Stumpf Farm – Soybean Board Population/Fertility Study

University of Nebraska – Lincoln Author

08/31/2020 Added

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Strahinja Stepanovic talks about the project description and preliminary results of soybean population and fertility study.
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[00:00:06.760]Hi, everyone Strahinja Stepanovic here,
[00:00:08.770]I'm gonna talk about Soybean Fertility Study
[00:00:11.220]we had last year in soybeans.
[00:00:12.660]We're repeating this study in 2020.
[00:00:15.590]And just to give you a brief history
[00:00:17.140]of why we did the study.
[00:00:19.210]When I first came into Southwest Nebraska,
[00:00:21.320]a lot of farmers that I talked to
[00:00:24.580]had the practice of chemigating nitrogen on soybeans
[00:00:29.580]later in a season.
[00:00:30.840]Now, there's a lot of research in Eastern Nebraska
[00:00:33.114]and Eastern Kansas that tells you that that's justified.
[00:00:37.020]But, I just wanted to double-check if that's really true.
[00:00:42.710]I ran a few tests just to see
[00:00:44.990]if there's any yield difference and it turned out it wasn't.
[00:00:48.950]So, I applied for a grant to Soybean Board
[00:00:53.450]and they supported me in doing three on-farm
[00:00:55.820]research studies in 2017,
[00:00:58.150]to do the replicated chemigation versus no chemigation
[00:01:02.170]on soybeans.
[00:01:03.240]We played a little bit with the rates applying
[00:01:06.230]between 50 and 80 pounds, between R3 and R5.
[00:01:10.520]And what was really surprising,
[00:01:11.730]there was no difference in yield
[00:01:13.270]on any of the three locations, very different soils.
[00:01:17.600]So with that being said, no yield benefit,
[00:01:21.980]no protein benefit as well.
[00:01:23.900]And we couldn't find any residual nitrogen in the soil.
[00:01:26.970]There was a little bit more nitrogen in a residue,
[00:01:30.110]but that wasn't enough to justify the expense
[00:01:32.601]of applying late season nitrogen in soybeans.
[00:01:36.680]So, we wanted to keep doing the research on this
[00:01:41.440]and especially on fertility.
[00:01:43.460]At that time, Jimmy Frederick from Eastern Nebraska,
[00:01:47.510]he had the record yielding dry land soybeans
[00:01:49.520]with 138 bushels per acre,
[00:01:52.530]and he did not use any nitrogen.
[00:01:54.970]So he used a lot of biological products, compost, et cetera.
[00:02:00.090]So we started thinking maybe we are doing something wrong.
[00:02:04.400]He used, I believe, chicken manure
[00:02:06.130]and some other biological products.
[00:02:07.820]So, is nitrogen fixation enough?
[00:02:12.040]Do we need to do something on a biological side?
[00:02:15.260]All those questions arose.
[00:02:17.090]And then we did compost in one of our agronomic studies
[00:02:21.170]that also dealt with planting dates
[00:02:22.950]and seeding rates, and row spacing.
[00:02:24.980]And what we have found is a very compelling evidence,
[00:02:28.140]that compost application gave us anywhere between 0 to 12
[00:02:32.470]bushel advantage.
[00:02:33.751]And we wanted to continue doing that fertility studies.
[00:02:37.330]We took this data to our farmers,
[00:02:39.820]and about 71% of them wanted to see
[00:02:43.450]some kind of fertility study the following year.
[00:02:47.160]So here we are, we came up with the list of treatments
[00:02:53.882]and we put out about 12 different fertility treatments
[00:02:59.320]of soybeans.
[00:03:00.700]The control was just inoculant
[00:03:02.550]and the second control was actually just urea
[00:03:07.100]and we applied 400 pounds of nitrogen in that plot.
[00:03:11.710]This is not for normal practice,
[00:03:15.410]but we just wanted to make sure we have one plot
[00:03:18.490]that's not going to have nitrogen
