"What we learned from three years of growing rye, vetch and mixture in Eastern Nebraska under variable precipitation seasons"

Tauana Ferriera De Almeida, Postdoctoral research Associate, Dept of Agronomy & Horticulture, University of Nebraska-Lincoln Author

03/27/2025 Added

2 Plays

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Tauana is an Agronomist, holds a master’s degree in soil science from Federal University of Rio Grande do Sul - Brazil, and completed her Ph.D. in Summer 2024. She is a key contributor to the Precision Sustainable Agriculture Coordinated Agriculture Project. She is researching the efficiency of cover crops under different management systems to improve soil health, control weeds and pests and increase cash crop yield.

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[00:00:00.760]- The following presentation
[00:00:02.200]is part of the Agronomy and Horticulture Seminar Series
[00:00:05.800]at the University of Nebraska-Lincoln.
[00:00:08.400]- So let's start.
[00:00:10.000]Good morning, everyone.
[00:00:10.840]Thank you for attending to this seminar.
[00:00:13.620]As every seminar, we will have a presentation
[00:00:16.880]of around 40, 45 minutes, and after the presentation,
[00:00:20.720]there is time for questions.
[00:00:23.100]Those who are online, please feel free to use the chat
[00:00:26.640]to ask your questions.
[00:00:29.120]So it's my pleasure today to present Dr. Tauana De Almeida.
[00:00:34.060]She has been a post-doctoral research associate
[00:00:36.380]in the Resilient Cropping System Lab
[00:00:38.320]here in the Department of Agronomy and Horticulture at UNL
[00:00:41.380]since August 2024, sorry.
[00:00:44.760]She earned her PhD in agronomy from UNL in 2024.
[00:00:48.080]Her research focuses on advancing cover crop management
[00:00:50.920]strategies to improve ecosystem services,
[00:00:53.400]water quality, and soil health.
[00:00:55.760]She has successfully collaborated with growers
[00:00:58.240]and industry professionals to implement
[00:01:00.020]sustainable agricultural practices that address soil
[00:01:02.740]health and water resource management.
[00:01:05.020]She's also passionate about driving innovation,
[00:01:07.660]advising the sustainability of cropping system,
[00:01:09.940]and transitioning complex research
[00:01:11.440]into practical applications.
[00:01:13.960]Today, Tauana will be presenting on what
[00:01:16.420]we learned from three years of growing rye, beech,
[00:01:20.020]and mixture in eastern Nebraska under variable precipitation
[00:01:23.300]seasons.
[00:01:24.500]Tauana, the floor is yours.
[00:01:27.060]So good morning.
[00:01:27.360]Good morning, everyone.
[00:01:28.960]It's a pleasure to be here today to talk with you
[00:01:32.700]about what we have learned in these past years working
[00:01:37.040]with rye, not Thai, as was in the announcement,
[00:01:41.340]hairy beech, and mix.
[00:01:43.480]I will start with a very brief introduction,
[00:01:49.480]and then I will jump to the projects that we developed.
[00:01:53.220]And I will talk about three different projects today, all
[00:01:56.600]of them
[00:01:57.120]focus on cover crop management.
[00:02:00.160]So in the first one, we evaluated
[00:02:03.360]the impact of cover crop species and termination time
[00:02:07.400]on seedling disease and corn yield.
[00:02:11.000]In the next one that I will talk about,
[00:02:13.140]we evaluated the cover crops decomposition and nitrogen
[00:02:16.940]released.
[00:02:18.120]And in the last one, but not least,
[00:02:20.900]we evaluated the impact of the cover crops
[00:02:24.020]on the optimum nitrogen rate for corn.
[00:02:26.680]So just to start with a brief introduction,
[00:02:31.400]these maps show some climate projections
[00:02:35.400]for different regions across the United States.
[00:02:39.000]And for a region and like thinking bigger
[00:02:43.820]for the Midwest and northern Corn Belt,
[00:02:46.680]these projections suggest an increase
[00:02:49.940]in the number of days of heavy precipitation events,
[00:02:53.900]which are days with more than
[00:02:56.600]one inch of rainfall per day,
[00:02:59.820]and also an increase in the intensity
[00:03:02.340]and frequency of drought.
[00:03:04.980]There are also projections showing an increase
[00:03:08.540]in the number of days of extremely high temperature events
[00:03:12.860]during critical crop development stages.
[00:03:16.200]So the current occurrence of these extreme weather events
[00:03:20.380]coupled with these projections showing a likely increase
[00:03:24.480]in the intensity and frequency
[00:03:26.520]as, for example, the health precipitation,
[00:03:29.680]increases the problems with nutrient leaching
[00:03:32.580]and consequently water pollution.
[00:03:35.700]And also, the increase in the number of days
[00:03:38.380]of extremely high temperature, for example,
[00:03:41.640]during the reproductive period of corn or other crops,
[00:03:46.140]exacerbates the challenge of keeping successful crop yields.
[00:03:51.840]So the main reason why I wanted to start my presentation with
[00:03:56.440]these maps showing these climate projections
[00:04:00.520]is because all the projects that I will show you today,
[00:04:04.860]we developed then from 2020 to 2024.
[00:04:09.860]And during these four cover crop corn growing seasons,
[00:04:15.340]we have a lot of variability in terms of rainfall,
[00:04:20.340]and this variability really impacted
[00:04:23.880]how the cover crops affected
[00:04:26.360]the next cash crop.
[00:04:28.060]And I will show you more about that
[00:04:29.900]when we go through project and the results.
[00:04:33.560]So cover crops.
[00:04:37.880]Cover crops is a climate smart agriculture practice
[00:04:41.360]that can provide a variety of ecosystem services
[00:04:44.780]and offset environmental issues related to agriculture.
[00:04:48.980]Some of these ecosystem services are reducing soil erosion
[00:04:53.420]to providing protective to the soil and
[00:04:56.280]growing soil roots.
[00:04:58.180]Cover crops also manage nutrients.
[00:05:01.260]Cedar rye, for example, which is the grass cover crop
[00:05:04.800]most used in the Midwest of the United States.
[00:05:09.660]Cedar rye scavenges nitrogen from the soil
[00:05:14.100]and decreases nitrate leaching.
[00:05:16.900]Hairy vetch, a legume cover crop that we also work with,
[00:05:21.720]biologically fixes atmospheric nitrogen, adding these new
[00:05:26.200]nutrients to the system.
[00:05:28.320]Cover crops also promote plant and microbial diversity,
[00:05:33.060]providing habitat for beneficial arthropods, predators,
[00:05:36.520]for example, and also enhance soil and water storage,
[00:05:41.420]increasing water infiltration and lowering soil temperature.
[00:05:46.920]Most of the services provided by cover crop, they are most
[00:05:51.000]dependent of the intrinsic factors that are affecting the
[00:05:54.580]cover crops.
