The Role of Conservation Management in Nitrogen Balance: Findings from the UNL-NRCS Collaboration

Adewole Adetunji, Postdoctoral research Associate, Dept of Agronomy & Horticulture, University of Nebraska-Lincoln Author

03/27/2025 Added

5 Plays

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Groundwater nitrate contamination and greenhouse gas emissions are critical environmental challenges in Nebraska's corn systems, driven largely by inefficient nitrogen use and management practices. This seminar will explore how integrated cover crop, no-till management, crop rotation, and optimized nitrogen rates can improve nitrogen use efficiency, boost economic returns, and reduce environmental impacts at two long-term corn tillage sites in Nebraska.

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[00:00:00.720]The following presentation is part of the agronomy and horticulture seminar series
[00:00:05.760]at the University of Nebraska-Lincoln.
[00:00:07.840]It's my pleasure to present to Dr. Adewole Adetunji has been a postdoctoral
[00:00:20.560]research associate in the department of agronomy and horticulture at the University of Nebraska-Lincoln
[00:00:25.920]since November 2022. He earned his PhD in environmental health from Cape Peninsula
[00:00:31.520]University of Technology in South Africa. His research focuses on soil health, nutrient
[00:00:37.040]management, water quality and sustainable agricultural practices. Today Dr. Adetunji
[00:00:42.720]will be presenting on the role of conservation management in nitrogen balance lessons from the
[00:00:47.520]UNL NRCS collaboration.
[00:00:49.520]Good morning everyone.
[00:00:55.440]Thank you for coming to my presentation this morning. I'm Adetunji Adewole and I'm a
[00:01:02.000]postdoctoral research associate at Iqbal Lab. Today I will be presenting to you a preliminary study
[00:01:08.880]on the role of conservation management in nitrogen balance at two long-term coal tillage sites.
[00:01:17.040]As we all know, Nebraska is the state's leading irrigated row crop production in the United States
[00:01:25.760]this extensive irrigation practice have helped Nebraska maintain high row crop
[00:01:30.960]yield production even under varying rainfall conditions. This is good, this is what we want.
[00:01:37.520]However, this success also comes with challenges. Groundwater nitrate concentration at the high one
[00:01:45.680]is a significant issue in Nebraska where some areas already exceed 20 ppm nitrate levels
[00:01:55.040]which is far above safe drinking water standards. Indeed several reports have shown that high nitrates
[00:02:03.120]in water causes human health effects. A typical example is that it causes various types of cancer,
[00:02:13.360]it causes blue baby syndrome, it also causes pregnancy issues.
[00:02:18.640]This map illustrates different areas in Nebraska
[00:02:24.000]that are with different nitrate contamination levels. We would notice here, we would see they
[00:02:32.160]are concentrated at different areas. We can see them in the south, east, we can see them in the
[00:02:37.840]northeast, different levels. So this is a critical problem which we really need to look into.
[00:02:45.760]This groundwater nitrate concentration levels is mostly driven by inefficient nitrogen use
[00:02:53.520]and management practices. Now let's look at some agricultural management practices
[00:03:00.560]driving inefficient nitrogen use and nitrate leaching. This tillage, which is one of the
[00:03:07.840]examples of tillage, tillage practices involves different types of disruption of the soil.
[00:03:16.720]This increases soil erosion. Even though this practice is good for crop production,
[00:03:23.040]but it increases soil erosion, which usually leads to nutrients runoff. The disruption of the soil
[00:03:30.800]through tillage practice also reduces the ability of the soil to retain nitrogen, which often leads
[00:03:38.240]to nitrate leaching into the soil. Another common practice is the monoculture practice,
[00:03:44.720]which can involve the planting of corn year after year. This practice is common, but it often
[00:03:52.560]depletes the soil thereby requiring more nitrogen input. This practice often also leads to groundwater
[00:03:59.920]nitrate concentration. It also leads to inefficient nitrogen uptake by the crop.
[00:04:06.160]Another one is excess nitrogen application. In an effort by the farmer to continue to
[00:04:12.800]improve corn yield, farmers usually put high nitrogen fertilizer in the soil, which usually
[00:04:22.240]far above crop utilization. This practice also often leads to nitrate contamination in the soil,
[00:04:29.440]and it also causes greenhouse gas emission. This environmental risk from inefficient nitrogen
[00:04:37.280]use and mismanagement not only affects our ecosystem, it also undermines agricultural
[00:04:45.440]sustainability. So how do we address this problem?
[00:04:51.600]This leads us to this critical question. Can integrated conservation and nutrient
[00:04:57.120]management practice be a sustainable approach to improve nitrogen efficiency?
[00:05:01.840]This is a question we really need to think about. To be more specific,
[00:05:06.800]can the combination of no-till crop rotation, cover crop, and optimum nitrogen rate be a
[00:05:13.120]sustainable approach to optimize nitrogen input for crop? Can the combination of these various
[00:05:21.120]management practices also increase nitrogen availability during the growing season?
[00:05:25.520]Again, can the combination of these various management practices reduce nitrogen losses
[00:05:32.320]to groundwater or to nitrous oxide emission? To address this question, our research objective
[00:05:42.640]focuses on how integrated conservation and nutrient management practice affects economic optimum nitrogen
[00:05:50.640]rates, nitrogen dynamics, and nitrogen balance. Here, we are looking at the integrated conservation
[00:05:57.920]practice which involves no-till crop rotation and cover crop. The nitrogen management will be
[00:06:05.200]the optimum nitrogen rate. We are checking the impact on economic optimum nitrogen rate for corn
[00:06:11.600]grain yield. Looking under nitrogen dynamics, we are seeing how these various management practices
[00:06:20.160]incise in nitrogen availability and how would it also influence fertilizer nitrogen
[00:06:26.320]equivalence of cover crop. We also look at nitrogen balance where we look into the nitrogen
[00:06:32.880]losses from nitrous oxide emission and nitrate leaching potential. We also look at residual
[00:06:40.000]nitrogen. This slide illustrates our experimental overview. This study was conducted at two sites.
[00:06:49.680]Two long-term tillage consites. The first one at Askala agricultural laboratory
[00:06:56.560]which ends for what I'll be calling HAAR. And the second one at South Central agricultural
[00:07:01.440]laboratory which I'll be calling SCAR from now. At HAAR, the study was is located at Concord,
[00:07:09.120]northeast Nebraska. The study was done in year 2023 and 2024 under city clay loam soil.
[00:07:19.200]It's rain-fed. Our experimental design was split, split, split plots with four replications.
[00:07:25.040]Our treatments are as follows. For tillage, we look into no-till and disk, which was the
[00:07:32.640]main plot. For crop rotation, we look into continuous corn and corn soybean,
[00:07:39.120]which was the subplot. We also check various nitrogen rates from 0 to 160 kg nitrogen, which was
[00:07:48.720]sub-subplot. The last one was cover crop, where we compared rye with no rye as the sub-sub-subplot.
