Nitrogen and Water Management Strategies to Reduce Nitrate Leaching in Irrigated Sandy Soils

Arshdeep Singh, PhD Candidate, Deparment of Agronomy and HOrticulture, University of Nebraska Lincoln Author

05/24/2024 Added

20 Plays

Description

Nitrogen and water are essential inputs for getting a high corn yield. However, excessive nitrogen and water inputs can deteriorate environmental quality. Optimizing these inputs can result in profitable corn production with less environmental impact. This presentation will focus on in-field strategies for optimizing nitrogen and water inputs to improve nitrogen use efficiency and decrease nitrate leaching losses in irrigated corn fields of Nebraska.

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[00:00:00.750]The following presentation
[00:00:02.220]is part of the Agronomy and Horticulture Seminar Series
[00:00:05.790]at the University of Nebraska-Lincoln.
[00:00:09.540]All right. Good afternoon, everyone.
[00:00:12.660]It's good to see everyone here coming back
[00:00:15.180]after spring break into the second half
[00:00:17.190]of our seminar series for the semester.
[00:00:19.710]A wonderful turnout today,
[00:00:21.420]so thank you all for being here.
[00:00:23.490]A special thank you to the graduate students
[00:00:27.150]who showed up here today to support Arshdeep.
[00:00:31.080]Just a quick reminder, we do still have
[00:00:34.020]one external speaker coming up later in April.
[00:00:39.360]It's the department head at the University of Auburn.
[00:00:42.150]Is that correct?
[00:00:43.590]So, be on the lookout for that.
[00:00:47.070]And so then without further ado,
[00:00:49.770]it is my great pleasure to introduce today Arshdeep Singh.
[00:00:55.470]Arshdeep is a graduate research assistant
[00:00:58.080]co-advised by Dr. Javed Iqbal and Daniel Snow.
[00:01:01.140]He's in the Department of Agronomy and Horticulture
[00:01:04.200]pursuing his PhD,
[00:01:06.420]which he will defend in about a month from now.
[00:01:11.010]He received his Bachelor of Science in Agriculture
[00:01:13.890]from Punjab Agriculture University
[00:01:16.290]and he received his master's degree in natural resources
[00:01:19.170]from Auburn University.
[00:01:21.090]His research focuses on optimizing nitrogen
[00:01:23.520]and water inputs in corn production
[00:01:25.710]to reduce nitrate leaching
[00:01:27.150]and that is what he will be telling us about today.
[00:01:30.540]And then when I was looking at Arshdeep's CV,
[00:01:34.650]it was very difficult for me to pick out
[00:01:37.830]from his many accolades that he has acquired
[00:01:40.920]over his tenure here at UNL and even before that.
[00:01:45.930]So I'm going to mention just a few of the highlights here.
[00:01:48.990]He's a member and former chair
[00:01:51.450]of the Soil Sensor Working Group
[00:01:53.490]for NSF's National Ecological Observatory Network or NEON.
[00:01:59.820]He was elected as Tri-societies 2022 and 2023
[00:02:03.660]Encompass Scholar which is sponsored by Bayer.
[00:02:07.200]He also has received a couple of awards,
[00:02:10.920]Tri-Societies of America 2021 Future Leaders in Science
[00:02:15.180]as well as the Crop Society's 2024 Gerald O. Mott Award,
[00:02:18.600]which he was just notified of last week.
[00:02:21.720]So that was nice that we could include that today.
[00:02:25.110]He also received the Agricultural and Environmental Letters
[00:02:28.470]Editor Citation for Excellence in Reviewing.
[00:02:31.380]He's regional editor for the Southern
[00:02:33.300]and Central Great Plains Region of Crops and Soils Magazine,
[00:02:36.480]which is issued by the American Society of Agronomy.
[00:02:39.660]He has published four peer-reviewed journal articles
[00:02:43.200]and there are some in the pipeline as well
[00:02:45.570]that I understand.
[00:02:46.980]And then one publication that he had with Dr. Iqbal
[00:02:50.010]was featured in CSA News.
[00:02:52.440]And so, I had the distinct pleasure
[00:02:55.800]of working with Arshdeep
[00:02:57.210]in my scientific writing and communication course
[00:03:00.480]where he served as TA for two years,
[00:03:02.730]which is why I know him well.
[00:03:04.680]And I know that beyond all of his wonderful
[00:03:08.520]accomplishments as a scientist and a researcher,
[00:03:11.070]he's also just a wonderful human being.
[00:03:13.260]And so I am very, very happy
[00:03:15.750]to present to you today Arshdeep,
[00:03:17.730]and I'm very excited to hear what you will share with us.
[00:03:20.938]Thank you.
[00:03:23.310]Thank you, Christine, for the introduction
[00:03:25.770]and thank you seminar committee for this great opportunity.
[00:03:30.570]And thank you all for coming here today.
[00:03:33.930]And as I understand correctly,
[00:03:37.140]my audience has a spectrum here
[00:03:39.870]from graduate students
[00:03:41.010]to the fellows of the scientific societies,
[00:03:43.530]which is really nice to see here.
[00:03:45.540]And thank you all again for coming up here today.
[00:03:49.590]So today I'll be presenting my presentation on the topic
[00:03:54.270]Nitrogen and Water Management Strategies
[00:03:56.490]to Reduce Nitrate Leaching in the Irrigated Sandy Soils.
[00:04:03.300]So as we all know that
[00:04:05.400]US is the largest corn producer in the world.
[00:04:08.490]So the US has increased the corn yields
[00:04:13.100]by 63% in last couple of years.
[00:04:19.470]In the same one of the major factors
[00:04:21.570]contributing to this increase in the corn yield
[00:04:24.420]is increase in the nitrogen fertilizer input
[00:04:27.210]which has increased substantially by 64%
[00:04:30.090]over the same time period.
[00:04:33.330]However, not all the nitrogen which we apply
[00:04:36.690]is uptaken by the crop.
[00:04:38.370]So about 50% of the nitrogen is uptaken,
[00:04:45.330]is uptaken by the plant
[00:04:47.670]and the other nitrogen which is applied
[00:04:50.130]is lost to the environment.
[00:04:54.300]So this slide here shows the transformation
[00:04:56.340]of convergence of the nitrogen.
[00:04:58.680]So as the farmer applies nitrogen mainly in the form of urea
[00:05:02.940]so it hydrolyzes to form ammonium.
[00:05:06.600]So this ammonium is uptaken by the plant
[00:05:09.660]or it is lost to the environment as ammonia volatilization.
[00:05:14.190]And the mid pathway which it goes through
[00:05:16.470]is through the process of green nitrification.
[00:05:19.530]It converts the ammonium into the nitrate form.
[00:05:22.530]So this nitrate form now can be either uptaken by the plant,
[00:05:26.490]it can be lost to the environment
[00:05:28.140]through the denitrification process,
[00:05:30.240]or, the third thing, what could happen to this nitrate is
[00:05:34.890]this could leach to the groundwater.
[00:05:37.380]And I will be talking about this pathway,
[00:05:40.080]the nitrate leaching to the groundwater today
[00:05:42.600]and how we can manage the nitrogen.
[00:05:46.770]So two of the major or important inputs
[00:05:49.860]which increase the nitrate leaching
[00:05:52.560]are known to be the first one is increase
[00:05:54.930]in the total nitrogen inputs increases the nitrate leaching.
[00:05:59.070]And the second factor which increases the nitrate leaching
[00:06:02.820]is the increase in the water inputs.
[00:06:05.730]So if the nitrate concentrations
[00:06:07.860]exceed the 10 parts per million in the groundwater,
[00:06:11.550]then they become harmful for us
[00:06:14.460]as humans and for the biodiversity as well.
[00:06:18.450]So this map here is a map from the USGS
[00:06:21.600]which shows that the more the red color is
[00:06:24.210]that there are high nitrogen inputs there
[00:06:27.330]and there are high nitrate concentrations
[00:06:30.380]in the groundwater for those regions.
[00:06:32.790]So if you see these farm regions
[00:06:35.940]where high value food crops in the US are grown,
[00:06:38.790]that's mainly the corn belt states.
[00:06:40.890]So we see here that here there are high nitrogen inputs
[00:06:45.540]and the groundwater is contaminated
[00:06:47.610]with high nitrate concentrations.
[00:06:50.820]Among these corn belt states is our great state of Nebraska.
[00:06:54.900]So Nebraska also has high nitrate concentrations.
[00:06:58.380]This graph map here shows the medium nitrate concentrations
[00:07:03.870]and if you pay close attention,
[00:07:06.360]so you will see mainly the red, purple,
[00:07:08.400]and the orange colors which show that
[00:07:12.720]the nitrate concentrations in Nebraska
[00:07:15.390]have exceeded the 10 parts per million limit already.
