[00:26:17.330]we've improved the microbial biomass carbon,
[00:26:20.960]we've influenced the plant growth, as well.
[00:26:24.380]And even to the point of improving yields, where we've looked at this,
[00:26:29.180]and just look at the yield column,
[00:26:32.660]not a difference between the oats and the mix,
[00:26:36.920]but the major improvement in productivity.
[00:26:39.620]And we see the same thing in green sorghas well.
[00:26:43.950]So we began to see all these different changes going on.
[00:26:46.500]So we do see a result in impact.
[00:26:48.690]And part of that is the improvement of the soil structure.
[00:26:51.960]We see these changes in soil structure occurring within, like I said,
[00:26:56.070]130 to 150 days of adding that cover crop.
[00:26:59.310]So we're always seeing that change in the aggregate piece of this,
[00:27:03.720]but I began to think about this overall aspect.
[00:27:08.550]everybody's familiar with the forearm. we talk about, fertilizer.
[00:27:13.080]We talk about nitrogen. We talk about the right rate.
[00:27:15.870]We talk about the right time. We talk about the right place in the right form.
[00:27:19.770]I got to thinking about that relative to water.
[00:27:23.970]and I came up with four RS for water. One is to revitalize it,
[00:27:28.500]that's add organic matter into it. One is to retain it,
[00:27:32.280]uh that's to infiltrate more water.
[00:27:35.730]The other piece of this is to reduce,
[00:27:38.490]the NAS to reduce the evaporation rate so that we're putting more back into this
[00:27:42.870]retrieved piece. That's the transpiration that's going through that crop,
[00:27:48.060]evaporation doesn't improve crop productivity. Transportation does.
[00:27:52.290]And so you look at all of this and it becomes a,
[00:27:56.060]a framework or how we can begin to look at this interaction between water
[00:28:01.080]and nitrogen, and then these different dynamics.
[00:28:04.320]And here's just a healthy cover crop.
[00:28:07.860]and then soybeans coming up out of that,
[00:28:09.960]this is some data that from Wayne Frederick's, up in Mitchell County, Iowa,
[00:28:14.610]where we've been looking at this,
[00:28:16.410]and the reason I show you this slide is that we're,
[00:28:18.540]we're really thinking about what are these attributes of soil health that impact
[00:28:23.490]water, in one of this is this continuous cover on the soil.
[00:28:28.530]we see the continuous cover provides three advantages for,
[00:28:32.430]so water one is it protects it against rain, raindrop energy,
[00:28:37.660]the soil aggregates are protected. We maintain those infiltration rates,
[00:28:42.270]that adding that residue out there reduces this whole water evaporation,
[00:28:46.530]so we can get more used by that plant for transpiration.
[00:28:50.250]And the third piece that we don't often think about is when we begin to
[00:28:55.200]modify that soil surface and protect it,
[00:28:57.750]so that as a cooler and wetter,
[00:29:00.930]as we find that there's a lot of plant roots near that surface,
[00:29:04.590]and they take advantage of small rains, half inch rains,
[00:29:09.180]don't penetrate very deep in there, but if the roots are there,
[00:29:11.820]we can make use of them. if we've got a conventional tilled system,
[00:29:16.320]we find out that our roots may be only six or,
[00:29:19.710]or they're not within that upper six inches.
[00:29:22.320]So it takes quite a bit of water and dry us all to move it down there.
[00:29:25.800]So we can take advantage of these small rainfall events and that,
[00:29:29.910]for a lot of our areas that becomes quite important.
[00:29:35.190]We'll look at soil health and water,
[00:29:37.590]there's attributes and soil health that, impact our water significantly,
[00:29:43.630]cover crops are continually supplying food to the microbial populations.
[00:29:48.580]they supply organic matter to the create that stable, organic,
[00:29:53.440]system, basically the, the glucose and the,
[00:29:56.560]and the carbohydrates coming out. And then there's a third,
[00:30:00.040]there's a recycling of nutrients. And we see that when we add to cover crops,
[00:30:04.750]we see an,
[00:30:05.530]an increase and a chlorophyll content late in that growing
[00:30:10.270]season, because we've been able to cycle those nutrients to keep it going.
[00:30:15.430]And if you look at this just a little simple diagram,
[00:30:18.520]if we have low aggregate stability, we get a raindrop or rain on it.
[00:30:23.260]we immediately start dissolving it back to sand, silt and clay.
[00:30:28.180]We clog up all the pores and we ended up with a slow infiltration and high
[00:30:33.010]runoff.
[00:30:34.060]If we've got really high aggregate stability of it stays together,
[00:30:38.920]and we continue to promote that infiltration rate, into the soil.
[00:30:44.680]So I, I just want to spend a little bit of time finishing up talking about some
[00:30:47.890]changes and fields,
[00:30:50.140]that occur because we often are concerned about when this occurs.
