Linking the Modification of Biochar Surface by Iron Oxides Under Field Conditions with Enhanced Nitrate Retention

Britt Fossum; M.S. ENVIRONMENTAL STUDIES. Department of Agronomy Author

12/11/2023 Added

10 Plays

Description

Efforts to develop soil management strategies that increase the retention of carbon, nutrients, and water have resulted in promising but inconsistent results. This study aims at clarifying the effects of biochar application and winter cover crops on soil carbon stocks, crop productivity, and potential mechanisms for nitrogen retention as analyzed under field conditions.

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[00:00:00.750]The following presentation
[00:00:02.220]is part of the Agronomy and Horticulture seminar series
[00:00:05.790]at the University of Nebraska Lincoln.
[00:00:08.550]All right, welcome everyone to today's seminar.
[00:00:11.670]I have the pleasure of introducing our speaker.
[00:00:14.370]Britt Fossum is on agronomy and horticulture
[00:00:17.310]doctoral student in environmental studies
[00:00:19.320]working under the supervision of Dr. Michael Kaiser
[00:00:22.080]and Dr. Aranda Malakar.
[00:00:24.210]Britt earned a bachelor of science in chemistry
[00:00:26.490]from Columbia University in New York
[00:00:28.860]and a master's of Science in Chemistry
[00:00:30.300]from the University of Chicago in inorganic chemistry.
[00:00:33.930]Now at UNL Britt works on research projects
[00:00:36.840]focusing on investigating how the production
[00:00:38.970]and application of Biochar may be combined
[00:00:41.100]with regenerative agricultural practices
[00:00:44.310]to support soil health.
[00:00:45.810]This interdisciplinary work aims to identify
[00:00:48.090]how soil management strategies
[00:00:49.530]may increase the retention of carbon, nutrients and water
[00:00:53.130]in agricultural soils,
[00:00:54.720]and incorporates techniques from both soil science
[00:00:57.180]and materials chemistry
[00:00:58.170]to answer questions about how Biochar behaves in soil.
[00:01:01.380]And then today, Britt will discuss key findings
[00:01:04.200]that address how the application of Biochar
[00:01:06.600]and use of winter cover crops influences soil carbon stocks,
[00:01:10.710]nitrate retention and potential mechanisms.
[00:01:12.930]So with that, I'll turn things over to Britt.
[00:01:15.390]Thank you. Hello.
[00:01:16.800]Thank you for the great introduction.
[00:01:19.140]So again, I'm Britt
[00:01:20.700]and I'm excited to share a little bit from the first year,
[00:01:25.710]year and a half of my time at UNL.
[00:01:28.500]Again, which is focusing on
[00:01:29.955]linking modification of Biochar surface by iron oxides
[00:01:34.770]under field conditions with observed nitrate retention.
[00:01:39.630]So to start with just a brief introduction
[00:01:41.820]discussing soil carbon,
[00:01:43.181]this is becoming an increasingly important topic
[00:01:46.020]in part because intensification of agriculture
[00:01:50.520]does lead to loss of soil carbon from the top soil.
[00:01:54.390]So zero to 30 centimeters,
[00:01:56.280]and this corresponds in turn to emission of carbon dioxide.
[00:02:00.180]Introduction of conservation practices
[00:02:02.100]can help to increase this soil carbon content
[00:02:05.340]and potentially can help to sequester some carbon dioxide.
[00:02:08.790]However, there are very few strategies
[00:02:11.250]that can really make up for the scale of the loss,
[00:02:14.730]especially as agriculture continues to grow
[00:02:18.390]and we continue to put more acres of land under cultivation.
[00:02:21.750]And so in this way it's seeking strategies
[00:02:24.090]that can help to increase soil carbon content
[00:02:26.880]becomes incredibly important.
[00:02:30.570]Increasing soil carbon can influence many properties
[00:02:33.420]that are critical for soils
[00:02:34.770]that are used for agriculture, including water.
[00:02:37.710]By improving soil structure and improving the way
[00:02:40.110]that water is managed throughout the soils.
[00:02:42.780]Soil carbon can additionally help
[00:02:44.310]to retain additional nutrients
[00:02:45.981]both through helping to keep water in soil,
[00:02:49.890]but additionally as a store of nutrients itself.
[00:02:53.280]It can additionally serve as a habitat
[00:02:55.230]and substrate for microbial growth,
[00:02:57.150]which is critical for soil health.
[00:02:59.040]And additionally has been discussed
[00:03:01.290]as a factor influencing remediation
[00:03:05.580]both of contaminants, heavy metals
[00:03:07.770]as well as helping to buffer pH changes throughout soil.
[00:03:11.280]And additionally, it's becoming increasingly popular
[00:03:13.770]as a potential target for carbon sequestration
[00:03:17.340]and way to store carbon from the atmosphere.
[00:03:22.380]However, many conventional methods
[00:03:24.720]of adding organic carbon to soils,
[00:03:26.670]including many common forms of organic amendment,
[00:03:29.730]are not necessarily as effective at sequestering carbon.
[00:03:33.540]And this is in part because many
[00:03:34.830]of these different forms are susceptible
[00:03:37.440]to decomposition over time.
[00:03:38.940]And so this is a great figure
[00:03:40.620]that just kind of outlies or lays out
[00:03:44.061]kind of the different behavior of Biochar
[00:03:47.160]as compared to many more conventional
[00:03:48.930]forms of organic amendment.
[00:03:50.700]And so this green line is showing
[00:03:52.290]what you would expect from sequential addition
[00:03:54.990]of a material like litter or compost,
[00:03:58.050]which tends to decompose fairly rapidly.
[00:04:00.570]If you're seeking to use one of these forms of amendment
[00:04:02.820]to try to increase carbon source in your soil,
[00:04:05.880]sequential addition is required
[00:04:07.500]and this will slowly build up to a steady state
[00:04:09.960]with higher carbon content.
[00:04:11.550]That is also potentially sensitive
[00:04:13.770]to carbon loss in the future
[00:04:15.270]depending on whether that management strategy changes.
[00:04:18.360]However, with addition of Biochar,
[00:04:20.100]which has a much slower decomposition rate in soil,
[00:04:23.340]and in fact it can kind of be difficult to determine
[00:04:26.520]how much Biochar decomposes.
[00:04:29.310]Sequential addition of Biochar actually kind of stacks.
[00:04:32.130]And so you can lead to an accumulation of carbon
[00:04:34.950]beyond what you would expect
[00:04:35.970]for more conventional amendments.
