Soil Health – How Management is Affecting the Pulse of Soil

Alan Franzluebbers, USDA – Agricultural Research Service, Raleigh, NC Author

02/16/2021 Added

63 Plays

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Soil is alive, and how we manage it reveals to us our ecological influence. We can be dominating or nurturing and soil will let us know what it can tolerate from us. This presentation will focus on soil ecology and management issues relevant for achieving more sustainable agricultural systems.

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[00:00:00.810]The following presentation is part
[00:00:02.720]of the Agronomy and Horticulture Seminar Series
[00:00:05.850]at the University of Nebraska-Lincoln.
[00:00:10.550]Welcome to today's department of agronomy
[00:00:13.250]and horticulture spring seminar series.
[00:00:16.580]Today, I get the pleasure
[00:00:17.670]of welcoming Dr. Alan Franzluebbers.
[00:00:21.086]Alan is a native Nebraskan,
[00:00:24.550]he receiving his bachelor's science
[00:00:26.980]and masters of science at the University of Nebraska-Lincoln
[00:00:31.360]and a PhD from Texas A and M University.
[00:00:36.320]Alan is a research ecologist
[00:00:38.707]with the USDA ARS Plant Sciences Research Unit
[00:00:43.720]out of Raleigh, North Carolina.
[00:00:46.160]And those of you that attended American Society of Agronomy
[00:00:50.090]Crop Science Society Soil science Society
[00:00:53.590]of America annual meetings,
[00:00:55.170]you've probably heard Alan speak before
[00:00:57.360]and that's where I first met Alan
[00:00:58.830]and I've always enjoyed hearing his talks.
[00:01:01.830]Some of his work includes working a lot
[00:01:04.550]with pastures and that's always been my research interest.
[00:01:08.630]And so that has fit well
[00:01:10.360]and I'm happy to happy to hear Alan speak today
[00:01:14.580]but a couple things also about Alan,
[00:01:17.920]he's a Fellow of the Soil and Water Conservation Society
[00:01:23.130]and a Fellow of the American Society of Agronomy
[00:01:25.780]and the Soil Science Society of America.
[00:01:29.580]But now Alan, when you're ready, I'll go ahead
[00:01:32.210]and turn it over to you and you can begin.
[00:01:35.240]Thanks.
[00:01:37.550]Thank you, John, for that introduction.
[00:01:39.480]Great to be here with you.
[00:01:40.620]And I was always talking, telling my wife
[00:01:43.010]I'm going to Lincoln today.
[00:01:44.360]So here I am in the cold weather of Lincoln, Nebraska.
[00:01:48.980]I remember it some 30 years ago
[00:01:52.140]I was born in the dust of Nebraska.
[00:01:55.850]I grew up in the Bohemian Alps of...
[00:01:59.120]Close to the Bohemian Alps
[00:02:00.380]of the Northeast part of the state.
[00:02:03.310]And I did do my undergraduate
[00:02:05.920]and a little bit of graduate work in Nebraska.
[00:02:09.660]And I had grandparents that lived near the Bohemian Alps
[00:02:14.560]and actually farmed in there.
[00:02:16.496]They called them that because they, you know,
[00:02:18.650]some rough Hills out there.
[00:02:20.410]And I'm showing you some pictures that I took back
[00:02:23.240]when I was in Nebraska as an undergraduate
[00:02:26.370]and researcher in my master's program
[00:02:29.393]to show you what would kind of inspired me
[00:02:33.740]and dust didn't truly inspire me but it was something
[00:02:37.900]that was quite devastating on my psyche.
[00:02:40.770]And I believe that that helped me to understand a little bit
[00:02:44.700]about nature and what we should be doing
[00:02:47.824]to kind of manage our natural system.
[00:02:51.510]There were a lot of good days in Nebraska
[00:02:53.490]but there were some tough days too.
[00:02:56.390]One of the things that I was charged with
[00:02:59.010]was to work on a project to look at nitrogen management
[00:03:02.600]in various cereal grain systems
[00:03:05.260]and of course that would mean corn, but also sorghum.
[00:03:09.460]And so we took a soil samples for deep nitrate
[00:03:12.750]and that was one of the primary reasons
[00:03:14.760]that we were conducting this research
[00:03:16.680]and we would harvest various plots
[00:03:19.590]either with strips or small plots
[00:03:21.439]and it gave me a really good experience.
[00:03:24.300]And it's interesting because some of my recent research
[00:03:27.640]returns to those same very techniques.
[00:03:30.620]So Dr. Charles Francis was my mentor and Dan Walters
[00:03:35.910]and I really enjoyed the time there
[00:03:38.768]and it's served me well.
[00:03:41.700]So these are some of the publications
[00:03:43.300]that we heard from the research that was done during
[00:03:46.540]when I was employed as a research technologist
[00:03:49.510]at the time with Dr. Mike Johnson
[00:03:51.556]and I worked as a student, a master's student
[00:03:56.110]under Charles Francis.
[00:03:57.640]So Chuck was a great mentor.
[00:03:59.840]He taught me a whole lot.
[00:04:02.540]And I know that those of you that know him
[00:04:05.371]know that he's got a lot of great ideas.
[00:04:08.690]And I learned to, I was really inspired
[00:04:11.250]by many of those great ideas
[00:04:13.650]but also you have to know that people have to do things
[00:04:17.110]and get things done
[00:04:18.020]and he was really able to assemble teams
[00:04:20.600]that that could do that.
[00:04:22.380]There's another person there at the university
[00:04:24.430]that inspired me as well.
[00:04:26.070]Dr. John Duran.
[00:04:28.710]Now, I did not study with him
[00:04:30.640]and did not have a close association
[00:04:32.830]but I understood what his work was about.
[00:04:36.610]I tried to be close to the thought process of him.
[00:04:42.100]And I know he was a big mentor in the world of soil quality
[00:04:47.710]which has transformed into the term soil health nowadays.
[00:04:51.280]And that's led me to explore more during my PhD when I moved
[00:04:55.740]to Texas and went to the Aggies and looking at soil quality.
[00:05:01.500]So we have a long list of soil chemical indicators.
[00:05:05.120]I'm familiar with many of them.
[00:05:07.040]I'm sure many of you are as well
[00:05:08.900]and these all can serve us well.
[00:05:10.980]There are a lot of physical indicators
[00:05:12.840]that we can be concerned with
[00:05:14.770]and these are something that I think
[00:05:16.870]that are important because a lot of them are visual
[00:05:19.420]and so we can kind of see them.
[00:05:21.250]We can see aggregate stability.
[00:05:22.810]We actually can see it rather than just measuring.
[00:05:26.180]And of course, you know water is important
[00:05:28.560]and temperature and porosity.
[00:05:30.730]All of these things are our long list of indicators.
[00:05:34.310]And of course, then the biological indicators
[00:05:37.060]which at the time when John Duran was researching
[00:05:41.160]and I overlapped during my time in Lincoln,
[00:05:44.180]I thought there was of course,
[00:05:46.110]this was a new area and this was something
[00:05:48.410]that we had opportunities to work on.
[00:05:52.087]And so when I moved to Texas I did actually explore
[00:05:54.700]a lot of these things and they gave me a good opportunity
[00:05:57.800]to focus in on some things.
[00:06:01.000]No, I really appreciated the NRCS movement
[00:06:04.940]and for soil health because although it had science
[00:06:08.710]as some background,
[00:06:10.510]it was more of an emotional push.
[00:06:13.447]And I think this was something that is really important
[00:06:18.830]by the leaders in the organization
[00:06:21.170]that if they feel strongly about it,
[00:06:22.830]they can make things happen.
[00:06:24.520]So I'm always encouraged by some aspects of government
[00:06:28.490]and of course, you know,
[00:06:29.323]there's some frustrating parts as well.
[00:06:32.430]But the soil health principles
[00:06:33.760]that they promoted ,I think are really important, you know
[00:06:36.350]of minimizing disturbance,
[00:06:38.180]maximizing soil cover,
[00:06:41.070]maximizing living roots and encouraging biodiversity
[00:06:45.240]whether that's plants or animals.
[00:06:46.870]And of course, we'd like to think
[00:06:48.460]that that occurs in the soil as well.
[00:06:50.860]And I think these principles are really important
[00:06:53.980]and we should really focus on them
[00:06:56.080]because we can actually have agricultural production
[00:06:59.180]with conventional approaches
[00:07:00.470]that don't follow these principles.
[00:07:02.540]But in fact, if we follow these principles,
[00:07:05.460]almost always we can find systems
[00:07:08.550]that can be developed that are equally productive
[00:07:11.460]but much more favorable for the environment
[00:07:14.070]and we really need to focus on the environment
[00:07:17.120]because it's our future.
[00:07:19.260]We can't destroy our environment.
[00:07:21.650]So in soil health science
[00:07:23.690]we want to focus on various functions
[00:07:25.710]and these are some of the functions
[00:07:27.080]that I think are important.
[00:07:28.500]There may be others but these are generally agreed upon.
[00:07:32.510]You know, such as producing plants for food and fiber
[00:07:35.440]and protecting water quality,
[00:07:37.330]storing carbon, cycling nutrients,
[00:07:40.370]creating a reservoir for biodiversity.
[00:07:43.170]All of these are very important.
[00:07:46.120]And you see in this graphic,
[00:07:48.820]I've assembled some of them.
[00:07:51.710]And this is where I'm going to take you down
[00:07:55.850]a little bit of research that I've conducted
[00:07:59.020]of focusing on two aspects,
[00:08:02.090]producing plants and food,
[00:08:03.590]and cycling nutrients.
[00:08:05.100]Because these are two of the very most important
[00:08:08.250]across many agricultural ecosystems.