[00:07:21.870]So what contributes to this high nitrate concentrations
[00:07:25.890]in the groundwater
[00:07:26.730]is mainly the input of the commercial nitrogen fertilizers
[00:07:30.480]in the irrigated corn fields
[00:07:32.100]and the sandy soils are where there are like shallow depth
[00:07:34.890]to the groundwater.
[00:07:38.490]In addition, we know that
[00:07:40.350]these nitrate-contaminated groundwater
[00:07:42.900]impacts the human health.
[00:07:44.340]So it can cause blue baby syndrome, pregnancy issues,
[00:07:48.660]it can cause various types of cancers
[00:07:50.430]and the list goes on.
[00:07:52.170]So, to combat with this issue,
[00:07:54.840]so Nebraskans are already paying millions of dollars
[00:07:57.960]for the treatment of this nitrate-contaminated groundwater.
[00:08:01.710]So for the smaller communities, even this treatment rate
[00:08:05.897]or the treatment costs go from $90
[00:08:08.700]to $650 per person annually.
[00:08:11.760]Therefore, it becomes a necessity for us
[00:08:14.677]to reduce this nitrate contamination.
[00:08:18.360]So to reduce this nitrate contamination
[00:08:20.460]in the groundwater in Nebraska or elsewhere globally,
[00:08:23.490]so there are various best management practices
[00:08:26.160]which could be adopted to reduce this nitrate contamination.
[00:08:31.260]So today I will be talking about
[00:08:33.150]some of those best management practices.
[00:08:35.280]So my first study will be focusing on
[00:08:37.740]using the different nitrogen recommendation tools
[00:08:40.890]to recommend the nitrogen right recommendation rate
[00:08:43.620]to improve the nitrogen management.
[00:08:46.200]My second study will focus on using the reduced irrigation
[00:08:50.790]and reduced nitrogen rates
[00:08:53.220]to improve the nitrogen management.
[00:08:56.160]And most of us also understand
[00:08:58.500]that the use of the enhanced efficiency fertilizers
[00:09:00.930]at different application timings have shown the potential
[00:09:03.630]to reduce nitrate leaching.
[00:09:05.040]Therefore, my third study will focus today on that.
[00:09:08.250]So in the end what I will be doing
[00:09:12.300]is I will be sharing the results
[00:09:14.010]and conclude these all the studies.
[00:09:20.490]So one, there are like various best management practices
[00:09:24.180]as I said earlier for the improvement
[00:09:27.060]or improving the nitrogen management.
[00:09:30.180]So one of those best management practices
[00:09:32.730]is the use of these four R's nitrogen management concept.
[00:09:36.510]So those four R's are the right source,
[00:09:39.750]right rate, right time, and right place.
[00:09:43.170]So among these four R's, one of the hardest
[00:09:47.880]to determine is the right nitrogen rate.
[00:09:51.660]So in the past there have been
[00:09:54.210]farmers are using like various methods
[00:09:56.910]to determine this right nitrogen rate on their own.
[00:10:00.540]However now we know like after several years
[00:10:03.240]or decades of research
[00:10:04.230]that there are different kinds of
[00:10:06.240]nitrogen recommendation tools which are available to us.
[00:10:09.150]So they are mostly categorized into two categories broadly.
[00:10:13.230]So one of the static nitrogen recommendation tools
[00:10:16.020]and the another one are dynamic
[00:10:17.580]nitrogen recommendation tools.
[00:10:20.400]So in the static nitrogen recommendation tools,
[00:10:24.120]what we need is a one-time information
[00:10:26.820]and then we put up, give that information to these tools
[00:10:30.510]to recommend the nitrogen.
[00:10:31.620]For example, the soil test preplant and pre-sidedress
[00:10:35.220]for nitrate are included in that.
[00:10:37.620]And then we have a web-based tool,
[00:10:40.410]the core nitrogen recommendation tool
[00:10:42.180]which comes here which takes,
[00:10:44.190]which is based on yield goal,
[00:10:46.050]takes the soil characteristics in there
[00:10:48.690]and take the prices of corn and fertilizers
[00:10:51.780]before recommending the nitrogen rate.
[00:10:54.780]So the other tools are the dynamic tools.
[00:10:56.670]Among those are the process-based models
[00:10:59.070]such as Maize-N, Adapt-N, Granular, APSIM, and many more.
[00:11:04.560]And those take in season weather data,
[00:11:09.330]then the soil data and other variable data
[00:11:12.090]to recommend the nitrogen.
[00:11:14.250]Apart from that we have the canopy reflectance sensing.
[00:11:17.970]So here the canopy sensors are used
[00:11:21.420]for the target area and the high reference nitrogen area
[00:11:25.320]to recommend the nitrogen.
[00:11:27.390]So one of the canopy reflectance sensing
[00:11:31.680]which we will be using in our project
[00:11:33.240]is based on the Holland Shepards equation
[00:11:37.410]which I'll be talking about later.
[00:11:40.320]So, this slide shows that like
[00:11:45.510]what was our big question to ask or like from this study.
[00:11:48.570]So from our first study
[00:11:49.860]where we'll be using the nitrogen documentation tools.
[00:11:53.640]So the question was
[00:11:55.110]that are dynamic nitrogen recommendation tools
[00:11:58.320]more accurate in improving the agronomic
[00:12:01.170]and environmental nitrogen performance
[00:12:03.630]compared to the static nitrogen recommendation tools?
[00:12:06.750]Therefore, the objectives of the study were
[00:12:09.660]to estimate the economic optimum nitrogen rate,
[00:12:12.780]evaluate and compare the core nitrogen recommendation tools
[00:12:16.700]to this estimated economic optimum nitrogen rate
[00:12:20.512]for corn yield,
[00:12:21.570]for nitrate leaching,
[00:12:22.740]and returns to nitrogen
[00:12:24.150]after considering the environmental costs.
[00:12:30.570]So this slide shows the site we chose for this study
[00:12:35.250]and all the other studies which I'll be sharing today.
[00:12:38.010]So the site was chosen in the northeast of Nebraska
[00:12:41.280]in the Bazile Groundwater Management Area.
[00:12:43.860]So this site was at the Carpenter's field
[00:12:47.490]which had a nitrate concentration of about 20 ppm
[00:12:51.744]in the groundwater.
[00:12:52.950]And we planned a two-year study
[00:12:54.600]of where we had our randomized complete block design
[00:12:57.780]with three replications.
[00:13:01.723]The soil in the site was loamy sand
[00:13:06.570]with more than 70% of the sand throughout the soil profile.
[00:13:11.907]The soil had low organic matter
[00:13:14.010]ranging from 1.3% in the top layer,
[00:13:16.560]2.6% in the bottom layer.
[00:13:20.160]We had a central pivot irrigation system, okay?
[00:13:23.850]And we chose the outer two spans for our study
[00:13:28.913]so that we can perform the variable rate fertigation
[00:13:31.590]which I'll be talking later in the slides.
[00:13:38.010]So this slide shows the timeline for the field events
[00:13:40.830]which we did for the both two years of the study.
[00:13:44.280]So before corn planting we applied the nitrogen
[00:13:48.030]using the barbed wire spreader as preplant.
[00:13:51.420]After the corn planting we installed
[00:13:54.210]suction couple lysimeter in every plot
[00:13:56.190]that I'll be talking in the next slide more.
[00:13:58.800]And then at core leaf stage we went up there,
[00:14:01.860]we applied nitrogen as sidedress
[00:14:04.980]and for one of the experiment we did the canopy sensing.
[00:14:09.101]For at V8 at 12-leaf stage
[00:14:11.123]and the tasseling stage we did the fertigations
[00:14:15.976]for the nitrogen.
[00:14:17.190]And then before the corn harvest we removed the lysimeters
[00:14:20.820]and after the corn harvest
[00:14:22.110]we did the deep course soil sampling as well.
[00:14:24.630]So as I mentioned earlier,
[00:14:25.770]now I'll be talking about
[00:14:26.970]the installation of these lysimeters
[00:14:29.640]and what purpose did they serve in our study.
[00:14:33.150]So, this study shows to collect the water samples
[00:14:37.380]we installed two suction cup lysimeters
[00:14:40.410]in every plot at four feet depth.
[00:14:43.920]So we had, we installed a total number,
[00:14:47.040]total number of lysimeter that were 168 every year.
[00:14:52.200]And we applied the suction
[00:14:54.090]and then after several hours we would go up there
[00:14:56.280]and take the water samples from those suction,
[00:14:59.160]those lysimeter tubes.
[00:15:01.770]The water samples were collected one to three times per week
[00:15:05.970]and the total number of water sample collection events
[00:15:08.861]were 23 and 26 for 2021 and 2022 respectively.
[00:15:13.980]So the total number of water samples
[00:15:15.900]which we analyzed for our studies exceeded 8,000.
[00:15:20.730]So those of you who have worked
[00:15:23.040]with the nitrate concentrations,
[00:15:24.330]you know what this number actually means.