[00:07:59.280]For scull, the location was at Clay Center, also done in year 2023 and 2024.
[00:08:07.440]Under silt loam, irrigated compared to hull. The design of our scull is a little bit different from hull.
[00:08:18.240]In the sense that we did not check rotation effects at scull. Here for scull, we checked the tillage,
[00:08:25.920]which was no till and disk for the main plot. The nitrogen rate was from 0 to 300 kg
[00:08:33.760]nitrogen per hectare as sub-plot. We also looked at cover crop, comparing rye with no rye.
[00:08:39.840]To achieve our objective, we calculated economic optimum nitrogen rates using
[00:08:47.760]regression model fit to nitrogen response curve. We did this to identify nitrogen rates
[00:08:56.240]maximizing profitability. In simple terms, economic optimum nitrogen rates is that
[00:09:03.120]nitrogen rate at which any other nitrogen applied to the soil will not generate profit
[00:09:09.520]or increase the yield. To also look into nitrogen dynamics, we took soil samples
[00:09:17.280]on bi-weekly basis from the topsoil to analyze nitrate and
[00:09:22.720]ammonium concentration for in-season nitrogen availability. Figure B shows
[00:09:30.960]soil sampling during the growing season for in-season nitrogen analysis. We also
[00:09:38.280]measured or calculated fertilizer nitrogen equivalents. Fertilizer nitrogen
[00:09:44.220]equivalents was calculated to be able to
[00:09:46.800]know the contribution of cover crop, contribution of nitrogen from cover
[00:09:51.480]crop. So here we calculated it by comparing yield with or without cover
[00:09:58.020]crop at zero nitrogen rates. We also tried to measure nitrogen losses by
[00:10:08.360]measuring nitrous oxide emission on weekly basis using the LyCoAnalyzer. Figure C shows
[00:10:16.320]nitrous oxide emission measurements during the growing season. We also
[00:10:21.720]measured nitrate leaching by monitoring pore water nitrate concentration from
[00:10:26.460]lysimeter.
[00:10:29.180]Again for residual soil nitrogen, we took D-Corp sampling. We collected it from zero
[00:10:38.220]down to 48 inches soil profile to be able to measure residual soil nitrogen. Figure D
[00:10:45.840]shows soil sampling to 48 inches depth and the separation of this soil into
[00:10:53.520]their respective depths. This was analyzed to measure residual nitrogen to
[00:11:01.020]be able to know the carryover after the growing season. Before I go into this
[00:11:15.360]slide, I want to point out that nitrogen was applied before planting. Yes, yes,
[00:11:22.900]before pre-planting. For Scal, it was incorporated, but for Hal, it was
[00:11:32.840]broadcasted. For Scal, it was anhydrous and for Hal, it was ammonium nitrate.
[00:11:44.880]So, before I go into the results, I would like to show how significant a variation in
[00:11:56.300]rye cover crop biomass production. For Hal in 2023, Figo Hay shows very low cover crop
[00:12:07.060]biomass production due to dry conditions for year 2022 through 2023.
[00:12:14.400]While in 2024, with weather conditions, we had significantly higher cover crop biomass
[00:12:23.520]production. I have to show this because I will be referring to this throughout the presentation.
[00:12:34.760]Because this biomass disparity in cover crop biomass production was affecting some of our
[00:12:40.840]results.
[00:12:43.920]This slide illustrates economic optimum nitrogen rates and yield at economic optimum nitrogen
[00:12:50.300]rates fitted for quadratic plateau regression for disk continuous corn system.
[00:12:59.060]So figure A and figure B compares economic optimal nitrogen rates and yield at economic
[00:13:04.820]optimal nitrogen rates with rye and without rye for disk continuous and for both of them.
[00:13:13.440]As you can see in 2023, the presence of rye did not affect economic optimum nitrogen rates
[00:13:23.320]and yield at economic optimum nitrogen rates.
[00:13:27.320]This is probably due to dry conditions in 2023, which resulted in low cover crop biomass
[00:13:34.200]production.
[00:13:35.200]Thus, we did not see cover crop effects.
[00:13:38.040]However, for 2024, with wetter conditions.
[00:13:42.960]And significantly higher cover crop biomass production, we saw cover crop effects.
[00:13:48.960]Where the cover crop, the presence of cover crop reduced economic optimum nitrogen rates
[00:13:56.400]by 18 pounds per acre, and it also reduced yield at economic optimum nitrogen rates by
[00:14:02.060]26 bushels per acre.
[00:14:04.160]Please, the color blue signifies the presence of rye, while the red shows no rye.
[00:14:12.480]So here, the presence of cover crop reduced economic optimum nitrogen rates and yield
[00:14:16.720]at economic optimum nitrogen rates probably due to increased cover crop biomass in 2024,
[00:14:23.700]which led to nitrogen immobilization by cover crop, which did not make nitrogen available
[00:14:31.340]to corn, especially during the early growth stage.
[00:14:36.020]Please note that economic optimum nitrogen rates are presented for results with strong
[00:14:42.000]relationship between nitrogen rates and cover crop, indicated by high coefficient of determination
[00:14:51.980]and statistically significant model coefficients.
[00:14:55.900]Since we did not get good fits for no-till system, figure C and D presents the effect
[00:15:07.500]of rotation and cover crop on corn grain yield.
[00:15:11.520]Here, optimum nitrogen rate for this site under no-till system.
[00:15:17.780]Figure C and D compares rotation and cover crop.
[00:15:24.080]Please note that the bar with the slash pattern represents the presence of cover crop for
[00:15:31.960]respective rotation.
[00:15:34.380]So that will be the same for most of the other slides.
[00:15:41.040]No significant management impacts on corn yield.
[00:15:46.140]This might be due to the very dry conditions in 2023, which also limited cover crop biomass
[00:15:53.280]production.
[00:15:54.280]However, in year 2024, where we had wet conditions that increased cover crop biomass production,
[00:16:03.800]management effects became more pronounced, whereby corn soybean without rye had significantly
[00:16:10.560]higher yield than corn soybean with rye and continuous corn wheat or without rye.
[00:16:18.660]Here, the presence of rye significantly reduced corn yield compared to corn soybean without
[00:16:27.580]rye, probably due to nitrogen immobilization as well, which did not make nitrogen available
[00:16:37.920]to the crop here.
[00:16:40.080]Under continuous corn, wheat or without rye, this system often have regular nitrogen inputs.
[00:16:52.780]Nitrogen applied annually compared to the corn soybean system, which nitrogen is applied
[00:16:59.740]every other year.
[00:17:01.800]Maybe the iron-maintained nitrogen here will have masked maybe cover crop effects.
[00:17:09.600]Thereby not seen cover crop effects here.