[00:04:38.340]And so a potential strategy rather than following the path
[00:04:41.340]of typical organic amendments,
[00:04:43.260]a potential strategy that you can use with Biochar
[00:04:45.720]that can be extremely effective
[00:04:47.460]is a one-time application of Biochar at a higher rate
[00:04:50.670]combined with no-till management
[00:04:52.080]and the use of cover crops that helps
[00:04:53.460]to maximize annual input in order
[00:04:55.560]to increase your organic carbon content.
[00:04:57.990]And so in this way, you can kind of get the benefits
[00:04:59.970]both of adding organic amendment
[00:05:01.860]along with some of the strategies like no-till
[00:05:03.930]that rely on not disturbing the soil.
[00:05:08.850]An additional problem with intensive agriculture is nitrogen
[00:05:12.270]and specifically nitrogen losses in places
[00:05:14.550]where we don't want it,
[00:05:15.780]which is anywhere besides the plant.
[00:05:17.550]And so this is a figure that just kind of outlines
[00:05:20.040]or out lays out, sorry, I keep doing that.
[00:05:22.290]Lays out kind of an overlay of both high rates
[00:05:26.850]of nitrogen input, which as we can see here,
[00:05:29.820]oh does kind of center across the US corn belt in Nebraska
[00:05:33.424]because of our high, high amounts of agriculture.
[00:05:36.390]And additionally matches it with high rates
[00:05:38.850]of aquifer vulnerability,
[00:05:40.170]which means that the groundwater is more susceptible
[00:05:42.630]to nitrate leaching.
[00:05:47.190]And so again, in Nebraska we have this hotspot
[00:05:49.424]where we both have very high aquifer vulnerability
[00:05:52.410]but also really high rates of nitrogen application,
[00:05:54.581]meaning that this is a region
[00:05:56.730]that could really use some strategies
[00:05:58.500]to help to minimize this.
[00:06:01.650]Now while carbon sequestration
[00:06:03.090]is one of the most reliable benefits
[00:06:05.479]that you see from Biochar application.
[00:06:07.950]It has been reported to have a number of effects
[00:06:10.170]on nutrient dynamics including both reducing
[00:06:12.990]the amount of nitrate leaching
[00:06:14.670]as well as influencing other transformations
[00:06:17.280]of nitrogen in your soil system.
[00:06:19.530]And so in this way, Biochar can potentially be used
[00:06:22.710]as a strategy to help mitigate nitrate leaching.
[00:06:28.410]And this is in part because Biochar soil
[00:06:30.180]interaction can be extremely complex.
[00:06:31.950]And so this is just kind of a really good diagram
[00:06:35.010]that illustrates both a Biochar particle
[00:06:37.024]as well as some of the potential interactions
[00:06:39.330]that you can see in soil that rapidly change
[00:06:41.730]that Biochar surface.
[00:06:43.560]And so again, the interactions are very complex
[00:06:46.350]and the Biochar surface weathers rapidly.
[00:06:48.390]Nothing is really constant in the soil.
[00:06:50.130]And so when you put your Biochar into the soil,
[00:06:52.620]it is going to undergo a number of reactions
[00:06:54.450]with components of the soil matrix, complexation,
[00:06:57.939]potentially even a liming effect,
[00:07:00.759]as well as incorporation into soil aggregates.
[00:07:03.660]And so the Biochar that you apply
[00:07:05.460]is not necessarily the Biochar
[00:07:07.170]that is leading to these observed benefits that we see.
[00:07:11.664]Nanoscale changes in the overall surface chemistry
[00:07:14.490]of the Biochar can have a large impact on soil.
[00:07:16.710]And so it's extremely critical to look at Biochar
[00:07:19.541]as it exists in the soil after application
[00:07:22.740]in order to better understand potential mechanisms
[00:07:25.590]that may be influencing
[00:07:27.210]both the nutrient retention
[00:07:28.860]as well as potential ways that Biochar
[00:07:30.870]is being incorporated into the soil better.
[00:07:37.830]In preparation for this project,
[00:07:39.630]the first step is to source Biochar feedstock.
[00:07:41.910]So that is a fairly common complaint
[00:07:44.370]that Biochar is not widely used in agriculture,
[00:07:47.820]especially not in Nebraska
[00:07:49.410]where we have a lot of very large scale field agriculture.
[00:07:52.650]And so sourcing both a feedstock
[00:07:55.800]as well as finding production conditions
[00:07:57.810]that can maximize kind of how homogenous
[00:08:00.224]that Biochar sample is can be somewhat difficult.
[00:08:02.670]And so this figure is coming out of a meta-analysis
[00:08:05.280]that we did to look at both feedstocks
[00:08:08.100]that are widely available in Nebraska.
[00:08:10.380]And so we looked specifically at corn stovers switch grass
[00:08:13.590]and wood as well as production conditions.
[00:08:16.920]And we hope to find a match between both properties
[00:08:19.980]that we desire, which in this case are carbon content
[00:08:23.130]of our Biochar and specific surface area of the Biochar,
[00:08:26.850]and then find a match between production conditions
[00:08:30.060]and feedstock choice that can give us
[00:08:32.280]both these desired properties
[00:08:34.770]and also can hopefully give us more consistent results
[00:08:37.980]in terms of Biochar production.
[00:08:40.200]And so again, we found a match
[00:08:41.610]between wood and high temperature
[00:08:43.740]for our production conditions in our feedstock.
[00:08:46.860]And luckily in Nebraska,
[00:08:47.940]we have a fairly readily available waste wood
[00:08:50.910]in the form of eastern red cedar,
[00:08:52.290]which is definitely unwanted
[00:08:54.919]in many parts of Nebraska's grasslands.
[00:08:57.690]And so utilizing this as our feedstock for Biochar
[00:09:01.380]means that we are also helping to use some waste product
[00:09:04.920]and turn it into something more productive.
[00:09:10.170]And overall, I would just like to help people
[00:09:13.470]think about the importance of scale overall.
[00:09:15.390]And so for this project, you really need
[00:09:17.460]to think about it on multiple different scales
[00:09:20.490]and Biochar operating and influencing things
[00:09:23.400]at multiple scales at once.