[00:30:55.180]These are some data we analyze from Wayne. Frederick's again,
[00:30:58.000]up in Mitchell County, 1992, he switched his system to no,
[00:31:02.290]till soybeans 2003.
[00:31:04.720]He switched it an added the strip till corn 2012.
[00:31:09.700]he really,
[00:31:10.690]had cover crops over all these fields and what we've seen in that time,
[00:31:15.550]and as just an example of, the strip till and the cover crops,
[00:31:19.990]you can see that there's a lot of residue between that,
[00:31:23.590]planning into that the strip-till condition with the cover crops still there.
[00:31:28.180]and he's, he's supplied us with lots of data. So we have so organic matter,
[00:31:33.190]we actually have yield monitor data that we analyze from 2003 to
[00:31:36.910]2018. and then we have the 19 and 20 data now as well.
[00:31:42.160]We have weather data.
[00:31:43.750]we also looked at the Mitchell County yield data because we were interested in
[00:31:47.650]what he was doing relative to the average County.
[00:31:51.100]We looked at saw organic matter changes. We've looked at fuel versus County,
[00:31:55.900]field uniformity of yield, and then weather resilience. So all of these things,
[00:32:00.190]what are they doing to us in terms of production system?
[00:32:04.570]Here's his, organic matter, 84.
[00:32:08.950]And then that red line is when he switched over to, do a no till soybeans.
[00:32:14.070]You see that we began to increase the organic matter over time.
[00:32:19.420]there's been a two and a half percent increase over 25 years.
[00:32:24.430]roughly he's been storing about, eight tenths of a ton,
[00:32:29.050]in that, soil on, on carbon over that period of time. And you'll see,
[00:32:33.610]we've changed some fields,
[00:32:36.010]from 3.3 to 6.1%,
[00:32:39.740]and that the fence rows are, and around that area are six to 9%.
[00:32:43.760]So we're getting those fields back up and all of this,
[00:32:48.230]what I've been more fascinating with as the, the change in the,
[00:32:52.880]the frequency distributions of yields within soils within the field,
[00:32:57.350]we took the yield monitor data. We segregated it by the soil types within that.
[00:33:02.420]this is just your stranded alone, soil. See in 2004,
[00:33:07.130]there's a lot of,
[00:33:08.420]frequencies in which we had low yields and by
[00:33:12.260]2018, we'd taken the low yielding parts of that saw out.
[00:33:17.240]and so we got a lot tighter distribution around that.
[00:33:22.160]we changed the skewness and kurtosis, and, and this yield distribution,
[00:33:27.290]just another soil. This is the Franklin silt loam.
[00:33:30.800]You can see that again, over that,
[00:33:33.350]2003 to 2017 for this particular
[00:33:37.970]field, that we saw that change.
[00:33:41.360]And so when we began to take the low yielding parts of that field out,
[00:33:45.050]we begin to really improve the profitability of that field.
[00:33:49.310]So if you look at the shifts from negative to positive,
[00:33:51.920]skewness increasing kurtosis,
[00:33:54.890]you're tightening that distribution amount in the mean,
[00:33:57.890]the more we shift to the right, the greater, the income in the field,
[00:34:01.130]because we have less low yielding areas and a greater proportion of that
[00:34:05.870]field becomes a profit center.
[00:34:07.620]And so when we start looking at profitability and,
[00:34:11.390]and resilience across that, we see all these different pieces coming into play.
[00:34:15.620]so we've analyzed this for
[00:34:19.850]all those years, and we actually had 10 fields, that we looked at.
[00:34:23.660]So it was quite a different piece of this,
[00:34:27.020]but I think this really kind of summarizes what we began to see is when we
[00:34:31.820]looked at his yields,
[00:34:34.880]and we looked at Mitchell County in particular,
[00:34:37.340]we found that county-level yields,
[00:34:40.430]were negatively correlated with April and may rainfall.
[00:34:44.660]the more it rains in April and may the lower the car average County yield,
[00:34:49.100]because, we have disruption, we may have delayed planning.
[00:34:52.910]We have may have poor vigor early in the season.
[00:34:56.840]yields are positively correlated with July, September rainfall.
[00:35:00.230]The more rains in those months, the better the yields,
[00:35:03.500]because we're water limited at that time.
[00:35:06.740]And if we look at the water use efficiency of your systems on corn,
[00:35:11.420]basically,
[00:35:13.220]somewhere in that 40 to 50% increase in terms of water use efficiency,
[00:35:17.750]we're making much more use of any raindrop that fell in there
[00:35:22.520]because we were reducing evaporation. We're putting in, into that crop.
[00:35:26.240]We improved the overall growing conditions.
[00:35:28.730]We saw about a 26 to 30% increase in soybean water use
[00:35:33.050]efficiency,
[00:35:34.280]and then the profitability of those fields increased because the yields became
[00:35:39.180]more uniform. We actually looked at field scale, uniformity changes,
[00:35:43.230]and we see those fields becoming more uniform, along with that.