[00:08:11.220]And I believe that soil test biological activity
[00:08:15.490]is a strong indicator of these two functions of soil
[00:08:20.200]but as well, it's likely,
[00:08:23.410]and we have some evidence
[00:08:24.760]but we don't have all the evidence,
[00:08:26.710]that is related to many of these other functions of soil.
[00:08:29.660]So a simple soil test indicator
[00:08:32.640]could be something that we could use very effectively
[00:08:35.930]to help us manage our land better.
[00:08:40.110]So what is soil-test biological activity?
[00:08:42.310]Well, it is the carbon mineralization that accumulates
[00:08:46.360]during an incubation.
[00:08:48.470]And when I say accumulate,
[00:08:50.640]we have this flush of activity
[00:08:52.310]when we dry a soil and re wet it,
[00:08:54.610]there's a burst of activity of CO2
[00:08:57.100]and then a stabilization of that activity
[00:08:59.980]called basal soil respiration.
[00:09:02.230]When I first started at Texas A and M,
[00:09:04.720]I was told you have to rid yourself
[00:09:07.020]of the flush and focus on basal soil respiration.
[00:09:10.440]That's what we should focus on.
[00:09:12.390]So at the time that was the general thought process
[00:09:16.040]but actually we looked at the flush
[00:09:19.210]of activity because the response that we get
[00:09:22.470]from the first few days relative in this case
[00:09:26.054]of these different depths here,
[00:09:28.930]is relatively the same whether it's at three days,
[00:09:32.720]at 10 days or 24 days.
[00:09:35.250]And so we looked at this more closely
[00:09:38.330]and looked at it to try to use the flush of activity.
[00:09:42.040]CFA could be some indicator that would be relatively simple
[00:09:46.270]or rapid and reliable.
[00:09:48.780]And so the procedure is simply incubating soil
[00:09:51.660]into a canning jar along with, in this case,
[00:09:55.090]the way that I've developed the procedure
[00:09:57.680]is to use an alkali trap.
[00:09:59.490]One could also use an infrared gas analyzer
[00:10:01.820]or a gas chromatograph but we have to detect the CO2
[00:10:04.970]that's evolved from the soil that has reread it.
[00:10:08.057]And that's the key here.
[00:10:09.440]Is simple incubation procedure
[00:10:12.770]that we measure the respiration of soil.
[00:10:16.690]So with that, perhaps, I don't know all
[00:10:20.450]of the reasons why it occurred this way
[00:10:22.370]but there are different methods
[00:10:24.020]that people have chosen to use
[00:10:25.710]for this simple respiration test.
[00:10:28.340]The key though, is that all of these methods
[00:10:30.670]whether it's in my lab
[00:10:32.140]at the Soil Ecology and Management Lab
[00:10:33.920]in NC state University
[00:10:35.552]or the Haney Soil Health Test
[00:10:38.050]or at Solvita-Woods End Lab
[00:10:40.520]or Cornell's Comprehensive Assessment of Soil Health,
[00:10:44.200]all of them use a dried soil that is re wetted.
[00:10:48.590]How you dry it,
[00:10:49.930]what happens to the soil
[00:10:51.500]and how it's manipulated prior to incubation
[00:10:55.500]can have an effect.
[00:10:56.720]So we've looked at some of that.
[00:10:58.338]We have some data on that
[00:11:00.030]and shared that in the public domain.
[00:11:03.370]It does matter but probably it wouldn't matter
[00:11:07.960]if one just settled on the method itself.
[00:11:11.100]So the actual soil mass is important as well.
[00:11:14.730]I believe that we have a lot of variability in soil
[00:11:17.840]and so more soil is better.
[00:11:19.960]Now I've looked at even more soil than what I've shown here
[00:11:23.020]for our 50 grams sub samples that I've used in my research.
[00:11:28.160]That's kind of what we settled on.
[00:11:30.040]We've tried to use more and actually we get some suppression
[00:11:33.196]of the respiration and so we're not detecting as much.
[00:11:35.760]So I think that we're at an optimal level
[00:11:38.470]but there are other research groups
[00:11:40.960]that are trying to use less soil.
[00:11:42.940]I think it's not wise to use less soil,
[00:11:45.890]say less than 10 grams.
[00:11:47.600]It's something that creates perhaps less sensitivity.
[00:11:53.820]How one adds water is also important.
[00:11:56.860]My colleague, Rick Haney developed a procedure
[00:11:59.680]to re wet the soil from capillary action
[00:12:03.360]by using basically small holes in a container
[00:12:06.450]allowing water to wick up
[00:12:08.150]and essentially reach near saturation.
[00:12:10.830]It's not fully saturated but it's near saturation
[00:12:13.640]and this causes problems in certain types of soils.
[00:12:16.850]And the research that I've done shows
[00:12:19.250]that it actually is more of a problem in sandy loam soils,
[00:12:23.982]sandier texture rather than finer textures.
[00:12:26.340]Which was a little bit opposite to my presumption
[00:12:30.400]but it does show that some soils are negatively affected.
[00:12:33.830]So optimizing the water content
[00:12:35.820]with air content is really important.
[00:12:38.920]And then the biggest thing that is really kind
[00:12:41.390]of different is that we now have
[00:12:43.470]in the literature showing methods
[00:12:45.640]that can incubate for one day,
[00:12:48.390]for three days, four days.
[00:12:50.990]Can be of course, longer 10 days, 24 days, 28 days, 60 days.
[00:12:56.600]But the point, if we want to use it as a soil testing tool
[00:12:59.730]we need to use a short period of time.
[00:13:02.320]My research would show that actually three days
[00:13:06.560]is really a good optimum.
[00:13:09.420]It's possible to use one day.
[00:13:11.290]It's just that of course
[00:13:13.640]the narrower timeframe creates more variability.
[00:13:18.960]And then how we detect the CO2 is also important.
[00:13:21.959]Not that I think it really matters too much
[00:13:24.590]because I think all of them are relatively reliable
[00:13:27.390]but there are different ways.
[00:13:29.160]In my lab we use an asset titration
[00:13:31.400]with a sodium hydroxide trap
[00:13:35.940]to capture the CO2 because CO2 is a weak acid
[00:13:39.840]if it's trapped in the sodium hydroxide
[00:13:42.600]and then we back titrate
[00:13:43.890]with acid to a phenolphthalein endpoint.
[00:13:46.910]You can use an infrared gas analyzer
[00:13:49.790]and of course the idea by Solvita
[00:13:52.610]to use a simple gel paddle makes it so that it's a quick
[00:13:57.670]and readily available test that people can use simply
[00:14:01.720]by ordering a kit and you can do it relatively easily.
[00:14:05.030]So that's of course an advantage.
[00:14:07.290]But of course, then you think
[00:14:08.500]about the cost that accumulates over time
[00:14:10.830]and that could be maybe a disadvantage at that point.
[00:14:13.780]So, but for a research situation
[00:14:16.200]we wanna use a good analytical methods.
[00:14:20.600]So, I believe there are some key considerations
[00:14:22.654]when we use the soil-test of biological activity
[00:14:25.324]and that's that we need to first start
[00:14:26.680]with a representative sample from the field of influence.
[00:14:30.120]This is important for any soil analysis
[00:14:32.250]but I think it's worth repeating here.
[00:14:35.050]We want to define the soil depth
[00:14:36.570]because as you see on the graphic here,
[00:14:38.270]that almost always the surface depth
[00:14:40.341]has more biological activity than deeper
[00:14:43.360]in the soil profile.
[00:14:44.710]So we want to make sure that we define
[00:14:46.470]the soil depth well.
[00:14:48.847]In this case, we dry the sample at 55 degrees Celsius
[00:14:52.880]for three days, and that's so that we are normalizing
[00:14:56.860]all soils to optimum condition.
[00:14:59.268]It's possible to perhaps go with an air-dried sample
[00:15:03.260]and I think that would be really interesting and valuable.
[00:15:06.110]It's just that getting a uniform dried sample
[00:15:08.690]takes more time than at a lower temperature.
[00:15:11.440]And so that's an issue.
[00:15:15.523]I believe that it's important to save the soil coarsely
[00:15:19.550]and this is somewhat of an optimization as well
[00:15:22.480]that traditionally soil is sieved to two millimeters
[00:15:26.690]but there's not really good evidence to why that occurs.
[00:15:30.480]I think it's just a historical precedence.
[00:15:33.290]And of course, if we get too course of the soil
[00:15:36.120]then we start getting into variability
[00:15:38.630]and certainly there's variability with 4.75
[00:15:42.000]but of course in sandy soils
[00:15:43.457]it doesn't matter if it's sieved
[00:15:45.350]through two millimeters or 4.75
[00:15:47.390]it's pretty much all the same condition.
[00:15:51.020]And then we re wet to 50% Water-Filled Pore Space
[00:15:54.310]So that half of it is water,
[00:15:55.810]half of it is air of the pore space,
[00:15:58.160]incubate at a constant temperature.
[00:16:00.110]This is really important because some research
[00:16:02.540]would indicate that if we're not defining
[00:16:06.390]the temperature very well we're getting variable results.
[00:16:10.260]And then you have to have some accurate determination
[00:16:12.207]of the CO2 and in this case,
[00:16:14.570]we use alkali trap with titration.
[00:16:18.180]So getting to the what does this represent?
[00:16:21.640]And then in this case,
[00:16:25.280]this was a task that was done in North Georgia
[00:16:28.250]where we had a longterm, no tillage
[00:16:30.510]versus disk tillage system.
[00:16:32.877]This graphic here shows that
[00:16:36.540]there's relatively uniform distribution
[00:16:38.430]with this disk tillage.