[00:03:20.370]as a yield limiting factor.
[00:03:22.180]So, if there's another 50 to 100 pounds left behind
[00:03:26.360]that soybeans in a soil,
[00:03:29.335]if they leave more nitrogen than any other treatment,
[00:03:31.910]we would know nitrogen was not a limiting factor.
[00:03:34.770]So we then, he had the chicken manure
[00:03:38.180]and cow manure, both broadcast,
[00:03:41.200]and we were able to powder some of that manure
[00:03:43.430]and put it at the right array, just with the seed.
[00:03:46.810]One of those things that came out in our previous studies
[00:03:50.110]is all the elements that we looked at in a tissue sampling
[00:03:54.350]were within the sufficiency level,
[00:03:55.960]except for one nutrient and that was magnesium.
[00:03:59.650]So our first step, we incorporated two more treatments,
[00:04:03.203]low and high magnesium rate.
[00:04:06.290]So that was the first thing to look at,
[00:04:08.010]just put magnesium out there.
[00:04:09.650]And then we contacted a lot of local experts
[00:04:14.150]from local co-ops and their fertility programs.
[00:04:18.820]So Aurora Co-op chimed him
[00:04:20.750]with their fertility program on soybeans,
[00:04:23.880]as well as Nutrien and Kugler.
[00:04:26.476]And it was interesting to see
[00:04:29.110]they had some micronutrients out there,
[00:04:31.270]specialty products, fungicide-like products,
[00:04:35.460]growth promoters, and foliar fertilizer.
[00:04:40.400]So it was very interesting to kind of,
[00:04:42.510]we're really anxious to see if any of them
[00:04:44.620]is going to be giving us that higher yield on soybeans.
[00:04:50.020]So here are the results.
[00:04:52.780]First of all,
[00:04:53.890]the most surprising result was there was absolutely
[00:04:56.410]no yield difference between any of the fertility treatments.
[00:05:00.300]So inoculum only was as good as everything else.
[00:05:04.340]And there was no really a difference in NEIL protein,
[00:05:07.160]but what was really interesting in the study was,
[00:05:12.120]and by the way, on that nitrogen treatments
[00:05:15.440]where we applied for 100 pounds of nitrogen,
[00:05:16.940]there were still 50, 60 pounds of nitrogen left in the soil.
[00:05:21.210]Whereas all the other ones had about 20 pounds of nitrogen
[00:05:26.381]in the soil after we harvested the crop.
[00:05:28.330]So nitrogen was not a limiting factor, at all.
[00:05:32.700]And water was not a limiting factor.
[00:05:34.863]They were all watered, the soil moisture was monitored,
[00:05:39.010]and we watered them regularly.
[00:05:41.150]And there was no difference in planting population
[00:05:43.330]or planting date.
[00:05:44.800]But what was really interesting is that in depth,
[00:05:47.880]a place where we put the study, every 30 foot,
[00:05:52.420]you would see a drop in pH going ...
[00:05:57.660]We have the range of soil pH ranging from 5 1/2 to 8.2.
[00:06:03.230]So any given plot in that study,
[00:06:07.820]you could have seen .3, .4, 1.5 difference in soil pH.
[00:06:13.230]And that was very, it was unintentional,
[00:06:15.760]but it was very interesting to see,
[00:06:17.610]and I'll just show you why.
[00:06:19.310]Because despite that we didn't have differences
[00:06:23.400]in fertility treatments,
[00:06:24.590]I tried to plot out those plots.
[00:06:30.420]For example, this plot had this much pH
[00:06:33.490]and yielded that much.
[00:06:34.610]So after you do that and plot out by soil pH,
[00:06:39.130]you quickly realize how impactful soil pH can be
[00:06:44.160]on soybean yield.
[00:06:45.520]So we had with this variety in soybean,
[00:06:50.910]when soybean pH was 7, 7.5 and over,
[00:06:55.740]we had 10 bushel yield decrease in soybeans.
[00:06:59.510]So you can kind of see those two clusters.