[00:17:17.580]This is for Scal site.
[00:17:20.480]This slide, if you go here and B, also presents economic optimum nitrogen rates and yield
[00:17:26.560]at economic optimum nitrogen rates fitted to quadratic plate 2 regression model.
[00:17:33.700]Here we also compare rye with no rye for economic optimum nitrogen rate and yield at economic
[00:17:39.120]optimum nitrogen rates.
[00:17:41.940]Again for 2023, dry conditions, no cover crop biomass, we did not see the effect of cover
[00:17:50.080]crop presence on economic optimum nitrogen rates and yield at economic optimum nitrogen
[00:17:54.400]rates.
[00:17:55.400]However, 2024 came with cover crop effects due to more cover crop biomass and wetter
[00:18:02.240]conditions.
[00:18:03.240]There is a slight difference between what we got here from HA.
[00:18:08.640]Instead, the presence of rye increased economic optimum nitrogen rates by 50 pounds per acre.
[00:18:16.640]It also increased yield at economic optimum nitrogen rates.
[00:18:21.900]Here, this might be due to nitrogen immobilization, but what seems to happen here was that even
[00:18:30.220]the addition, extra addition of nitrogen now led to the increase in crop yield, which was
[00:18:38.160]different from what we got at R. Just like I said for R, since we did not get a good
[00:18:46.160]fit for no-till, C and D present cover crop effects on grain yield at near optimum nitrogen
[00:18:57.380]rates under no-till for this site.
[00:19:02.720]For year 2023, cover crop had no significant effect.
[00:19:07.680]However, if we look at 2024, with increased cover crop biomass, wetter conditions, the
[00:19:19.180]presence of rye significantly reduced corn yield compared to no rye.
[00:19:27.820]This could have been also as a result of nitrogen scavenging ability of cover crop, which reduced
[00:19:36.160]nitrogen availability to corn.
[00:19:37.200]This slide illustrates the effect of tillage, rotation, nitrogen rates, and cover crop on
[00:19:55.040]nitrate availability during the growing season.
[00:20:02.520]Figures A to D show spatial and temporal variation.
[00:20:06.720]Figures B to D show spatial and temporal variation in nitrate availability during the growing
[00:20:09.600]season.
[00:20:10.600]Figures C to D show spatial and temporal variation in nitrogen availability during the growing
[00:20:11.600]season.
[00:20:12.600]Please note that the dash represents cover crop presence compared to no cover crop, and
[00:20:20.020]for each figure, we compare nitrogen rates and rye without rye.
[00:20:30.060]Figure A to D shows that nitrogen availability fluctuated over time during the growing season.
[00:20:36.240]This also shows that cover crop did not have any effects on nitrate availability during
[00:20:45.760]the growing season, possibly due to the very low cover crop biomass.
[00:20:50.740]However, we found effects of nitrogen rates here, which also happened here.
[00:20:59.600]We also found some effect of tillage.
[00:21:05.760]However, 2024, which came with more moisture and higher cover crop biomass, we found cover
[00:21:15.340]crop effects.
[00:21:19.640]We found cover crop effects where cover crop was reducing nitrate availability during the
[00:21:25.200]growing season.
[00:21:27.020]We also found effect of tillage as well.
[00:21:31.480]This shows us the weather conditions.
[00:21:35.280]Weather conditions affect a result and the presence of cover crop leading to lesser nitrate
[00:21:44.640]availability during the growing season.
[00:21:49.680]This slide illustrates the ammonium concentration.
[00:21:52.640]The previous one that I presented was nitrate.
[00:21:55.800]This is for ammonium concentration.
[00:21:57.940]We also had similar results whereby cover crop did not have significant effects
[00:22:04.800]due to low cover crop biomass production.
[00:22:08.240]We see trend of fluctuation during the growing season.
[00:22:11.560]We also noticed that higher rates was having higher ammonium concentration, same with nitrate.
[00:22:17.560]This is expected because we added nitrogen and zero nitrogen would not result to higher
[00:22:24.520]one.
[00:22:27.520]There's a little bit of a shift here whereby despite significantly higher cover
[00:22:34.320]crop biomass production, still cover crop did not have any significant effects on ammonium
[00:22:42.760]concentration, our availability during the growing season.
[00:22:46.680]Instead, we had the effect of nitrogen rates and disk at some point.
[00:22:55.360]Since we did not see cover crop effects in year 2023 at all, this slide shows the average
[00:23:03.840]impact of tillage and rotation on nitrate and ammonium availability during the growing
[00:23:11.080]season.
[00:23:14.500]Figure A and B shows disk tillage and also compares it under different rotation practices.
[00:23:22.720]Figure A shows significant interaction between tillage and rotation system, the same for
[00:23:29.800]ammonium concentration.
[00:23:32.320]Under disk tillage.
[00:23:33.360]Rotation did not have any significant impact on nitrate availability.
[00:23:40.480]However, let's look at here.
[00:23:43.840]Under ammonium, for ammonium here, it has significant impact, but we would notice here
[00:23:49.400]that continuous contributed to, even though not significant, contributed to slightly higher
[00:23:56.440]nitrate concentration, but we found significant increase here.
[00:24:03.220]Here, this increase in nitrogen from continuous corn under disk tillage could be as a result
[00:24:12.460]of two things.
[00:24:13.460]It could be as a result of disturbance, soil disturbance from disk tillage and higher nitrogen
[00:24:19.320]inputs on the continuous corn system.
[00:24:22.760]For example, continuous corn, nitrogen fertilizer is applied annually compared to corn soybean
[00:24:32.460]rotation.
[00:24:33.220]Here, nitrogen fertilizer is applied every other year.
[00:24:38.060]So then under disk tillage, soil disturbance happen here, which often increase soil aeration,
[00:24:46.420]which accelerates nitrogen mineralization in the soil.
[00:24:51.420]So higher nitrogen inputs compared to -- higher nitrogen inputs combined with the disturbance
[00:25:03.220]must have led to increasing mineralization that led to -- that now led to availability
[00:25:09.460]-- nitrogen availability during the growing season, especially under continuous corn,
[00:25:14.540]whereas the corn soybean did not have much input.
[00:25:19.900]So even mineralization under it as well could not match up to the continuous corn.
[00:25:25.340]But there is a difference under no-till system, whereby corn-soybean rotation led to increase
[00:25:33.220]to significantly higher nitrate availability compared to continuous corn.
[00:25:40.900]Under no-till system, there's less disturbance, and this also allows residue cover.
[00:25:49.140]Under this system, microbial activity and even nitrogen mineralization is kind of slow,
[00:25:55.440]is very slow compared to this.
[00:25:57.680]So here, continuous corn has higher carbon dioxide.