[00:05:56.120]Where we are using them as soil and weather, and the intrinsic
[00:06:02.180]factors of the cover crops as species selection, planting
[00:06:06.320]date, seeding rate, and termination time.
[00:06:11.000]So as I said, it was a very brief introduction.
[00:06:14.840]And then starting with the first project, the main
[00:06:19.280]question we wanted to answer in this project
[00:06:22.160]was, when should I terminate my cover crops
[00:06:26.040]to have most of the benefits and not decrease corn yield?
[00:06:30.800]So here in these two photos, we have CDRI.
[00:06:34.680]And these pictures, they were took in the same day
[00:06:37.920]that we terminated this CDRI.
[00:06:41.100]So here in the left one, we have CDRI terminated early.
[00:06:45.560]And here, CDRI terminated late.
[00:06:48.540]And you can see a huge difference
[00:06:50.740]in biomass production between these two photos, right?
[00:06:54.840]And this difference--
[00:06:55.960]this difference in biomass production
[00:06:58.340]really impacted differently the factors of the next cash crop.
[00:07:05.200]So to contextualize the methods of this study,
[00:07:09.720]we had six different cover crop treatments
[00:07:12.880]that we were testing--
[00:07:14.560]a no cover crop, a treatment of CDRI,
[00:07:18.200]and one treatment of hairy vetch terminated early.
[00:07:21.760]And when I say terminated early, they were terminated 10 days
[00:07:25.880]before we planting corn.
[00:07:28.260]And then a treatment of CDRI and a treatment of hairy vetch
[00:07:32.420]terminated late.
[00:07:33.740]And then they were terminated seven days after planting corn.
[00:07:38.360]And this last treatment here was CDRI
[00:07:42.320]terminated late, seven days after planting corn,
[00:07:45.620]plus an extra nitrogen rate.
[00:07:47.960]So for the first five treatments that I mentioned,
[00:07:51.500]when we planted corn, we applied 168 kilograms
[00:07:55.800]of nitrogen per hectare to corn.
[00:07:59.040]And in this one, we applied 224 kilograms of nitrogen.
[00:08:04.040]So the reason why we did that,
[00:08:06.140]it's because as we were late terminating CDRI,
[00:08:11.140]there was a potential of some immobilization of nitrogen
[00:08:16.120]caused by CDRI.
[00:08:17.800]And then with this extra nitrogen rate,
[00:08:20.660]we wanted to see if this could offset some of this potential
[00:08:25.720]immobilization caused by CDRI.
[00:08:29.920]And this study was developed in the cover crop
[00:08:33.360]corn growing season of 2020, 2021 and 2021 to 2022.
[00:08:38.360]So then to evaluate the seedling disease and corn yield,
[00:08:45.860]we sampled cover crop biomass above ground.
[00:08:49.480]We didn't sample roots and corn plants at the V3 stage
[00:08:55.640]to evaluate the seedling disease and corn yield.
[00:08:59.200]So before I start with the results,
[00:09:03.500]I wanted to show you the rainfall variability
[00:09:06.880]during these two years of this study,
[00:09:09.100]as I mentioned in my previous slide,
[00:09:11.320]that it varied a lot during the time
[00:09:14.160]that we were developing these research.
[00:09:16.460]So here in these graphs,
[00:09:18.300]we have the precipitation in millimeters per day,
[00:09:21.000]and here is the corn growing season of 2021
[00:09:25.560]and 2022.
[00:09:28.160]In 2021, the total precipitation
[00:09:31.740]during the whole corn growing season
[00:09:34.240]was of 606 millimeters,
[00:09:36.900]and it was considered a normal precipitation
[00:09:39.800]in terms of amount and distribution.
[00:09:42.840]In 2022 was a very dry season,
[00:09:47.120]and the total precipitation was of 269,
[00:09:51.220]55% less than in 2021.
[00:09:55.480]And you see the impact of this dry season in the results.
[00:10:00.480]So starting with the biomass production.
[00:10:05.660]In 2021, the treatments of CDRI,
[00:10:09.660]both terminated late and early,
[00:10:11.620]they didn't differ statistically,
[00:10:14.780]and CDRI produced more biomass
[00:10:18.880]than both treatments of hairy veg,
[00:10:21.120]terminated early and terminated late.
[00:10:24.560]In 2020,
[00:10:25.400]both treatments of CDRI terminated late
[00:10:29.440]produced more biomass than rye early
[00:10:32.280]in both treatments of hairy veg.
[00:10:34.640]And rye early still produced more biomass than veg early,
[00:10:38.940]but didn't differ from the hairy veg terminated late.
[00:10:42.920]This plot here shows the root rot severity in percent.
[00:10:49.520]So the root rot severity is the symptom
[00:10:52.760]of seedling disease that we analyzed.
[00:10:55.320]It is a visual analyze.
[00:10:57.960]And then here we have the root rot severity in percent
[00:11:02.060]for corn following each one of the cover crop treatments
[00:11:05.900]and the no cover crop treatment.
[00:11:08.660]So in 2021, there was no difference among the cover crops
[00:11:13.480]and no cover crop treatment in the root rot severity.
[00:11:17.580]In 2022, which was the drier year,
[00:11:21.780]that the total rainfall was 50% less
[00:11:25.240]than in 2021, both treatments of cereal rye
[00:11:29.420]terminated late increased the root rot severity for corn.
[00:11:34.420]And the other cover crop treatments didn't differ
[00:11:39.280]statistically from the no cover crop treatment
[00:11:42.460]in their impact on the root rot severity.
[00:11:45.700]And here we have the corn grain yield
[00:11:51.840]in kilograms per hectare following each one of the
[00:11:55.160]cover crop treatments and the no cover crop.
[00:11:57.860]In 2021, both treatments of cereal rye terminated
[00:12:03.520]late with and without an extra nitrogen rate
[00:12:07.640]decreased the corn yield.
[00:12:10.160]However, this decline was more accentuated when
[00:12:14.980]no extra nitrogen was applied to corn,
[00:12:18.240]decreasing to 28.1% compared to the no cover crop.
[00:12:25.080]Extra nitrogen rate was applied.
[00:12:27.120]It did offset a little bit of this decline,
[00:12:31.700]but it was still 15% lower than when following
[00:12:36.340]no cover crop treatment.
[00:12:38.260]And in 2022, as you can see here,
[00:12:43.160]in general, following all the treatments,
[00:12:46.820]even the no cover crop treatment,
[00:12:48.720]the yield of corn decreased compared to 2021.
[00:12:55.000]And this is probably due to the very dry season
[00:12:58.080]as the total rainfall was half than in the previous year.
[00:13:02.620]But then the late termination of cereal rye
[00:13:07.940]accentuated a lot this decline.
[00:13:11.260]When no extra nitrogen was applied,
[00:13:13.980]it decreased 76% compared to the no cover.
