Typically, mid thru late July is the time for the county fairs, with their livestock exhibits and grandstand entertainment, leading up the state fair and finally the Clay Country extravaganza. But not this year. Already the county fairs, state fair and Farm Progress Show have all been ‘postponed into 2021. We have to hope that society will have calmed down by then and life, school and baseball are back to normal. Those have all been events we have been able to participate in and enjoy in the past. There have been a few livestock expos to substitute for them, but it’s just not the same.
As we enter the last week of July things could go either way as to yields. Most measurable rains seem to have been diverted away from western Iowa with I-35 seem to be the dividing line. Right now the Ames area has received about 7” of precipitation during the growing season while Waterloo has measured nearly 15”. There are chances for western Iowan to get a few showers this week, but so far this summer most of the fronts have dried out as they moved over eastern Nebraska. In my check of the U.S. Drought monitor 73% of the High Plains states are in the extremely dry to moderate drought category. This includes NE, KS, ND, SD and OK. The Midwest region, which includes IA, MN, MO, WI and IL has 34% of their territory in the abnormally dry to moderate drought category. The % of the territories in coverage and severity of drought conditions increased dramatically in the past week. This is exactly while the corn has been pollinating and kernels are early in their formation stages.
Strong Winds and the Aftermath
When some of those rains did arrive this past week they came very strong winds that clocking up to and over 60 MPH. The first feeling the corn growers felt when they saw many of their corn fields holding flattened corn was a sick feeling of apprehension as plants that had been 6 to 8 feet tall were now one to three feet. A high percent of those fields looked much improved within 2 – 3 days as most of those fields grew brace roots that righted the plants and appeared to be none the worse for the experience. Questions arose as to why so many acres were affected. A knowledgeable crops person could point to four potential causes: 1: Genetic families differ in root size, shape, depth of soil penetration, and ability to regrow to form new roots. 2: With flat sweeps on most field cultivators smear layers can be formed down 3 to 4” that restrict root penetration. 3. The corn plants added about 48” of growth in about ten days. Normally rooting depth matches top growth. This year when the soils warmed up the plants focus was on adding plant height and new leaf tissue and often did not have excess energy and sugars available for root growth. Typically, when root lodging occurs there is heavy CRW feedings. That wasn’t the case this year.
The question from growers was “will the plants stand up”, “will the plants it be healthy thru fall”, and “might the yield be affected”. The answers to all of those typically started with ‘it depends’. For many Nebraska farmers the issues were with hail and greensnap. For those unfortunate growers the answer to greensnap is that final yields are typically trimmed by the same percentage that the stalks were snapped at. Research done in that state showed the yield reduction comes from the diversion of plant energy away from silking and pollination to forming new root tissue. They give a yield reduction estimate based on stage of growth of the corn plants. Corn blown over at V10 to 12 typically show a 2 -6% loss; V13 to 15 plants show a 5 to 15% reduction, and at V17 and later the loss was projected to be 12 to 31%.
Corn that got flattened just before tasseling that does not return to upright can get hit with a 50% yield loss it the rest of the summer is hot with high humidity. That happened back in 1985 east of Carroll. The horizontal plants get cooked. If the temps thru the rest of July and August are moderate or cooler and rainfall is moderate the yields can be close to normal. That was the case west of Marshalltown about two decades ago.
Excessive Temperatures
So far June and July have been excessively hot. Fields in the SW 1/4th and west central part of he state have seen their corn leaves roll for the last three weeks and often take on the ghastly gray green color. What will be occurring in such fields? Elwynn Taylor uses a figure called accumulated stress days. The optimum temp for growing corn is typically believed to be 86 F. There can be a GDU gain when temps exceed 86 F and up to 92 F if that plant has sufficient moisture. When the plant is short of moisture and temps exceed 86 it is considered under stress, which reduces yields. In Dr. Taylor’s and Louie Thompson’s long term observations and calculations when stress days exceed 140 for the season the corn yields will be X bushels less than trend line. The current Iowa Mesonet figures as of 7/20 show a few locations are already close to 140. For example, Clay Co is already at 153. Carroll Co is at 131. Cass Co is at 148. Story Co is at 98. Much of extreme SW IA is 112 to 147. If the temperature predictions for the next few weeks proved correct and are in the low to mid 90s the cumulative totals could greatly exceed 140 by a wide margin.