[00:16:39.620]Of course, there's a little bit of stratification.
[00:16:41.230]And again, all soils tend to have higher
[00:16:43.610]or higher biological activity,
[00:16:45.160]higher organic matter very near the surface
[00:16:47.600]and declining with depth
[00:16:48.970]but it's much more stratified with no tillage.
[00:16:52.060]And in this case, it shows that a trend between no tillage
[00:16:55.270]and disk tillage that is very similar
[00:16:56.780]to soil organic carbon
[00:16:58.966]or total nitrogen or soil organic matter.
[00:17:02.590]And so something that seems to reflect
[00:17:04.491]the organic distribution.
[00:17:08.530]We've also tested it in grazing systems.
[00:17:10.900]In this case here the soil test biological activity
[00:17:13.910]on the Y-axis compared to years of management
[00:17:16.682]of establishing a Bermuda grass pasture
[00:17:20.550]whether it's hayed, unharvested
[00:17:23.140]or with low or high grazing pressure.
[00:17:25.720]And this Bermuda grass pasture
[00:17:27.050]was following a tilled crop land situation.
[00:17:29.670]So there was a large increase
[00:17:31.650]that occurred with all systems
[00:17:34.490]but there was a greater increase that was occurring
[00:17:36.830]with the recycling of the pasture forage
[00:17:40.410]through the dung and the consumption by the animal
[00:17:43.080]through the dung and re deposition onto the pasture.
[00:17:45.990]So we were improving the soil more
[00:17:48.270]with the grazing than without grazing.
[00:17:53.630]Interestingly, we also looked at some aggregation data
[00:17:58.330]and this was from a study in North Georgia as well.
[00:18:02.220]And we looked at the relationship
[00:18:03.820]between soil tests biological activity
[00:18:05.800]and mean-weight diameter of water stable aggregates
[00:18:09.080]and there was a relatively reasonable relationship.
[00:18:13.180]I think there's more data that could be developed
[00:18:16.720]to show that there's probably some association.
[00:18:19.530]There should not be a strict association
[00:18:21.670]because aggregation is also
[00:18:23.195]a mineralogically determined property
[00:18:26.852]but it is affected by biological activity
[00:18:29.970]and it does show that there is some effect here.
[00:18:34.470]And finally, I wanted to bring your attention
[00:18:37.090]to possibly some work that needs
[00:18:39.130]to be developed even further
[00:18:40.920]but this shows the bacterial diversity in soil
[00:18:43.531]was related to the biological activity.
[00:18:46.360]So diversity and activity could be related
[00:18:49.460]under some situations
[00:18:51.390]but I don't know that it's always going to be related
[00:18:54.190]but in this case my colleague was able to sample soils
[00:18:58.230]from Lake of Prairie
[00:19:00.310]and then from our studies in Georgia
[00:19:02.790]both under grassland systems
[00:19:05.370]and showing that with higher activity
[00:19:08.220]there tended to be greater bacterial diversity.
[00:19:11.750]But there was a point here where there was not
[00:19:14.146]such a strong relationship.
[00:19:15.710]And so if we exclude this point,
[00:19:18.830]this is significant statistically
[00:19:20.830]but if we include this one,
[00:19:22.310]it's really just a marginal relationship there.
[00:19:25.510]So I think there is a possibility
[00:19:27.110]that there can be some association
[00:19:29.591]but I don't know that it's a strict association.
[00:19:33.800]I'd like to take you now to what I believe
[00:19:35.820]are, you know, relatively solid, strict,
[00:19:39.680]repeatable relationships that I've observed over a decade,
[00:19:45.599]more than a decade of research.
[00:19:47.890]So this is between the biological activity
[00:19:50.590]that flush of activity and the basal Soil respiration.
[00:19:53.720]Basal soil respiration being the more linear portion
[00:19:56.660]of the cumulative carbon mineralization curve
[00:19:59.750]and looking at soils from throughout the Eastern US,
[00:20:04.700]we basically see a direct relationship
[00:20:07.040]between basal soill respiration
[00:20:09.390]and soil-test biological activity.
[00:20:14.180]We can go to the tropics and I've had collaborations
[00:20:17.330]with students from from the tropical regions
[00:20:20.120]primarily in Brazil, as well as in Guam
[00:20:23.250]and that's those samples incubated
[00:20:25.810]in the laboratory show a very similar response
[00:20:28.340]if we get this by the flush of activity
[00:20:30.770]compared to the basal respiration,
[00:20:32.570]very similar response.
[00:20:34.200]And we take samples from collaborations from out West,
[00:20:38.295]we also see a strong association
[00:20:41.840]and the point being that really across all three
[00:20:44.510]of these regions there's really very little variation
[00:20:46.940]in the slope that occurs here.
[00:20:48.910]And so really the internally,
[00:20:51.180]the cumulative carbon mineralization curve
[00:20:53.560]can easily be predicted from just the flush of activity.
[00:20:57.470]So that gives us a lot of confidence
[00:20:59.220]because these are very different types of soils.
[00:21:03.260]So I wanted to also bring your attention
[00:21:05.180]to a fact that most everyone asked me,
[00:21:07.970]well, yeah, this could work for certain soil types
[00:21:11.870]but maybe not for all.
[00:21:12.870]And texture is one of the biggest things
[00:21:14.640]that we can see as differences among regions.
[00:21:17.630]So we looked at soils from throughout North Carolina
[00:21:20.930]and Virginia and we have a great diversity
[00:21:23.360]of conditions that we can identify in this region.
[00:21:26.502]And in soils that were relatively sandy
[00:21:29.600]or with less than 20% clay,
[00:21:32.340]we see a strong relationship
[00:21:33.870]between Soil test biological activity
[00:21:36.370]and net nitrogen mineralization.
[00:21:39.060]So this nitrogen mineralization is during 24 days,
[00:21:43.292]we standardize this procedure for nitrogen mineralization
[00:21:47.180]just as much as the standardization
[00:21:48.880]for this whole test biological activity.
[00:21:50.930]And over and over we see kind of similar relationships.
[00:21:54.600]And I'm gonna say that even with medium textured soils
[00:21:58.430]with 20 to 30% clay,
[00:21:59.970]which I suppose would be considered,
[00:22:02.340]you could imagine that silt loans
[00:22:04.390]and perhaps even silty clay loans
[00:22:06.390]in Nebraska might fit this textural class.
[00:22:09.540]And then if we have even soils
[00:22:11.150]with greater than 30% clay,
[00:22:12.950]essentially we're getting about the same relationship.
[00:22:15.960]And if we plot them all together
[00:22:17.490]we do essentially have one relationship
[00:22:20.110]and our square of 87% indicating
[00:22:23.080]that we have a pretty good association
[00:22:25.220]between net nitrogen mineralization
[00:22:27.890]and soil test biological activity.
[00:22:30.290]Which of course then begs the question,
[00:22:31.977]"Well why would you measure nitrogen mineralization
[00:22:34.900]if you can actually get it with a simple test
[00:22:37.910]of soil test biological activity?"
[00:22:40.300]That's the theme that I want to develop further.
[00:22:44.160]So in this case if we know how much biological activity
[00:22:47.090]we have we could actually start predicting.
[00:22:49.020]Well, how much nitrogen mineralization could be there.
[00:22:51.800]So if we have low biological activity,
[00:22:53.930]we have low nitrogen mineralization.
[00:22:55.810]We have high biological activity,
[00:22:57.360]we have high nitrogen mineralization.
[00:22:59.530]And in this case, you know, the simple units
[00:23:01.710]of nitrogen per kilogram soil for 24 days,
[00:23:05.610]the values of 55 and 127 could easily be equated
[00:23:09.590]to relatively closely to pounds of nitrogen per acre
[00:23:14.780]in a given period.
[00:23:17.410]In this case it would be 24 days under ideal conditions
[00:23:20.230]so that means that perhaps you have to take that times three
[00:23:24.720]or four to get into a field condition
[00:23:27.020]because the temperature and moisture
[00:23:28.510]in the field will be suboptimal in most cases
[00:23:31.610]and so it takes a longer period of time
[00:23:33.600]but it shows that actually we could actually
[00:23:35.390]start predicting the nitrogen mineral mineralized from soil.
[00:23:40.880]And this is another dataset from soils that were taken
[00:23:44.810]from throughout the state of North Carolina
[00:23:47.620]under no cover cropping, single species cover cropping
[00:23:51.480]and multi-species cover cropping.
[00:23:53.590]And essentially we get a very similar association
[00:23:56.700]relatively strong relationship of our square of 0.82.
[00:24:01.099]The slope is slightly different
[00:24:03.490]but it's essentially in the same range that was before.
[00:24:09.770]So our next step was to conduct some greenhouse trials
[00:24:12.340]to perhaps convince ourselves,
[00:24:14.544]I did need to convince myself
[00:24:17.660]but of course, to convince our colleagues, right?
[00:24:20.030]I mean, that's always the challenge in science,
[00:24:22.580]is to tell a story that is convincing
[00:24:25.330]and compelling that we can actually use the information.
[00:24:28.870]So we took the soils that we were collecting from the field
[00:24:32.270]dried them, set them to 4.75
[00:24:34.880]and you can see that some of these soils anytime
[00:24:37.190]they have a little bit of clay in them,
[00:24:38.520]they tend to have aggregates.
[00:24:40.300]And those soils that have very little clay in them
[00:24:43.370]their sandier texture, they don't have aggregates.
[00:24:46.700]So they distribute differently
[00:24:49.580]in the size of the aggregates.
[00:24:52.340]But it shows that we have different types of soils.