[00:13:18.740]And when we applied an extra nitrogen rate,
[00:13:21.680]it decreased 36.3%.
[00:13:24.920]compared to the no cover crop treatment.
[00:13:27.640]So some conclusions for this first study
[00:13:33.320]is that the late termination of cereal rye
[00:13:36.860]had a negative impact in corn.
[00:13:39.320]And this is probably due to the nitrogen immobilization
[00:13:42.980]that happens because of this late termination.
[00:13:46.600]As we saw when we applied an extra nitrogen rate,
[00:13:49.880]it did offset some of this yield decline.
[00:13:54.840]And the early termination of cereal rye
[00:13:58.560]and both termination times of hairy vetch
[00:14:02.840]did not increase seedling disease in none of the years,
[00:14:07.220]even in the drier year,
[00:14:09.320]and also did not decrease corn yield,
[00:14:12.360]even in the drier year.
[00:14:14.040]So both cereal rye terminated early
[00:14:17.260]and both treatments of hairy vetch terminated early
[00:14:20.520]and late can be an option of cover
[00:14:24.760]crops that do not decrease corn yield.
[00:14:28.100]And if you are interested in seeing more
[00:14:32.240]about this study, we published last year
[00:14:35.420]in the Agronomy Journal.
[00:14:36.900]So jumping to the next project,
[00:14:41.240]in this one, we evaluated how much nitrogen
[00:14:45.660]do different cover crop species uptake and release.
[00:14:49.420]And when is this nitrogen being released?
[00:14:54.680]So for this study, we had four different
[00:14:58.500]cover crop treatments.
[00:15:00.040]Cereal rye, hairy vetch, a mixture of rye and vetch,
[00:15:05.040]and a no cover crop control.
[00:15:07.420]And the cover crops were planted in fall of 2020,
[00:15:12.340]21, and 22, and terminated in the spring of next year,
[00:15:18.240]around 15 days before we planting corn.
[00:15:21.820]So in this study, we are not evaluating
[00:15:24.600]the termination times.
[00:15:26.380]All the cover crops were terminated at the same time
[00:15:30.000]all the years.
[00:15:31.060]We are just looking at the species of the cover crop.
[00:15:34.580]So to evaluate the decomposition of the cover crops
[00:15:39.980]and their nitrogen release,
[00:15:41.680]we use the litter bags methodology.
[00:15:44.180]So I will explain you about this methodology.
[00:15:48.580]Basically, in the same day of the termination
[00:15:52.220]of the cover crops, the same day
[00:15:54.520]because we wanted to have a sample
[00:15:57.520]of the highest growth.
[00:16:00.440]So in the same day that we were going
[00:16:02.700]to terminate the cover crops,
[00:16:04.440]we sampled one meter square of cover crop
[00:16:07.480]above ground biomass.
[00:16:08.720]And then we weighed that and we split in six equal parts.
[00:16:13.740]One of these parts we brought to the lab
[00:16:17.940]in the same day that we sample.
[00:16:20.400]The other five, oh, first, we put in this mesh
[00:16:24.440]bags, as you can see here in these pictures.
[00:16:27.020]And these mesh bags, they have one millimeter mesh size,
[00:16:31.080]which is what we call litter bags,
[00:16:34.900]when we have the residue of the cover crop inside of the bags.
[00:16:39.460]So this one, we brought to the lab in the same day
[00:16:43.340]and put in the dryer.
[00:16:44.720]And after dried, we ground and we evaluated
[00:16:49.100]for nitrogen content.
[00:16:50.760]The other five litter bags, we placed
[00:16:54.360]it in the field exactly as you can see here
[00:16:56.960]in this picture, and we retrieved them
[00:16:59.820]throughout the corn growing season
[00:17:02.240]at 2, 4, 7, 11, and 16 weeks
[00:17:06.720]after the termination of the cover crops.
[00:17:09.980]And then with these times of retrieval,
[00:17:14.200]we estimated the decomposition
[00:17:17.380]and the nitrogen release.
[00:17:19.560]So jumping to the results, first I want
[00:17:24.280]to show you the cover crop biomass production
[00:17:26.980]in this study.
[00:17:28.520]In 2021, both cereal rye and mixed treatments
[00:17:33.900]produced higher biomass amounts than hairy vetch,
[00:17:37.320]averaging 7,000 kilograms per hectare,
[00:17:40.600]while hairy vetch produced around 2,000 kilograms.
[00:17:43.640]In 2022, there was no difference in the biomass production
[00:17:49.200]among the different cover crop species,
[00:17:51.520]and they averaged 3,000 kilograms
[00:17:54.200]per hectare.
[00:17:55.080]And in 2023, again, CDRI and MIX produced more biomass,
[00:18:00.780]averaging 5,000, while hairy vetch averaged 2,000
[00:18:04.580]kilograms per hectare.
[00:18:06.220]So the decomposition and the nitrogen release of the cover
[00:18:12.940]crops is highly influenced by the quantity and quality
[00:18:16.720]of the biomass and the weather affecting this decomposition.
[00:18:20.860]In this study that was
[00:18:24.120]developed in the northeast of the United States, Tapa et al.,
[00:18:28.400]they found that the number of rainy days and the cumulative
[00:18:32.160]precipitation in the first six days after cover crop
[00:18:36.340]termination highly impacted the decomposition.
[00:18:40.040]And we saw in our results the impact also of the rainfall
[00:18:45.540]variability.
[00:18:46.380]So this study was developed very close to the first one that I
[00:18:53.320]showed you.
[00:18:54.040]And here I have a similar graph as the previous study showing
[00:18:58.040]the precipitation in millimeters per day.
[00:19:00.840]The difference here is that this timeline here is the
[00:19:07.220]decomposition days.
[00:19:09.040]It's not just the corn season.
[00:19:12.360]So it counts from the day that we terminated the cover crop
[00:19:16.700]until the day that we harvest corn.
[00:19:19.380]Because when we harvested corn was the last time that we
[00:19:23.960]retrieved the last litter bag from the field.
[00:19:26.960]So you can see that there is variability.
[00:19:30.080]539 millimeters in 2021, 219 in 2022, and 421 in 2023.
[00:19:38.760]And I'll talk more about that right now.
[00:19:42.540]So these curves, they are showing, those here, they are
[00:19:47.640]showing the decomposition of the cover crops in 2021, 2022,
[00:19:53.880]and 2023.
[00:19:54.520]And this one is showing the nitrogen release from the
[00:19:59.180]decomposition of the cover crops in 21, 22, and 23.
[00:20:04.220]So in 2021, there was no difference in the decomposition
[00:20:10.980]rate of the cover crop among the cover crop species.
[00:20:15.000]And also there was no difference in the nitrogen release rate
[00:20:20.200]among the cover crop species.
[00:20:23.800]By the end of the season, when we retrieved the last litter bag
[00:20:27.800]16 weeks after the termination of the cover crops,
[00:20:31.800]20% of the total initial biomass remained undecomposed in the field.