[00:26:03.220]Carbon to nitrogen ratio, which under this phase, it means for microbial activity to
[00:26:11.280]keep happening, more nitrogen is needed by the microorganism to continue to break down
[00:26:18.280]the high carbon on the continuous corn system.
[00:26:22.580]This must have led to the reduced nitrate here.
[00:26:27.220]However, for corn soybean, rather, it has lower carbon dioxide.
[00:26:33.220]This makes it happen, but for continuous corn system, remobilization happen whereby most
[00:26:45.600]of the nitrogen, most of the total nitrogen are still on the corn residue and are not
[00:26:51.640]yet released into the soil.
[00:26:57.120]The same thing could also be applicable here.
[00:27:03.220]This slide shows the result for 2024.
[00:27:07.660]This slide shows the impact of rotation and cover crop on soil nitrates and ammonium availability
[00:27:13.340]during the growing season.
[00:27:17.500]In this slide, we excluded the analysis of tillage because we did not see the effect
[00:27:25.540]of tillage.
[00:27:26.540]Instead, we found rotation and rye interactions, significant interaction.
[00:27:33.220]So under this figure, figure A and B, we compare rye with no rye under each rotation system.
[00:27:45.640]Figure A shows that the presence of rye led to significantly lower nitrates under corn
[00:27:53.780]soybean here, but we did not see effect here.
[00:27:58.840]Under corn soybean here, cover crop reduced.
[00:28:03.220]Nitrate availability probably due to nitrogen immobilization, which did not make nitrogen
[00:28:12.900]available, especially in nitrate.
[00:28:15.920]But under continuous corn, even though we see a difference, this is not significant.
[00:28:22.280]And the same result, similar result we get in here could be as a result of high nitrogen
[00:28:32.220]input.
[00:28:33.220]So regular nitrogen inputs, which could have maybe masked the nitrogen scavenging ability
[00:28:41.420]of cover crop.
[00:28:43.960]But under ammonium, we did not see any effects of Arai.
[00:28:49.040]Instead, we found significant main effects of rotation, whereby continuous corn had higher
[00:28:57.760]ammonium concentration than corn soybean system.
[00:29:03.220]This result is for scar.
[00:29:09.080]So this slide illustrates the effect of tillage, nitrogen rate, and cover crop on soil nitrate
[00:29:15.460]and ammonium availability, also during the growing season.
[00:29:23.400]Under each of them, we compare nitrogen rate and cover crop for each figure.
[00:29:31.200]Figure A and B shows.
[00:29:33.220]Nitrate availability during the growing season, while figure B shows ammonium concentration.
[00:29:41.040]We found that nitrate and ammonium availability fluctuated over time.
[00:29:47.280]We also saw that nitrogen presence showed higher availability for nitrate and ammonium,
[00:29:56.360]which is expected.
[00:29:59.220]Then for 2024, with cover crop biomass in year 2024.
[00:30:03.220]We also found that we can see, like I said, the dash represents cover crop biomass presence,
[00:30:09.220]cover crop presence, rather.
[00:30:11.220]So we found some reduction in nitrate and ammonium availability at some point during the growing season.
[00:30:19.220]We did not take in-season soil nitrogen availability for 2023.
[00:30:24.220]We only had for 2024 for SCAR.
[00:30:30.220]This slide illustrates the impact of T.
[00:30:33.220]Sealed and cover crop on soil nitrates and ammonium, the average impact.
[00:30:39.220]Again, we compare cover crop with no cover crop on that tillage system.
[00:30:47.220]Figure A and B shows similar trend for nitrate and ammonium availability during the growing season,
[00:30:55.220]whereby under no till, the presence of cover crop still reduced nitrogen availability during the growing season.
[00:31:03.220]Why there was no effect on that tillage?
[00:31:07.220]Cover crop probably had no effect on that tillage, probably due to soil disturbance that accelerated nitrogen mineralization.
[00:31:19.220]The accelerated nitrogen mineralization which quickened and we couldn't get the effects because cover crop must have broken down very easily.
[00:31:30.220]But under no till system,
[00:31:33.220]it allowed the effect whereby under no till system, there's less disturbance.
[00:31:38.220]There's less disturbance there. We were able to see cover crop nitrogen scavenging ability, whereby immobilization.
[00:31:48.220]up and under this system.
[00:31:50.650]This slide illustrates fertilizer nitrogen equivalents
[00:31:57.910]provided to corn by rye cover crop.
[00:32:02.290]Here we are looking at the nitrogen inputs
[00:32:07.290]from cover crop into the corn.
[00:32:09.910]Figure A and B shows 2023 and 2024 nitrogen inputs
[00:32:17.090]nitrogen, fertilizer nitrogen equivalents.
[00:32:19.970]Figure A shows for har and figure B shows for scar.
[00:32:24.890]These figures shows that cover crop did not
[00:32:28.910]give any nitrogen to corn for year 2023 and 2024.
[00:32:35.750]We can see it from the negative value here.
[00:32:41.010]We would also notice that it was more significant in 2024
[00:32:46.470]for both sides due to higher,
[00:32:50.150]significantly higher cover crop biomass in this year
[00:32:54.230]compared to the previous year.
[00:32:56.830]This shows that cover crop did not add nitrogen to corn.
[00:33:01.830]This, we attribute this to nitrogen immobilization.
[00:33:06.070]We did not make nitrogen available to corn,
[00:33:09.770]especially during the growing season
[00:33:11.290]and early growing season.
[00:33:15.930]Now let's take a short break
[00:33:17.650]and see some of our moments,
[00:33:21.230]our extension outreach efforts at UNN,
[00:33:26.230]Atzkela Ikotura Laboratory Lab
[00:33:29.650]during our cover crop feed day in April, 2024,
[00:33:32.950]where we showcased our research.
[00:33:37.090]Figohe captures NRCS personnel, the farmers,
[00:33:45.390]and researchers engaging with our research field
[00:33:50.390]and looking at our treatment plots.
[00:33:53.330]Figohe captures Dr. Iqbal, our principal investigator,
[00:33:59.770]explaining the different management practices in the field
[00:34:04.410]and also showing, explaining our plots layout to everyone.
[00:34:09.410]Figohe illustrates participants
[00:34:14.850]listening to my presentation during the field day as well.
[00:34:19.450]This is one of our efforts
[00:34:21.350]to continue collaborative discussion
[00:34:24.490]in cover crop management and ways to improve,
[00:34:28.390]to continue to bring awareness for cover crop adaptability.
[00:34:33.390]And also one of our ways to bring,
[00:34:36.510]to bridge gap between scientific research findings
[00:34:41.510]and practical applications
[00:34:44.310]in the farm.
[00:34:45.150]Now let's go back to the results.
[00:34:48.890]This slide shows the effect of tillage and rotation
[00:34:55.690]on nitrous oxide emission during the growing season.
[00:34:59.430]We excluded cover crop from this analysis
[00:35:03.470]because cover crop had no significant effects in year 2023.