[00:24:54.610]And basically all we did was re wet the soil,
[00:24:58.370]plant some sorghum sudangrass,
[00:25:01.160]cover them with a shallow layer of sand, wash sand,
[00:25:04.770]so that we'd get no cross-contamination
[00:25:07.940]and let (indistinct) for six weeks.
[00:25:11.810]So this is during the development of them.
[00:25:13.700]We're basically giving them water only
[00:25:16.710]and allowing the soil to (indistinct) grass
[00:25:19.610]it's nitrogen mineralization potential.
[00:25:22.050]So we're gonna then look at harvesting these plants
[00:25:24.500]after six weeks.
[00:25:25.930]And we did not measure anything in the roots
[00:25:28.300]but it just wanted to point out
[00:25:29.690]that the roots explored almost all of the soil
[00:25:32.680]that was in there because it was a relatively
[00:25:34.460]small amount of soil.
[00:25:35.310]It was roughly 150 grams in each of these containers.
[00:25:40.540]And so the plants became nitrogen stressed of course.
[00:25:45.460]You see that the leaves are turning yellow.
[00:25:48.420]That was our goal.
[00:25:49.500]We wanted to stress them.
[00:25:50.670]We wanted the plants to take all of the available nitrogen
[00:25:53.730]and express the nitrogen that was mineralized
[00:25:56.460]into the plant dry matter.
[00:25:59.040]So the plant dry matter was measured
[00:26:01.200]against what we measured in the laboratory
[00:26:03.900]of net nitrogen mineralization.
[00:26:05.970]And you can see that from the coastal plain
[00:26:07.960]we get a pretty good relationship,
[00:26:09.670]very strong association here.
[00:26:11.840]So net nitrogen mineralization,
[00:26:13.810]the mineralization of organic matter
[00:26:17.370]is important for plant dry matter production.
[00:26:21.550]And from the Piedmont we get another relationship.
[00:26:24.300]It's slightly different in this case.
[00:26:26.665]And from the Appalachian region we had soil samples as well.
[00:26:31.580]But we put them all together and essentially, of course we
[00:26:34.320]have some scattered but association would indicate
[00:26:37.830]that 83% of the plant dry matter production
[00:26:40.500]could be predicted by net nitrogen mineralization alone.
[00:26:43.720]Now we did measure residual soil nitrate
[00:26:45.820]and there were some variations
[00:26:47.030]and that's probably why we had some slope
[00:26:50.329]or intercept that was greater than zero.
[00:26:53.590]And so there's some plant production.
[00:26:56.340]Of course the seed has some reserves as well
[00:26:58.411]and so there's a reason for that value greater than zero.
[00:27:04.320]But it shows that the plant dry matter production
[00:27:07.230]was really a function of net nitrogen mineralization.
[00:27:13.150]And we also measured plant nitrogen uptake.
[00:27:15.310]The total nitrogen uptake by the plant.
[00:27:17.330]And then expressed it in association
[00:27:20.090]with soil test biological activity.
[00:27:22.340]It was not quite as strong
[00:27:23.910]but it was a relatively good relationship
[00:27:26.080]of 81% of the plant nitrogen uptake could be expressed
[00:27:29.790]by soil test biological activity.
[00:27:32.030]This gave me confidence that what we were observing
[00:27:34.440]in the laboratory could be expressed
[00:27:36.860]in plants in the greenhouse.
[00:27:39.270]and it also begged the question,
[00:27:43.240]well, why don't we just use organic carbon
[00:27:45.280]to predict nitrogen mineralization?
[00:27:47.200]Because this is a question that I get
[00:27:49.730]on every presentation I have.
[00:27:52.110]And so I thought I might share that information with you.
[00:27:55.870]Nitrogen mineralization is related to total organic carbon.
[00:27:59.490]It's certainly more related
[00:28:01.000]to total soil nitrogen in this case
[00:28:03.640]because we have some variations in our soils
[00:28:06.290]in North Carolina and probably in other States
[00:28:09.920]and regions of the world as well.
[00:28:11.970]But it does show that yes there is an association
[00:28:14.590]between nitrogen mineralization and total organic carbon
[00:28:17.950]but it's not that strong.
[00:28:21.170]There are a lot of variations.
[00:28:22.420]And in this case, of course, I've picked some soils
[00:28:26.820]that I think are important to illustrate.
[00:28:29.590]So these soils were taken
[00:28:32.340]from three different physiographic regions
[00:28:34.180]in North Carolina and there are some reasons why
[00:28:36.990]there were different associations among these regions.
[00:28:41.090]So in the Appalachian region,
[00:28:43.148]we have a really strong relationship
[00:28:45.630]between net nitrogen mineralization
[00:28:47.170]and total organic carbon.
[00:28:48.540]In the Piedmont we have a really strong relationship
[00:28:51.440]and in the coastal plain, we do,
[00:28:52.830]but there are differences among these soils.
[00:28:54.791]In the coastal plain there's a large pool
[00:28:56.940]of resistant soil organic matter
[00:28:58.800]that was submerged and so that old organic matter
[00:29:01.810]that was submerged is not very biologically active.
[00:29:05.600]And so we do measure it as organic carbon
[00:29:07.810]but we don't measure it in an expression
[00:29:10.060]of nitrogen mineralization.
[00:29:13.234]The difference between the Piedmont and the Blue Ridge
[00:29:16.700]or the Appalachian region was because in the Appalachians
[00:29:19.640]we tend to have crop land in Sandy bottom lands
[00:29:23.150]and so they don't have as much clay as in the Piedmont
[00:29:26.390]and so that sandy texture helps to elevate
[00:29:30.440]the nitrogen mineralization per unit of organic Carbon.
[00:29:35.020]But if we were to use these same soils
[00:29:37.130]that I just showed you and plot nitrogen mineralization
[00:29:40.410]against soil-test biological activity,
[00:29:42.530]there was only one association that was needed.
[00:29:44.900]We didn't have to know where the samples came from.
[00:29:47.770]Or physiographic region.
[00:29:49.510]The soil test biological activity was good enough
[00:29:53.070]just by itself to just predict
[00:29:54.730]the net nitrogen mineralization.
[00:29:56.630]And in this case, the R square being 94%
[00:29:59.290]even a stronger association than other datasets.
[00:30:04.570]Well, I'm going to shift to the theme of the rest
[00:30:09.100]of the seminar into how we can actually use this indicator
[00:30:13.320]of soil-test biological activity
[00:30:15.400]as a way of predicting nitrogen availability.
[00:30:19.460]In this case this graphic shows
[00:30:21.490]that a relative yield is a function of available nitrogen.
[00:30:25.020]We know that if we had a soil from the beach
[00:30:28.190]that had no nitrogen in it at all
[00:30:30.960]we would grow no plants.
[00:30:33.430]Or a sand from the kids sand pile.
[00:30:37.260]It has no organic matter.
[00:30:39.751]It would have no growth.
[00:30:41.210]We know this will occur
[00:30:42.430]because plant dry matter production has to have nutrients.
[00:30:46.000]So there's this nonlinear function
[00:30:48.170]that is going to occur
[00:30:49.500]there's going to be a plat owing
[00:30:51.180]of their response with available nitrogen.
[00:30:53.760]But where does the nitrogen come from?
[00:30:55.450]That's our key question.
[00:30:56.890]And that's where we need to focus our attention.
[00:30:59.036]It's gonna come from inorganic nitrogen.
[00:31:01.620]It's right to be able to measure residual soil nitrate.
[00:31:05.000]It's a very good thing to do.
[00:31:07.140]And we can do that in the surface soil
[00:31:09.190]or we can have it residual in the profile.
[00:31:11.100]And of course in Nebraska you would measure residual
[00:31:13.350]in the profile because it's more of
[00:31:14.670]a semi-arid subhumid region.
[00:31:17.590]In North Carolina I've been told
[00:31:19.820]that we don't want to do this
[00:31:21.520]because we don't really carry over any nitrate
[00:31:24.230]in the soil profile.
[00:31:25.310]We have excess precipitation.
[00:31:27.320]I'm not sure that that's always the case
[00:31:29.470]but that's the current strategy.
[00:31:32.490]What we missed in the past though is this organic nitrogen.
[00:31:36.500]If we measure only the total organic nitrogen,
[00:31:39.460]we're always...
[00:31:43.210]I would just say that it's not yet clear.
[00:31:47.410]We're confused because we're not focusing on
[00:31:50.290]that portion, which is biologically active.
[00:31:54.420]So if we had sites with low nitrogen availability
[00:31:57.490]we would likely have high nitrogen fertilizer response.
[00:32:00.880]We would definitely increase profit.
[00:32:02.730]This is the current paradigm.
[00:32:04.390]This is what we definitely should do when we have
[00:32:07.330]low available nitrogen.
[00:32:08.976]The idea is how do we characterize that available nitrogen?
[00:32:13.020]There are sites around the country,
[00:32:15.150]certainly in North Carolina, Virginia,
[00:32:17.290]where I've done some of the research
[00:32:18.915]where we have high nitrogen availability
[00:32:21.580]and we see very low nitrogen fertilizer response.
[00:32:25.600]If we were to reduce the nitrogen input
[00:32:29.900]from fertilizers then we could reduce
[00:32:31.710]our environmental impact.
[00:32:33.140]This would be a very good thing.
[00:32:36.020]Of course, we should try to elevate
[00:32:38.520]the available nitrogen pool into...
[00:32:41.040]If we do it strategically into a more organic form,
[00:32:45.460]then we're sequestering nitrogen,
[00:32:47.190]as well as releasing it simultaneously.
[00:32:49.500]And that will protect us from environmental impact.
[00:32:52.570]Now, that's a simple statement
[00:32:54.560]but it's not quite as simple in reality.
[00:32:57.110]So we do want to increase the organic nitrogen availability
[00:33:01.560]but be able to release it as well.