[00:20:39.800]And 30% of the initial nitrogen content in this cover crop biomass
[00:20:47.800]remained present in this 20% of cover crop residue that
[00:20:53.720]remained undecomposed in the field.
[00:20:55.880]Then in 2022, the total rainfall was only 290.
[00:21:04.120]However, there was this kind of a concentration of rainfall
[00:21:08.040]in the beginning after the termination of the cover crops
[00:21:11.400]in which 106 millimeters, 55% of the total rainfall occurred here.
[00:21:17.640]And this happens in the first seven weeks after cover crop termination.
[00:21:23.640]And it coincided with corn at around V4, V5 stage,
[00:21:29.960]which is when corn is like taking more nitrogen.
[00:21:35.320]And in 2022, 90% of the total decomposition of the cover crops
[00:21:43.160]occurred in these first seven weeks.
[00:21:46.600]And more than 90% of the total nitrogen released by the different cover crop species
[00:21:53.560]also occurred in the first seven weeks.
[00:21:56.920]And we can see here in the graph that Hairy Vetch
[00:22:02.040]had a faster rate of nitrogen release than Myx and Rye.
[00:22:08.520]And by the end of the season in 2022,
[00:22:13.000]30% of the total initial biomass remained undecomposed.
[00:22:19.080]And in this 30%, 30% of the total nitrogen
[00:22:23.480]in CDRI and Myx remained in this residue.
[00:22:29.000]And around 20% of the nitrogen from the Hairy Vetch
[00:22:34.200]remained in the Hairy Vetch residue.
[00:22:38.600]In 2023, the total rainfall during the decomposition period
[00:22:43.960]was of 421 millimeters.
[00:22:47.800]However, you can see here that there
[00:22:50.280]is a lack of precipitation in the beginning
[00:22:53.400]of the decomposition season.
[00:22:55.640]So from the day that we terminated the cover crops,
[00:22:59.800]in the first 34 days, the total rainfall
[00:23:03.800]was of only 4 millimeters.
[00:23:06.520]And this impacted the start of the decomposition
[00:23:12.120]of the cover crop that was delayed,
[00:23:15.000]and also the start of the nitrogen
[00:23:17.720]released for all the cover crop treatments.
[00:23:22.200]And then after--
[00:23:23.320]after that, there was a concentration of rainfall.
[00:23:27.800]And then the cover crops started decomposing.
[00:23:33.640]And there was no difference in the decomposition rate here.
[00:23:38.920]But there was difference in the nitrogen release rate.
[00:23:43.600]So in this year, in 2023, Perivetch
[00:23:47.640]released nitrogen much faster than mix and cereal
[00:23:53.240]rye.
[00:23:54.920]In the end of the season, 20% of the initial biomass
[00:24:00.560]remained undecomposed.
[00:24:02.920]And regarding the nitrogen, only 45%
[00:24:08.540]of the total initial nitrogen present in cereal rye
[00:24:12.740]had been released in the seventh week after cover crop
[00:24:17.240]termination, which was the week that
[00:24:19.580]coincided with corn around V4, V5.
[00:24:23.160]And 70% had been released from mix,
[00:24:30.160]and 90% of its initial nitrogen had
[00:24:34.020]been released from hairy vetch.
[00:24:38.460]And by the end of the season, around 10% of the nitrogen
[00:24:43.860]remained in the residue of the cover crops
[00:24:48.220]that wasn't decomposed.
[00:24:51.920]So in this--
[00:24:53.080]last graph here, what I want to show you is--
[00:24:56.640]so the first result that I show you
[00:24:59.160]was the biomass in kilograms per hectare, right?
[00:25:02.500]And then we have for each one of the years.
[00:25:05.440]Well, in this one here, we have the nitrogen
[00:25:09.040]in kilograms per hectare in the dark blue that
[00:25:12.520]was uptaken by each one of the cover crops
[00:25:15.940]and in the light blue that was released by each one
[00:25:19.420]of the cover crops.
[00:25:21.080]And what I want to call your attention
[00:25:23.000]here is like, for example, in 2021,
[00:25:27.180]the total nitrogen released by the cover crops
[00:25:31.200]was an average of 6 to 90 kilograms per hectare.
[00:25:35.540]And there was no statistical difference in the release.
[00:25:39.060]However, look at this biomass production.
[00:25:42.060]We had around 7,000 kilograms of biomass for cereal rye and mix,
[00:25:47.460]while we had 2,000 kilograms of biomass produced by hairy vetch.
[00:25:52.920]This is showing us that, yes, cereal rye and mix can release
[00:25:57.600]the same amount of nitrogen, but we need three times more biomass
[00:26:02.260]than hairy vetch to release a similar amount.
[00:26:06.560]While, for example, in 2022, hairy vetch released 85
[00:26:12.200]kilograms, while rye and mix released around 42 kilograms.
[00:26:17.540]So hairy vetch released twice more nitrogen than the other two
[00:26:21.580]treatments.
[00:26:22.840]So there was no difference in the biomass production.
[00:26:26.880]Well, in 2023, there was no statistical difference in the
[00:26:31.680]nitrogen released, and cereal rye and mix produced more biomass
[00:26:37.460]than hairy vetch.
[00:26:38.920]So this was the only year that there was no statistical
[00:26:42.220]difference, while the production of biomass was higher for this
[00:26:46.660]treatment.
[00:26:47.760]But I think the main takeaway that we can have from this is we
[00:26:52.760]need to look at what is the main goal of our cover crop.
[00:26:57.060]We are more interested in the services like soil cover to
[00:27:02.100]increase water infiltration and decrease runoff, so maybe CDY is
[00:27:08.740]more interesting because of its fast-growing fall and more
[00:27:13.180]aggressive growth than hairy vetch.
[00:27:15.120]While if we are interested in adding biological nitrogen from
[00:27:20.020]our system, we are interested in hairy vetch, which is
[00:27:22.680]a legume and will fix nitrogen, even with a lower amount of
[00:27:29.480]biomass than cereal rye.
[00:27:32.360]So answering the question that we had in the beginning, how
[00:27:37.600]much nitrogen do different cover crop species uptake and
[00:27:41.660]release, and when is this nitrogen being released?
[00:27:45.800]Well, between 60 to 90 percent of the nitrogen was released in
[00:27:51.080]the first seven weeks.
[00:27:52.600]After cover crop termination.
[00:27:54.700]However, this is dependent on the amount and the distribution
[00:27:59.140]of precipitation during that period.
[00:28:02.040]As we saw that when we had a gap of precipitation in the
[00:28:05.920]beginning of the season, it delayed the decomposition of
[00:28:09.520]the cover crops and consequently the nitrogen.
[00:28:12.160]released. Also, cereal rye and mix, as I just mentioned, can release a similar amount of
[00:28:19.580]nitrogen than hairy vetch. However, this requires at least two times the amount of biomass.