[00:07:01.220]What was also very interesting is the effect of soil pH
[00:07:05.270]on grain protein.
[00:07:06.970]The grain protein was about 1.5% lower
[00:07:10.508]at that 7.5 and over range for soil pH.
[00:07:16.960]We analyzed magnesium and tissue.
[00:07:18.750]I'm not going to talk about other nutrients,
[00:07:22.410]macro nutrient, because none of them were limiting
[00:07:25.340]in a tissue, but magnesium was.
[00:07:27.570]We kind of anticipated this.
[00:07:29.670]And if you plot the tissue analysis over time,
[00:07:34.950]you can see that right around the R3 growth stage,
[00:07:39.390]you can see the calcium uptake just kind of take off,
[00:07:42.650]and there was a lot of calcium.
[00:07:43.990]But at the same time, the magnesium uptake goes down.
[00:07:47.580]So that was kind of very interesting.
[00:07:50.910]And we thought maybe magnesium uptake was hindered somewhat
[00:07:54.500]by calcium uptake.
[00:07:56.520]So we wanted to see also,
[00:08:02.289]did pH affect the availability of magnesium?
[00:08:06.110]It turns out that concentration of calcium in the soil
[00:08:09.386]was at the high or over sufficiency level all the time,
[00:08:13.970]regardless of where you're at.
[00:08:16.120]Whereas magnesium in the soil was always
[00:08:20.350]at the lower sufficiency level.
[00:08:22.540]So those critical levels for magnesium
[00:08:24.520]were always at the lower end.
[00:08:26.550]So that was another thing.
[00:08:29.346]And then we try kind of, to look at, what's really changing.
[00:08:35.870]Here, you can see that magnesium concentration in a soil
[00:08:40.100]somewhat increases as the soil pH increases,
[00:08:43.310]which is the same for soil calcium.
[00:08:45.470]But you can see that here,
[00:08:47.800]when you look at the saturation ratio,
[00:08:50.090]we found also another interesting point,
[00:08:52.240]that after the soil pH gets 6.7, right here,
[00:08:58.450]the calcium to magnesium ratio really starts to increase.
[00:09:02.870]So it goes, from four,
[00:09:06.950]that ratio goes from four to about six,
[00:09:10.260]between 6.7 pH and 8.0 pH.
[00:09:14.480]So that ratio really changes at those higher pH levels.
[00:09:19.300]And that stands also for ratio of potassium to magnesium.
[00:09:22.770]So a lot of guys that are trying to fertilize
[00:09:26.230]with potassium,
[00:09:27.920]I would really caution you against that.
[00:09:30.560]We have not seen any deficiency of potassium in the tissue.
[00:09:34.530]And among the micronutrient,
[00:09:36.690]all of the nutrients were within the sufficiency levels,
[00:09:40.140]except for molybdenum,
[00:09:41.630]especially at the late reproductive stages.
[00:09:44.000]We know molybdenum is a critical part of the enzyme
[00:09:46.900]that does the nitrogen fixation.
[00:09:49.340]And at this point,
[00:09:50.173]we know that nitrogen fixation starts to decline.
[00:09:53.050]So is it possible that we need more molybdenum?
[00:09:55.860]That was another takeaway from this study.
[00:10:00.020]So we are repeating this study.
[00:10:02.260]Again, this year, we had the great year.
[00:10:04.380]We have another great year for soybean.
[00:10:06.910]Possibly this time, we might see yielding 80, 90 bushels,
[00:10:10.630]and we maybe see the difference in fertility treatments.
[00:10:14.440]So with that,
[00:10:15.273]I would like to encourage you to read the guide
[00:10:17.160]for soybean production in Western Nebraska,
[00:10:21.580]that we published.
[00:10:22.540]And you can read this study, more in depth.
[00:10:26.430]It's online, published in Crop Watch.
[00:10:29.040]And with that, I would like to answer any questions.

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Stumpf Farm – Soybean Board Population/Fertility Study

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