[00:33:03.360]And that's our real goal.
[00:33:06.410]So the research really focused on surface soil,
[00:33:09.410]inorganic nitrogen
[00:33:10.400]and the biologically active organic nitrogen.
[00:33:14.440]So, if we have this scenario where we have a target
[00:33:17.240]of 200 bushel an acre corn grain yield,
[00:33:19.710]we might have some expectations
[00:33:21.580]on how much nitrogen might be taken out by the corn crop.
[00:33:25.360]Well, we know that sometimes we have actually,
[00:33:28.180]if we do not apply nitrogen fertilizer,
[00:33:29.930]we might have 20% of the relative yield
[00:33:32.300]without any nitrogen.
[00:33:33.870]That means that it's gonna come
[00:33:35.080]from any one of these sources of nitrogen in the soil
[00:33:39.140]and then we supplement with the nitrogen fertilizer.
[00:33:41.690]That means that we should actually
[00:33:42.980]be able to calculate how much nitrogen uptake comes
[00:33:45.660]from this available nitrogen pool.
[00:33:48.749]We might have a soil that has 60% relative yield, okay?
[00:33:52.100]Then that means that we're having a larger nitrogen uptake
[00:33:55.630]and a larger available nitrogen pool.
[00:33:58.020]Something is occurring here.
[00:33:59.340]It could be from residual inorganic nitrogen,
[00:34:02.120]it could be from biological activity.
[00:34:04.250]We have to define that.
[00:34:06.100]And then finally we have some yield response curves
[00:34:09.085]that look more like this.
[00:34:10.640]where we get almost 90% of relative yield
[00:34:13.060]without any fertilizer input.
[00:34:15.030]And only a 10% yield increase
[00:34:17.420]if we we add fertilizer.
[00:34:19.480]This means that we have a large available nitrogen pool
[00:34:22.868]and it could be from inorganic or organic nitrogen sources.
[00:34:27.320]So hacking back to my days in Nebraska
[00:34:30.130]this was one of our goals,
[00:34:31.410]is to find out well, is it coming
[00:34:33.020]from residual soil nitrate?
[00:34:34.829]That was an interesting thing.
[00:34:36.740]Unfortunately I never got to the point of
[00:34:38.960]exploring organic nitrogen.
[00:34:40.880]And fortunately, I've been able to do that
[00:34:42.847]in my research since then.
[00:34:46.510]So if we would focus on a case scenario,
[00:34:49.780]in this case we're applying a 50 pound unit
[00:34:53.130]of nitrogen that yields us 82 bushel an acre more grain.
[00:34:57.910]Well, that yield response,
[00:34:59.030]this 50 pounds and yielding 82 bushel an acre more grain
[00:35:02.950]is equivalent to 92 pounds of grain per pound of nitrogen.
[00:35:06.150]If we just divide these out,
[00:35:07.750]take the 82 times the 56 and then divide that product,
[00:35:12.554]divided by 50, and then we get 92.
[00:35:15.970]So that's a good yield response.
[00:35:17.560]That's something that's obviously 92 pounds
[00:35:19.720]of grain per pound of nitrogen.
[00:35:21.490]You're gonna make money if you apply nitrogen in this case.
[00:35:26.850]But we might also have a case where we apply an increment
[00:35:29.700]of 50 pounds of nitrogen
[00:35:31.260]and only get 27 bushel an acre more grain.
[00:35:33.800]Well, that equals 30 pounds of grain per pound of nitrogen.
[00:35:37.200]I'm highlighting these units of pounds of grain
[00:35:40.730]per pound of nitrogen because these are
[00:35:42.340]the units I'm gonna use further down on in the presentation.
[00:35:45.910]And these are what I believe are important
[00:35:48.440]to understand our yield response intensity
[00:35:52.040]to nitrogen fertilizer.
[00:35:54.240]And then in the case where we have
[00:35:55.993]a 50 pound unit of nitrogen
[00:35:58.540]and then we only get nine bushel an acre more grain,
[00:36:00.850]we're only getting 10 pounds of grain for common nitrogen.
[00:36:03.570]This is getting to the marginal cost
[00:36:05.140]of the yield return from our fertilizer investment.
[00:36:12.760]So the intensity of yield response
[00:36:14.610]at the first dose of nitrogen fertilizer declines
[00:36:17.460]as soil nitrogen availability increases.
[00:36:20.090]This is basically the hypothesis that I'm working with.
[00:36:23.150]So we went to the field and determined yield response
[00:36:26.856]to nitrogen fertilizer at a number of locations.
[00:36:29.680]They were 47 trials in 11 counties over three years
[00:36:33.158]in four different physiographic regions.
[00:36:36.930]So a wide diversity of conditions really.
[00:36:40.570]And so there were some challenges with that
[00:36:44.070]but also some opportunities with that.
[00:36:46.570]And basically what we found was this intensity
[00:36:49.800]of yield response to the initial dose
[00:36:51.590]of fertilizer is the response that I was looking for.
[00:36:54.920]Pounds of grain per pound of nitrogen
[00:36:57.320]and I related that to soil test biological activity
[00:37:00.120]and we saw from field studies of measuring this
[00:37:04.210]with replicated small plot trials
[00:37:06.430]and then taking a simple test prior to the growing season
[00:37:10.000]we can estimate 64% of this yield response
[00:37:13.300]to the initial dose just by soil-test biological activity.
[00:37:17.390]And to illustrate that these conditions here
[00:37:21.040]at the left hand side of the graphic would be
[00:37:23.770]this high yield response condition
[00:37:26.580]whereas those in the middle might be those
[00:37:28.900]that have a more moderate level
[00:37:30.960]of yield response to nitrogen fertilizer.
[00:37:33.050]And certainly those that didn't respond much to,
[00:37:36.000]would follow that scenario
[00:37:37.260]where I explained where we have very little yield response
[00:37:40.249]to nitrogen fertilizer.
[00:37:42.100]So these were really encouraging results
[00:37:44.180]and pretty much astounded me my myself
[00:37:47.550]at the beginning.
[00:37:49.410]Looking at this and trying to kind of average
[00:37:51.610]over a few different levels of the yield response.
[00:37:56.020]These are the nitrogen factors
[00:37:58.290]for economically optimum production.
[00:38:00.490]I'm sure most of you in agronomy
[00:38:03.160]in Nebraska know that the pounds of nitrogen per bushel
[00:38:06.660]of grain is pretty much sat around anywhere
[00:38:08.900]from one to 1.2, something like that.
[00:38:11.100]I'm not sure exactly what you use these days
[00:38:13.440]but the theoretical factor should be closer to 1.4.
[00:38:18.250]But the reality is that there's always some nitrogen
[00:38:21.040]in soil so may be you use 1.0 or 1.2
[00:38:24.990]but this relationship suggested
[00:38:27.010]that actually we could modify the nitrogen factor based
[00:38:31.250]on the soil test biological activity.
[00:38:33.310]We could now start differentiating between a soil
[00:38:37.360]with low biological activity and low nitrogen availability
[00:38:41.050]and one with high biological activity
[00:38:43.120]and high nitrogen availability.
[00:38:45.440]So that range of conditions could be set
[00:38:48.690]but that range of conditions of 0.9 to 1.5
[00:38:51.800]would be an over estimate for a lot of fields,
[00:38:54.700]at least in this study.
[00:38:56.230]And they would be fitting for (indistinct) fields
[00:38:58.950]that were on the low end of the biological activity.
[00:39:02.940]Well, it was encouraging result
[00:39:06.527]but as anybody that knows when a study is conducted
[00:39:12.530]we need to repeat it.
[00:39:13.690]Well, I was definitely willing to repeat it
[00:39:16.570]because I couldn't really believe
[00:39:18.450]for sure that the results were true.
[00:39:20.490]So I definitely needed to repeat it again.
[00:39:22.730]So I went in more sites,
[00:39:24.200]had 111 field trials in 39 counties
[00:39:27.120]during two different years,
[00:39:29.020]had an excellent collaboration
[00:39:30.800]with many different farmers from around the region.
[00:39:33.510]And these people are just, you know
[00:39:35.350]gems as far as research are concerned.
[00:39:37.940]And it was an interesting step for me
[00:39:40.820]because it was exactly what Chuck Francis told me to do
[00:39:44.930]back in 1989 when I was in Nebraska.
[00:39:47.830]To go out to farmers and actually let's do
[00:39:49.820]the research on their fields.
[00:39:51.830]And so I learned a lot from that process.
[00:39:54.829]Well, the results,
[00:39:56.170]I'm just gonna show you the results and not the process.
[00:39:59.010]In this case, we basically got about
[00:40:01.350]the same kind of result.
[00:40:03.080]The same association occurred.
[00:40:05.110]It didn't matter whether we were
[00:40:06.290]on research stations or private farms.
[00:40:08.540]We saw that the nitrogen factor
[00:40:10.260]for economically optimum production,
[00:40:12.090]the factor for fertilization could be reduced
[00:40:16.440]if we had greater biological activity.
[00:40:19.230]This was an important result
[00:40:20.460]because I think this is how we can actually
[00:40:22.150]start modifying our fertilizer inputs
[00:40:25.840]and controlling the loss of nitrogen to the environment.
[00:40:30.260]Well, I wanted to bring you now
[00:40:32.250]to just a review of these corn nitrogen trials.
[00:40:36.890]We separated the data into, in this case here
[00:40:39.520]conventional tillage or no tillage.
[00:40:41.520]We had obviously lot more producers that I'm interested in
[00:40:45.714]of addressing the conservation approach
[00:40:49.000]and so maybe it was a bias on my part
[00:40:51.970]but of course I was interested in
[00:40:54.230]finding information to support this type
[00:40:56.790]of agricultural approach.