[00:28:25.680]And the last study, but not least, in this one, we were evaluating how the cover crops impacted
[00:28:37.480]the agronomic optimal nitrogen rate of corn. So this study was developed in the same field
[00:28:45.640]experiment as the previous one, the one of the litter bags and the decomposition. So again,
[00:28:51.580]it happens in the cover crop corn growing season of 2021, 21, 22, and 22, 23.
[00:28:59.220]Cover crops planted in the fall and terminated in the spring, around 15 days,
[00:29:07.120]both.
[00:29:07.460]Before corn planting.
[00:29:09.100]And then we applied six different nitrogen rates to corn.
[00:29:14.940]0, 45, 90, 180, 207, and 360 kilograms of nitrogen per hectare being 45
[00:29:24.540]kilograms applied at pre-plant and the rest of the rate at a V4 corn stage.
[00:29:32.280]So just a concept here, the agronomic optimum.
[00:29:37.240]Nitrogen rate is defined as the lowest rate of nitrogen fertilizer
[00:29:42.580]required to maximize yield.
[00:29:44.940]And here I want to show you how we estimated the agronomic optimum
[00:29:51.420]nitrogen rate in our study.
[00:29:53.200]So we use it a linear plateau model.
[00:29:56.640]So here, just an example, we have corn yield in megagrams per hectare.
[00:30:02.440]And in the XX, the nitrogen rate in kilograms.
[00:30:07.020]Holograms per hectare.
[00:30:08.200]And then it's the corn yield following a hairy vetch treatment.
[00:30:13.040]Just as an example to explain the model.
[00:30:15.820]So the intercept, what we call the A factor,
[00:30:21.660]which means when no nitrogen was applied.
[00:30:24.720]At zero nitrogen is the A.
[00:30:28.640]And then when I show you the results, I will call this again to explain to you.
[00:30:34.180]And then the B factor.
[00:30:36.800]Which is the slope is the corn yield increment per unit of nitrogen apply.
[00:30:42.240]So for each one kilogram of nitrogen that we applied,
[00:30:46.560]how many kilograms of corn yield increased?
[00:30:50.600]Oops.
[00:30:52.720]And then the Xs is the agronomic
[00:30:56.880]optimum nitrogen rate in kilograms per hectare,
[00:31:00.380]which is the lowest rate of nitrogen to maximize the corn yield.
[00:31:05.220]And here
[00:31:06.580]is the corny yield when we apply the agronomic optimum nitrogen rate.
[00:31:12.020]So
[00:31:15.000]when we were analyzing the data of this study,
[00:31:21.200]we started using an approach in which we treated
[00:31:26.120]the overall effect of cover crops by treating years as a random effect
[00:31:31.580]along with the replicates, which accounted for an inter-annual variability.
[00:31:36.360]So basically, here we evaluated all the three years together:
[00:31:41.640]2021, '22, and '23.
[00:31:44.760]So in this graph, we have the corn yielding megagrams per hectare,
[00:31:50.600]the nitrogen rate in kilograms per hectare,
[00:31:53.400]the estimated curves of the agronomic optimum nitrogen rate,
[00:31:58.160]followed by cereal rye, hairy vetch, mix, and no cover.
[00:32:02.600]And in this table, we had the values of these
[00:32:06.140]estimated for inter-annual variability,
[00:32:11.100]as I mentioned, all the three years together.
[00:32:14.620]So when no nitrogen was applied to corn,
[00:32:18.680]corn following cereal rye had a lower yield
[00:32:24.420]than when following the other cover crop
[00:32:28.220]and no cover crop treatment
[00:32:30.520]using this inter-annual variability approach.
[00:32:35.920]However, there was no statistical difference
[00:32:39.060]in the agronomic optimum nitrogen rate
[00:32:42.620]nor in the corn yield at the agronomic
[00:32:45.920]optimum nitrogen rate.
[00:32:48.420]This tells us that even that cereal rye
[00:32:52.880]is immobilizing some nitrogen here
[00:32:56.320]and decreasing the corn yield when no nitrogen was applied,
[00:33:00.300]when we apply the optimum nitrogen rate,
[00:33:04.040]this potential immobilization
[00:33:05.700]is offset and there is no impact in corn yield
[00:33:10.700]following cereal rye compared to none
[00:33:14.620]of the other treatments.
[00:33:16.480]As I mentioned, this study was developed
[00:33:21.920]in the same field as the previous one.
[00:33:24.540]So it was the same precipitation
[00:33:26.780]and we had this variability.
[00:33:29.100]So due to this variability in the total rainfall,
[00:33:34.100]we decided to analyze
[00:33:35.480]our data using a second approach as well,
[00:33:39.440]in which cover crop treatments and nitrogen rates
[00:33:42.920]were considered fixed effects within each year,
[00:33:46.620]which allow us to observe the annual variations directly.
[00:33:50.700]So here now we have the same idea as before,
[00:33:57.500]but now we are considering only 2021,
[00:34:01.480]which was a year considered of a normal
[00:34:05.260]rainfall and there was no like a dry season in 2021.
[00:34:10.260]So again, the corn yield in megagrams per hectare,
[00:34:17.740]the nitrogen rate in kilograms per hectare,
[00:34:20.820]following each one of the cover crop treatments
[00:34:23.280]and here the estimated values.
[00:34:25.500]So in 2021, again, corn following CDRI had a lower yield
[00:34:30.500]when no nitrogen was applied.
[00:34:35.040]But only compared to hairy vetch.
[00:34:38.560]In the 2021 isolated year, there was already no difference.
[00:34:43.020]Even if no nitrogen was applied,
[00:34:45.040]it was not different from the no cover crop treatment.
[00:34:48.400]And regarding the agronomic optimal nitrogen rate,
[00:34:53.640]there was a difference between mixed treatment
[00:34:56.980]and no cover crop.
[00:34:58.700]But this difference is positive for the mixed treatment
[00:35:03.120]that had a lower
[00:35:04.820]agronomic optimal nitrogen rate
[00:35:07.300]than when following the no cover crop treatment.
[00:35:11.740]And the corn yield also had differences,
[00:35:16.100]but it was only between hairy vetch and mixed treatment
[00:35:20.460]when the optimal nitrogen rate was applied.
[00:35:23.240]So all the three cover crop treatments,
[00:35:26.180]they didn't differ from the no cover crop treatment
[00:35:30.420]in terms of next corn yield.
[00:35:33.660]Here we have the 2022 data.
[00:35:39.260]Again, the same idea as before,
[00:35:42.040]the graphs of the curves and the estimated values.
[00:35:45.340]And in 2022, which was a very dry season,
[00:35:49.780]the impact on corn yield when no nitrogen was applied
[00:35:54.720]was a little bit higher following CDRI.
[00:35:59.120]That decreased corn yield compared to hairy vetch
[00:36:03.120]and mixed.