[00:15:28.980]So this slide shows
[00:15:31.170]like once we had those nitrate concentrations,
[00:15:34.350]then we went ahead to calculate the nitrate leaching load.
[00:15:37.890]So we used simple water balance model
[00:15:41.370]to calculate the deep percolation here.
[00:15:43.530]So first we had these precipitation
[00:15:46.320]and irrigation as inputs here
[00:15:48.360]and then we used the nearest weather station
[00:15:51.540]to calculate the vapor transpiration.
[00:15:53.850]And then we used these vapor transpiration values
[00:15:56.730]to calculate the deep percolation.
[00:15:58.470]And once we had the daily deep percolations,
[00:16:00.870]then we multiplied those deep percolation values
[00:16:04.680]with the nitrate concentrations which we got
[00:16:06.870]from the lysimeter water samples.
[00:16:09.150]And then we summed that up for the whole season
[00:16:12.600]to calculate the seasonal nitrate leaching losses.
[00:16:18.943]Okay.
[00:16:20.040]So this slide shows the treatment layout
[00:16:22.920]for the first study.
[00:16:24.780]So we had six nitrogen rates
[00:16:29.640]and this was, they were used
[00:16:31.920]for estimating the economic optimum nitrogen rate
[00:16:34.650]for both years.
[00:16:36.630]So the nitrogen rates ranged from zero
[00:16:39.523]through 336 kilograms of nitrogen per hectare
[00:16:43.170]at an increment of about 67 kg per hectare.
[00:16:49.442]And 1/3 of the nitrogen was applied as preplant
[00:16:52.710]using the Agrotain-coated urea for all that treatments.
[00:16:57.060]And the 2/3 of the nitrogen was applied as
[00:16:59.790]either sidedress and fertigation using the UAN.
[00:17:04.560]And once we calculated the economic optimum nitrogen rate,
[00:17:07.650]then we went to address our second objective
[00:17:11.940]to compare the nitrogen recommendation tools
[00:17:14.760]to the economic optimum nitrogen rate.
[00:17:17.820]So we had five nitrogen recommendation tools,
[00:17:21.540]the one static nitrogen recommendation tool,
[00:17:24.810]that's the Nebraska yield goal.
[00:17:26.280]And then we had four
[00:17:27.360]of the dynamic nitrogen recommendation tools:
[00:17:29.490]Maize-N, Canopy reflectance sensing,
[00:17:31.410]Granular, and Adapt-N.
[00:17:34.350]And for all the nitrogen recommendation tools
[00:17:37.200]except for the Canopy reflectance sensing,
[00:17:39.030]we had five times split application.
[00:17:46.170]So this slide shows how we calculated
[00:17:50.400]the economic optimal nitrogen rates.
[00:17:52.470]So here on the x-axis you see the nitrogen application rate,
[00:17:55.710]on the y-axis would observe the grain yields.
[00:18:00.160]Okay, so for both years we found the quadratic plateau
[00:18:04.020]response to increase in the nitrogen rates.
[00:18:07.710]At the lower rates we definitely see increase
[00:18:10.920]of the grain yield as nitrogen rates increased.
[00:18:13.440]But then as we go near
[00:18:16.050]to the economic optimal nitrogen rate, there is no increase,
[00:18:19.521]further increase in the grain yield
[00:18:21.300]with the increase of nitrogen rates.
[00:18:27.030]Then once we had those economic optimum nitrogen rates,
[00:18:30.540]we calculated the economic optimum nitrogen rates ranges.
[00:18:34.140]Okay, we used dollar one per acre method
[00:18:38.340]to calculate those and these white areas here
[00:18:41.160]show those EONR ranges for both years.
[00:18:44.580]So this shows that when the nitrogen rates were lower,
[00:18:50.220]this clinical issue that when the nitrogen rates were lower
[00:18:52.410]than the economic optimum nitrogen rate,
[00:18:55.170]although there were lower returns to nitrogen
[00:18:57.810]but there were less environmental losses, okay?
[00:19:02.310]And as soon as we move on the right side of the graph,
[00:19:05.370]we go into the red area,
[00:19:06.690]which means that addition of the nitrogen,
[00:19:08.940]any nitrogen above the economic optimal nitrogen rate,
[00:19:12.480]we not only have the,
[00:19:14.490]we don't only lose the dollar amount on that,
[00:19:17.670]we also lose, we have like
[00:19:19.560]more and more environmental losses, okay?
[00:19:22.530]And for year 2021 the economic optimum nitrogen rate
[00:19:25.650]was 258, yielding about 16 milligrams per hectare.
[00:19:31.290]And in 2022 the EONR was 252
[00:19:34.470]yielding in 50 milligrams of corn yield.
[00:19:39.010]Okay.
[00:19:39.960]So, sorry.
[00:19:41.250]So before moving to the next slide, I would like to mention
[00:19:43.980]that we use this economic optimum nitrogen rates
[00:19:46.260]to compare the nitrogen recommendation models,
[00:19:49.800]which I'll be talking about later.
[00:19:51.840]But before that I'll be talking about the seasonal nitrate,
[00:19:56.430]temporal nitrate concentrations in this.
[00:19:58.740]So this graph, slide shows here the water inputs for 2021.
[00:20:06.000]And then for the whole season
[00:20:07.890]we divided it into the three parts.
[00:20:09.750]So we referred from planting to eight-leaf stage,
[00:20:14.640]we called it as early vegetative stage.
[00:20:16.830]From eight-leaf stage 'till tasseling
[00:20:18.780]we called it as late vegetative stage.
[00:20:20.550]And then from R1 to R6 we call it as reproductive stage.
[00:20:25.920]And then these graphs,
[00:20:26.940]although like it's a very busy slide here,
[00:20:29.370]but this shows the daily pore water concentrations
[00:20:31.920]which we collected through 23 leaching events in 2021.
[00:20:36.450]So if we just look like overall,
[00:20:39.180]okay, so what we see is that the early vegetative phase
[00:20:41.610]had higher daily pore water concentrations
[00:20:45.180]compared to the late vegetative stage
[00:20:46.950]and the reproductive stage.
[00:20:49.920]So to sum up this slide, so what we observed
[00:20:53.220]was that with the increase in the nitrogen rates,
[00:20:55.710]there was a linear increase in the sub seasonal average
[00:21:00.930]for water nitrate concentrations in early vegetative
[00:21:03.300]and late vegetative stages.
[00:21:05.550]However, we observed that in the reproductive stage
[00:21:09.780]as the nitrogen went...
[00:21:14.550]As the nitrogen rate was applied
[00:21:16.050]was higher than the economic optimum nitrogen rate,
[00:21:18.007]there was a rapid increase in the nitrate concentrations.
[00:21:22.860]So this similar to 2021, this slide shows the water inputs
[00:21:26.820]for all the three different phases.
[00:21:29.010]In 2022 these graphs show here
[00:21:32.580]the daily pore water concentrations
[00:21:34.410]for 2022 for all the six nitrogen rates.
[00:21:37.620]Here we see that in the late vegetative stage
[00:21:41.490]we have higher nitrate concentrations
[00:21:44.160]compared to the early vegetative
[00:21:45.810]or the reproductive stages.
[00:21:49.080]So for the second year we also observed
[00:21:52.320]that there was an exponential increase
[00:21:55.080]in the nitrate concentrations for all the three phases
[00:21:58.440]when as the nitrogen rates were increased.
[00:22:01.440]If we just pay attention to the late vegetative stage here,
[00:22:04.950]so this shows that as the optimum,
[00:22:07.890]at the optimum nitrogen rate
[00:22:09.120]as the crop nitrogen needs were met,
[00:22:11.250]any extra nitrogen led to higher nitrogen concentrations
[00:22:14.520]leading to the groundwater contamination.
[00:22:19.950]So this slide, I mean you have seen earlier
[00:22:22.530]but there is one more added parameter
[00:22:24.390]which I want to talk about here
[00:22:25.890]is that is on the study y-axis,
[00:22:27.780]the seasonal nitrate leaching losses.
[00:22:31.110]Okay.
[00:22:31.943]And these triangles and the solid line
[00:22:35.100]shows the seasonal nitrate leaching losses
[00:22:38.604]to the, at nitrogen application rate.
[00:22:42.912]Okay?
[00:22:43.745]So what we observed was that in year 2021
[00:22:47.610]the range for the nitrate leaching was from zero
[00:22:51.450]through about 25 kg nitrogen per layer.
[00:22:55.067]In the second year we found it range is from zero to 80 kg.
[00:23:01.890]We also observed that in 2021 there was a linear increase
[00:23:06.530]in the nitrate leaching losses
[00:23:08.460]and in the second year we found
[00:23:10.530]that there was an exponential increase
[00:23:12.810]of nitrate leaching as the nitrogen rates increased, okay?
[00:23:17.310]And overall there was 2.3 times
[00:23:20.190]more nitrate leaching losses in 2022 compared to 2021.
