21 - 2020 Soybean Management Field Days - Varietal Maturity Group Choice
Soy Planting Date – Varietal Maturity Group Choice - Jim Specht, UNL Emeritus Professor of Agronomy and Horticulture covers the following: Inserting a Winter Annual Cover Crop into a soybean-corn crop rotation involves two considerations, the first of which we have already discussed (delaying the soybean planting date to allow more CC dry matter), but one must also consider using an earlier varietal MG to permit better establishment of the CC after soybean harvest. Let’s consider some tools for making decision to use an earlier MG.
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[00:00:07.730]Okay, my name is Jim Specht.
[00:00:09.660]I'm Professor in Agronomy
[00:00:11.300]now retired at the University of Nebraska
[00:00:13.600]and my specialty was soybean physiology and production
[00:00:18.160]in addition to genetics genomics,
[00:00:20.090]but today we're gonna focus
[00:00:21.320]on physiology and production of soybean.
[00:00:24.020]Aside from planting date,
[00:00:25.800]the next soybean management practice
[00:00:28.860]that can influence soybean yield
[00:00:30.400]is the appropriate maturity group.
[00:00:32.520]And you need to select one
[00:00:34.210]that's suitable for your planting date.
[00:00:39.470]So here you can see the old maturity group system
[00:00:41.920]developed back in the 70s
[00:00:43.530]where we had 13 maturity groups
[00:00:45.490]spread across the United States.
[00:00:48.210]Recently Wisconsin researchers
[00:00:50.530]come up with a better way of taking a look at that.
[00:00:53.770]This is the soybean distribution these days in 2015.
[00:00:58.107]You can see the concentration along the Mississippi River,
[00:01:02.140]the central, more central region,
[00:01:04.390]and the Great Plains states.
[00:01:06.830]If you taking a look at the yield trials
[00:01:08.590]that have been conducted there
[00:01:09.720]and you can use that 'cause they generally have 23 years
[00:01:13.830]of real trial data that you can find out
[00:01:15.930]which maturity group was the best
[00:01:18.250]in every one of those trials.
[00:01:20.930]And you plot it this way.
[00:01:22.150]You can see what they've come up with
[00:01:23.680]for maturity rating across the U.S.
[00:01:26.690]You can see that a lot later soybean varieties
[00:01:30.840]in the South are no longer used
[00:01:32.740]in favor of maturity group six.
[00:01:36.290]You can see Nebraska a little bit there.
[00:01:38.990]You can see we're on the three line right there
[00:01:43.850]where it intersex Nebraska.
[00:01:46.080]Now if we go directly to Nebraska,
[00:01:47.930]this is the current maturity group zones from Nebraska
[00:01:51.290]and you'll note they follow the GDD,
[00:01:53.180]the growing degree patterns
[00:01:55.100]shown on the underlying map there.
[00:01:57.700]And so this doesn't mean you have
[00:02:00.560]to plant only three majority groups
[00:02:03.492]south of the three line and only two north of,
[00:02:08.720]this is not a distinct line,
[00:02:11.020]but merely a prescriptive line where it's best
[00:02:15.220]to shift to a lighter maturity group
[00:02:17.520]if you're going south east.
[00:02:21.590]Producers in Nebraska are unique.
[00:02:24.040]And note they have irrigated and rain fed county yields.
[00:02:26.780]And you can see here that
[00:02:28.540]under rain field fields, most rain fed producers
[00:02:33.070]south of the three line maturity group three line
[00:02:35.560]grow maturity group three or later varieties.
[00:02:38.820]Whereas under area conditions,
[00:02:41.600]producers and south of the maturity group three line
[00:02:45.700]actually grow maturity group have two varieties.
[00:02:48.650]There are different reasons offered for this
[00:02:50.794]as we talked about here.
[00:02:52.960]Generally speaking, you can grow an earlier
[00:02:55.070]maturing variety with irrigation.
[00:02:56.515]They will not be subject to August's drought stress.
[00:02:59.410]Which can hasten your maturity group readings.
[00:03:04.330]So irrigation predictions can expect to get high yields
[00:03:08.544]with maturity group varieties in that region,
[00:03:10.540]but many years, the lows and rain fed fields
[00:03:13.500]south of the maturity group line have to grow threes
[00:03:16.370]so they can get at least a chance to catch a rainfall
[00:03:20.830]in late August and early September.
[00:03:23.810]I think this data clearly shows here
[00:03:25.570]that maturity group is from Wisconsin
[00:03:27.800]and it shows that maturity group selection.
[00:03:30.320]If you notice the curved lines,
[00:03:31.770]all those are the models for planting.
[00:03:34.200]And you can see
[00:03:35.033]on the left of your planting, just to the midpoint variety
[00:03:38.115]and each maturity group zone, your yield is lower
[00:03:42.010]starting with earlier planting,
[00:03:43.520]and then declines after that.
[00:03:46.320]Whereas if you're planting the latest maturity group
[00:03:49.180]at each location in your region, the longest one,
[00:03:53.280]you can see the yield is higher
[00:03:55.420]on the order of 86% versus on 98%.
[00:04:01.950]So this says that if you're gonna go for a high yields
[00:04:05.180]with early plantings, you need to use the most,
[00:04:09.000]the longest maturity group you can
[00:04:12.390]from a thorough point of view
[00:04:14.520]and from an irrigated point of view.
[00:04:17.080]So again, here you need to consider a latitude
[00:04:21.030]and then in the Great Plain state, altitude
[00:04:24.250]'cause both for the period and thermo period are important
[00:04:27.160]in measuring maturity group selection and varieties
[00:04:30.670]with the best adapted fits for a given production zone
[00:04:34.570]and optimum planning will generally
[00:04:36.630]have maturity groups that span
[00:04:38.820]narrow to you that ranges in maturity group number.
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