[00:36:03.660]But it was not statistically different from the no cover
[00:36:07.260]crop treatment.
[00:36:08.820]And again, there was no statistical difference
[00:36:12.540]in the agronomic optimum nitrogen rate of corn.
[00:36:17.040]And no statistical difference in the corn yield
[00:36:22.220]at the agronomic optimum nitrogen rate in 2022.
[00:36:27.540]You guys can see that we can say that this
[00:36:30.720]is a numerical difference, right?
[00:36:32.420]259.
[00:36:33.120]59 kilograms of nitrogen following hairy vetch compared to this other treatment. Well, it wasn't
[00:36:40.440]a statistical difference in the model, but it is a high difference in terms of number. And we think
[00:36:49.840]that this difference is because of the model, because our starting point was very high following
[00:36:58.280]hairy vetch compared to the other cover crops and no cover crop treatment. And in 2023,
[00:37:06.780]there was no difference in none of the factors evaluated. Even when no nitrogen was applied,
[00:37:14.700]there was no difference following CDRI, which was a difference that we saw in the other two years
[00:37:21.200]and also we saw in the inter-annual approach.
[00:37:25.760]So, from this study, we concluded that cover crops influenced the nitrogen supply to the corn crop
[00:37:35.520]as we saw when no nitrogen was applied. In the inter-annual variability approach in 2021 and in
[00:37:44.720]2022, CDRI decreased corn yield. However, there was no difference in the agronomic optimum nitrogen
[00:37:54.040]rate. And also, there was no difference in the agronomic optimum nitrogen rate. And also,
[00:37:55.740]CDRI decreased corn yield. However, there was no difference in the agronomic optimum nitrogen rate.
[00:37:55.740]And also, there was no difference in the agronomic optimum nitrogen rate. And also, there was no
[00:37:56.020]difference in the agronomic optimum nitrogen rate. And also, there was no difference in the
[00:37:57.060]corn yield at the agronomic optimum nitrogen rate of corn. So, as I mentioned, this shows us
[00:38:04.340]that when we apply an optimum nitrogen rate to corn, this rate is offsetting this negative
[00:38:12.340]yield that is happening following CDRI. And the main message, like cover crops,
[00:38:19.640]did not decrease the corn grain yield at the AONR, nor did they increase the AONR.
[00:38:25.720]And the main takeaways that we learned from these three studies that I showed you today
[00:38:34.500]is that both CDRI terminated early and hairy vetch, regardless of its termination time,
[00:38:41.860]early or late, are great options to have a biomass and not increase seedling disease
[00:38:49.160]or decrease corn yield. CDRI and mix can release a similar amount
[00:38:55.700]of nitrogen as hairy vetch. However, this requires at least two times the amount of biomass.
[00:39:03.060]And cover crops did not decrease the corny grain yield at the agronomic optimum nitrogen rate,
[00:39:10.020]nor did they increase the agronomic optimum nitrogen rate compared to the no cover crop
[00:39:16.560]treatment. I want to thank you everyone and I want to thank you my research group.
[00:39:25.680]All this research, all these studies, these wouldn't be possible without our group.
[00:39:31.880]And let me tell you, we are not only doing science in our group.
[00:39:36.880]We are sharing values, kindness, respect, and supporting each other, which I think it's very
[00:39:44.260]important in the environment that we are having in the world right now.
[00:39:49.580]So I am very proud to be part of the group that I am.
[00:39:54.300]Thank you so much.
[00:39:55.660]And I'll take any questions.
[00:39:57.040]Thank you so much.
[00:40:04.580]I want to thank you for your presentation.
[00:40:07.160]So we have around 15 minutes for questions.
[00:40:10.780]That was very nice.
[00:40:18.540]Thank you.
[00:40:19.200]How did you terminate your cover crops?
[00:40:22.840]It's spraying with herbicide.
[00:40:26.180]Which herbicide?
[00:40:26.920]Herbicide, yes.
[00:40:27.760]In all of the studies, in all of the treatment.
[00:40:31.180]But was it Roundup or what?
[00:40:32.960]We used Roundup and we used a 2,4-D.
[00:40:36.640]Okay.
[00:40:37.640]And did you also treat your no cover crop plots with the same herbicide?
[00:40:44.180]Yes, we did.
[00:40:45.780]We did, but in the same time that we terminated our cover crops.
[00:40:51.440]In some of the no cover crop plots,
[00:40:55.620]we had some weeds.
[00:40:56.720]And we evaluated that,
[00:40:59.340]but I didn't bring it here.
[00:41:02.100]But we used the same treatment as in the cover crop.
[00:41:06.900]Yeah.
[00:41:10.500]So in the first study that I showed you,
[00:41:15.460]that we were evaluating the termination time
[00:41:18.060]of cereal rye and hairy veg.
[00:41:20.300]When we terminated cereal rye late,
[00:41:23.820]it decreased,
[00:41:25.600]almost 100% of the weeds.
[00:41:28.800]It was about 94 or 96%,
[00:41:32.940]the weeds biomass.
[00:41:34.260]We have a crop watch with these results.
[00:41:36.920]And then this was followed by cereal rye terminated early,
[00:41:41.160]that decreased around 70%.
[00:41:44.040]Hairy veg terminated late,
[00:41:45.920]decreased around 40%.
[00:41:47.920]And I remember that hairy veg terminated early
[00:41:51.320]was the lower impact in weeds,
[00:41:53.920]I would say.
[00:41:55.580]It decreased 16%,
[00:41:57.360]but it still was effective
[00:41:59.600]compared to the no cover crop.
[00:42:01.280]Those are statistical differences
[00:42:03.840]that we evaluated.
[00:42:05.220]And in the other two studies,
[00:42:08.500]the decomposition of the cover crops
[00:42:11.140]and the agronomic optimal nitrogen rate
[00:42:13.100]that were developed in the same field experiment,
[00:42:15.840]cereal rye was the cover crop
[00:42:20.220]that most decreased weeds
[00:42:24.100]and then followed,
[00:42:25.560]by mix and by hairy vetch.
[00:42:27.800]So how much of this was
[00:42:31.040]as a result of allelopathy
[00:42:34.040]or toxins, so to speak,
[00:42:37.420]coming out of the ryegrass?
[00:42:39.520]We didn't directly evaluate the allelopathy,
[00:42:45.360]but in the first study that I mentioned,
[00:42:48.540]I came across a lot of literature
[00:42:53.280]when I was writing
[00:42:55.540]my dissertation that mentioned
[00:42:57.680]about the allelopathy
[00:42:59.300]regarding the seedling disease.
[00:43:01.500]For the other two studies,
[00:43:04.100]we didn't look at that,
[00:43:06.760]but in this first one,
[00:43:08.700]we saw some other studies
[00:43:10.620]that mentioned that,
[00:43:11.620]but I didn't evaluate that,
[00:43:13.800]unfortunately.