[00:40:58.670]But we did have some conventional tillage fields
[00:41:01.540]and so then we looked at the actual soil responses.
[00:41:04.920]Well, biological activity was statistically greater
[00:41:07.520]with no tillage than in conventional tillage.
[00:41:09.710]These are all farmed zero to 10 centimeters.
[00:41:12.140]We did measure at 10 to 20 and 20 to 30 centimeter depth
[00:41:16.000]but essentially in our region
[00:41:18.600]only the zero to 10 centimeters matters
[00:41:21.150]in these yield responses to nitrogen fertilizer.
[00:41:24.800]So these are only of the zero to 10 centimeters.
[00:41:28.520]We also looked at nitrogen mineralization
[00:41:30.320]and statistically greater nitrogen mineralization
[00:41:33.110]with no tillage than conventional tillage.
[00:41:35.310]Corn grain yield was actually statistically
[00:41:37.580]different as well
[00:41:39.030]and this, I don't think this is necessarily
[00:41:42.820]the reality of conservation tillage in our region
[00:41:46.590]but it does show that we have a great opportunity
[00:41:49.480]to elevate a yield to overcome moisture deficits
[00:41:52.570]and to use nitrogen efficiently.
[00:41:55.420]So in the end, the economic return over the STD
[00:41:59.920]which is called, this is short for Standard Recommendation
[00:42:03.440]of 1.2 pounds of nitrogen per bushel of grain.
[00:42:06.550]If we use that standard recommendation,
[00:42:09.490]how do we improve this
[00:42:10.660]with a relationship using soil-test biological activity?
[00:42:13.860]We could actually return $19 and 11 cents.
[00:42:17.110]If we use the biological activity approach compared
[00:42:20.051]to the standard condition.
[00:42:21.890]And that was statistically greater than zero.
[00:42:26.460]But it was not statistically different
[00:42:28.180]than if we just use the conventional tillage
[00:42:30.500]in that, 8.89 is not different than 19.11
[00:42:34.500]but 19.11 is significantly positive.
[00:42:41.260]So these were encouraging results.
[00:42:43.290]These are in results that I share
[00:42:44.560]with farmers in our region.
[00:42:45.780]They're really interested in them.
[00:42:48.380]We also looked at animal manure amendment
[00:42:50.460]whether there was no organic amendment
[00:42:52.540]or with organic amendment
[00:42:54.170]and we had more observations without organic amendment.
[00:42:57.620]Soil-test biological activity was greater
[00:42:59.510]with organic amendment.
[00:43:01.150]This is typically poultry litter.
[00:43:02.790]It is can also be beef pack manure, dairy pack
[00:43:07.290]and nitrogen mineralization also greater than
[00:43:10.040]with no organic amendment.
[00:43:12.070]Corn grain yield in this case was no different
[00:43:14.690]whether it had organic amendment or organic amendment.
[00:43:18.920]And the return over the standard nitrogen recommendation
[00:43:22.020]was greater with organic amendment
[00:43:23.730]than without organic amendment.
[00:43:25.440]And quite significantly in that $36 and 34 cents
[00:43:29.760]could be returned more so
[00:43:31.860]because we were reducing the amount of nitrogen fertilizer
[00:43:34.910]over the standard recommendation using this
[00:43:37.870]whenever there was both no organic amendment
[00:43:40.918]or organic amendment.
[00:43:45.620]Shifting to cover cropping.
[00:43:47.080]We had trials that had no cover crop
[00:43:49.350]a single species cover crop
[00:43:50.810]and a lot of them that were using multi-species cover crop.
[00:43:54.400]And then again, this is the biased approach
[00:43:57.270]that I use to get on farmer's fields that are adopting some
[00:44:00.730]of these practices and understanding what's going on there.
[00:44:03.680]But we of course had some comparisons that we could make.
[00:44:06.820]And here we see that multi-species cover crop leading
[00:44:10.030]to greater surface residue retention
[00:44:12.400]greater soil biological activity
[00:44:15.870]and greater net nitrogen mineralization.
[00:44:20.470]The corn grain yield tended to be greater
[00:44:22.520]with any type of a cover crop than without cover crop.
[00:44:27.950]And the results for the economic return
[00:44:30.810]were significant with the multi-species cover crops.
[00:44:33.700]So this is getting to the point where perhaps
[00:44:36.070]we could be using these multi-species cover crop
[00:44:38.330]to cover the cost of reducing our nitrogen fertilizer
[00:44:41.760]or reducing our nitrogen fertilizer to cover the cost
[00:44:44.280]of the multi-species cover crop.
[00:44:46.600]And this could become a win-win situation
[00:44:49.280]for growers, knowing that they just need that information
[00:44:53.030]to be able to make those adjustments in their practices.
[00:44:57.990]So this system that I'm trying to promote here is
[00:45:01.880]that we need to know something about the soil.
[00:45:04.170]Why do we make nitrogen fertilizer recommendations
[00:45:06.720]if we don't know anything about the soil?
[00:45:09.600]You need to knew more about soil.
[00:45:11.130]This is my simple point that I try to make.
[00:45:14.130]So in this case here we have three different...
[00:45:16.164]Let me just go back.
[00:45:17.690]We have three different costs-to-value thresholds.
[00:45:19.600]We have this low threshold where the fertilizer
[00:45:23.490]would be low price and the grain yield would be a high price
[00:45:27.970]or the grain value would be a high price.
[00:45:30.010]In this case this would be medium
[00:45:31.400]where we have 10 pounds of grains per pound of nitrogen,
[00:45:34.940]intermediate fertilizer costs
[00:45:36.600]and then an intermediate corn grain value.
[00:45:39.700]And then in this case
[00:45:40.900]where the fertilizer cost is very high
[00:45:43.200]and the corn grain price might be quite low.
[00:45:46.390]So we can use these different economic thresholds
[00:45:49.160]and we can start using this
[00:45:50.760]into a soil testing category system
[00:45:54.010]where in under very low soil test biological activity.
[00:45:57.250]We actually see that that's the current recommendation
[00:46:00.260]of one to 1.2 pounds of nitrogen per bushel of grain
[00:46:03.700]is quite adequate.
[00:46:05.680]But if you're a farmer that actually has higher
[00:46:07.920]soil-test biological activity
[00:46:10.130]there may be opportunity for you
[00:46:12.040]to start reducing quite significantly
[00:46:14.350]the amount of nitrogen fertilizer that's applied.
[00:46:17.020]That means that the cycling
[00:46:18.410]of the nitrogen in the soil is going to contribute.
[00:46:21.290]That is not a never-ending process
[00:46:23.190]but that's the reason for saying some periodic testing
[00:46:26.510]and to keep after the conservation approach
[00:46:29.260]to build soil fertility and this could lead to
[00:46:32.303]a more efficient nitrogen fertilizer utilization,
[00:46:35.030]getting more of that nitrogen
[00:46:36.280]into the plant and less of it to the environment.
[00:46:40.360]So the standard approach is to use,
[00:46:42.740]say one pound of nitrogen per bushel of grain
[00:46:46.640]irrespective of what the soil condition is.
[00:46:49.030]But the soil health approach
[00:46:50.180]that I'm trying to explain here would be
[00:46:52.130]that we actually modify the nitrogen factor depending
[00:46:55.405]upon what the soil test biological activity is
[00:46:59.730]which predicts nitrogen mineralization in the soil.
[00:47:04.070]I'm not creating magic here.
[00:47:05.350]I'm just making an association
[00:47:07.090]between soil test biological activity
[00:47:09.120]and nitrogen mineralization in the soil.
[00:47:11.380]So there may be situations where actually we're
[00:47:14.260]under fertilizing with the standard approach.
[00:47:16.170]We should maybe be applying a greater nitrogen
[00:47:19.330]when there's a very low soil-test biological activity
[00:47:22.800]but there are probably conditions where we're over-applying
[00:47:25.950]and that we could be saving fertilizer
[00:47:27.733]and increasing economic return
[00:47:30.350]and decreasing environmental impact
[00:47:33.000]by knowing what the soil-test biological activity is.
[00:47:36.140]If we can measure nitrogen mineralization very effectively
[00:47:38.910]it would be a better tool
[00:47:40.300]but this is a test that is relatively easy to measure
[00:47:45.580]and simple and rapid.
[00:47:47.700]So just to explain, I'm almost done.
[00:47:50.060]I just wanted to explain a little bit
[00:47:52.070]that we've not limited this to corn production,
[00:47:55.320]we have conducted it in wheat
[00:47:56.620]but also I wanted to share a few results in tall fescue.
[00:48:00.210]We stockpile tall fescue in the Southeastern region
[00:48:03.580]where there's an issue with the endophyte
[00:48:06.210]and we can have negative impacts of the tall fescue
[00:48:09.030]on animal gain, on animal performance
[00:48:12.000]because of the fungal endophyte that's in the tall fescue.
[00:48:16.070]And we can avoid this by stockpiling.
[00:48:18.530]So the grass is allowed to grow from about September 1st
[00:48:21.950]until mid December, mid January
[00:48:25.740]and then cattle are grazing this somewhat desiccated forage.
[00:48:32.336]Tall fescue withstands the mild winters
[00:48:35.700]that we have, relatively mild winters
[00:48:37.990]and it actually holds up in nutrient value.
[00:48:40.310]So this is a good strategy
[00:48:42.100]but that stockpiling,
[00:48:43.090]that freezing and thawing that occurs
[00:48:45.390]on the fall stockpile reduces ergot alkaloids concentration
[00:48:49.875]of this, of this fungus.