[00:23:24.990]So, now the question comes, why could this have happened?
[00:23:29.580]So one of the possible reasons could be,
[00:23:31.800]so in 2021 we had a no-till system
[00:23:35.310]and there was a really good corn growth.
[00:23:41.370]In year 2022 there were a lot of corn troubles
[00:23:43.980]in the early season
[00:23:46.020]and there was a lot of volunteer corn
[00:23:48.210]so the farmer decided to till the farm
[00:23:50.850]and that might have led to increase
[00:23:52.667]in the nitrate leaching losses in the second year.
[00:23:56.310]If we pay close attention,
[00:23:57.510]we also observed that the nitrate leaching in 2021,
[00:24:00.270]which we got at about the highest rate,
[00:24:03.660]okay, we got that in 2022 only at the second rate
[00:24:08.280]or like near the 70 kg of nitrogen inputs.
[00:24:11.790]So this also indicates
[00:24:13.170]that apart from the nitrogen rates itself
[00:24:15.600]impacting the nitrate leaching,
[00:24:17.370]therefore the year to year variability
[00:24:19.710]in the management practices
[00:24:21.570]and possibly the growth conditions
[00:24:23.490]can have more impact than the nitrogen rates itself
[00:24:27.120]on nitrate leaching.
[00:24:31.320]So this slide will show our second objective
[00:24:36.180]of the first study where we'll be comparing
[00:24:38.430]the different nitrogen recommendation tools
[00:24:40.350]to the economic optimum nitrogen rate.
[00:24:42.480]Okay, so I will be showing 2021 like here
[00:24:45.810]and 2022 year here.
[00:24:48.180]And for the nitrogen recommendation rates
[00:24:50.610]will be compared here.
[00:24:51.720]Corn yields, nitrate leaching, and returns to nitrogen
[00:24:55.200]after considering environmental losses will be shown here.
[00:24:58.830]Just a second.
[00:25:09.930]So before I move to the models,
[00:25:11.976]for every graph you will see this pink color range
[00:25:16.410]which will show the economic optimum nitrogen rates
[00:25:18.840]which was shown in the verticals
[00:25:19.860]in the previous test.
[00:25:21.450]Okay, so the first model which we compared here
[00:25:24.660]was the Nebraska yield goal.
[00:25:26.610]So what we found was that for the both years
[00:25:29.790]nitrogen recommendation from this Nebraska yield goal
[00:25:32.430]was close to economic optimum nitrogen rate
[00:25:35.730]with no difference in yield,
[00:25:38.340]nitrate leaching, or returns to nitrogen
[00:25:41.100]after considering the environmental costs.
[00:25:44.490]The second model which we compared here was the Maize-N,
[00:25:47.820]okay, develop by UNL again.
[00:25:49.830]So here we had 6% higher nitrogen recommendation
[00:25:53.130]than economic optimum nitrogen rate
[00:25:55.020]leading to approximately 5% higher corn yield
[00:25:58.530]or no significant corn yield
[00:25:59.730]and then 6% higher nitrate leaching here
[00:26:02.670]without impacting the returns to nitrogen
[00:26:04.680]after considering the environmental costs.
[00:26:08.010]For year 2022, the nitrogen recommendation
[00:26:10.410]from this Maize-N was higher by 40%.
[00:26:14.310]And then on top of it we accidentally over applied nitrogen,
[00:26:18.480]therefore we call this model Excess-N
[00:26:20.520]and therefore I'm not discussing these results here.
[00:26:24.810]And the third tool which we used here
[00:26:27.240]was the Canopy reflectance sensing.
[00:26:29.910]So for both years this Canopy reflectance sensing
[00:26:33.150]recommended nitrogen rate which was 20 to 30% lower
[00:26:36.750]than the economic optimum nitrogen rate
[00:26:39.510]resulting in significant decrease
[00:26:41.400]of corn yields for both years.
[00:26:43.890]And for year 2021 it significantly decreased
[00:26:47.730]nitrate leaching and returns to nitrogen
[00:26:50.400]after considering the environmental costs.
[00:26:52.740]There was no difference, significant difference
[00:26:55.500]for nitrate leaching and returns to nitrogen
[00:26:58.440]after considering environmental costs
[00:26:59.730]for the second year for this tool.
[00:27:03.090]Then comes the Granular and Adapt-N.
[00:27:05.370]So these both models also recommended
[00:27:09.780]lower nitrogen rates for both years
[00:27:13.050]resulting in lower corn yields but not significantly.
[00:27:18.090]Okay and significantly lowering the nitrate leaching
[00:27:21.270]in the year first but not in the second
[00:27:24.000]but add no difference when we consider
[00:27:28.230]the returns to nitrogen after calculating
[00:27:30.630]the environmental costs for them.
[00:27:33.720]So this shows that there that the complexity
[00:27:36.600]of these models to recommend the nitrogen.
[00:27:40.590]And so the major takeaway from takeaways from this study
[00:27:44.790]overall were therefore nitrogen recommendations.
[00:27:48.570]The static Nebraska Yield Goal tool was the best tool
[00:27:53.460]as it was the most close for nitrogen recommendation
[00:27:57.810]to the economic optimal nitrogen rate
[00:27:59.820]while other nitrogen recommendation tools
[00:28:02.220]either underestimated or overestimated the nitrogen.
[00:28:07.290]So all nitrogen tools also had similar grain yield
[00:28:11.310]except for the Canopy reflectance sensing.
[00:28:13.860]And this was because it underestimated the nitrogen rate.
[00:28:17.790]So therefore there is a room for improvement
[00:28:20.520]for the Canopy Reflectance performance.
[00:28:22.920]And this could be done
[00:28:24.150]by increasing the sensing frequency
[00:28:26.460]at the earlier crop growth mainly in the sandy soils.
[00:28:31.020]So the third takeaway here is that
[00:28:33.660]though both static and the dynamic tools,
[00:28:36.660]the Adapt-N and Granular had similar returns to nitrogen
[00:28:39.270]after considering environmental costs.
[00:28:42.120]Therefore loading the nitrogen rate
[00:28:43.710]with dynamic tools can help reduce nitrate leaching
[00:28:46.710]by about 20 to 25%
[00:28:48.570]in the Bazile Groundwater Management Area.
[00:28:53.070]So, we all now know that
[00:28:56.370]there is a complexity in determining the nitrogen rate
[00:29:01.260]even by using the dynamic tools.
[00:29:03.660]So there are some researchers which have suggested
[00:29:05.910]that we might go for using
[00:29:07.560]the static nitrogen recommendation tools
[00:29:09.840]but at the lower nitrogen rates.
[00:29:12.240]So here what we evaluated were to see
[00:29:18.030]that if we can use these reduced nitrogen rates, okay,
[00:29:22.253]and how they impact the nitrate leaching
[00:29:24.210]from the literature first.
[00:29:25.860]Okay, so we got three scenarios when the suboptimal
[00:29:30.136]or the lower nitrogen rates were applied.
[00:29:34.020]So the one was that with the,
[00:29:37.170]in Canada that as the suboptimal nitrogen rate was used,
[00:29:41.520]there was no impact on the corn yield
[00:29:43.410]but there were lower nitrate leaching losses.
[00:29:46.530]And then the second was that both the corn yield
[00:29:49.373]and the nitrate leaching reduced
[00:29:52.230]when the suboptimal nitrogen rates were used.
[00:29:55.170]And contrary to these
[00:29:56.550]and there was one study we we also found
[00:29:59.070]that when the suboptimal nitrogen rates are used,
[00:30:01.320]the corn yield decreased but not the nitrate leaching.
[00:30:04.680]So similar to the nitrogen rates,
[00:30:06.960]what can be the other strategy that can be used
[00:30:10.320]to reduce the nitrate leaching
[00:30:12.570]that could be reduction in the irrigation water?
[00:30:15.870]So as we all know that when we have excessive irrigation
[00:30:19.140]it leads to high deep percolation
[00:30:21.510]resulting in high nitrate leaching.
[00:30:24.540]And we are well-aware now that here in the Midwest
[00:30:28.530]that the droughts are increasing.
[00:30:30.630]We're depleting our groundwater table
[00:30:32.910]and there is a need for the deficit irrigation
[00:30:36.240]to reduce, to grow the crops.
[00:30:38.820]And it would be really good if we can do both things,
[00:30:41.730]if we can reduce, improve the crop yields with that
[00:30:45.450]and also reduce the nitrate leaching.
[00:30:47.880]Okay.
[00:30:48.713]And since, so therefore we conducted this study
[00:30:52.050]to see the effect of this reduced irrigation
[00:30:55.530]and reduced nitrogen rates on nitrate leaching
[00:30:58.500]in the groundwater-contaminated areas.