[00:35:08.470]Figure A shows precipitation and temperature changes.
[00:35:13.770]The temperature trend during the growing season.
[00:35:17.170]Figure B and C shows spatial and temporal variation
[00:35:22.170]in nitrous oxide emission during the growing season.
[00:35:27.790]While figure D and figure A shows
[00:35:30.730]cumulative nitrous oxide emission on the disk
[00:35:35.690]for this figure comparing rotation and no till here.
[00:35:40.690]Figure B and C
[00:35:43.230]shows that nitrous oxide emission fluctuated over time
[00:35:48.230]with a peak in the early growing season.
[00:35:53.230]This was around June 12th,
[00:35:56.010]which could have been as a result of high precipitation,
[00:36:00.710]high precipitation and active nitrogen transformation
[00:36:05.670]from early season fertilization.
[00:36:08.170]Let's look at cumulative nitrous oxide emission.
[00:36:13.570]We noticed that no-till contributed
[00:36:15.970]to lesser nitrous oxide emission compared to deep stillage.
[00:36:20.970]This is as a result of less soil disturbance under no-till,
[00:36:27.510]which reduce soil oxygen,
[00:36:34.790]which must have limited microbial activity
[00:36:38.590]that produce nitrous oxide here.
[00:36:42.150]However, when we look at DISC,
[00:36:43.730]we see higher nitrous oxide emission,
[00:36:47.750]which could be from soil disturbance.
[00:36:49.990]We would also notice that combination of DISC stillage
[00:36:53.810]with continuous corn led to significantly high,
[00:36:58.750]higher nitrous oxide emission compared to corn soybean.
[00:37:03.750]This could be as a result of first from the DISC stillage,
[00:37:08.030]there is more disruption of the soil
[00:37:11.610]which accelerates mineralization.
[00:37:16.550]And also the more nitrogen input from continuous corn,
[00:37:20.410]all this must have contributed to all this.
[00:37:23.950]This shows us how no-till system significantly contribute
[00:37:27.790]to lesser nitrous oxide emission.
[00:37:30.030]And if we can combine DISC stillage
[00:37:34.450]with corn soybean rotation,
[00:37:37.990]we would still get lesser nitrous oxide,
[00:37:41.070]oxide emission than comparing it,
[00:37:43.750]than combining DISC with continuous corn.
[00:37:46.830]This is for 2024, nitrous oxide emission for 2024.
[00:37:53.570]We included cover crop in this analysis
[00:37:58.270]because we got cover crop effects
[00:38:00.930]from since we also got higher cover crop biomass production.
[00:38:04.310]Figure H shows precipitation and temperature,
[00:38:10.530]temperature trends during the growing season.
[00:38:13.230]Figure B and C highlights nitrous oxide spatial
[00:38:20.030]and temporal variability during the growing season
[00:38:23.670]for distillage and no-till,
[00:38:27.170]air comparing, rotation, and cover crop.
[00:38:31.490]We notice flotation in nitrous oxide emission
[00:38:37.130]during the growing season, and we also notice
[00:38:39.990]this peak during the early season as well.
[00:38:43.850]This is also around early June, similar to the previous year.
[00:38:48.350]Could be as a result of IRM4,
[00:38:51.950]then active nitrogen transformation
[00:38:55.130]from the early season nitrogen application.
[00:38:59.050]Looking at cumulative nitrous oxide emission
[00:39:02.850]on that disk and no-till,
[00:39:06.330]we realize that the presence of cover crop
[00:39:09.450]resulted in significantly higher nitrous oxide emission,
[00:39:14.290]irrespective of the rotation system.
[00:39:17.550]This could have been as a result
[00:39:22.250]of the cover crop biomass presence,
[00:39:25.750]which must have maybe increased nitrogen mineralization,
[00:39:29.410]but more substrates also from cover crop biomass.
[00:39:33.610]And deep stillage as well,
[00:39:36.050]which also involved the, and here,
[00:39:38.910]we saw cover crop increase in nitrous oxide emission.
[00:39:42.050]However, under no-till system,
[00:39:44.230]we see the differences in the effects,
[00:39:49.050]whereby the combination of corn's soybean with rye
[00:39:54.050]contributed to significantly lesser nitrous oxide emission
[00:39:58.950]compared to the other treatment combinations.
[00:40:03.030]This slide illustrates
[00:40:08.910]poor water nitrate concentration
[00:40:12.030]and nitrate leaching potential effects,
[00:40:15.730]response under tillage, rotation,
[00:40:21.170]and cover crop during the growing season.
[00:40:23.310]Figure A illustrates precipitation
[00:40:26.690]and temperature trends as well,
[00:40:28.470]while figure B and C show poor water nitrate concentration
[00:40:34.330]for disk and no-till, respectively,
[00:40:37.510]where
[00:40:38.430]we're comparing the rotation and rye here.
[00:40:43.430]We saw that poor water nitrate concentration
[00:40:49.710]also fluctuated during the growing season.
[00:40:54.650]For this part, we did not see tillage
[00:40:59.650]and rotation effects, significant effect.
[00:41:04.550]Instead, we found that cover crop
[00:41:07.810]was the one having main effects.
[00:41:10.830]This shows that cover crop was the main driver
[00:41:14.790]of this process, of this management practice
[00:41:18.390]compared to tillage and rotation system.
[00:41:21.370]Therefore, figure D shows compared cover crop
[00:41:25.810]with not cover crop,
[00:41:27.550]but average poor water nitrate concentration.
[00:41:30.210]We see that the presence of cover crop
[00:41:33.090]contributed to significantly lower
[00:41:36.070]poor water nitrate concentration
[00:41:37.190]compared to without rye.
[00:41:40.630]This shows that cover crop
[00:41:46.450]can actually reduce nitrate leaching potential,
[00:41:52.350]as we can see from this study,
[00:41:54.850]due to their nitrogen immobilization activity.
[00:41:59.690]This slide illustrates residual soil nitrogen
[00:42:06.570]concentration from 0 to 48 inches soil profile.
[00:42:11.570]Here, we compare rye with no rye
[00:42:16.850]under disc and corn soybean,
[00:42:20.230]disc, continuous corn, and disc,
[00:42:22.390]so we compare rye under.
[00:42:24.790]Like I previously said,
[00:42:26.370]the dash represents cover crop presence,
[00:42:29.730]while the other one, no rye.
[00:42:33.030]So we observe that cover crop
[00:42:35.950]reduce residual soy nitrate at some levels.
[00:42:40.950]Under corn soybean rotation,
[00:42:47.770]irrespective of tillage system,
[00:42:50.130]but under continuous corn system,
[00:42:52.130]cover crop had no effect.
[00:42:56.290]For ammonium concentration,
[00:42:59.890]we only found that cover crop
[00:43:01.990]reduced residual ammonium concentration
[00:43:05.330]under no-tea corn soybean system.
