Late rains offer opportunities to nudge soybean yields higher

Here's crop consultant Bob Streit's field observations and recommendations released today.

August 13, 2021  By Bob Streit  The tightrope walk of the 2021 growing season continues. Finally, after weeks and months of waiting for widespread rains to fall in the Midwest, we are seeing such moisture fall. Luckily this is happening early enough to benefit the seed fill on both major crops and for revival of different forages.

It will not be early enough to fully benefit the cornfields where the leaves were rolling their leaves by mid-morning for weeks on end. A high percentage of the yields that we will get can be contributed to most major corn breeding companies having established research stations during the 1980s in the western reaches of the cornbelt in traditional irrigated country.

By cutting off the irrigation midway thru the summer they subjected each hybrid cross to severe drought stress, heat stress and wind events. As proof of the return of rains to our part of the world, our neighbors in Lincoln, Nebraska ended the 24-hour period with up to 8” of rain during the Aug 8th to 9th time period. This front then moved east to benefit our western IA growers.

There were fields that on July 5th looked to be sending up flag leaves when they were only 5 ft tall and had that silvery color indicating a near death experience was at hand. Ear size will likely be smaller in them. There are fields that late last week begin to yellow on the top leaves as the proteins began to be denatured. Can these be revived thru foliar applied slow-release nitrogen? We will have to see how this turns out.

Bob Streit

Over the last two weeks and this past weekend I had the chance to check out the crops north of Hwy 3, in the Mason City area, and into Northern MO and western Wisconsin. The corn in northern Iowa was as dark green as people have ever seen. They have had more rain than the rest of Iowa, except for the SE portion. No huge downpours, so their N loss due to leaching or denitrification has been minimal. The Canadian wildfire smog created a haze which we see more commonly over West Coast cities. (One person asked if anyone has identified and quantified what minerals might be contained in that smoke.)

The small NE Iowa town of Stacyville had their Bratwurst Days celebration over Friday and Saturday. It provided the chance to travel and visit with a number of people I had not seen in years. One high school journalist friend,Chuck Hackenmiller, wrote and did photography work for several Iowa newspapers. He has written several books about growing up in rural Iowa. His most recent one is entitled With Twelve You get Goulash. Coming back on Sunday we happened into the Gobbler’s Roost in Grafton for their 10-year anniversary BBQ. We were treated to a great meal and the chance to listen to a pair of first-class musicians that are definitely worth following and listening to (check out Will Bartz, Colby Fossey and Bad Habits). Try to catch them if possible.

Market Happenings

Getting a pulse on the grain markets for the next twelve months has been difficult for all prognosticators. To add to the lack of clarity were the several nights of frosty and freezing nights in Brazil last week. Those fields were reportedly only in the mild to dough stage, which is way behind normal.

The SB crop was planted two or three times due to the late and erratic rainy spells. Those delays resulted in the safrina corn crop being planted much later than the normal drop-dead date of Feb 15th or March 1st. Now it sounds like their corn production amounts will be lowered dramatically in the coming harvest months. Those importing countries will have to look elsewhere for feed grains in the coming months.

 

Crop Development

Daily moisture use by corn during the late blister to early dough stage will be declining slightly but will still be in the .20-.23”/day range. In soybean fields the R3 plants will be using nearly as much moisture per days as corn at VT. Beans have the increased chance of capitalizing on late rains as the pods will fill more in size. With corn, a shortage of water in the blister stage can result in kernel abortion without the means to recover what was lost. In beans, we are seeing that a portion of the plants have formed their terminal flower cluster and at best would only be able to capitalize on these late July rains by forming new flowers at the current nodes and increasing seed size.

A common observation by both growers and professional meteorologists was that the crops in the drier states still looked good for as little rain fell. One explanation by Eric Snodgrass that is borne out in his data was that although much of July was very hot and dry, most days had high humidity and heavy dew most mornings.

The moisture was moving thru the state and provided lots of clouds, but not have enough fronts to wring the rain from those clouds. Most mornings there were moist circles of dripping dew around each plant where roots could pull in the moisture. The Stockton, IA grower who developed the Y-drop saw  this happening in his own fields during several dry seasons. That led him to build a Y-drop setup to target that rooted circle as the ideal spot to apply liquid N for maximize plant uptake.

As of this date we are seeing that in most corn fields — in spite of the extremely dry conditions during most of the season — the ears have actually filled out much more that would be expected. The average kernel count is lower, with more of 14 to 16 kernels around rather than 18 or 20. The length is good, at 34 to 42 kernels, but we will have to see how many maximize kernel fill and contribute to yield. The accuracy and variance will depend heavily on kernel depth.