[00:31:01.805]To answer the question that suboptimum rates of nitrogen,
[00:31:06.930]if we couple them with the suboptimal,
[00:31:09.390]deficit irrigation rates,
[00:31:10.950]can we improve the water quality
[00:31:12.750]without impacting the corn yields or economic returns?
[00:31:17.130]Therefore, the objectives of this study
[00:31:18.690]were to assess the impacts of these reduced nitrogen rates
[00:31:21.810]and reduced irrigation rates
[00:31:24.120]under the split nitrogen application system
[00:31:26.730]on nitrate leaching, on corn yields,
[00:31:29.010]on returns to nitrogen
[00:31:30.570]after considering the environmental costs.
[00:31:33.930]This slide shows here the treatment layout.
[00:31:37.170]So we had three irrigation rates
[00:31:39.390]and three nitrogen rates for this study.
[00:31:46.470]So we had full farmer's irrigation.
[00:31:49.470]80% of what farmer applied
[00:31:51.030]and 60% of what farmer would apply.
[00:31:54.720]And for each of these irrigation treatments,
[00:31:56.850]we had three nitrogen rates, the low nitrogen rate,
[00:31:59.940]suboptimal nitrogen rate,
[00:32:01.470]and the optimum nitrogen rate.
[00:32:05.280]All of these nitrogens, okay,
[00:32:08.820]so 1/3 of all these nitrogen rates were applied as
[00:32:11.640]at preplant, as urea coated, Agrotain-coated urea.
[00:32:15.840]And the 2/3 of this nitrogen was applied
[00:32:19.710]as UAN add sidedress and fertigation.
[00:32:26.040]So this slide shows the results
[00:32:27.570]that how these nitrogen rates and irrigation rates
[00:32:30.690]impacted corn yield shown here in the purple circles
[00:32:35.970]and impacted the nitrate leaching
[00:32:38.520]shown here in these red scales,
[00:32:41.220]and how these states impacted the returns to nitrogen
[00:32:45.540]after considering the environmental costs
[00:32:47.400]in these hollow green triangles.
[00:32:49.530]So what we observed was that as we moved from optimum
[00:32:52.200]to suboptimum and low nitrogen rates,
[00:32:55.412]there was eight to 11% decrease in the corn yields,
[00:32:59.640]which was significant.
[00:33:01.950]And when we moved, when we observed these
[00:33:05.160]on nitrate leaching,
[00:33:06.510]we found that there was 24% decrease
[00:33:09.240]as we moved from optimum to suboptimum.
[00:33:11.370]And as we moved from optimum to low,
[00:33:13.050]we saw the 51% decrease in nitrate leaching losses.
[00:33:18.630]And we did not see any difference
[00:33:20.670]or any impact of different nitrogen rates
[00:33:23.990]or returns to nitrogen
[00:33:25.320]after considering the environmental costs.
[00:33:28.620]And this graph here shows the different irrigation rates.
[00:33:33.210]So this FIT is the full farmer's irrigation
[00:33:35.820]as mentioned earlier
[00:33:37.410]then the 80% of what farmer applied and 60%.
[00:33:40.950]Similarly the colors show the same thing
[00:33:42.930]as the earlier graph.
[00:33:44.730]So we observed that if as
[00:33:48.690]we do not see any difference for 80%
[00:33:51.330]and full farmer's irrigation impact on the corn yields.
[00:33:55.170]But if there is 40% deficit
[00:33:58.050]or the 60% of what farmer is supplying,
[00:34:00.540]so we saw a significant decrease in the corn yields.
[00:34:05.280]For nitrate leaching we observed that this 80%
[00:34:08.010]of farmer's irrigation had lower nitrate leaching
[00:34:12.270]compared to the 60% of what farmer is supply
[00:34:14.610]and the full farmer's irrigation
[00:34:16.740]by 13 and 21%.
[00:34:21.369]And this could be because at 80%
[00:34:24.030]all the water requirements of the crop were met
[00:34:30.090]and any extra water would lead
[00:34:33.990]to more nitrate leaching losses.
[00:34:35.700]On the other hand, when there is a water stress
[00:34:40.288]there is low AT that is
[00:34:44.040]reducing the overall corn yield
[00:34:46.290]and therefore increasing the nitrate leaching losses.
[00:34:48.780]However, we did not see any significant impact
[00:34:51.690]of these treatments on
[00:34:57.030]returns to nitrogen after considering
[00:34:58.260]the environmental costs as well.
[00:35:00.930]So overall what we observed here was
[00:35:03.240]that though the suboptimal nitrogen rates
[00:35:05.550]reduces the nitrate leaching,
[00:35:07.320]it also results in a yield penalty.
[00:35:11.660]So also that reducing the irrigation
[00:35:13.820]to 80% of what farmer is supplying
[00:35:16.410]can minimize the nitrate leaching
[00:35:18.990]without impacting the corn yield.
[00:35:22.330]The use of low to suboptimal nitrogen rate
[00:35:24.690]and the deficit irrigation of about
[00:35:27.510]80% of what farmer is supplying
[00:35:29.430]could substantially reduce nitrate leaching
[00:35:31.950]without impacting returns to nitrogen
[00:35:33.690]after considering environmental losses.
[00:35:37.050]So we know that like if we think from a farmer's perspective
[00:35:39.900]and we say, use the low to suboptimal nitrogen rate,
[00:35:44.160]I mean, will anybody listen to us?
[00:35:46.530]Because we might say that there are returns to nitrogen,
[00:35:49.560]there's no difference in returns to nitrogen.
[00:35:52.500]The answer would be no.
[00:35:54.600]So can there be any other strategies which can be used?
[00:35:58.740]There is and that's the enhanced efficiency fertilizers.
[00:36:03.180]So we have already seen
[00:36:05.370]that how these enhanced efficiency fertilizers
[00:36:07.950]have been used in the past.
[00:36:09.570]So we have seen that when these
[00:36:11.040]enhanced efficiency fertilizers are used
[00:36:13.560]at the suboptimal nitrogen rate,
[00:36:16.650]they reduce the nitrate loss, nitrogen losses
[00:36:19.170]without impacting corn yield
[00:36:20.277]and resulting in higher returns.
[00:36:23.250]Similarly, another one study showed
[00:36:25.530]that when we use these enhanced efficiency fertilizers
[00:36:28.280]as preplant at optimum nitrogen rate,
[00:36:31.800]they significantly reduce nitrate leaching by 29%
[00:36:35.370]without impacting corn yield
[00:36:37.500]and leading to overall total higher economic returns.
[00:36:43.260]A recent meta-analysis also showed
[00:36:45.510]that a suboptimum nitrogen rate
[00:36:48.360]with the enhanced efficiency fertilizers
[00:36:50.490]as preplant application has the potential
[00:36:53.070]to reduce the nitrate leaching losses
[00:36:55.260]without impacting corn yield
[00:36:57.120]resulting in higher economic returns.
[00:37:01.140]So therefore we use these enhanced efficiency fertilizers
[00:37:06.450]at suboptimal nitrogen rate
[00:37:07.950]because they were not,
[00:37:09.900]they have not been studied well in the soils
[00:37:12.150]that were enabled to nitrate contamination,
[00:37:14.220]especially in the US Midwest.
[00:37:17.370]So to answer the question
[00:37:18.510]that can enhanced efficiency fertilizers
[00:37:20.670]reduce nitrate leaching while maintaining the corn yield
[00:37:24.300]at suboptimal nitrogen rate?
[00:37:27.600]So using a suboptimal nitrogen rate,
[00:37:29.520]the objectives of this study were to evaluate
[00:37:31.530]the effects of conventional urea-UAN
[00:37:34.950]five-time split application which is done in the region
[00:37:38.280]to one-time or the single preplant application
[00:37:41.190]of the enhanced efficiency fertilizers and urea.
[00:37:44.850]The second objective was to compare
[00:37:46.980]the effect of the split application
[00:37:49.020]of these enhanced efficiency fertilizers
[00:37:50.820]to a single preplant application
[00:37:53.040]of enhanced efficiency fertilizers and urea
[00:37:55.500]on corn yield, on nitrate leaching, on returns to nitrogen
[00:37:59.400]after considering the environmental costs.
[00:38:03.360]So, this might show like the different treatments
[00:38:05.910]which we used here.
[00:38:08.808]So here when the PP stands for the preplant, okay.
[00:38:13.326]So when we had the urea preplant
[00:38:15.030]we applied all the urea as preplant here in this treatment
[00:38:20.130]for Usplit, which is urea-UAN split application,
[00:38:23.730]we applied 1/3 of the urea as preplant
[00:38:28.275]and 2/3 of the nitrogen as UAN, okay?
[00:38:32.820]Then we had these next two where we had Agrotain preplant
[00:38:37.710]where we applied Agrotain-coated urea as preplant
[00:38:40.486]which is a urease inhibitor.