[00:09:25.410]And so to start with,
[00:09:27.150]we discussed the nanoscale very briefly
[00:09:29.040]in Biochar surface properties,
[00:09:31.080]but these nanoscale properties such as changes
[00:09:33.150]in the surface chemistry of Biochar particles
[00:09:35.670]and interactions and redox processes
[00:09:37.593]that may be happening at the Biochar soil
[00:09:40.410]and Biochar water interface
[00:09:41.941]can then influence properties
[00:09:45.180]that we see at the soil scale,
[00:09:46.980]including changes in retention of water
[00:09:48.930]and nutrients throughout the soil profile.
[00:09:51.630]These soil scale properties in turn
[00:09:53.670]can influence our larger field scale properties,
[00:09:56.040]which is the outcome that we hope to see.
[00:09:58.500]And this includes net nitrogen use in the system,
[00:10:01.500]our crop and cover crop uptake in yield,
[00:10:03.510]as well as overall carbon sequestration.
[00:10:06.870]And this overall trend does not go just one way.
[00:10:11.160]Irrigation, fertilizer type, management decisions
[00:10:14.220]and all of these other large scale field operations
[00:10:17.670]can then have a strong impact
[00:10:19.530]on the chemical environment of Biochar
[00:10:21.660]by influencing that soil environment as well.
[00:10:28.170]So as an overview of our field sites
[00:10:30.690]and set up, our Biochar producer is located in state
[00:10:34.860]in kind of north central Nebraska.
[00:10:37.500]And our two field sites are both located
[00:10:39.540]at University of Nebraska Lincoln research sites.
[00:10:43.500]So one is located at the ENREEC facility
[00:10:46.530]near Mead, Nebraska, and that is our figure on the left.
[00:10:49.530]That is one of our Biochar plots
[00:10:51.030]immediately after application
[00:10:53.430]and this site is irrigated.
[00:10:56.010]And then on the right we have our second site,
[00:10:57.900]which is at the SCAL South Central agronomic lab,
[00:11:01.650]and that is near Clay Center, Nebraska.
[00:11:03.870]And this site is irrigated from July through August.
[00:11:07.200]However, both sites do have the same crop,
[00:11:09.737]corn soybean rotation,
[00:11:11.400]and they're both corn in the same year.
[00:11:14.010]And they both utilize the same cover crop,
[00:11:16.020]which is a rye cover crop planted in the winter
[00:11:18.900]and ended in the spring.
[00:11:21.870]And Biochar was applied at the same rate
[00:11:23.910]at both sites at approximately 28 tons per acre
[00:11:27.360]corresponding to approximately 70 megagrams per hectare.
[00:11:33.390]Our treatment design involves both incorporating
[00:11:36.030]the initial design of these experimental sites.
[00:11:38.820]So before we applied Biochar at all,
[00:11:41.220]these were experiments in no-till
[00:11:42.810]and cover crop combinations.
[00:11:44.700]And so we keep these reference soils
[00:11:46.200]so that we are able to test for differences
[00:11:48.450]that are in effect of our application method
[00:11:50.370]and not the Biochar itself.
[00:11:52.890]And then we take both our cover crop system
[00:11:55.620]and our control system with no cover crop
[00:11:58.350]and subject all of our plots
[00:11:59.790]to a one-time disking at the time of Biochar application
[00:12:03.330]so that we are then able to compare
[00:12:05.610]directly the interactions between cover crop and Biochar.
[00:12:12.630]And overall, our objectives for this study
[00:12:14.670]are to look at both the agronomic scale,
[00:12:16.890]to monitor soil organic carbon storage
[00:12:18.990]and our crop and cover crop yield.
[00:12:20.970]And this is in part to look at the efficacy of our strategy.
[00:12:23.430]If you're negatively impacting your yield
[00:12:25.500]even in the first year, that could be something
[00:12:27.390]that ends up making this Biochar strategy less appealing.
[00:12:31.050]At the soil scale, we hope to determine the effect
[00:12:33.090]of Biochar on nutrient retention throughout the soil profile
[00:12:36.150]and determine if we are seeing an impact
[00:12:38.340]from the Biochar application
[00:12:40.080]on whether we see nitrate leaching deeper into the profile
[00:12:43.200]or even if we just see nitrate retention in the top soil.
[00:12:46.860]And finally at the nanoscale,
[00:12:48.570]we hope to link Biochar surface properties
[00:12:51.330]to potential nutrient retention mechanisms
[00:12:53.490]and find a little bit more evidence
[00:12:55.530]to support that Biochar
[00:12:56.730]is really helping with this nutrient retention.
[00:12:59.490]And it's not just an increase of organic carbon
[00:13:02.370]leading to greater potential structure in the soil.
[00:13:08.040]For our methods, we assess both yield and biomass
[00:13:10.710]for row crops and cover crops,
[00:13:12.510]and we conduct a annual soil sampling campaign in the fall
[00:13:16.140]with a slightly smaller follow up in the spring,
[00:13:18.300]only going to 30 centimeters this past year.
[00:13:21.540]These samples are composed from four cores
[00:13:23.940]taken from each plot and are taken to 90 centimeters.
[00:13:27.330]And then subs sampled.
[00:13:29.100]Our first subsample from zero to 10 centimeters
[00:13:31.560]roughly corresponds to the depth
[00:13:33.030]of Biochar incorporation.
[00:13:34.830]There is occasionally some that gets a little bit deeper,
[00:13:37.530]but that is what we estimate is the depth.
[00:13:40.680]From 10 to 30 centimeters makes up
[00:13:42.360]the remainder of our top soil.
[00:13:44.520]And then from 30 to 60 centimeters
[00:13:46.560]and 60 to 90 centimeters,
[00:13:48.210]we mainly just assess for carbon,
[00:13:50.040]nitrogen, nitrate, and ammonia.
[00:13:52.350]And these represent our,
[00:13:55.020]these represent our soil samples
[00:13:57.000]that allow us to look at nitrate leaching.
[00:13:59.430]Our top soil samples receive
[00:14:01.110]slightly more extensive analysis,
[00:14:02.700]including most critical nutrients,
[00:14:06.210]cation exchange capacity, bulk density, and pH.
[00:14:09.420]And again, all soils are tested
[00:14:11.490]and analyzed for total carbon and nitrogen,
[00:14:14.160]nitrate and ammonia.
[00:14:15.870]And additionally, we isolate the Biochar particles
[00:14:19.860]and subject them to a technique
[00:14:21.180]called x-ray photo electrons spectroscopy,
[00:14:24.090]which allows us to get details
[00:14:25.530]about the chemical environment at the Biochar surface.
[00:14:31.320]So just to get into a little bit of the results,
[00:14:33.660]the first is probably the least surprising,
[00:14:35.970]and this is our carbon storage result.