[00:48:51.460]And so the cattle can consume this forage
[00:48:54.550]without having negative the ergovaline effect.
[00:48:59.070]So this research was conducted over 92 field trials
[00:49:02.200]in three different years.
[00:49:03.660]And I just wanted to give you one snippet of the results.
[00:49:06.560]This is the forage yield response to initial dose
[00:49:08.860]of nitrogen fertilizer,
[00:49:10.280]a similar response where we have pounds of forage
[00:49:12.680]per pound of nitrogen
[00:49:14.254]that I showed you for corn.
[00:49:15.860]And it shows that this value declines
[00:49:18.790]with increasing soil-test biological activity.
[00:49:21.550]In this case, in a non-linear manner.
[00:49:24.750]This follows very closely to what our recommendations are
[00:49:28.030]for fertilization of tall fescue for optimal growth.
[00:49:34.140]In that we are recommending approximately 50 to 60 pounds
[00:49:38.390]of nitrogen per ton of forage for all stock stockpile
[00:49:42.590]across the board.
[00:49:43.854]But unfortunately most of our progressive grazers
[00:49:49.480]in the region are actually having biological activity
[00:49:52.520]that are much greater in this 300 to 400 part
[00:49:56.320]per million range.
[00:49:57.250]And so really our recommendations are not accurate
[00:50:00.580]for a lot of our producers in the region.
[00:50:03.274]It is accurate for those that are the most vulnerable.
[00:50:07.651]Those that respond very much to nitrogen fertilizer.
[00:50:11.460]But it's not accurate for most of the producers
[00:50:15.570]that we have in the region.
[00:50:18.350]We've also looked at this soil test biological activity
[00:50:23.040]geo spatially in pastures across a diversity
[00:50:26.240]of farms in the region.
[00:50:27.490]In three different regions
[00:50:28.720]in the coastal plain, the flat area near the coast,
[00:50:31.210]the Piedmont, the hilly region
[00:50:32.720]and then the Appalachian Blue Ridge region in the mountains.
[00:50:38.660]And what did this research really informed us
[00:50:42.760]was that both organic estimates of soil health
[00:50:46.760]and inorganic estimates,
[00:50:48.560]I think soil test P and K are really still important
[00:50:51.900]but we need to have that combined with organic tests.
[00:50:55.090]So the soil-test biological activity combined
[00:50:57.610]with inorganic tasks are really what we need
[00:51:00.012]for a comprehensive strategy.
[00:51:02.290]And this will tell us a lot more about
[00:51:04.124]this sort of nutrient distribution in perennial pastures.
[00:51:08.790]So to kind of finalize
[00:51:12.400]there are some key soil health indicators.
[00:51:14.720]I'd started the presentation
[00:51:16.040]with a long list of many indicators
[00:51:18.130]under the chemical physical and biological categories.
[00:51:22.100]I believe that there's really only a handful, you know
[00:51:25.290]less than the digits on your hand,
[00:51:27.710]but there are a few key soil health indicators.
[00:51:33.876]Organic matter or as we measured
[00:51:37.190]as carbon or nitrogen is really key.
[00:51:39.530]It's something that we really should be measuring
[00:51:41.560]because it's one of the broadest indicators of soil health.
[00:51:45.860]The routine soil testing for soil chemical fertility
[00:51:49.040]is also still very important.
[00:51:51.330]I think harmonizing that across States would be ideal.
[00:51:56.140]Maybe it has to be separated by regions
[00:51:58.420]because there are some reasons why we have certain extract
[00:52:01.390]and for certain regions
[00:52:02.660]but I think harmonizing would be good
[00:52:04.350]but we should we should not throw out
[00:52:06.041]the routine soil testing but we should modify it.
[00:52:11.130]And of course we should have some indicator
[00:52:13.030]of soil physical condition.
[00:52:14.370]And I think water infiltration would be the best.
[00:52:17.110]It has to be determined in the field
[00:52:19.410]but as a proxy soil aggregation would be a good indicator
[00:52:23.940]I believe and that should be done.
[00:52:27.220]But the biological component
[00:52:28.690]I think there are many opportunities to expand this
[00:52:31.340]in the biological component
[00:52:32.470]but one of the key ones is just
[00:52:34.210]the biological activity itself.
[00:52:36.600]It tells us a lot about the fertility
[00:52:39.630]as well as the physical and biochemical reactions
[00:52:43.430]that are going to occur.
[00:52:45.510]So in the end I would probably recommend four,
[00:52:48.130]but in the very end I think we can actually get rid of
[00:52:51.700]the organic matter and the aggregation
[00:52:53.900]because they are influenced so dramatically
[00:52:56.950]by soil test biological activity.
[00:52:58.680]If we know that indicator right there
[00:53:01.170]we could actually delete the information that we would need
[00:53:04.560]from the aggregation and organic matter
[00:53:07.520]because it becomes a little bit more redundant.
[00:53:09.910]So we might be left with only two sets of analyses.
[00:53:13.760]And the routines all testing is a suite of analysis, right?
[00:53:16.980]We need to know a lot about the different chemicals
[00:53:19.720]and the biological might be also a suite
[00:53:22.280]that we might have to develop further
[00:53:24.360]because I'm not sure there should be a strong association
[00:53:27.020]between activity, biomass and diversity
[00:53:30.300]but they can be linked in some ways.
[00:53:34.330]To summarize, soil health is a vital underpinning
[00:53:37.780]of sustainable agriculture.
[00:53:39.010]I think that we know already.
[00:53:43.643]And then there are various forms
[00:53:44.864]of that sustainability.
[00:53:46.860]Conservation tillage, crop diversity, cover cropping
[00:53:49.610]and organic amendments are key management factors
[00:53:52.000]affecting soil health.
[00:53:53.330]We have available evidence in the literature
[00:53:56.330]to indicate that.
[00:53:57.890]We can see it in the fields.
[00:53:59.680]So it's something that we should be aware of.
[00:54:01.920]Soil-test biological activity.
[00:54:03.460]It's a simple, rapid and robust indicator
[00:54:05.580]of soil nitrogen availability.
[00:54:08.434]What I've shared with you today shows
[00:54:11.000]that it's related to soil nitrogen availability
[00:54:13.650]but I believe that it's much broader than that.
[00:54:15.480]It includes a lot of other things as well.
[00:54:17.880]So it's some indicator that should be of use.
[00:54:21.620]And soil health and nutrient management
[00:54:23.100]are strongly linked through assessment
[00:54:25.550]with soil-test biological activity.
[00:54:27.220]So we can actually start using soil health
[00:54:29.770]as a nutrient management strategy as well.
[00:54:34.060]So to really conclude soil-test biological activity
[00:54:38.100]or as I used to call it,
[00:54:39.450]the flush of CO2,
[00:54:41.090]should be considered a valuable soil testing tool
[00:54:43.130]to indicate potential soil nitrogen mineralization
[00:54:46.040]and the need for supplemental nitrogen fertilizer.
[00:54:48.750]I think we have great opportunity to use this
[00:54:51.190]to more effective use.
[00:54:52.940]Now it just needs more testing
[00:54:54.530]around the country, around the world.
[00:54:56.880]And I believe that we can recognize
[00:54:59.838]that organic fertility is important.
[00:55:03.090]And if we don't have it in our soul fertility
[00:55:06.750]cadre of analysis then we're missing out.
[00:55:11.800]But it also indicates available carbon resources
[00:55:14.730]in soil necessary to promote soil carbon sequestration.
[00:55:17.540]And of course, soil carbon sequestration is a good thing
[00:55:20.480]but we're can only reach a level
[00:55:22.650]that is steady state for a region.
[00:55:24.700]We have to be able to show carbon sequestration,
[00:55:27.660]but always, always when we have soil carbon sequestration.
[00:55:31.580]We're always going to have mineralization.
[00:55:33.540]We're gonna be building and taking down.
[00:55:36.820]It's a continual process.
[00:55:38.320]And we should always keep that in mind that it is dynamic.
[00:55:41.680]But it also indicates potential microbial activity
[00:55:45.120]to transform nutrients, foster soil aggregation
[00:55:48.220]and create a biologically diverse soil habitat.
[00:55:51.760]So it has a lot of value to other soil functions.
[00:55:59.150]I was raised in the Bohemian Alps of Nebraska
[00:56:04.960]and I've shifted to the rolling Hills
[00:56:08.740]of the Appalachian Piedmont
[00:56:11.840]and I just think that the functions
[00:56:14.850]of soil are very similar in the different environments
[00:56:18.040]but we have to be aware, of course,
[00:56:20.193]the environmental constraints
[00:56:21.640]but the processes that occur are very similar.
[00:56:24.200]So I appreciate the opportunity to share
[00:56:26.240]with you today at the University of Nebraska seminar
[00:56:29.750]and I would welcome any questions that you might have.
[00:56:32.880]Thanks so much
[00:56:37.050]Alan, we have a question from Bijash
[00:56:41.040]and his question is how does your STBA compare
[00:56:44.260]with other respiration tests?
[00:56:48.840]Right.
[00:56:49.673]As I tried to explain there are other tests
[00:56:51.860]that are out there,
[00:56:52.693]the Cornell CASH, they actually don't use it anymore.
[00:56:55.440]I believe they now use permanganate oxidizable carbon
[00:56:59.720]instead of respiration but the Woods-Ends Solvita,
[00:57:03.380]they use the CO2 burst.
[00:57:05.250]The Haney Soil Health Test uses a CO2 burst test.
[00:57:08.530]Those use a one day test
[00:57:11.980]and the Cornell used to use a four day test.
[00:57:15.330]They may still use it.
[00:57:16.350]I just saw that they replaced it.
[00:57:19.850]So there are other tests out there.