[00:38:42.780]And then the fourth treatment here we had was
[00:38:45.930]Agrotain-UAN split
[00:38:48.330]where we applied 1/3 of the nitrogen
[00:38:51.426]as Agrotain-coated UEA and two third of the nitrogen as UAN.
[00:38:56.940]Then we had our dual inhibitor,
[00:38:59.190]urease and nitrification inhibitor, which is SuperU.
[00:39:02.910]So we applied all the nitrogen as SuperU
[00:39:07.020]as preplant in this treatment.
[00:39:09.300]For the SuperU-UAN split application,
[00:39:12.060]we had 1/3 of the nitrogen as preplant using the SuperU
[00:39:17.376]and 2/3 of the nitrogen as UAN at sidedress and fertigation.
[00:39:21.990]And then we also had the control treatment
[00:39:23.790]where there was no fertilizer applied.
[00:39:25.890]So it is important to mention here
[00:39:27.570]that we had urea-UAN five-time split application
[00:39:30.540]only in one year.
[00:39:39.630]So this slide shows the corn yield responses
[00:39:42.630]to enhanced efficiency fertilizers.
[00:39:45.120]Okay.
[00:39:45.953]So first, as we all know that
[00:39:49.830]or expects that use of the nitrogen fertilizers
[00:39:52.200]have higher yields compared to the control.
[00:39:55.857]Okay.
[00:39:56.700]And then comes the interesting part here now, okay.
[00:40:00.780]So the urea-UAN five-time split application
[00:40:03.360]had no difference in grain yield compared to urea preplant
[00:40:08.550]and this could be because this was a dry year, okay?
[00:40:12.870]And then if we compare the Agrotain preplant
[00:40:17.070]and SuperU preplant to the split application
[00:40:20.370]of the Agrotain UAN.
[00:40:24.990]So we see that there was eight to 16% increase
[00:40:29.340]in the corn yield using the Agrotain preplant
[00:40:32.190]compared to the Agrotain-UAN split application.
[00:40:36.690]And when compared to the SuperU-UAN split application here,
[00:40:41.040]again the Agrotain preplant had
[00:40:43.352]two to 3% higher grain yield.
[00:40:46.170]So this could be because when we apply
[00:40:48.360]any of the enhanced efficiency fertilizers,
[00:40:50.250]mainly the Agrotain or SuperU,
[00:40:53.370]so they stabilize the nitrogen in the soil
[00:40:55.677]for the longer duration of times
[00:40:57.570]compared to urea or UAN when,
[00:41:01.620]which are like supplied as
[00:41:03.240]at the split application
[00:41:05.040]which they tend to lose easily.
[00:41:09.330]So this slide shows the nitrate leaching response
[00:41:12.270]to enhanced efficiency fertilizers, okay?
[00:41:15.540]Again, like we see like the control
[00:41:17.490]had the lower nitrate leaching losses,
[00:41:19.590]but as expected, we observed
[00:41:21.990]that the urea-UAN split application
[00:41:24.510]had lower nitrate leaching losses
[00:41:26.730]than the urea preplant application.
[00:41:30.960]Okay.
[00:41:31.793]Now, how did our enhanced efficiency fertilizers
[00:41:35.730]when they are used as preplant they performed?
[00:41:39.690]So we observed that compared to urea-UAN split application
[00:41:44.831]there was 60 to 67% reduction in nitrate leaching
[00:41:50.160]by these enhanced efficiency fertilizers
[00:41:52.500]when they were used as preplant.
[00:41:55.110]We also observed that when we compare this
[00:41:57.960]with the Agrotain-UAN split application,
[00:42:01.470]the nitrate leaching was reduced by 23 to 46%
[00:42:06.090]by these enhanced efficiency fertilizers
[00:42:08.395]when they were used as preplant.
[00:42:12.430]Also, when we compare these
[00:42:13.920]to the SuperU-UAN split application here,
[00:42:17.370]we observed that these preplant application
[00:42:20.190]of enhanced efficiency fertilizers
[00:42:22.770]tended to decrease the nitrogen by 35 to 77%.
[00:42:29.250]So, this could be because,
[00:42:31.620]again, as I mentioned in the last slide,
[00:42:33.330]that this nitrogen,
[00:42:35.520]this enhanced efficiency fertilizer stabilizes the nitrogen
[00:42:38.700]for longer duration of the times
[00:42:40.950]compared to urea or UAN,
[00:42:43.320]which tend to lose immediately after application.
[00:42:47.280]This slide shows the returns to nitrogen
[00:42:49.470]after considering the environmental costs
[00:42:51.690]and how they perform
[00:42:52.620]to these enhanced efficiency fertilizers.
[00:42:56.160]So we observed that the urea-UAN application
[00:42:58.590]had higher returns
[00:43:01.140]compared to the urea preplant application, okay?
[00:43:05.160]And overall, what we observed because of higher corn yields
[00:43:09.180]and lower nitrate leaching losses
[00:43:10.590]as shown in the previous slides,
[00:43:12.240]these enhanced efficiency fertilizers
[00:43:14.340]both the Agrotain and SuperU
[00:43:15.780]when they're applied as preplant,
[00:43:17.610]they have higher returns to nitrogen
[00:43:20.670]after considering environmental costs.
[00:43:24.300]So the takeaway message from this study
[00:43:27.450]is that the single preplant application
[00:43:30.420]of enhanced efficiency fertilizers
[00:43:32.670]at suboptimal nitrogen rate
[00:43:34.710]could be a very effective strategy
[00:43:37.380]in mitigating nitrate leaching losses
[00:43:39.690]along with higher corn yields
[00:43:41.940]and higher returns to nitrogen
[00:43:44.160]after considering the environmental costs
[00:43:46.380]in the groundwater management areas.
[00:43:50.520]So this slide is intended to showcase a special scenario.
[00:43:55.170]So here we are comparing our first study,
[00:43:57.810]the economic optimum nitrogen rate
[00:43:59.190]which we calculated in our first study,
[00:44:00.750]to the results which we got from the last study
[00:44:04.590]where we have the enhanced efficiency fertilizers
[00:44:06.690]as preplant at the suboptimum nitrogen rate.
[00:44:11.070]So what we observed here
[00:44:13.350]was that the suboptimal nitrogen rates were 20 to 22% lower
[00:44:18.810]than the economic optimum nitrogen rate, okay?
[00:44:22.680]So, in three out of the four scenarios
[00:44:27.720]and we observed that the corn yields were higher
[00:44:31.920]for the enhanced efficiency fertilizers
[00:44:34.020]when used as preplant at suboptimal nitrogen rate
[00:44:36.840]compared to the five-time split application
[00:44:40.530]of Agrotain and UAN.
[00:44:45.000]It was interesting, the most interesting part was this,
[00:44:47.580]that we observed that even by decreasing
[00:44:50.880]the nitrogen rate by 20 to 22%,
[00:44:53.880]these enhanced efficiency fertilizers
[00:44:56.250]when used as preplant at suboptimum nitrogen rate
[00:45:00.330]they can reduce the nitrate leaching by 58 to 66%
[00:45:03.720]in case of say Agrotain preplant
[00:45:06.840]and by 41 to 59% in case of SuperU preplant.
[00:45:12.360]So overall, so reduction in the nitrogen inputs here
[00:45:16.500]by 20 or 22% we can have some of the corn yield gains
[00:45:24.450]while it has the potential to decrease
[00:45:27.900]the nitrate leaching by more than 40% in all cases.
[00:45:33.120]So this slide shows the conclusions from all of my studies.
[00:45:37.890]So from first study what we observed
[00:45:40.110]was that compared to economic optimum nitrogen rate,
[00:45:42.900]the static nitrogen recommendation tool,
[00:45:44.610]the Nebraska Yield Goal, performed better at it
[00:45:47.160]as it recommended nitrogen rate
[00:45:50.070]which was closest to economic optimum nitrogen rate
[00:45:52.710]with no difference in grain yield or nitrate leaching.
[00:45:55.830]And compared to economic optimum nitrogen rate,
[00:45:58.710]these dynamic nitrogen recommendation tools
[00:46:00.900]recommended 20 to 30% lower nitrogen rates,
[00:46:04.920]decreasing the nitrate leaching
[00:46:06.020]by 25% with some yield penalty.
[00:46:08.850]Therefore, there is a room
[00:46:09.990]for additional development of these tools
[00:46:12.870]so that we can better optimize the nitrogen
[00:46:15.450]for lower nitrate leaching and higher nitrogen,
[00:46:18.960]higher economic returns in the water contaminated areas.
[00:46:23.520]From our second study,
[00:46:25.440]we found that low to suboptimal nitrogen rates
[00:46:28.800]and the use of deficit irrigation
[00:46:32.130]could reduce nitrate leaching by 24 to 51%
[00:46:35.460]without impacting returns to nitrogen
[00:46:37.560]after considering the environmental costs.