[00:14:38.490]At six months post application
[00:14:40.410]we do see that Biochar led to a significant increase
[00:14:43.260]in carbon storage in our top soil
[00:14:45.180]from zero to 30 centimeters.
[00:14:46.980]And of course we don't expect it,
[00:14:48.240]or we are not surprised by this.
[00:14:50.837]We applied a very large amount of Biochar.
[00:14:52.230]However, one thing that was interesting
[00:14:54.090]is our Biochar application rate of 70 megagrams per hectare
[00:14:57.780]should correspond to approximately 58 milligrams per hectare
[00:15:01.080]of carbon appearing in the soil.
[00:15:03.360]And while for some of our treatments,
[00:15:04.560]we do see that we had most of this showing up
[00:15:08.010]where we expect to in the soil,
[00:15:09.720]we did see some losses,
[00:15:11.220]specifically from our cover crop and Biochar treatment
[00:15:14.280]at our irrigated site.
[00:15:15.990]Although there were also some differences
[00:15:17.820]between some of the other treatments.
[00:15:20.100]And this is something that we will want
[00:15:21.570]to look at next year.
[00:15:22.680]At the application time there's a lot of variability.
[00:15:25.500]And so it's possible that this could be
[00:15:27.794]an effect of our application method or sampling method,
[00:15:34.200]but overall, this is not the most surprising result
[00:15:37.770]that we could see.
[00:15:38.820]This is one of the main
[00:15:40.470]and well-established effects of Biochar.
[00:15:42.480]So to see that we improve carbon storage is to be expected.
[00:15:45.660]The real question is whether
[00:15:47.010]we continue to see this over time
[00:15:49.260]and whether we see any losses.
[00:15:53.100]Now looking at our inorganic nitrogen,
[00:15:54.810]so looking here on the Y-axis,
[00:15:58.110]we have our stock value in kilograms per hectare.
[00:16:01.620]And on our Y-axis, this is just laying out Biochar
[00:16:05.130]and no Biochar treatments with nitrate listed in red
[00:16:09.360]and ammonia in blue.
[00:16:11.370]And so to look at this here,
[00:16:12.870]the main result that we observed was first
[00:16:14.730]that there was no impact on post-harvest subsoil nitrate.
[00:16:17.910]We didn't really see that Biochar
[00:16:21.090]reduce the amount of nitrate leaching,
[00:16:22.770]but we also didn't see that there was any differences there.
[00:16:25.320]And so what we then look at
[00:16:27.480]as a somewhat more important result
[00:16:29.550]is that in our top soil from zero to 30 centimeters
[00:16:32.850]for the specific combination of cover crop with Biochar
[00:16:36.270]at our rain-fed site, we did see a significant,
[00:16:40.775]a significantly greater amount of nitrate retained
[00:16:44.220]in the top soil from zero to 30 centimeters.
[00:16:48.870]There was a slight trend at our irrigated site,
[00:16:51.900]at least for our,
[00:16:54.673]sorry, there was a slight trend towards,
[00:16:57.682]at our irrigated site slightly more nitrate was retained
[00:17:01.320]by the Biochar cover crop combination as well.
[00:17:03.720]However, it's really at that rain-fed site where we saw it.
[00:17:08.580]This actually was what inspired a second soil sampling
[00:17:12.120]attempt in the spring
[00:17:13.200]to look at zero to 30 centimeters again,
[00:17:15.240]and this was in part to see
[00:17:17.160]how much was retained into the spring,
[00:17:19.320]because that's really the more important value.
[00:17:22.740]So looking at our post harvest samples
[00:17:24.930]compared to our spring,
[00:17:26.490]again, we here in the spring,
[00:17:28.050]we only sampled from zero to 10 and 10 to 30 centimeters.
[00:17:31.500]We obviously see that we lost quite a lot
[00:17:33.360]of this nitrate over the winter.
[00:17:35.670]However, we also see this time
[00:17:38.070]for our irrigated site that we had slightly more nitrate
[00:17:40.680]retained in the top soil for our Biochar treatments.
[00:17:47.100]And now just to get into a little bit about our methods
[00:17:50.730]for surface characterization.
[00:17:52.170]And specifically to describe
[00:17:53.490]x-ray photoelectron spectroscopy a little bit more
[00:17:55.860]because it's a technique that is not as widely used
[00:17:58.728]and it can be a little bit complicated.
[00:18:01.500]So just to outline a little bit.
[00:18:04.200]So to start with, it uses the photoelectron effect,
[00:18:07.110]which is essentially using energy
[00:18:10.020]in the form of, in this case, x-rays,
[00:18:12.510]to excite an electron in on one of your elements,
[00:18:17.460]which will then emit a photoelectron.
[00:18:20.130]And so here we know our input, x-ray energy,
[00:18:23.610]we know the kinetic energy
[00:18:25.050]of the photoelectron that's been emitted, which we measure.
[00:18:28.080]And from that, we are able to calculate the binding energy,
[00:18:31.710]which gives us information
[00:18:32.820]about the element in chemical bonding state.
[00:18:34.800]So essentially, where did that electron originate from.
[00:18:39.990]And why we use this is it is a fingerprinting technique
[00:18:42.900]for identification of the element composition
[00:18:45.554]and chemical and electronic state,
[00:18:48.060]and it gives you a quantitative
[00:18:49.320]determination of composition.
[00:18:51.030]So if you take one of these spectra and look at it,
[00:18:54.150]you are able to get exact values telling you
[00:18:57.150]how much of each species that you identify as present.
[00:19:00.000]And additionally, it's limited only to the surface
[00:19:02.310]zero to 10 nanometers, which for us is critical,
[00:19:04.980]because we only care about the surface.
[00:19:09.060]Our methods include handpicking Biochar particles,
[00:19:12.450]visible size greater than two millimeters
[00:19:14.730]and clean using sonacation for two minutes,
[00:19:16.800]which should remove anything
[00:19:18.690]that is not actually attached to the Biochar surface.
[00:19:22.770]And our XPS spectra were obtained for nitrogen.
[00:19:25.500]In this case, the 1s region, iron, carbon, and oxygen.
[00:19:30.990]Pristine Biochar from both delivery dates were analyzed.
[00:19:33.660]And at minimum three measurements
[00:19:35.310]were performed on each sample.
[00:19:37.440]And here sample means basically Biochar particles
[00:19:40.830]collected from each plot.
[00:19:42.270]Each particle was analyzed individually.