[00:43:08.950]We did not expect to find cover crop effects
[00:43:13.950]on residual nitrogen in year 2023,
[00:43:18.350]because there was no cover crop main effects
[00:43:22.310]or interactive effects.
[00:43:24.310]So maybe this effect could be on a random basis.
[00:43:29.310]We did not expect to see any results.
[00:43:34.710]Any results, any effect of cover crop.
[00:43:37.930]So since cover crop had no main or interactive effects
[00:43:42.930]on residual nitrogen,
[00:43:45.150]this slide illustrates the average residual
[00:43:49.590]soil nitrate and ammonium concentration
[00:43:51.990]as affected by tillage and rotation system.
[00:43:55.450]On the Dix tillage,
[00:44:00.210]we found significant tillage and rotation effects
[00:44:04.090]here, interactive effects rather.
[00:44:08.630]So on the Dix tillage for nitrates,
[00:44:12.270]for residual nitrates and ammonium as well,
[00:44:15.750]we found that corn-soybean rotation
[00:44:21.270]led to lower residual soil nitrates
[00:44:25.470]and ammonium concentration,
[00:44:27.430]respectively compared to continuous corn.
[00:44:33.470]- What you're showing,
[00:44:34.950]to which nitrogen rate correspond?
[00:44:37.730]- Oh, at the near optimum nitrogen rates, at one rate.
[00:44:41.350]- At the optimum nitrogen rate for each treatment or?
[00:44:45.610]- No, for all, for each site.
[00:44:48.790]For example, for Al, the near optimum nitrogen rate
[00:44:52.710]was 120 kg nitrogen per hectare.
[00:44:55.730]So we use it at that near optimum nitrogen rate.
[00:44:58.950]- Okay, but that value can change
[00:45:00.830]according to treatment if you got rotation
[00:45:02.850]or you have cover crop or not.
[00:45:06.250]So for each treatment, you are looking at the value
[00:45:10.530]for each treatment at the economically optimal
[00:45:12.670]nitrogen rate or you are using like an average
[00:45:15.110]economically optimal nitrogen rate for each site?
[00:45:18.010]- No, at optimum nitrogen rates for these ones.
[00:45:22.670]So for Scal, that was different,
[00:45:28.350]which was 150 kg nitrogen per hectare.
[00:45:32.230]So we noticed here that corn soybean
[00:45:36.790]had lower residual nitrates and ammonium concentration
[00:45:40.350]compared to continuous corn.
[00:45:43.290]Again, this could be as a result of one soil disturbance
[00:45:49.570]on the distillate which accelerates nitrogen mineralization
[00:45:56.350]and continuous corn having regular, more regular
[00:46:01.610]nitrogen imputes compared to corn soybean.
[00:46:05.650]So in a case like this, where the mineralization is still up
[00:46:12.390]on the continuous corn with higher nitrogen,
[00:46:16.870]more nitrogen inputs compared to this,
[00:46:21.010]during this process, mineralization happens
[00:46:25.530]which under the distillate with this,
[00:46:28.690]usually as there's usually high
[00:46:30.990]corn uptake, lesser corn uptake,
[00:46:34.530]which must have led to this.
[00:46:36.750]However, on the notes you rotation system
[00:46:39.530]had no significant effect.
[00:46:41.890]You could be asked as a result of lesser soil disturbance.
[00:46:46.450]We will also see significantly lower nitrate concentration.
[00:46:51.450]It could be as a result of high carbon to nitrogen ratio
[00:46:55.510]from continuous corn, which often requires
[00:47:00.730]that more nitrogen is needed from the microbes,
[00:47:05.310]thereby using more nitrogen here.
[00:47:08.410]But for note, the corn soybean,
[00:47:10.130]it has lesser carbon to nitrogen ratio.
[00:47:12.890]Even though mineralization happened,
[00:47:14.470]it's at a slower pace compared to the dig stillage,
[00:47:18.410]thereby probably balancing heat up.
[00:47:21.570]This is for 2024.
[00:47:25.990]Here we found cover crop and
[00:47:30.470]rotation effects, no tillage effect was found here.
[00:47:34.030]Thus, we're providing you the rotation
[00:47:38.510]and cover crop effects.
[00:47:39.850]This figure showed that cover crop reduce nitrates,
[00:47:45.610]residual nitrates here at 24 to 36 soil depths.
[00:47:51.750]And if you also look at here for B,
[00:47:54.970]it also reduced it at the top soil air.
[00:47:58.710]No effect was found for,
[00:48:00.210]for the amount of ammonium concentration.
[00:48:02.390]For scalp, we provide you the results
[00:48:08.890]for cover crop residual whereby we are comparing rye
[00:48:14.070]and no rye.
[00:48:15.110]Here we did not see tillage main effects.
[00:48:18.310]Instead, we found that significant interaction
[00:48:21.810]between rye and depths whereby at the top soil,
[00:48:26.810]cover crop significantly reduced residual
[00:48:29.950]soil nitrates and reverse was the case at this lower depth.
[00:48:34.770]At the top soil, it could have been
[00:48:36.390]the nitrogen immobilization by cover crop.
[00:48:39.810]Here, I'm not sure what happens here,
[00:48:41.830]but it could be as a result of maybe the cover crop
[00:48:45.330]later mineralized and nitrates leach down into the soil.
[00:48:50.330]No effect was found here.
[00:48:54.010]Here is a summary.
[00:48:59.690]Of our findings.
[00:49:02.070]Cover crop influenced nitrogen dynamics
[00:49:10.650]and yield differently across years and locations.
[00:49:14.950]For example, in 2023 with dry conditions,
[00:49:20.070]cover crop had no significant impact
[00:49:22.390]on economic optimal nitrogen rates
[00:49:24.310]and yield at economic optimal nitrogen rates,
[00:49:26.970]probably due to low cover crop biomass production.
[00:49:29.430]For 2024, wet spring, cover crop reduced
[00:49:34.370]economic optimal nitrogen rates,
[00:49:36.110]likely due to nitrogen immobilization
[00:49:39.530]from higher cover crop biomass.
[00:49:41.690]For 2024 also with wet spring,
[00:49:45.850]instead cover crop increased
[00:49:47.230]economic optimal nitrogen rates and yield.
[00:49:50.250]This shows us that more nitrogen fertilizer
[00:49:53.650]was needed here at this site
[00:49:56.410]to offset nitrogen immobilization.
[00:49:59.170]We also observed that corn yield response
[00:50:03.290]to nitrogen varied with cover crop biomass.
[00:50:06.590]Example we found at Arles where cover crop biomass
[00:50:10.650]did not increase corn yield.
[00:50:12.630]Even with higher nitrogen rates,
[00:50:17.290]this indicates nitrogen immobilization
[00:50:19.550]exceeded crop demand.