[00:46:40.290]From third study,
[00:46:41.370]we observe that use of enhanced efficiency fertilizers
[00:46:45.810]as preplant at suboptimal nitrogen rate
[00:46:49.380]decreases nitrate leaching by half
[00:46:51.750]without impacting corn yield or
[00:46:54.360]and increasing the returns to nitrogen
[00:46:56.610]after considering the environmental costs.
[00:46:59.100]From our special case scenario,
[00:47:01.500]we observed that use of these
[00:47:04.080]enhanced efficiency fertilizers
[00:47:06.060]as preplant at suboptimal nitrogen rate
[00:47:08.910]decreases nitrate leaching by 41 to 66%
[00:47:12.330]without impacting corn yield.
[00:47:14.406]So overall, from all these studies we conclude
[00:47:17.490]that the use of these enhanced efficiency fertilizers
[00:47:20.610]seems to be a promising strategy
[00:47:22.800]to improve agronomic, environmental,
[00:47:24.660]and economic performance
[00:47:26.040]but this needs validation across more sites
[00:47:28.260]and climatic conditions.
[00:47:31.890]So, as you all know, nothing can be done alone.
[00:47:36.090]So there were a lot of input from various people,
[00:47:40.560]from the members
[00:47:41.393]of the Bazile Groundwater Management Area project.
[00:47:45.129]I also would like to thank the Carpenter family
[00:47:47.280]for the family farm they provided us for this research.
[00:47:50.790]The Nebraska Environmental Trust Center
[00:47:52.320]Daugherty Water for Food Global Institute
[00:47:54.180]for the funding.
[00:47:56.430]And the UNL team, Dr. Chris, Dr. Jeremy,
[00:47:59.280]Steve Melvin, Amy Timmerman, Mitiku Mamo.
[00:48:02.010]My committee members, my advisor, Dr. Javed Iqbal,
[00:48:04.710]Dan Snow, Daran, and Laila Puntel.
[00:48:07.770]They helped me a lot, a lot of good conversations.
[00:48:11.160]And my special thanks to those two people who went
[00:48:18.600]with me for thousands of hours.
[00:48:20.563]It was 3 1/2 hours away from here
[00:48:22.800]and every day almost
[00:48:23.910]and that, if you remember that 2021 was a COVID year,
[00:48:27.330]so we couldn't even stop.
[00:48:28.470]So, I really would like to thank Richard Little here
[00:48:31.530]for all his contributions
[00:48:33.390]and Christopher Misar here
[00:48:35.550]for going for all those two years
[00:48:37.890]and spending thousands of hours with me.
[00:48:40.800]And I would also like to thank William Neels
[00:48:42.930]who was a master's students in our lab.
[00:48:45.780]With that, I would like to thank you all again.
[00:48:50.460]Any questions?
[00:48:57.720]Thank you, Arshdeep.
[00:48:58.553]If there are any questions,
[00:48:59.880]please just wait until I can bring the microphone to you
[00:49:02.790]so that those who are online can also hear.
[00:49:08.370]Thank you, Arshdeep.
[00:49:09.203]That was a very insightful presentation
[00:49:11.670]and a lot of work.
[00:49:13.320]I do have a question.
[00:49:15.720]So why did your return to nitrogen
[00:49:19.260]not higher for the lower nitrogen rate
[00:49:21.960]in your second study?
[00:49:23.610]Can you like give some idea how did you calculate
[00:49:28.170]return to nitrogen considering the environmental loss?
[00:49:32.040]Okay. Yeah.
[00:49:33.120]Thank you for the question.
[00:49:34.104]So, we used the cost for the nitrate leaching,
[00:49:38.730]which we used from some of the earlier studies
[00:49:41.100]as so one kg of nitrate leaching loss
[00:49:46.650]had a monetary value of $18.54.
[00:49:51.420]So when we subtracted all that value
[00:49:53.940]from the leaching losses,
[00:49:55.350]overall we did not find any significant difference
[00:49:58.410]on the irrigation rates.
[00:50:04.620]Any other questions?
[00:50:09.351]Hello, Arshdeep.
[00:50:10.184]Thank you for the presentation and your work.
[00:50:12.330]And my question is that
[00:50:14.100]how accessible are the enhanced efficiency fertilizers?
[00:50:17.940]I mean, are they affordable
[00:50:20.670]and are they in the market readily available?
[00:50:25.590]Yes, they are readily available
[00:50:26.970]and they're a little costlier than the urea or UAN, yes.
[00:50:32.910]Yep?
[00:50:34.650]And it's just like year to year thing, you know?
[00:50:36.570]Like as a fertilizer cost for every year differs,
[00:50:39.600]but overall yes, enhanced efficiency fertilizers
[00:50:41.730]are costlier than the normal, natural (indistinct).
[00:50:45.538](faintly speaking)
[00:50:58.110]Cost of nitrate leaching and the increase in yield.
[00:51:03.360]So how is the difference in the cost
[00:51:06.960]between the regular and enhanced efficient fertilizers?
[00:51:10.440]Yes, I mean, if we consider only the yields, then yes.
[00:51:13.800]I mean at the same rates, yes, they're cost clear
[00:51:16.740]but like if we incorporate the nitrate leaching losses
[00:51:20.520]and those monetary value into that,
[00:51:22.440]then these enhanced efficiency fertilizers
[00:51:25.983]tend to increase the returns to nitrogen
[00:51:28.500]after we consider those environmental costs.
[00:51:31.200]Yep.
[00:51:37.554]That was a nice presentation.
[00:51:39.300]Did you put the same,
[00:51:41.220]the second year crop back on the same place
[00:51:43.620]as the first year?
[00:51:44.520]Yes sir.
[00:51:46.710]So there'll be a bias in there then
[00:51:49.830]of the effect of the first year on the second year.
[00:51:52.950]Okay.
[00:51:53.783]The second question is
[00:51:55.260]you had some very high nitrogen rates in there.
[00:51:58.440]You were dealing with sandy soils
[00:52:01.440]and so, do you have tissue analysis
[00:52:06.000]to know that you didn't have a negative nitrogen
[00:52:10.080]to sulfur reaction in there?
[00:52:13.410]'cause with that much nitrogen,
[00:52:15.660]if you don't have enough sulfur,
[00:52:17.670]you're gonna have a stunted plant.
[00:52:20.730]So that's just a comment.
[00:52:22.920]And finally, you've got nitrogen rates
[00:52:26.670]from zero up to high rates.
[00:52:30.210]I would suggest you calculate the nitrogen use efficiency
[00:52:33.870]for each one of those
[00:52:36.030]and then think about when you present this to the public,
[00:52:40.950]some of those nitrogen efficiencies are gonna be very poor.
[00:52:46.530]So, you need to be ready to explain that,
[00:52:49.470]explain why farmers should be allowed to do this.
[00:52:56.580]Yeah, thank you for the comment and the question.
[00:52:59.760]So yes, I mean we had the tissue analysis
[00:53:02.100]for the nitrogen concentrations but not for the sulfur.
[00:53:06.780]And regarding the nitrogen use efficiencies,
[00:53:09.330]we have calculated nitrogen use efficiencies
[00:53:11.520]for all the studies
[00:53:12.660]but due to the time limitation here,
[00:53:14.340]so I have to pick some things
[00:53:16.347]and not other things to present, so.
[00:53:20.310]But yeah, thank you very much for the comment.
[00:53:28.560]Well, nice presentation.
[00:53:29.670]I enjoyed that a lot
[00:53:30.810]and a lot of good work in there too.
[00:53:32.940]Couple just kind of quick technical questions
[00:53:36.180]and perhaps a suggestion depending on the answers
[00:53:40.830]for the suction cup lysimeters,
[00:53:43.500]how long did you apply the suction
[00:53:46.350]before you collected the sample out?
[00:53:48.570]Because you collected them every five days
[00:53:50.370]but just kind of, how long was that suction on
[00:53:52.950]before each sampling?
[00:53:54.330]Okay, so what we observed, Aaron,
[00:53:56.460]was that like after four or five hours
[00:53:59.250]there was no like pressure left in that.
[00:54:02.340]So we would go there, apply the suction
[00:54:05.910]and then after four or five hours
[00:54:07.320]we will take the water samples out.
[00:54:09.000]Okay, so they're four or five hour window
[00:54:11.160]that you've sampled in
[00:54:12.150]that those samples are reflective of.
[00:54:15.270]So nitrate leaching and water,
[00:54:18.390]especially in sandy soils like this,
[00:54:19.950]it's very pulsey, you know?
[00:54:21.900]So you get a pulse after irrigation,
[00:54:23.730]you get a pulse after a rainfall,
[00:54:25.260]and whatever in acidic conditions
[00:54:27.510]kinda drive how much you end up pulsing down.
[00:54:31.230]So those pulses are very hard to capture for it
[00:54:36.087]and your sampling window, which is very common
[00:54:38.430]of suction cup lysimeters
[00:54:40.200]is probably capturing what's left over
[00:54:42.870]after the pulse has already gone through,
[00:54:45.270]especially when it's a four or five hour window
[00:54:48.810]that you're sampling in,
[00:54:50.730]which is common for sandy soils
[00:54:52.100]to have that kind of window too.