[00:19:46.290]So just as a little bit of a review,
[00:19:47.790]because these spectra can be kind of confusing,
[00:19:50.160]this is a periodic table of elements.
[00:19:52.500]And here if we want to look at carbon,
[00:19:54.300]nitrogen or oxygen, we look at the 1s electron.
[00:19:58.800]And in this case, this gives us a singlet peak.
[00:20:02.340]However, if we want to move up to iron
[00:20:04.320]as it's slightly heavier element
[00:20:05.610]in the transition metal area,
[00:20:07.560]we look at the 2p region
[00:20:09.000]and this gives us a doublet peak.
[00:20:11.310]So that's why the peaks look a little
[00:20:13.453]different for these two elements.
[00:20:14.610]And then just as an explanation for why we're able
[00:20:16.860]to see differences between different species,
[00:20:19.380]differences in the redox state of the element
[00:20:21.570]gives you differences in electron binding energy.
[00:20:23.760]And so here we have nitrate and we have ammonia.
[00:20:26.820]We look at this, our higher end 1s binding energy
[00:20:29.490]will be for the nitrogen in nitrate.
[00:20:33.960]And our lower N 1s binding energy will be
[00:20:36.180]for our nitrogen in ammonia.
[00:20:39.720]Looking at the iron 2p region,
[00:20:42.090]here on the left we have our pristine Biochar.
[00:20:45.060]And on the on the right, this is a example spectrum
[00:20:48.360]from one of the particles from SCAL,
[00:20:50.460]which is our irrigated site, six months post application.
[00:20:54.114]And so here you can see the characteristic doublet peak.
[00:20:57.360]I'm just gonna start with the irrigated site peak
[00:20:59.460]because it's a bit easier to explain something
[00:21:01.200]when there is something there to be explained.
[00:21:03.330]And so actually the peaks are,
[00:21:08.490]the two peaks that you see here,
[00:21:09.810]the blue and the red are fitted peaks.
[00:21:12.900]And so we fit these to our observed data
[00:21:15.210]and determine how well they match.
[00:21:17.040]So one feature that is somewhat common
[00:21:19.710]in all of the spectrum that I've been looking at at least,
[00:21:22.020]is that these peaks tend to have a shoulder.
[00:21:24.870]So we can tell that there are clearly multiple species
[00:21:27.360]present in our iron spectrum.
[00:21:31.170]So here we identify that our reduced species
[00:21:34.980]iron 2p correspond to these blue peaks
[00:21:37.154]at a somewhat lower binding energy.
[00:21:41.610]And meanwhile, our oxidized iron,
[00:21:44.040]corresponding here to this red peak,
[00:21:45.960]will appear at a slightly higher binding energy.
[00:21:49.320]And then once we have analyzed this,
[00:21:51.690]you can actually determine the relative composition,
[00:21:54.270]how much of iron is in each redox state
[00:21:57.000]relative to each other.
[00:21:59.580]And when we look at our pristine Biochar species
[00:22:02.130]for 50% of rain fed Biochar
[00:22:05.637]and 95% of irrigated Biochar
[00:22:07.770]contained surface iron of some kind.
[00:22:10.320]And out of this a hundred percent
[00:22:12.270]had some contribution from iron species.
[00:22:15.570]On the other hand, absolutely none of the Biochar
[00:22:18.510]pristine particle samples ever analyzed
[00:22:21.270]had detectable iron present at the surface.
[00:22:23.975]And so this is clearly something
[00:22:24.808]that is coming out of the soil
[00:22:26.490]and only happening after the Biochar
[00:22:28.290]has been aged under field conditions.
[00:22:31.560]And now tying this back into our nitrogen results.
[00:22:35.730]So this is looking at the nitrogen 1s region.
[00:22:38.070]Again, here you see only a singlet peak.
[00:22:40.530]Our pristine Biochar is on the left.
[00:22:42.720]There will be nitrogen present in pristine Biochar.
[00:22:45.900]It is produced from wood.
[00:22:48.300]But here we primarily see that nitrogen
[00:22:50.340]as either organic nitrogen
[00:22:52.470]or as various potential ammonia species.
[00:22:56.370]However, six months post application,
[00:22:58.200]and this is actually the nitrogen spectrum
[00:23:00.960]from that same particle.
[00:23:02.160]So it's at that the same position.
[00:23:04.470]We do see still organic nitrogen
[00:23:06.840]and potential other species,
[00:23:08.730]but for some of these we start to see
[00:23:11.117]a very small nitrate feature.
[00:23:14.910]Less than 5% of our iron functionalized particles
[00:23:17.670]from the irrigated site
[00:23:19.050]contain this nitrate feature that can be resolved.
[00:23:23.220]However, even a very small peak at the nanoscale
[00:23:26.010]can correspond to a nearly 400 centimeter squared
[00:23:31.350]of Biochar surface just in one cubic centimeter of soil.
[00:23:34.770]And so if you think about the scale of this,
[00:23:37.500]even though this feature is a very small component
[00:23:39.720]of the total amount of nitrogen present
[00:23:41.220]at the Biochar surface, scaled up across,
[00:23:43.860]not just that single Biochar particle,
[00:23:45.634]but across all of the Biochar added into your soil,
[00:23:48.780]this can quickly correspond
[00:23:50.340]to a significant amount of nitrate retention.
[00:23:56.070]Potential mechanisms, especially including
[00:23:59.430]some of the dynamics between our rain fed system
[00:24:01.440]and our irrigated system may be influenced
[00:24:03.840]by how much of the Biochar surface
[00:24:06.030]is in contact with soil water during the growing season.
[00:24:09.600]And so last year, 2022 was a somewhat unusual one.
[00:24:14.730]It was very dry, there was very little moisture,
[00:24:16.770]especially at our rain-fed site.
[00:24:18.450]And so the Biochar particle is not necessarily in contact
[00:24:21.360]with soil water for extended periods of time,
[00:24:24.420]which could potentially explain the fact
[00:24:27.660]that we have much fewer particles
[00:24:29.850]at our rain fed site that are modified.
[00:24:33.420]However, at our irrigated system,
[00:24:35.190]we did have much more moisture,
[00:24:37.200]especially during the growing season,
[00:24:38.970]which could lead to an explanation
[00:24:40.890]for why we see so much more
[00:24:43.050]of the Biochar here under irrigated conditions
[00:24:45.840]that has been modified.
[00:24:47.760]And so we seem to see that the influence
[00:24:51.030]of water management is greater than the influence
[00:24:52.950]of soil type.