In the bean fields, most early and mid-season plantings have formed their apical flower cluster and are now filling the seed to enlarge the pods. The practices of the yield winning bean growers at to react to the plants’ mineral hunger during the later R stages by supplying the minerals using foliar applications. Dry soils are less able to carry minerals to the roots and up the stem to the leaves where the sugars are made. Minerals chelated by PO3 or amino acids are in the form best accepted and most capable of moving systemically in the plant.

With $12 to $15 soybeans in sight, now is the time when a dedicated high yield producer is asking what products would be capable of increasing their yields the most. There are a number of different of different minerals and product mixes that have been developed and shown to add bushels. The recipes for there vary between companies.

The minerals such as K, Ca, Bo, Cu, S, Mo and others are often mentioned. N mixes along with sugar, as well as biological components can also be important. Early season silica sprays to form a deeper layer of chloroplast containing cells can also factor in. Once the rows close application options are limited. Applying P and sugar at two to three week intervals will shorten internode length and plant height to permit ground applications later into the season. This can lower applications cost and decrease the risk of white mold becoming a problem.

Two very smart crops people shared their 2020 recipe with me. It produced a very significant yield increases for a number of fields to our east. We will post that on our website for interested growers. We also like the Seed Set and Advance for how they perform. I was in Kip’s field that yielded 154 Bu/A with a seed size of 1900 per lb. Wow, that is a lofty goal, but has been achieved.

 Leaf Cupping

The topic of Dicamba drift and volatilization and subsequent cupping and potential yield loss is still on many grower’s minds. Many have read a few current articles on the topic but still need an authority’s take on the matter. If they need to confront the guilty parties they need to know what amount of damage they can expect to see this fall at harvest time. The two best article and research papers were those by Drs Rich Behrens and Bill Lueschen at the Waseca Research Station back in 1979, and then the one by David Mortensen and his crew at Penn State. Mortensen gives actual yield results while the Waseca typically rated the injury levels.

A term that arose last season to describe the movement of Dicamba was ‘atmospheric loading’, meaning large clouds of the evaporated product formed on the hot, windy days and nights with dry soils and recently sprayed fields. Enough volatiles were in the air and descending on susceptible fields that identifying the offending party was difficult. In those cases, plants thru the entire field were evenly affected. When varying levels of damage could be observed pinpointing the nearly offending party (s) guilty party was possible. Harry Stine was included in one article and stated that he thought this drift damage was the most expensive crime every committed in many Midwest states. Having the two major traits named ‘Extend’ and ‘Enlist’ led to some of the confusion, so who wanted the buying public to be confused?

 

Other Tasks at Hand

Once the tasks of pollination and fertilization are completed by the plant, growers need to be observant about the health of their corn plants. In a best-case scenario, they have been thinking about plant health as they managed their residue program last fall, then when they formulated their fertilizer and planting programs over the winter. Delaying any action until then and relying totally on applying hard chemistry places too much of a burden on those products. This was discussed at an CCA training session last week. The presenters voiced the opinion that corn and soybean growers were going down the same pathway with fungicides as happened in herbicides where over reliance on one or two families over the last two decades led to their loss in efficacy.

As the plants’ energy sources become dedicated to reproduction and grain fill, and if moisture on the leaves become common, plants deficient in different minerals can develop serious leaf and/or stalk diseases. Those can include GLS, eyespot, Physoderma, NCLB, the New Goss’s, Tar spot and possibly others.

In soybeans the assortment of diseases can include Septoria, Frogeye spot, Cercospora leaf blight, bacterial pustule, brown stem rot, downey mildew, Charcoal rot or SDS. The incidence of each depends on mineral sufficiency, stage of growth, and duration and amounts of dew. As the days of August get cooler and the dews get heavier, previously clean fields often develop the diseases lesions if the inoculum is present in the soil or moves in from a southern source. Be sure to scout your fields with a known idea of diseases need to be assessed. Be equipped with pictured field guides and pertinent information such as soil and tissue test results for each field as well as knowledge such as projected yields, market value of the crop, treatment thresholds, and past ROI for each product.

 

Insect Notes

For those who planted conventional corn, be aware that the second brood of European moths are beginning to fly. Also note that Western Bean Cutworm moth trap catches have been very heavy in the UNL Concord station traps. Those eggs are tough to scout for and basically require a person to carry a stepladder into each field to find the eggs laid on the upper side of the top leaves. Why these insects are important is there can be up to 29 worms feeding on a single ear and the larvae will move up to 8 plants down the row in each direction.

SB insects remain low in the source areas for SB aphids in MN and SD, thus IA populations remain low. The most feeding damage on the pods has been done by bean leaf beetles This feeding often causes holes in the pod which allow seeds to rot and be lost to harvest. A good scout has to envision what pest or disease could reach damaging levels through the rest of August using past years pest and disease actions. Lots can happen during these last three weeks of August so be sure to stay on top of everything.

 

Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143 or www.CentralIowaAg.com.