[00:43:14.560]Thank you, Dawn.
[00:43:18.560]Any other questions?
[00:43:19.280]This is a really nice set of research
[00:43:25.520]studies, so really,
[00:43:27.700]I agree with Jim
[00:43:29.560]that this is some really nice work.
[00:43:31.580]I've seen
[00:43:35.480]a lot of cover crop research
[00:43:37.380]over the years, and we do need to do
[00:43:39.380]this research,
[00:43:40.300]especially in different states with different
[00:43:43.160]environments, but I'm curious,
[00:43:45.460]what do you think
[00:43:46.700]is really needed to make
[00:43:49.380]cover crops
[00:43:51.100]a common tool
[00:43:53.240]for growers who think they want to
[00:43:55.500]use them, or maybe
[00:43:56.820]common across the Midwest?
[00:43:59.480]Is it more
[00:44:01.180]research? Do we need
[00:44:02.980]new varieties
[00:44:05.160]of these cover crops, or even
[00:44:07.020]alternative species?
[00:44:09.480]Or is it more
[00:44:10.840]demonstrations showing farmers
[00:44:13.020]how they can actually deploy
[00:44:15.020]cover crops?
[00:44:15.900]Thanks for your question.
[00:44:19.140]I think
[00:44:21.560]that we
[00:44:23.400]have a lot of
[00:44:25.480]varieties of cover crops. I don't
[00:44:27.580]think this is a limitation.
[00:44:28.920]As I mentioned in the beginning,
[00:44:30.900]the different species can
[00:44:33.360]provide different ecosystem services
[00:44:35.500]and offset different issues.
[00:44:37.220]And I think
[00:44:39.300]with the varieties we have
[00:44:41.520]nowadays, we
[00:44:43.380]can choose and pick
[00:44:45.500]the species that we want
[00:44:47.160]for our purpose.
[00:44:48.960]One thing
[00:44:50.520]that I heard a lot
[00:44:53.200]is the challenge of
[00:44:55.460]the time for the farmers.
[00:44:57.040]I had the opportunity
[00:44:59.380]to talk in the
[00:45:01.220]crops conference
[00:45:03.120]in Missouri
[00:45:04.640]two months ago, and
[00:45:07.260]one of the things that I most
[00:45:09.120]heard there is the challenge
[00:45:11.380]of having time
[00:45:13.000]to plant your cover crops
[00:45:15.240]in order to have a successful
[00:45:17.620]growth during the fall
[00:45:19.120]for this cover crop to overwinter
[00:45:21.460]and continue growing in the
[00:45:23.400]spring to have enough
[00:45:25.440]biomass that when you will
[00:45:27.340]terminate your cover crop
[00:45:28.980]looking at not decrease
[00:45:31.280]your yields as we saw like
[00:45:33.020]an acceptable termination
[00:45:35.560]time is
[00:45:37.340]a real challenge
[00:45:38.380]having the machinery
[00:45:41.200]available to plant
[00:45:43.300]and the time available
[00:45:45.140]so I think that
[00:45:47.340]more and more the
[00:45:49.020]farmers they are seeing
[00:45:51.220]the benefits of cover
[00:45:53.280]crops and how they
[00:45:55.420]can provide
[00:45:57.580]services
[00:45:58.980]and for example the legumes
[00:46:01.240]adding nitrogen to the soil because
[00:46:03.420]in the long term
[00:46:04.840]we can maybe start decreasing
[00:46:07.700]the amount of nitrogen that
[00:46:09.380]will be applied however
[00:46:11.140]the time that the farmers
[00:46:13.620]have available I think
[00:46:15.640]something that is
[00:46:17.320]limiting them they don't
[00:46:19.420]have the available
[00:46:21.240]labor to put the cover
[00:46:23.660]crops in the field on time
[00:46:25.400]to have the benefits
[00:46:27.500]of this cover crop
[00:46:28.780]that's my perception
[00:46:31.480]regarding that
[00:46:32.360]question here
[00:46:34.660]it's about the weed management
[00:46:37.080]plan during the corn
[00:46:38.840]season so it says
[00:46:41.060]what was the in season weed management plan
[00:46:43.360]did you use similar
[00:46:45.240]herbicides for in season weed management
[00:46:47.020]in cover crop and no cover crop plots
[00:46:49.300]we applied
[00:46:51.340]herbicides in our plots
[00:46:53.640]when we were terminating our
[00:46:55.380]cover crops
[00:46:56.480]and after that
[00:46:59.400]we didn't do management
[00:47:01.420]during the corn season
[00:47:03.040]the management was only
[00:47:05.300]done to terminate
[00:47:07.140]the cover crops and
[00:47:09.320]in the no cover
[00:47:11.380]crop plots we
[00:47:13.260]applied herbicide
[00:47:15.440]in the late
[00:47:17.360]fall not late fall
[00:47:19.180]would say I think
[00:47:21.480]it was November depending
[00:47:23.480]on the year but then after
[00:47:25.360]that we just apply to terminate
[00:47:27.720]the cover crops and then we applied again
[00:47:29.500]in the no cover crop plots but
[00:47:31.520]we didn't apply again during the corn
[00:47:33.540]season
[00:47:33.880]just have a quick question about
[00:47:39.140]I may miss this but did you look
[00:47:41.440]at economically optimal nitrogen rate
[00:47:43.640]as well?
[00:47:44.580]we didn't look at the economic
[00:47:47.500]we look at the agronomic optimal
[00:47:49.600]nitrogen rate
[00:47:50.640]do you think there might be some
[00:47:53.300]subtleties between the two?