[00:24:54.750]We also have to account for the fact
[00:24:56.520]that whatever this mode of interaction is,
[00:24:58.470]it has to preserve some iron to reduced iron species.
[00:25:02.400]And so this diagram is showing
[00:25:03.930]a couple of potential modes of interaction.
[00:25:06.360]And so methods such as absorption
[00:25:08.010]of poorly crystalline phases
[00:25:09.330]that may be able to protect
[00:25:10.590]some of these reduced iron species
[00:25:12.600]link an exchange processes
[00:25:14.430]that may result in a reduced iron species present
[00:25:17.190]at the surface of Biochar, as well as other redox
[00:25:19.350]mediated processes may be critical
[00:25:21.600]to understand what's going on here.
[00:25:24.060]And then finally, the most unfortunate part
[00:25:25.800]is that the form and structure of iron species
[00:25:27.630]cannot be determined with XPS alone.
[00:25:29.820]The spectrum just gets too complex.
[00:25:31.800]You really can't get any more detailed
[00:25:33.720]than maybe one or two species.
[00:25:38.790]Our next steps for the project
[00:25:39.990]do involve looking a little bit more closely
[00:25:41.880]at some of the carbon dynamics.
[00:25:43.830]And so starting at 18 months post application,
[00:25:47.070]which would be about this month,
[00:25:49.980]we're looking at combined physical
[00:25:51.330]and chemical approach to monitor
[00:25:52.860]the distribution of Biochar carbon after application.
[00:25:55.740]So to do this, we are using a both density
[00:25:58.417]through electrostatic attraction
[00:26:00.390]of free particulate organic matter
[00:26:02.070]to isolate that component, physical fractionation
[00:26:05.836]including aggregate disruption using ultrasonication
[00:26:08.820]to target some of those occluded particulate organic matter,
[00:26:12.180]and additionally chemical using water
[00:26:14.190]to extract water extractable organic matter.
[00:26:19.260]Additional next steps include both scaling up
[00:26:22.110]and scaling down in some ways.
[00:26:23.640]So reducing the overall application rate of Biochar
[00:26:26.490]by combining it with other forms of organic amendment.
[00:26:29.190]So this is actually from a second project
[00:26:31.770]that began in spring 2023,
[00:26:34.350]and this is in the city of Lincoln,
[00:26:36.840]just off 70th street if you ever wanna drive by.
[00:26:39.900]And here we actually scaled up to one acre size plots
[00:26:43.650]in order to get a better idea of how this works
[00:26:45.840]at a more agronomic relevant scale.
[00:26:48.210]And so here the Biochar is applied
[00:26:49.710]at only a rate of eight tons per acre,
[00:26:51.750]so much lower than we did for our other project,
[00:26:55.260]and was combined with Biosolid source
[00:26:56.940]from the city of Lincoln,
[00:26:59.131]which is a form of organic amendment
[00:27:00.360]that is used oftentimes
[00:27:02.010]and also includes turning a waste product
[00:27:04.470]into something more productive.
[00:27:06.570]The crop management is the same
[00:27:09.390]as well as the cover crop use,
[00:27:12.480]and it is also managed under no-till
[00:27:14.940]with the entire field being dissed one time
[00:27:16.860]at the time of Biochar application.
[00:27:19.020]And this way we're able to combine
[00:27:21.168]both Biochar, Biosolid and the combination in order
[00:27:23.520]to determine if we can still see some
[00:27:25.140]of these effects at a lower application rate,
[00:27:27.900]but in combination with other amendments.
[00:27:31.530]And this is just a image aerially of the field.
[00:27:34.050]And so here on the left we have our combined treatment
[00:27:36.420]with Biochar/Biosolid, Biosolid in the center
[00:27:39.707]and a Biochar plot on the right.
[00:27:42.900]So it is really cool that you can see these
[00:27:45.190]just so distinctly.
[00:27:48.600]Again, Biochar is a very new development,
[00:27:51.405]and so a lot of extension and outreach is,
[00:27:53.947]that's something I've been doing a lot of at least
[00:27:56.730]in order to talk to people
[00:27:57.870]and kind of get the temperature
[00:27:59.610]on what people are thinking about.
[00:28:00.840]And I get more questions every single time
[00:28:03.750]that I go out to UNL field days.
[00:28:06.171]And additionally, it's been great to work with
[00:28:09.930]some education including City of Lincoln Public Schools.
[00:28:15.270]And then finally, just for some take home messages
[00:28:17.340]at high application rate
[00:28:18.510]losses varied mostly by treatment and site.
[00:28:21.227]And then our nitrate retention
[00:28:23.550]was influenced by Biochar edition,
[00:28:25.440]but really only with the interaction of cover crop.
[00:28:29.340]And it was additionally influenced
[00:28:30.720]by the water management dependent on our site.
[00:28:33.783]And finally, functionalization of Biochar
[00:28:36.240]with soil derived iron oxides
[00:28:38.100]occurs within the first six months of application
[00:28:40.830]and is associated with increased nitrate species present
[00:28:43.710]at the Biochar surface.
[00:28:45.930]And so finally, the influence of scale
[00:28:48.048]is something that I think everybody should consider
[00:28:50.880]that these nanoscale interactions
[00:28:52.710]can have cumulative effects on field scale properties
[00:28:55.680]and are incredibly important.
[00:28:58.650]So just some acknowledgements
[00:29:00.120]both to all the people who who've helped,
[00:29:02.367]including both Chris and Mahmoud, who are here today.
[00:29:05.467]And then thanks to the Nebraska Nanoscale facility
[00:29:09.450]for letting me come in and use their XPS instrument,
[00:29:14.040]all funding agencies.
[00:29:15.060]And again, also thank you
[00:29:17.105]especially to all the field technicians who have helped us,
[00:29:19.440]especially with that Biosolid/Biochar project
[00:29:21.870]that took a lot of work.
[00:29:23.790]So thank you all.
[00:29:26.430]Thank you so much, Britt. Who would like to start?
[00:29:33.480]Okay, then I'll start.
[00:29:36.570]Okay, thank you, Britt.
[00:29:38.070]Wondering the relationship you saw with iron oxide,
[00:29:41.220]is that something that you expected
[00:29:42.690]to come out with Biochar surface interactions?
[00:29:45.690]This was something that had been observed
[00:29:47.610]by a previous project in a greenhouse study.