[00:35:48.860]So when you think about not all of those with the cover crops and the reduced
[00:35:53.420]tillage is that that soil is capable of storing more water.
[00:35:58.310]we ended up greater infiltration of rainfall events.
[00:36:02.120]We have more resilience in years with an uneven distribution rainfall.
[00:36:06.260]We went back and looked at rainfall distributions,
[00:36:09.110]find out that he's really a little more resilient to those
[00:36:13.700]reduction in correlations with the excessive spring and deficit summer rainfall.
[00:36:18.800]is that his fields over time,
[00:36:21.680]we're not showing those same correlations,
[00:36:24.650]because he's able to plan on time because he can traffic when the cover crop,
[00:36:29.210]you can do all these different things,
[00:36:31.730]but the ultimate is that that increased ability to convert Seoul water into
[00:36:35.570]grain.
[00:36:36.350]And that's really what we're all about when we think about these different
[00:36:39.590]dynamics going on.
[00:36:42.050]So you look at this overall aspect and there's a piece of this puzzle that we've
[00:36:46.010]begun to explore in these data,
[00:36:47.990]as well as other pieces of our data sets is that there's enhancing soil
[00:36:52.760]health, recycles, nutrients, both macro and micronutrients.
[00:36:58.190]we see this when we look at leaf chlorophyll maintenance during the
[00:37:02.150]greenfielding period, when we improve our soil health,
[00:37:06.530]and we begin to change that soil is that we do maintain a greater
[00:37:11.360]length of Greenleaf area, in all of this.
[00:37:15.950]and there is a linkage between effective use of
[00:37:20.420]nutrients and water visibility.
[00:37:23.420]as we have that water to grow that plant,
[00:37:25.610]we can make more use of the nutrients that are there,
[00:37:28.430]and the more we can increase our soil health,
[00:37:30.980]we can decrease the nutrient input of nutrients as well,
[00:37:34.280]because we get a lot of that recycling going on throughout the whole group long
[00:37:38.090]season. So if we want to enhance our soil,
[00:37:43.130]we've got to,
[00:37:46.190]think about the fact that for growth of that microbial system in there is that
[00:37:51.110]we need excess energy above maintenance cover crops,
[00:37:54.500]or the way in which we get our excess energy. Um,
[00:37:57.500]because that energy that we're putting into the soil is really carbon,
[00:38:02.090]and it's carbohydrates.
[00:38:03.500]And so cover crops are taking that same process that we're trying to
[00:38:08.300]grow grain with and taking,
[00:38:11.780]sunlight and CO2 and water and converting it into carbohydrates,
[00:38:16.160]putting that into the soil,
[00:38:18.110]that we can create that excess energy to be able to change the soil.
[00:38:22.240]And we need to understand more about why, and, and the length of that process.
[00:38:27.800]We also ended up with a water questions, you know, gay Basque, you know,
[00:38:32.150]what's carbon really worth in the soil. And if you look Wayne's day,
[00:38:35.810]you look at some of these other pieces,
[00:38:37.690]we're talking about him and prove profitability.
[00:38:40.900]That may be on the order of 50 to a hundred dollars per acre. Um,
[00:38:45.310]now the one is what's more valuable water or nutrients. you know,
[00:38:49.750]both are valuable, but our whole goal and,
[00:38:54.370]and challenge will be,
[00:38:55.480]as we go into the future is how do we manage water and how do we manage this,
[00:38:59.800]more variable water supply for the precipitation?
[00:39:04.180]Always get a question on what's the upper limit of soil carbon. you know,
[00:39:08.350]you go back to our Prairie soils across the Midwest. you know,
[00:39:11.980]we were at that nine to 10, 12%. and so, you know,
[00:39:16.600]I think that we can get there,
[00:39:18.490]but we were going to have to think strategically of,
[00:39:21.380]of how we began to change that part of that soil or that cropping system to do
[00:39:26.110]that. But ultimately,
[00:39:31.180]our change in farming systems,
[00:39:33.820]we need to be thinking about how do we become more efficient in our use of water
[00:39:38.140]or efficient use of nutrients and our fishing use of light,
[00:39:41.130]because we're really all in the solar capture business.
[00:39:45.190]that's what we're doing when we're growing crops. Um,
[00:39:47.800]but we relying on water nutrients to be able to do that. So,
[00:39:52.480]with that, then the slide deck that, that you get, if you want it,
[00:39:57.250]here's my contact information. I have a Gmail account.
[00:40:02.110]they take away my government account and as soon as I retire, so,
[00:40:06.160]in all of that, so I'll
[00:40:09.460]be
[00:40:09.700]able to answer any questions.
[00:40:12.420]As well. So.

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2021 Nebraska Cover Crop and Soil Health Conference - Jerry Hatfield

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