[00:50:21.750]That was why we found reduction
[00:50:24.850]in economic optimal nitrogen and reduction in yield.
[00:50:28.910]While where we had moderate cover crop biomass,
[00:50:32.490]although this still led to nitrogen immobilization,
[00:50:36.190]but increasing nitrogen application
[00:50:39.210]actually now improved corn yield.
[00:50:43.990]To continue with the summary,
[00:50:47.890]we also found out that nitrogen availability
[00:50:50.710]and retention varied with tillage and crop rotation.
[00:50:55.350]Example was where we found cover crop reduced incision
[00:50:58.650]in nitrates and ammonium availability
[00:51:01.390]under no till but had no effects on the tillage.
[00:51:07.270]This could be likely due to soil disturbance
[00:51:11.970]that enhanced nitrogen mineralization.
[00:51:14.870]We also found out that corn-soybean rotation
[00:51:18.090]led to higher nitrates and ammonium than continuous corn
[00:51:22.070]under no till,
[00:51:28.390]but reverse was the case under dig stillage.
[00:51:31.250]For nitrogen losses, nitrogen losses were influenced
[00:51:35.970]by tillage and crop management,
[00:51:38.150]where we saw that no till significantly reduced
[00:51:42.630]nitrous oxide emission compared to dig stillage,
[00:51:45.370]probably due to minimizing soil disturbance.
[00:51:51.190]Cover crop increased nitrous oxide emission
[00:51:54.890]under dig stillage.
[00:51:56.650]This could be as a result
[00:51:58.130]of enhanced microbial activity
[00:52:00.690]and nitrogen mineralization.
[00:52:02.450]Cover crop also significantly reduced nitrous leaching,
[00:52:07.510]showing us that cover crop has potential
[00:52:11.430]to protect water quality.
[00:52:14.730]These are management implications from our findings.
[00:52:21.610]Since we found that year to year,
[00:52:27.870]differences in weather condition
[00:52:32.070]led to cover crop biomass variability.
[00:52:35.030]This shows us that a one size fit
[00:52:39.690]or nitrogen management practices may not work every year.
[00:52:44.690]This shows us that there is need
[00:52:49.650]for nitrogen management practices or strategies
[00:52:54.250]that can adapt to different conditions.
[00:52:57.610]We also found out that cover crop
[00:53:01.810]can reduce potential nitrate leaching,
[00:53:04.210]but it can also increase nitrogen immobilization
[00:53:08.430]and nitrous oxide emission.
[00:53:10.030]There is need to balance cover crop effects
[00:53:15.310]against corn yield,
[00:53:19.610]particularly under continuous corn system.
[00:53:22.410]We found that no till and crop rotation remains
[00:53:27.350]an effective strategy to reduce nitrous oxide emission
[00:53:32.230]than cover crop.
[00:53:33.650]Building up on our findings, here are future directions.
[00:53:41.770]Like I earlier said, our study was conducted
[00:53:46.890]at two long-term corn tillage sites.
[00:53:50.270]We're talking about 30 years.
[00:53:52.610]So there is need to continually
[00:53:57.090]evaluate cover crop effects
[00:54:01.470]for us to be able to get a stronger conclusion
[00:54:06.010]and to be able to refine what is working
[00:54:09.370]with regards to nitrogen dynamics and crop yield.
[00:54:12.570]There is need to also optimize cover crop management
[00:54:16.630]where we identify strategies
[00:54:18.990]that minimize nitrogen immobilization
[00:54:21.130]while we are still maximizing soy fertility
[00:54:25.050]on that cover crop.
[00:54:26.830]This, we also plan as we continue in our research
[00:54:34.870]to develop nitrogen recommendations
[00:54:37.470]that can account for cover crop presence
[00:54:39.830]to improve nitrogen management decisions.
[00:54:44.790]We acknowledge the support of NRCS
[00:54:52.670]and Dana,
[00:54:56.570]Michael and Glenn for their technical support
[00:55:01.570]and help as well.
[00:55:04.350]Thank you.
[00:55:05.190]- Thank you very much.
[00:55:11.870]Very nice research and presentation.
[00:55:14.870]So we have only five minutes for question.
[00:55:18.230]Someone has questions.
[00:55:19.330]- Yeah, very good presentation.
[00:55:22.330]I like it because you show a lot of data
[00:55:24.630]and also I really like your,
[00:55:26.310]your conclusions at the end.
[00:55:27.550]Very, very balanced and based on your data.
[00:55:30.190]So congratulations for that.
[00:55:32.370]I have two questions.
[00:55:33.450]Sorry, Walter.
[00:55:35.090]The first one is a short one
[00:55:36.410]and the second one is a little bit longer,
[00:55:37.830]but the first one is that at the very beginning,
[00:55:40.190]you associate, you made a direct link
[00:55:42.950]between nitrates in water and cancer.
[00:55:46.170]And it is true, there are some studies
[00:55:47.610]showing that relationship,
[00:55:48.630]but then there are other studies
[00:55:49.910]that show that there are no relationship.
[00:55:52.050]So I want to ask you,
[00:55:53.290]is that an established thing from the USDA
[00:55:56.050]perspective or we are still doing research
[00:55:58.750]to establish that link between nitrates
[00:56:00.890]in water and cancer?
[00:56:02.090]So that's question one.
[00:56:03.730]Question two is, according to USDA,
[00:56:07.730]we want to reduce environmental pollution
[00:56:10.530]by 50% and increase the economic performance
[00:56:14.990]of our systems.
[00:56:16.370]That means high yields with lower
[00:56:18.610]environmental footprint.
[00:56:19.830]All your presentation, you show consistently
[00:56:23.010]that the most effective strategy is to increase
[00:56:25.790]yield and to reduce environmental footprint
[00:56:28.850]are number one, rotation, and number two,
[00:56:31.390]choosing the right economic optimal nitrogen rate.
[00:56:34.610]So basically, adjusting nitrogen rate
[00:56:37.070]to bring it closer to the optimum
[00:56:39.050]and adoption of crop rotation.
[00:56:42.490]Now, when you see what we are investing
[00:56:44.930]and what we are funding on research,
[00:56:46.910]well, all our money is going into research
[00:56:50.410]or subsidies for adoption of cover crops
[00:56:53.390]or things like soil health.
[00:56:55.530]We don't even know if they work.
[00:56:57.830]And there is so little money to do the kind of research
[00:56:59.950]that you are doing.
[00:57:01.290]For example, playing with rotation
[00:57:03.030]or trying to adjust the incision nitrogen management.
[00:57:05.570]Or for example, research trying to do more adaptive nitrogen
[00:57:09.350]management, as you mentioned.
[00:57:10.910]So what are we missing here?
[00:57:13.430]Why didn't show us that there are two or three things that we
[00:57:17.350]are so effective at increasing yields
[00:57:20.590]and reducing the environmental footprint at the same time?