[00:57:21.800]The issue is that if we use different approaches
[00:57:26.090]we're gonna get different numbers.
[00:57:27.300]It's the same as if we used may lick one
[00:57:30.830]versus may lick three.
[00:57:32.140]Now, that might not be such a big difference
[00:57:34.440]but it's the same concept,
[00:57:36.800]that we have to use standard protocol
[00:57:39.010]otherwise we're gonna get a different number.
[00:57:40.810]So if I get a number of 101
[00:57:43.230]and another test uses a one day test
[00:57:45.197]and I used a three day test,
[00:57:46.930]it's likely that the other test will only get 41.
[00:57:51.150]It's just a simple matter of the calibration
[00:57:54.100]of the tests to get to a common ground.
[00:57:57.250]And that research just needs to be done.
[00:58:00.570]To tell you the truth,
[00:58:01.403]I think that it's important to use a robust method
[00:58:06.000]not something that is gonna be less than robust.
[00:58:09.150]And I just have to be proven wrong
[00:58:10.780]that the other tests are equally as good.
[00:58:13.150]That's all.
[00:58:16.010]Alan, you have several other questions.
[00:58:19.480]What are the primary carbon substrates
[00:58:22.230]fueling the flush?
[00:58:23.920]Is it similar across different soils?
[00:58:29.360]Ah, the substrates will be of course
[00:58:31.360]from a surface residues and routes.
[00:58:33.900]Those are the primary sources.
[00:58:35.210]Of course, animal manures can be in there.
[00:58:36.970]If that's a system that's well developed.
[00:58:40.300]They're organic sources of carbon and nitrogen
[00:58:43.730]so the organic matter that feeds,
[00:58:46.590]any system that builds organic matter.
[00:58:50.120]And I say builds, we can see activity
[00:58:54.180]from this soil-test biological activity
[00:58:55.810]that is immediately available from the Risal deposition
[00:59:00.160]of growing plants.
[00:59:01.730]So the carbon substrates that are exuded
[00:59:04.680]by living plant roots are easily decomposed
[00:59:08.470]and they can be captured in this test as well.
[00:59:12.030]Alan, the next question is,
[00:59:15.810]do you have any producers that are using your approach
[00:59:18.930]for nitrogen application rate?
[00:59:22.060]Well, thanks.
[00:59:23.330]The issue is that I'm funded by the USDA.
[00:59:26.210]I'm a research operation.
[00:59:28.330]I don't have a commercial lab.
[00:59:29.614]I won't have a commercial lab.
[00:59:34.440]You know, just to be honest about it,
[00:59:36.800]my colleague Rick Haney and I
[00:59:38.280]were in graduate school together,
[00:59:40.530]he decided to push one day evaluation.
[00:59:44.210]I simply used three days.
[00:59:46.520]All of the data that I have could be transformed
[00:59:49.400]into a one day test.
[00:59:50.860]I believe though the way I would measure the CO2
[00:59:54.030]from the incubation using an alkali trap
[00:59:59.050]with acid titration is not necessarily
[01:00:01.840]the most appropriate for a one day test.
[01:00:04.430]So the test would have...
[01:00:05.920]If one uses a one day test
[01:00:07.680]you have to use an infrared gas analyzer
[01:00:09.640]or gas chromatograph
[01:00:10.970]something that's really much more sensitive.
[01:00:13.740]I believe that the alkali trap is sensitive for three days.
[01:00:16.700]I'm confident of that.
[01:00:18.250]We show that in repeated analysis we can get down
[01:00:21.560]to about four to 8% coefficient of variation.
[01:00:24.610]This is very reasonable for a soil test analysis.
[01:00:27.520]So I'm confident that the alkali trap works.
[01:00:30.720]The problem though is that one has to have
[01:00:34.320]the standardized approach.
[01:00:36.030]I mean if commercial labs want to use one day test only
[01:00:40.210]then we have to use this information.
[01:00:43.560]We have to calibrate it with a one day approach.
[01:00:46.290]Well, the data that I have is only three days.
[01:00:49.190]Now, mathematically, I could actually make a number
[01:00:53.360]that fits one day.
[01:00:54.410]It is possible for me to do that
[01:00:56.210]because all of the data that I collected
[01:00:58.190]has been from three 10 and 24 days.
[01:01:01.140]The fit or the mathematical fit is just extra,
[01:01:03.750]almost always 99% or greater.
[01:01:06.820]So I can easily predict one day so that could be done.
[01:01:11.861]It's gonna require a collaboration.
[01:01:14.582]That's what it's gonna require.
[01:01:17.370]Well, Alan you've had several shout outs
[01:01:20.070]for the great presentation
[01:01:21.540]and they've appreciated
[01:01:23.430]the shout out to the Bohemian Alps
[01:01:27.520]but there's one last question here
[01:01:29.400]and it's from Orange River
[01:01:31.310]and she asks how well does the STBA correlate
[01:01:35.700]to measures this soil microbial biomass
[01:01:40.080]say as measured by fumigation or extraction procedures?
[01:01:46.400]Okay, yeah that's a good question.
[01:01:48.571]It relates pretty well.
[01:01:50.691]So the soil-test biological activity related
[01:01:55.810]to microbial biomass from fumigation incubation
[01:01:59.750]that's the only technique I've used
[01:02:02.130]in the past.
[01:02:04.650]It's pretty strong.
[01:02:07.147]It depends on the data set
[01:02:08.320]but if I were to plot all of the data that I have,
[01:02:11.200]I would say that the R square is somewhere around 70%.
[01:02:15.235]It's pretty good but, you know
[01:02:17.410]the fumigation step is a unique thing.
[01:02:22.864]It's is significantly different
[01:02:23.960]than just simply drying the soil
[01:02:25.950]and so it does give some variation there.
[01:02:28.390]And as far as fumigation extraction,
[01:02:30.160]I just, you know I have some thoughts
[01:02:31.880]and I'll probably should leave them to myself
[01:02:34.020]but it's the more common approach
[01:02:37.630]for microbial biomass but I'm not sure it's the best.
[01:02:41.200]I'm just saying that I don't think we have great methods
[01:02:50.686]for it but I don't have enough data in my mind
[01:02:53.320]to know what the relationship would be
[01:02:54.930]with CFE, fumigation extraction.
[01:02:57.770]Sorry about that.
[01:02:58.603]Well, we're about out of time
[01:03:00.037]but there's one more question
[01:03:01.653]if you guys can hold on
[01:03:03.880]and it's from Tom Hogan Meyer
[01:03:06.160]and he says that one of the big issues
[01:03:08.667]with getting farmers to adopt some of the practices
[01:03:11.870]like cover crops, no till is a yield lag,
[01:03:15.460]a three to five-year lag
[01:03:17.030]between you increased costs and decreased yield or profit.
[01:03:21.740]Do you have suggestions to relieve this?
[01:03:26.530]Yeah, that's a good question.
[01:03:29.210]You know, just conceptually having a tilled field
[01:03:33.710]and then switching it to no tillage,
[01:03:35.618]it's kinda like stopping smoking, isn't it?
[01:03:38.970]It's difficult, you have that urge
[01:03:43.190]and not the farmer necessarily
[01:03:45.010]but the soil maybe.
[01:03:46.300]The soil is looking for something
[01:03:49.030]because it's used to being tilled
[01:03:50.740]and I'm not sure that we should put it into those terms
[01:03:53.730]but there are some reasons why.
[01:03:56.410]We're basically starving the soil
[01:03:59.300]when we switched shift to no tillage.
[01:04:01.880]We are putting residues at the surface.
[01:04:04.738]We're not getting the routine mineralization
[01:04:09.000]that's there so it's possible
[01:04:10.880]that there's a greater need for nitrogen.
[01:04:14.970]It depends on the other nutrients,
[01:04:16.570]but it could be for other nutrients as well
[01:04:18.380]but primarily nitrogen.
[01:04:19.590]There could be a greater need for nitrogen early
[01:04:22.270]in that transition period.
[01:04:24.140]And it may be not just the total amount of nitrogen
[01:04:27.390]but the timing of that nitrogen
[01:04:28.980]and the placement of that nitrogen.
[01:04:30.280]Making it very effective for the corn crop.
[01:04:34.350]But the issue is somewhat related
[01:04:37.370]to the corn itself.
[01:04:39.090]It likes to have a good pores for the roots to explore.
[01:04:44.300]The other crops don't seem
[01:04:45.520]to have that dramatic shift.
[01:04:49.000]So soybean, I think, is pretty resilient.
[01:04:51.780]It probably doesn't have such a yield drag
[01:04:54.921]with conversion to no tillage.
[01:04:57.750]I think it does take time.
[01:04:59.310]I think that one of the ways,
[01:05:01.160]the quickest ways to overcome that of course,
[01:05:02.950]is to come out of some situation
[01:05:04.610]that is not a tilled soil,
[01:05:07.270]is maybe there's, there's a forage crop
[01:05:10.120]that could be as a rotational crop.
[01:05:12.230]This is one of the best ways to build up
[01:05:14.080]a little bit of organic matter
[01:05:15.600]and to create a situation of the soil surface
[01:05:20.850]that it's much more receptive
[01:05:22.250]and that yield lag will disappear.
[01:05:27.170]Thanks, for the question though.
[01:05:28.900]Alan, we're gonna wrap up.
[01:05:31.560]That's gonna end the seminar today
[01:05:33.780]so thank you again, Alan.
[01:05:36.667]It was a great seminar,
[01:05:38.330]particularly enjoyed it
[01:05:39.937]and making the University of Nebraska proud as well.
[01:05:43.100]So thanks.
[01:05:44.910]Thank you all.

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Soil Health – How Management is Affecting the Pulse of Soil

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