[00:29:50.820]And so this was kind of hoping
[00:29:52.350]to see whether we could still observe it
[00:29:55.140]under field conditions.
[00:29:57.180]And I think it was not necessarily guaranteed
[00:30:01.170]that it would be something seen after only the first year.
[00:30:04.050]That was very interesting and very exciting.
[00:30:07.140]So yeah.
[00:30:08.310]Awesome, thank you.
[00:30:10.448]Okay, great.
[00:30:15.090]There is any other student
[00:30:16.530]that you're also looking for the microbiology
[00:30:18.688]at the soil when you look for that Biochar?
[00:30:23.040]Yeah, the microbiology? Yes.
[00:30:25.920]Like how is the interaction?
[00:30:28.393]That's a really good question.
[00:30:30.448]That's something that we're actually just beginning to do.
[00:30:32.102]And so we are primarily looking
[00:30:33.960]at using FAM instead of something
[00:30:36.630]a little bit more granular, like DNA sequencing
[00:30:39.180]and FAM really is kind of what we wanna see.
[00:30:41.340]We just wanna see are there general changes
[00:30:43.110]in our microbial communities.
[00:30:45.570]And so we are starting to do that
[00:30:47.220]and that will definitely be incorporated
[00:30:48.930]into especially the carbon infractionation
[00:30:51.630]as a way to support any evidence we see there.
[00:30:59.820]From an agronomic point of view,
[00:31:02.790]what's the stuff cost?
[00:31:04.770]Too much.
[00:31:06.600]It really depends.
[00:31:08.272]Some people that I've spoken to
[00:31:10.080]have gone to the point of trying to make it themselves.
[00:31:12.600]And so in that case, it's whatever your cost
[00:31:14.310]of time and effort is.
[00:31:15.720]But even up to like a thousand per ton,
[00:31:20.790]per acre or something.
[00:31:22.260]It depends a bit.
[00:31:23.670]Right now it's between $500 and $2000 per charge.
[00:31:28.454]And we are, that's still expense on...
[00:31:32.430]So it's 500 to $2,000 per ton
[00:31:35.040]depending on who we are working with.
[00:31:38.520]We got donations because we have collaboration partners
[00:31:42.193]at the west coast.
[00:31:44.193]Right now the big issue is upscaling.
[00:31:47.280]And that is more on a political,
[00:31:49.350]a political problem that we upscale this.
[00:31:52.230]So we need more plans.
[00:31:54.090]City of Lincoln is building a plan right now
[00:31:56.332]that's in the planning, so we got funding for this.
[00:32:00.570]But it needs to be a nationwide effort to upscale this
[00:32:04.140]because you need to upscale the production
[00:32:06.660]to make it cheaper,
[00:32:07.830]but you need to upscale the production
[00:32:09.974]to apply it large scale.
[00:32:12.330]But that's an issue, right?
[00:32:14.370]But the work of put is laying with many other projects,
[00:32:20.610]the foundation, why we should do this.
[00:32:29.790]I will just comment
[00:32:32.289]that in the recent issue of "Successful Farming"
[00:32:35.070]or "Nebraska Farmer",
[00:32:37.230]they were talking about the value of farmland.
[00:32:40.500]There was some farmland out by York
[00:32:43.350]that sold for 13,000 an acre.
[00:32:46.050]Now if you were putting on 28 ton of this stuff,
[00:32:48.960]you've got another 14,000 on there.
[00:32:53.372]So you've got an uphill battle.
[00:33:06.000]All right, Britt,
[00:33:07.433]I got a question online for you.
[00:33:08.700]Is there a higher goal to sequester carbon
[00:33:11.610]or diminish nitrate leaching in your Biochar projects
[00:33:16.950]or are both equally important?
[00:33:20.520]I would say to me they're both equally important
[00:33:23.370]in terms of the overall project scope.
[00:33:25.230]One that is really important
[00:33:26.880]for kind of delivering on what we are doing
[00:33:30.450]with our project is nitrate leaching.
[00:33:32.250]But carbon sequestration is also incredibly important.
[00:33:35.100]And personally to me that is one thing
[00:33:38.250]that I care about quite a lot
[00:33:40.497]and trying to just reduce the amount of carbon dioxide
[00:33:43.560]in the atmosphere and slow global warming.
[00:33:45.540]But again, there are all kinds of health dangers
[00:33:49.320]and risks that come with contamination
[00:33:51.540]of groundwater resources.
[00:33:52.860]And so honestly, maintenance of environmental
[00:33:57.162]and water health is also extremely critical
[00:34:00.570]and extremely important.
[00:34:08.750]Thanks Britt, I have two question.
[00:34:12.120]One is, what is the effect of the irrigation chemistry
[00:34:16.650]on the interactions
[00:34:18.090]that maybe you have looked at,
[00:34:21.090]including nitrate input from the irrigation water
[00:34:24.210]and iron input from the irrigation water?
[00:34:26.721]My second question follows what was asked
[00:34:30.981]in relation to the debate between carbon sequestration.
[00:34:40.110]Since you are adding carbon
[00:34:42.300]and is that really carbon sequestration
[00:34:46.080]or you're just putting an input
[00:34:47.730]to call it a carbon sequestration?
[00:34:49.440]So if you can clarify and along that line
[00:34:52.500]maybe also talk about the energy footprint
[00:34:57.360]to produce the Biochar. Yes.
[00:34:59.121]That is a really excellent question.
[00:35:01.170]I'll answer the second one first
[00:35:03.120]and then go back to the first one.
[00:35:05.057]'cause that one is a little bit more,
[00:35:06.270]I need to consider it a little bit more.
[00:35:07.620]But for the second, the second one,
[00:35:10.110]that is absolutely something that is not guaranteed.
[00:35:12.510]We did not do a full lifecycle analysis
[00:35:15.180]of the Biochar we used for our first project,
[00:35:17.370]although assessing the footprint
[00:35:19.140]is a part of the second project.
[00:35:21.270]That is something that we're hoping to do.
[00:35:23.040]And that one does have a little bit more
[00:35:24.780]about looking at nitrous oxide emissions.
[00:35:28.320]And so even though Biochar production,
[00:35:31.470]it's a process called pyrolysis,
[00:35:33.450]it can also release carbon dioxide into the atmosphere
[00:35:37.410]and you are using biomass.
[00:35:39.570]So I mean, to be fair, a lot of these trees
[00:35:42.060]may have just ended up being burned anyways.
[00:35:44.070]And so again, seeking waste material
[00:35:46.680]helps you offset that a little bit.