[00:57:23.810]However, we are investing on things
[00:57:25.270]that seem to have a marginal impact.
[00:57:29.510]And also, they are very risky to adopt,
[00:57:31.510]because you show that in one year,
[00:57:33.390]the cover crop grow OK.
[00:57:35.030]In the next year, didn't grow.
[00:57:36.610]So very difficult to adopt that.
[00:57:38.470]So anyway, two questions.
[00:57:40.150]The first one, link between cancer and nitrates.
[00:57:43.210]And the second one, why we are setting our priorities
[00:57:48.770]against what the evidence is showing us?
[00:57:52.750]Thank you for your question.
[00:57:55.010]So for the nitrates, for the impacts on cancer,
[00:58:00.490]this is what I said is based on literature
[00:58:03.650]is not established from--
[00:58:06.310]I don't know if it's established, but based on literature
[00:58:08.570]and what we read.
[00:58:12.070]So it's established or not?
[00:58:14.370]So I won't say that it's established or not,
[00:58:16.330]but this is based on literature on what we found.
[00:58:20.410]Part of literature.
[00:58:21.370]Yeah.
[00:58:23.870]So can you please repeat your second question, please?
[00:58:28.550]Oh, it was very simple.
[00:58:29.670]You were showing that rotation and nitrogen management
[00:58:32.830]were the most effective to increase yields
[00:58:35.770]and reduce environmental pollution.
[00:58:38.310]So however, when you see what USDA is funding
[00:58:41.370]or what we are subsidizing is mostly cover crops
[00:58:44.230]or things like soil health.
[00:58:45.790]So why we are putting so much focus on cover crops
[00:58:50.790]or on soil health when the things that seem to be
[00:58:53.770]working very well at increasing yield
[00:58:55.510]and reducing environmental footprint are others
[00:58:57.790]like a better adjustment of the nitrogen rate
[00:59:00.310]and a use of crop rotation.
[00:59:02.730]Why there is this mismatch between what we are,
[00:59:08.470]between our priority setting for funding versus what works?
[00:59:14.230]- Mainly one of the main reason of hiding cover crop
[00:59:20.990]to these practices is to see how
[00:59:23.670]no cover crop will actually contribute
[00:59:26.250]to affect the environment.
[00:59:28.990]One of it being the, maybe the nitrates leaching
[00:59:32.190]is one of the reasons why we had it.
[00:59:34.590]So we're able to see that it's reduced it,
[00:59:36.690]even though the effects is not all true
[00:59:39.590]because it's also contributing to lower corn grain yield.
[00:59:44.010]And that was why we also suggested in our conclusion
[00:59:46.710]that we had an established tillage site,
[00:59:49.930]but we will continue to see
[00:59:51.630]because the first year no cover crop
[00:59:53.570]we saw the disparity in the effect of the year.
[00:59:56.950]That's why we also suggested that we will see
[00:59:58.810]how the trend looks over year
[01:00:00.870]to see if there anything is going to change or be to help.
[01:00:03.930]- Any other question?
[01:00:07.750]Okay.
[01:00:12.970]- Okay, we have one question, sorry.
[01:00:23.470]Sorry if I missed something,
[01:00:24.710]but can you speak on nitrous oxide emissions
[01:00:27.550]in no tillage system and rotations in non-growing season?
[01:00:30.950]Yeah, I assume that he's talking about the cover crop season
[01:00:37.130]if you were measuring nitrous oxide emissions
[01:00:39.810]like before planting the corn.
[01:00:42.150]- No, we were measuring it during the growing season.
[01:00:45.390]- Okay, and the second one.
[01:00:47.330]Do you have any standard soil property data
[01:00:50.370]to compare between all of the treatments or the main
[01:00:53.370]village treatments such as soil organic carbon levels?
[01:00:57.330]What soil testing analysis are you completing
[01:01:00.190]for the large main plots?
[01:01:01.610]If you have any additional soil analysis.
[01:01:08.630]- We did not do additional soil analysis.
[01:01:10.870]Although we had our soil sampling to be able to take
[01:01:13.310]the impact of this various management on soil health.
[01:01:16.270]So that we're actually working on the data.
[01:01:18.610]So we want to be able to see impact of this on soil health
[01:01:21.310]generally, where we look at the soil
[01:01:23.270]physical, chemical, and biological properties.
[01:01:26.990]OK, and the last question is, which
[01:01:29.150]were the seeding date and termination
[01:01:33.430]dates of the cover crops?
[01:01:36.730]So in date and termination date of the cover crops.
[01:01:38.870]So cover crop was seeded just immediately after harvest.
[01:01:44.370]And the termination dates was in the spring, early spring,
[01:01:52.070]before planting.
[01:01:53.170]So we're trying to let the cover crop grow
[01:01:57.110]from throughout the fall to the winter
[01:01:59.670]when the feed was lay fallow to be able to see how it's helped.
[01:02:06.370]The seeding rate was 60 pounds.
[01:02:08.570]60 pounds.
[01:02:09.070]OK.
[01:02:11.570]Any other question?
[01:02:12.570]We have time for one more question.
[01:02:16.170]OK.
[01:02:16.670]Yeah.
[01:02:17.170]Let's use the time.
[01:02:18.170]Let's use the time as well.
[01:02:20.170]Just curious how your results will change
[01:02:23.070]if your nitrogen management was the best possible one.
[01:02:26.570]You put all the nitrogen at planting time.
[01:02:29.070]So that will tend to--
[01:02:32.070]so I have the feeling that that results--
[01:02:36.570]they overestimate a little bit the potential benefit
[01:02:40.070]of cover crops or nitrogen leaching
[01:02:42.570]because your control was a kind of a poor nitrogen management
[01:02:47.070]in which you dump all the nitrogen at planting time.
[01:02:49.570]How will those results change if, for example,
[01:02:52.970]you split the nitrogen application,
[01:02:54.970]you put 30% of the nitrogen at planting
[01:02:57.970]and the other 2/3 during the season?
[01:03:00.970]I like this question because it really makes sense.
[01:03:03.970]And it's one of the things we also thought about
[01:03:05.970]because we're thinking if nitrogen--
[01:03:07.970]if a cover crop immobilizes nitrogen,
[01:03:09.970]what if we split it?
[01:03:10.970]This could have actually helped.
[01:03:12.970]That's a good one, which we also already thought about.
[01:03:16.970]OK, thank you so much.
[01:03:22.870]Thank you, all of you, for attending.
[01:03:25.770]Thank you.
[01:03:26.670]Thank you.
[01:03:28.570]Thank you.
[01:03:29.470]Thank you.
[01:03:32.370]Thank you.

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The Role of Conservation Management in Nitrogen Balance: Findings from the UNL-NRCS Collaboration

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