Early Harvest Agronomic Update

We asked Glenn Longabaugh, Regional Agronomist for Winfield United, to give us an agronomic update as we move right into Harvest 2020.

Corn has progressed very quickly and the April plantings have reached physiological maturity. May and June planting should have reached physiological maturity this week, the first week of October.

How could corn planted so different temporally mature so near the same time, you might ask? Remember that April plantings experienced very sub-optimal temperatures this spring and accumulated GDD’s (Growing Degree Days) very slowly. This slow accumulation hindered emergence and early development which allowed the later plantings to keep pace, effectively compressing maturation into a much shorter window than what you might expect. 

Corn yields look good to excellent and late season foliar health is considerably better than what you might expect. Why is the corn as free of pathogens as it is? First, the diseases that normally impact our yields most, like Grey Leaf Spot were impeded because of dry conditions earlier in grand growth, discouraging their jump from residue to the lower leaves of the plant. Second, when corn did get flowering and the plant was more susceptible, we also started getting timely rainfall. That would normally lead you to expect disease to go rampant. Why didn’t it? Those tropical depressions that brought us rainfall a month or better ago didn’t come as a single event, rather it was several rainfall events and cooler temps. Those rainfall events that deposited a few spores and created enough moisture for them to germinate came in such a sequential manner that it also washed off the largest portion of the inoculum. Just an example that we are not always so clever at prognosticating epidemics! Lastly, I would like to think that the increased use of early fungicides has had some impact on overall plant health and inoculum levels.

Soybeans are also progressing well and with the timely August rainfall it could be one of our best soybean years ever. It’s important to remember that even with intensive management the story of soybean yield is most often written in August and we had excellent soil moisture in the 8th month. Early maturing soybean fields that are being harvested are bearing that out.

With the abundant rainfall comes some issues in soybeans that are concerning. First many fields suffered from anaerobic conditions long enough that it actually smothered the plants and symptomology ranges from chlorosis, (yellowing) to full necrosis (brown/dead tissue). Those fields that are chlorotic are showing this symptomology from various reasons yet unfortunately most have not immediate solution. 

Why did soybeans turn yellow early? 1) Oxygen, soybean roots do not photosynthesize but, they do respire, and saturated conditions lead to an anaerobic environment. 2) Nitrogen, soybeans are intensive users of nitrogen and the estimates are somewhere between 4-5 lbs are necessary per bushel of soybeans. We don’t supplement soybeans with nitrogen because we expect Brady Rhizobium to live in symbiosis with the soybean roots and produce enough ureides (organic nitrogen compounds) to fulfill the soybeans needs. By R4 ureide production is already waning and anaerobic conditions only exacerbate the problem. 3) Sulfur and manganese are also limiting mineral nutrients that are causing chlorosis in fields exposed to too much rainfall. 4) Disease: Stem Canker, Charcoal rot, Brown stem rot, Phomopsis, Sclerentinia white mold, Phytophthora root rot and of course Sudden death syndrome (SDS) all have culpability in predisposing crops. 

With the yield advantages of early planting comes the caveat of increased soil borne pathogens, but SDS is probably the most common and thus the most yield-reducing of the group. SDS is the common name for Fusarium Vurguliforme a soil borne pathogen that cannot be treated in season and typically causes premature death by plugging the vascular system and causing premature senescence. Even tolerant varieties often have SDS but can finish seed production before succumbing to the symptoms. Variety selection and seed treatments are the best line of defense against SDS.

Lastly, Soybean insect pressure in August and September really ballooned, especially stinkbugs. (I guess they finally found their way out of our laundry room.) For future reference, we do not often think about amendments in August but, depending on planting date and maturity, R4 soybeans that are still 30-45 days from physiological maturity, so pod sucking is not acceptable!

Our Harvest Land team wishes you a safe and bountiful harvest.

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