[00:54:54.360]So something that in your calculations
[00:54:58.110]of how much leaching occurred,
[00:55:00.960]my interpretation or the way that you might consider
[00:55:03.810]interpreting it is that this is kind of a,
[00:55:06.840]perhaps a minimum nitrate loss amount that's in there.
[00:55:10.830]There is some potential for higher amounts
[00:55:13.350]from the pulses that are hard to quantify.
[00:55:17.130]And then my last thing, it would be interesting
[00:55:20.370]and useful to know if you were to put in at this site
[00:55:24.690]like a pan lysimeter down at four feet
[00:55:28.320]or however deep your suction cup lysimeters.
[00:55:31.560]If you had a pan lysimeter down there,
[00:55:33.060]whether it was underneath tension or not,
[00:55:35.010]just to be able to compare when you take cumulative samples
[00:55:38.760]over a sample area in a pan,
[00:55:41.970]what does that nitrate leaching loss look like
[00:55:45.000]compared to the suction cup lysimeters?
[00:55:48.360]Do the suction cup lysimeters, are they equal?
[00:55:52.800]Are they always estimating 5%, 20%,
[00:55:56.400]50% underestimation?
[00:55:58.620]It'd be interesting and useful to know too.
[00:56:01.990]Yeah, thanks, Aaron for the comment, suggestions,
[00:56:04.564]and the question.
[00:56:05.850]So yeah, we even, so what we tried was that
[00:56:09.750]for water sampling, so after every irrigation
[00:56:12.570]and every precipitation event,
[00:56:14.280]we tried to go up there
[00:56:16.680]and take the water samples in order to capture the peaks.
[00:56:19.140]However I understand that, yes, I mean we can lose those
[00:56:22.380]but yes we tried our best to capture those things.
[00:56:35.010]Online question is,
[00:56:36.270]do you have any data about any season nitrate leaching
[00:56:40.140]versus all the season nitrate leaching (faintly speaking)
[00:56:46.453]technique inspired during in all season?
[00:56:50.370]Yes, we have the residual nitrogen at the end
[00:56:53.460]which I didn't show here,
[00:56:54.630]and which were higher than the total
[00:56:57.750]seasonal nitrate leaching.
[00:56:59.520]So therefore, which can, in the off-season,
[00:57:01.680]have more nitrate leaching losses
[00:57:03.090]than the in-season nitrate leaching losses.
[00:57:06.570]Okay.
[00:57:07.403]Does that satisfy?
[00:57:08.797]So can you mention
[00:57:10.097]what of the residual nitrate and ammonium
[00:57:12.758]at the end of the season for the first year.
[00:57:14.579]I think it was quite low.
[00:57:17.141]Yeah.
[00:57:19.354](faintly speaking)
[00:57:22.975]So in terminal (indistinct) regarding the variables.
[00:57:28.770]So what we found...
[00:57:32.850]So what we found that there was really,
[00:57:34.770]even with the higher nitrogen the rate,
[00:57:36.690]there was no nitrogen left there.
[00:57:41.460]Yeah because it's loamy sand,
[00:57:43.860]it will just flush out whatever nitrate,
[00:57:46.260]nitrogen that you put in.
[00:57:53.730]Have any other questions in the room?
[00:57:58.860]Very nice presentation.
[00:58:00.300]I would ask you a question in regards to comparing
[00:58:03.960]where your site was as far as how,
[00:58:07.860]what the sand percentage and clay and so forth
[00:58:10.890]compared to what we've seen in the Platte River Valley
[00:58:13.680]where we have probably higher sandy soils
[00:58:17.940]and greater potential for leaching
[00:58:21.990]with lesser amount of water taking it out of the root zone.
[00:58:27.150]What's the comparison between your site maybe
[00:58:29.610]and just what you would envision
[00:58:32.100]for the Platte River bottoms that are sandy soils?
[00:58:39.180]So I don't know like what the sand conditions there are
[00:58:43.380]but yes, for our site, yeah, yeah.
[00:58:46.500]For our site, like we had more than 70% of the sand
[00:58:48.900]until four feet.
[00:58:49.830]So, it was pretty sandy I would say.
[00:58:53.670]Yeah.
[00:59:00.750]So as I recall,
[00:59:01.583]there are different Agrotain products.
[00:59:03.870]Was the Agrotain that you used,
[00:59:05.730]did it have only the urease inhibitor
[00:59:08.460]or did it contain a nitrification inhibitor as well?
[00:59:12.300]So, the Agrotain which we used had urease inhibitor
[00:59:15.840]and then we had a SuperU which had both urease inhibitor
[00:59:18.690]and the nitrification inhibitor.
[00:59:22.071]So I would say that
[00:59:23.010]those results were unexpected,
[00:59:24.840]that the Agrotain treatment alone
[00:59:28.830]had such a great effect even greater than the SuperU.
[00:59:33.180]Is that right?
[00:59:34.013]Yes sir and this was because like
[00:59:36.420]this was dry years,
[00:59:38.010]there was like less precipitation in the early season
[00:59:41.340]and that could be one of the reason why there was less,
[00:59:45.420]that there was a delay in the transformation
[00:59:47.880]of urea to ammonium
[00:59:50.097]and that might have led to lower nitrate leaching losses,
[00:59:53.490]and like the nitrogen would have been available
[00:59:55.950]for the plant when needed.
[01:00:00.660]So, I think that's really a good point.
[01:00:03.210]We were not expecting,
[01:00:04.860]we were actually not expecting at all.
[01:00:07.020]We were just comparing urease inhibitor,
[01:00:09.780]with nitrification inhibitor,
[01:00:11.040]with just with urease inhibitor.
[01:00:13.050]So we thought that definitely there would be no,
[01:00:16.380]maybe no leaching effect
[01:00:17.880]from the urease inhibitor, Agrotain.
[01:00:21.240]And then when we saw the reserves we were surprised
[01:00:24.420]and we thought that maybe
[01:00:26.580]some of the nitrogen would be lost any other pathways.
[01:00:30.600]If not nitrate nitrogen,
[01:00:32.040]maybe urea it might have been lost to other pathways.
[01:00:34.830]And then we analyzed those samples for urea as well
[01:00:39.150]and we did not find urea in those two.
[01:00:41.730]But at that time we were kind of surprised to see,
[01:00:45.540]how is this Agrotain reducing nitrate leaching?
[01:00:49.260]Until we saw many other papers that have reported the same,
[01:00:53.700]that the Agrotain with urease inhibitor
[01:00:57.240]and then even other urease inhibitor,
[01:00:59.490]they tend to reduce nitrate leaching too.
[01:01:10.650]So the question about the application
[01:01:12.240]of the results to the central plot, that's a good question.
[01:01:15.180]So I ask, can you see how some of these decision tools
[01:01:19.980]could be improved using your results?
[01:01:22.740]Have you been able to look into those tools at all,
[01:01:26.850]including the code
[01:01:28.050]or is it likely someone's going to make use of your data
[01:01:31.890]to improve those tools so they are more effective
[01:01:34.890]that the information it'd be widely applied?
[01:01:37.650]Yes sir. Thank you for that.
[01:01:38.880]And yes, I mean there is a potential to improve the tools,
[01:01:42.270]especially like the industrial tools,
[01:01:44.430]both the Adapt-N and the Granular they can be improved
[01:01:47.910]because they do not take into consideration the nitrate
[01:01:51.420]which is in the irrigated water.
[01:01:53.910]So, if they do that,
[01:01:56.790]there is a potential to increase that.
[01:01:58.650]For the Canopy sensing reflectance,
[01:02:01.740]what we have seen is that since
[01:02:04.890]like the application timing suggested is eight-leaf stage
[01:02:09.210]and if there is like more crop,
[01:02:11.730]sensing before that
[01:02:12.960]and the nitrogen recommendations are based on that,
[01:02:15.810]that can help to improve the nitrogen recommendations
[01:02:19.200]for that tool.
[01:02:22.950]I think we are out of time
[01:02:24.300]so I am going to wrap things up here.
[01:02:27.840]I think Arshdeep would be willing to stay behind
[01:02:30.000]if there are any more questions.
[01:02:31.530]Please feel free to come up and talk afterwards.
[01:02:34.410]Thank you again very much, Arshdeep, for your presentation.
[01:02:37.110]We really appreciate it.
[01:02:38.370]Thank you to everyone who is here today for showing up.
[01:02:40.950]We appreciate your presence here
[01:02:42.597]and all the wonderful questions.
[01:02:44.370]We hope to see you again next week.
[01:02:47.584](audience applauding)

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Nitrogen and Water Management Strategies to Reduce Nitrate Leaching in Irrigated Sandy Soils

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