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18
Oct
2018
Poor Soybean Seed Quality Seen for a Second Year
Author: Jeremy Ross, Extension Agronomist - Soybeans

By Jeremy Ross, Extension Soybean Agronomist

This growing season is the second year in a row where Arkansas soybean producers have seen poor quality soybean during harvest (Figure 1).  In a Blog post I wrote last year (Poor Soybean Seed Quality), many of the same issues that caused the poor quality seed last year were seen in 2018. The one major difference in 2018 was the absence of Redbanded stink bug, so we can’t blame this pest for the damage that we have seen so far during the 2018 harvest.

Figure 1. Typically damage seen in harvested soybean in the Mid-south US (courtesy of Todd Spivey, LSU AgCenter)

Figure 1. Typically damage seen in harvested soybean in the Mid-south US (courtesy of Todd Spivey, LSU AgCenter)

I can’t put my finger on just one event, agronomic practice, or other factor that caused the poor seed quality this year.  I think it was several factors that coalesced to get us to this point.  The major player in this problem is Mother Nature. With the less than ideal growing conditions during most of the summer, most of our soybean crop was stressed due to the above normal temperatures and lack of significant rainfall in most of the State during May, June, and July.  We finally got a break in August with cooler temperatures and frequent rainfall.  This rainfall continued into September, and now October, preventing timely harvest of not only the soybean crop, but the other commodities we produce here in Arkansas.  The delay in harvesting the 2018 soybean crop due to the poor weather conditions seen during the last month and a half are reflected by the USDA-NASS harvest numbers.  For the week ending October 14, 2018, Arkansas soybean producers have only harvested 44% of the 2018 soybean crop compared to 71% in 2017 and 60% for the 5-year average.  Almost half of the crop (46%) is considered very poor to fair with 54% considered good to excellent.

Figure 2. Soybean grain sample graded at 5-6% damage (courtesy of Russ Parker, University of Arkansas Division of Agriculture)

Figure 2. Soybean grain sample graded at 5-6% damage (courtesy of Russ Parker, University of Arkansas System Division of Agriculture)

Prior to last week, a large percentage of the soybean crop being delivered to elevators had some form of damage.  Depending on the elevator, as much as 80% of the truck loads being delivered had 2-5% damage (Figure 2).  The remaining 20% of truck loads being delivered had even higher damage (Figure 3 and 4). The soybean crop that was harvested last week seemed to be somewhat better in quality, but damage was still present.

With the favorable weather conditions seen late in the 2018 growing season, we saw a tremendous amount of foliar and pod diseases.  Some of the most common have been Cercospora leaf blight and purple seed stain, pod and stem blight, and Phomopsis seed decay (Figure 5.).  Many of the producers and consultants that I have spoken to in the last 3-4 weeks indicated that they applied a fungicide during R3.  Looking back, these applications were made during late-June to mid-July.  At that time, many were hard pressed to find much disease development if any in their soybean crop.  These R3 applications would have played out long before our soybean crop reached maturity (likely in 14-21 days).  As with any plant disease, there are three factors needed for disease development: 1) a susceptible host; 2) the pathogen; and, 3) an environment favorable for disease development.  With the warm, wet conditions seen during September and October, mature soybean remaining in the fields, and the late buildup of several soybean diseases, there was a perfect scenario for deterioration of the soybean seed.

Evidence suggests earlier plantings (early- to late-April) of soybean produce higher yields than late plantings.  In addition, the trend for the last few years has been to plant earlier maturing soybean varieties.  Many are planting late-MG3’s and early-MG4’s.  Many of these “early” maturing varieties are not tested in the University of Arkansas System Division of Agriculture Soybean Performance Tests, and I have no data on yield or performance to make a recommendation on specific varieties.  These varieties are also typically grown further north.  Talking to several seed company representatives, many of the “early” maturing soybean varieties have very good yields, but some have average seed quality when grown in their intended location.  When these varieties are put under the environmental stresses we typically have here in the Mid-South, we could potentially see increased quality problems.

Figure 3. Soybean grain sample graded at 10-12% damage (courtesy of Russ Parker, University of Arkansas Division of Agriculture)

Figure 3. Soybean grain sample graded at 10-12% damage (courtesy of Russ Parker, University of Arkansas System Division of Agriculture)

The most concerning problem I have observed over the past few years is too many acres of soybean needing to be harvested while producers harvest their rice and corn crops.  Producers need to consider when they typically harvest rice and corn compared to soybean, harvest capacity, and delivery logistics. One tool that was developed by Dr. Larry Purcell that may help in determining soybean harvest is SOYMAP (SOYMAP).  SOYMAP is a software tool to assist producers with choosing a soybean maturity group and planting date.  Some of the results that can get generated from SOYMAP include expected yield, irrigation needs, and the time window for different growth stages.  If a producer is considering either changing the planting date or soybean maturity group from what they have done in the past, I would recommend running several scenarios in SOYMAP to determine the approximate harvest window for their soybean crop.  This would give producers an idea on when the soybean crop will be ready to harvest.

The last part of this puzzle is the current soybean market.  I’m no economist, I can barely keep my checkbook balanced, but here is what I have learned over the last few weeks; The current tariffs on US soybean have depressed the soybean price along with reducing the amount of soybean being exported. With no market, soybean inventory is starting to back up at the Gulf, causing elevators along the Mississippi River to put more soybean into storage.  No one is wanting to purchase heavily damaged soybean.  With the lack of “good” quality soybean to blend with damaged soybean, companies are not able to move these soybean.  With the current price, discounts, basis, and other deductions, some producers are getting less than $7/bu for their soybean crop, and we all know that a producer will be hard-pressed survive at that level.

Figure 4. Soybean grain sample graded at 20-50% damage (courtesy of Russ Parker, University of Arkansas System Division of Agriculture)

Figure 4. Soybean grain sample graded at 20-50% damage (courtesy of Russ Parker, University of Arkansas System Division of Agriculture)

Even though we have had rainfall across most of the State for the last five days, the cooler temperatures expected over the next week or so should slow down some of the fungal damage we have been seeing.  The only other problem is that fields will not dry as fast with these cooler temperatures, and we could potentially see more rutted fields trying to get the rest of the soybean crop harvested.  I don’t think there was much we could have done to prevent the quality problems we have experienced so far this fall.  My recommendation at this point is get your soybean crop harvested as quickly as possible.

Figure 5. Pod and seed damage caused by Phomopsis and other fungal species. This image was taken in mid-August in a field near Earle, AR that had remained wet for an extended period of time (courtesy of Terry Spurlock, University of Arkansas Division of Agriculture).

Figure 5. Pod and seed damage caused by Phomopsis and other fungal species. This image was taken in mid-August in a field near Earle, AR that had remained wet for an extended period of time (courtesy of Terry Spurlock, University of Arkansas System Division of Agriculture).


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