[00:35:49.770]But again, looking at a full lifecycle analysis
[00:35:52.380]and determining just how much carbon are we sequestering,
[00:35:55.200]just how much emissions are we offsetting or preventing,
[00:35:58.530]especially if there is an influence
[00:36:00.930]of Biochar on reducing nitrous oxide emissions.
[00:36:04.290]So that is absolutely something
[00:36:05.970]that is not guaranteed from this project,
[00:36:07.650]but it is something that we're looking at,
[00:36:10.230]especially with the second one.
[00:36:12.270]And then to go back to the first.
[00:36:14.520]In terms of the water differences,
[00:36:16.980]I believe they do use vertigation at SCAL,
[00:36:19.050]but it is the same rate for nitrogen application.
[00:36:23.500]And that is something, especially with the iron,
[00:36:27.180]I have not even considered that.
[00:36:28.620]But we did look at both kind of a,
[00:36:32.241]it's a generic ward lapse characterization
[00:36:34.770]of plant available iron using a weak acid.
[00:36:37.410]And we also did some other iron extractions
[00:36:40.410]including oxalate and DCB, which essentially
[00:36:46.260]our ENREEC site actually did have
[00:36:48.720]a larger amount overall on average
[00:36:50.850]of especially oxalate extractable iron.
[00:36:53.010]And so even if there is something
[00:36:56.130]coming from the irrigation water,
[00:36:59.520]I would have to look at that a little bit more closely.
[00:37:02.610]But I don't know that that would have an influence
[00:37:04.950]over the amount currently present in the soil.
[00:37:09.150]Yeah.
[00:37:12.180]Okay, Britt, I have,
[00:37:14.280]Daniel Shockman has two questions,
[00:37:15.960]so I'm just gonna ask one
[00:37:17.903]and then we'll go back to the other one, okay.
[00:37:19.583]Okay.
[00:37:20.416]It says nice talk.
[00:37:21.270]And why use XPSs instead of
[00:37:24.390]standard chemical based analysis?
[00:37:28.260]So again, a part of this is what we wanted to look at,
[00:37:31.920]which is the Biochar surface.
[00:37:33.780]You have a kind of unique substrate
[00:37:35.790]where you can isolate just the Biochar itself
[00:37:39.060]and then you can look at it
[00:37:40.020]with slightly more detailed techniques.
[00:37:42.540]A part of that is that we are, again, as I said,
[00:37:45.150]this was something that had been seen
[00:37:47.500]in some greenhouse work previously.
[00:37:49.800]And so we did wanna use that same technique,
[00:37:51.930]but it was chosen in the first place
[00:37:53.700]because looking at a broader range of different elements,
[00:37:57.420]you can look at other things,
[00:37:58.380]you can look at phosphate,
[00:37:59.460]you can look at calcium,
[00:38:00.450]you can look at all kinds of things.
[00:38:02.040]And actually to start with,
[00:38:03.750]you just kind of scan across a wide range of energies
[00:38:07.830]and see which elements are present.
[00:38:09.540]And so for our samples this time,
[00:38:13.080]almost never did I see phosphorus or calcium present.
[00:38:16.950]I did occasionally see iron even
[00:38:18.960]visible at kind of that larger scale
[00:38:21.360]and almost always saw a nitrogen, oxygen, all that stuff.
[00:38:24.510]So again, it gives you the ability
[00:38:26.670]to look at a wide range of different elements
[00:38:28.680]and then get extremely detailed information
[00:38:30.600]about speciation.
[00:38:31.860]And again, that localization
[00:38:34.140]only to the surface is important
[00:38:36.450]because we really want to see the surface.
[00:38:38.940]We don't wanna see all of this stuff happening deep
[00:38:42.060]inside the Biochar
[00:38:42.893]where it is not affecting soil processes.
[00:38:47.100]I lied, he has three.
[00:38:48.901]Okay.
[00:38:49.734]Have you considered
[00:38:51.583]measuring soil respiration instead of FAMs?
[00:38:55.560]I had not considered that,
[00:38:57.861]but that is, I'm not sure if that would provide
[00:39:00.780]the information that we're looking for.
[00:39:03.030]I don't know that there would be differences
[00:39:04.770]in soil respiration between the treatments
[00:39:06.720]that would be enough that we could see
[00:39:09.270]a difference from that.
[00:39:10.103]So FAM is kind of a good middle ground between that
[00:39:12.960]and between DNA extraction where it's not too fine grain.
[00:39:17.190]So we're not overwhelmed with data.
[00:39:18.780]And it's also detailed enough
[00:39:20.460]that we can see some of the information we're looking for.
[00:39:24.300]And he just told me that his last question
[00:39:26.550]was already answered, so...
[00:39:28.041]Okay, cool.
[00:39:38.160]It wasn't clear to me,
[00:39:41.310]we're in this, this corn soybean rotation
[00:39:45.060]with and without the rye, your sampling was done.
[00:39:48.480]After corn.
[00:39:49.380]After corn, and then rye is planted
[00:39:51.960]in the fall after harvest.
[00:39:53.460]So this year it was in soybean.
[00:39:55.637]And so our second year samples will be after soybean.
[00:39:58.770]And I hope that is a simple.
[00:40:01.470]So are you expecting some differences
[00:40:03.270]now that you're gonna be sampling
[00:40:04.620]after soybean instead of corn?
[00:40:06.030]Yes, absolutely.
[00:40:08.970]There were no, I will just say this,
[00:40:10.530]I didn't show this data,
[00:40:12.223]but there were no differences in yield between treatments
[00:40:13.830]and at least for a rain-fed site,
[00:40:15.600]I am already seeing some impacts
[00:40:17.670]mostly from cover crops
[00:40:18.870]where it caused some very low yields.
[00:40:21.900]But we are expecting to see differences
[00:40:25.170]and it'll be interesting
[00:40:26.003]to see how that changes what we see with the nitrate,
[00:40:28.710]especially because we, there was no additional nitrate
[00:40:30.960]applied for soybean this year.
[00:40:33.720]So you're gonna change your take home message
[00:40:35.879]after this year's data, right?
[00:40:39.240]After applied nitrogen.
[00:40:49.710]All right, any other questions?
[00:40:54.000]All right.
[00:40:54.833]Fantastic job.
[00:40:55.666]Thank you so much Britt. (audience applauding)

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Linking the Modification of Biochar Surface by Iron Oxides Under Field Conditions with Enhanced Nitrate Retention

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