[00:47:55.340]when you look at it
[00:47:56.840]including some of your input costs
[00:47:58.920]I think
[00:48:01.640]the agronomic and the
[00:48:03.460]economic optimal nitrogen rate
[00:48:05.580]they would be very similar
[00:48:07.620]in this study
[00:48:08.520]the reason why I'm telling this is because
[00:48:11.220]this study is part
[00:48:13.340]of the precision sustainable
[00:48:15.060]agriculture project
[00:48:16.500]which is a project that was developed
[00:48:18.880]in 15 states across the
[00:48:21.080]United States
[00:48:21.880]we were just responsible for Nebraska
[00:48:24.240]but
[00:48:25.320]we shared knowledge
[00:48:27.220]with our peers
[00:48:29.260]in this case and
[00:48:30.620]there was one paper that's
[00:48:33.080]getting ready to be submitted that
[00:48:35.080]evaluated all the
[00:48:36.580]states together
[00:48:38.020]separating by cover
[00:48:41.120]crop and cash crop
[00:48:42.920]only and they
[00:48:44.820]included Nebraska and the states
[00:48:47.000]here and they evaluated
[00:48:49.060]both, they evaluated the
[00:48:50.900]agronomic and the economic
[00:48:52.680]and there was no difference in these
[00:48:55.300]values among the two of them
[00:48:57.180]in this study
[00:48:59.280]but specifically for our
[00:49:01.280]data isolated in Nebraska
[00:49:03.040]we don't have these results
[00:49:05.500]You kind of alluded
[00:49:13.660]to the answer that
[00:49:15.360]I'm looking for in this question
[00:49:17.580]earlier
[00:49:18.080]one of the things that
[00:49:20.760]causes problems for the
[00:49:23.260]cover crop use is the
[00:49:25.280]timing of planting
[00:49:26.280]and I noticed that with your times you were
[00:49:29.340]looking at like a late August
[00:49:30.960]through September time frame
[00:49:33.000]which
[00:49:34.240]does not fit the
[00:49:37.240]common
[00:49:37.800]corn or soybean cropping system
[00:49:41.620]typically
[00:49:43.480]it's going to have to be quite a bit later
[00:49:45.180]than that so
[00:49:46.540]you had an opportunity to establish
[00:49:49.400]your cover crops
[00:49:50.860]much more
[00:49:52.560]effectively with that longer
[00:49:55.260]growth period than normally
[00:49:57.520]might be seen in situations
[00:49:59.680]speculate for me
[00:50:02.780]what you think your results
[00:50:05.380]would have been like
[00:50:06.400]had you waited
[00:50:08.980]until the normal planting time
[00:50:11.200]might have existed in the fall
[00:50:12.740]with your rye
[00:50:14.600]your mix
[00:50:15.700]your vetch plantings
[00:50:18.220]thanks for your question
[00:50:20.620]well in the
[00:50:23.020]study that I showed you about the
[00:50:25.240]nitrogen, the decomposition
[00:50:26.940]of cover crops and the
[00:50:28.880]optimum nitrogen rate
[00:50:30.340]the cover crops were planted
[00:50:32.840]following oats
[00:50:34.000]so in August as you were saying
[00:50:36.540]but in the other one in the study
[00:50:39.020]of the seedling disease
[00:50:40.520]the first one that I showed you
[00:50:42.780]the cover crops were planted
[00:50:44.900]following soybean
[00:50:46.100]the rotation was soybean
[00:50:48.700]cover crops corn, soybean
[00:50:50.820]cover crops corn
[00:50:52.560]so the cover crops in that
[00:50:55.220]study they were planted in late
[00:50:57.180]October
[00:50:57.820]and we still had like
[00:51:00.760]successful results
[00:51:02.400]but let's talk about then the one
[00:51:04.960]that we planted earlier
[00:51:06.480]that we planted following oats
[00:51:08.620]probably
[00:51:10.420]we would not have all this
[00:51:13.200]biomass amount as you just
[00:51:14.920]mentioned because we are not having
[00:51:16.980]all this time
[00:51:18.100]of growth for the cover
[00:51:20.980]crops I think
[00:51:22.620]thinking about
[00:51:25.200]hairy vetch
[00:51:26.260]I think the main
[00:51:28.860]challenge is that hairy vetch
[00:51:30.700]be not
[00:51:32.800]over killed so
[00:51:34.760]then can continue growing
[00:51:36.600]in the spring
[00:51:38.920]but I've seen
[00:51:40.760]some very interesting results
[00:51:43.140]from some colleagues that are
[00:51:44.880]working and they are
[00:51:46.580]planting hairy vetch
[00:51:48.560]before harvesting corn
[00:51:50.840]and
[00:51:52.560]I think this may be
[00:51:55.180]an interesting
[00:51:56.100]option
[00:51:59.180]to have a higher
[00:52:01.160]growth but again we come
[00:52:03.340]to the point that do I have
[00:52:05.400]the McNair available to do that
[00:52:07.280]so again I think
[00:52:09.360]it's all around
[00:52:10.760]the time and what
[00:52:13.160]you have available that you can use
[00:52:15.300]to incorporate your cover
[00:52:17.240]crop. I don't think
[00:52:19.020]that the limitation is
[00:52:21.160]because of the potential negative
[00:52:23.460]effects anymore. I
[00:52:25.160]think that we are being very
[00:52:27.180]successful spreading
[00:52:28.760]all the benefits that cover
[00:52:31.080]crop can provide and those studies
[00:52:33.320]they are showing us well if
[00:52:35.200]I terminate late I will have
[00:52:37.240]a negative impact. So
[00:52:38.940]I know that I need terminate early
[00:52:41.260]if I am using a grass for example.
[00:52:43.200]I observed
[00:52:47.120]that in your 50
[00:52:49.260]kilo rate you had
[00:52:51.200]lower yields in some
[00:52:53.240]cases than 50
[00:52:55.140]the line so to speak
[00:52:56.640]and also more variability.
[00:52:58.320]This is just a comment. I think
[00:53:01.120]what's happening there is your
[00:53:03.140]pretreatment of 45 kilos
[00:53:05.200]was enough
[00:53:07.260]to get the plant started
[00:53:08.860]and it had
[00:53:11.240]a good signal. Here we go.
[00:53:12.800]You applied
[00:53:14.480]50 and it said
[00:53:17.080]oh that's enough. Let's go for the rest
[00:53:19.180]of the year. Well it typically
[00:53:21.260]will run out
[00:53:22.140]and those rates
[00:53:25.120]will end up being
[00:53:27.260]atypical. On the
[00:53:29.220]other end if you apply your 300
[00:53:31.320]pound rate
[00:53:32.140]that could be screwing up the
[00:53:35.200]nitrogen to sulfur ratio
[00:53:37.080]and so now you're
[00:53:39.100]playing with photosynthesis
[00:53:40.260]and we've
[00:53:43.340]seen this happen. That's only to
[00:53:45.220]mention explanation
[00:53:47.020]for some of the variability especially
[00:53:49.060]at your high nitrogen rate
[00:53:50.780]you had a lot of variability in
[00:53:53.180]yield. Yes.
[00:53:55.100]Thank you.
[00:53:55.980]Thank you so much.
[00:53:58.620]We have time for one extra question
[00:54:01.100]or comment.
[00:54:02.840]Okay. I will do the last one.
[00:54:07.280]So I'm kind of curious that
[00:54:09.220]because you have a lot of experience working here in
[00:54:11.220]Nebraska with cover crops
[00:54:12.560]which is the
[00:54:14.920]ecosystem service that farmers
[00:54:17.020]are looking for in the cover crops
[00:54:19.120]which is the main ecosystem service?
[00:54:25.080]Thank you.
[00:54:55.060]Thank you.
[00:55:25.040]Thank you.
[00:55:55.020]Okay, thank you so much.
[00:56:15.320]Thank you so much.
[00:56:15.380]Thank you.
[00:56:15.420]Thank you.
[00:56:15.480]Thank you.
[00:56:22.780]Thank you.

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"What we learned from three years of growing rye, vetch and mixture in Eastern Nebraska under variable precipitation seasons"

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