The question then is ‘what will be the effect on yield’? The calculations aren’t clear to this rookie meteorologist, but the guidance given by Louie Thompson was that if the July temps average 4 F above normal, corn yields could be diminished by 600 K/ha. That is verbatim from the Agronomy 541 lesson. That translates in our measurements to a yield decrease of 9.5 Bu/A. Does that mean that July temps ran 8 degrees above normal the yields would be reduced 19 Bu/A? How about having a SDD above 200 by the time August is over with? We are going to examine Dr. Thompson’s old papers.
The common assumptions are that we cannot do anything about the temperatures and weather extremes. That was in the past. There are now several things that can be managed to help crops survive drought and heat. Improving soil health and increasing microbial life will improve rainfall infiltration, lower soil temps, and will allow soil biology to serve as a moisture reserve. The use of cover crops can play a large role in both. Keeping mineral levels high allows corn tolerate drier conditions. Fertilization with silica can increase moisture use efficiency by 33% by building a more intact vascular system.
Two new items to add to the above list from the last two years would be a seed treatment or foliar application of BioEnsure (Protect + or Heat Shield) that allows plants to tolerate temps up to 160 F. There is also a new product called Respite from BioDyne Midwest that when applied foliarly will lower the canopy temps by 8 to 9 degrees for two to three weeks per application. Thermographic imaging done in NCGA winning contest fields showed the product slowed ethylene formation and told the plants to keep forming sugars. That product is still available and can be applied for about $3/A. Dr. Isolde Haun Hahn, head of fungicide physiology research with Bayer, was gracious enough to give me her morning time when I was at their headquarters and open her books showing me the value of ethylene inhibition properties of the strobe fungicides. Keeping the plant canopy cooler is important.
Insect and Disease Issues
Currently the damaging insect populations are remaining low for all insects except Japanese Beetles. My best results in terminating them two weekends ago were with a combination of Mustang and Steward. Hero has been effective for me in the past. Be sure to lower the water pH to 5.5 and add oil to penetrate the chitin shell. We have also heard that a combination of O2YS (a chitinase elicitor compound) and Beauveria bassiana foliarly worked very well against this insect. Make a point to apply the BB to grassy areas as an inoculant as their eggs are laid there and their larvae feed on grass roots in the spring.
Aphids are appearing in SB in northern Iowa but at almost invisible levels. Unless they explode in numbers in S Dakota or Minn in the next few weeks it would be difficult to justify making a preventative application at R3. Maintain high Mo and Mn levels in your bean plants.
Leaf disease incidence remain at low levels in western IA but will increase in wetter areas to the east. In recent weeks I am seeing the first GLS and common rust at very low levels. Physoderma stalk lesions have become common with infected plants seeming to be very brittle at the lower internodes.
In soybeans the pathogens which can be found are early Septoria, which is the norm as rows close, a bit of bacterial spotting, and Cercospora. The evaluation and decision to apply a fungicide to beans should take maturity of your varieties into account. Fuller season varieties typically benefit the most from a strobe or strobe mix application. Remember that strobes alone are not controlling Cercospora any longer. Strobe and Triazoles don’t move systemically as do the carboxamides. Thus coverage and gallonage are important to their successful use.
The field observations on the Impulse treated fields are impressive. Having a nearly full spectrum of minerals applied in s fully systemic mix has definite benefits. Even in those fields one or more applications thru R4 and R5 of a targeted mineral mix will plump bean size by 20 to 40% to offer high ROI benefits. I was in Kip’s field that yielded 154 Bu/a and used a very precise lab scale to measure his bean size: approx 1915 per lb. I still have some of his plants stored in an acrylic cylinder for viewing.
My quiz of the week. What is an Ibex? It can be a type of goat. It can also be a growing system developed by an inquisitive and innovative specialty crop grower from Fort Wayne, Indiana that the BioDyne Company is partnering with. It offers great ease in producing several food crops grown in very profitable ‘pick your own’ operations where healthy, locally grown food is in demand.
Lyme Disease Summit
Microbe Formulas was instrumental in developing the Farmer’s Shield product bundle to detox glyphosate and other toxins from the body. You may have seen Dr. Allan Lindsley and Ryan Riley speak at our conference earlier this year.
Microbe Formals is putting on a FREE on-line Lyme Disease Summit from July 27 – August 2. Over 36 specialists will be talking about Lyme Disease and how it affects the body. Difficult to diagnose and treat, Lyme disease has over 150 different possible symptoms: fatigue, mood problems, insomnia, neurological impairments, brain fog, migraines, gut issues, neuropathy, joint pain and others. If not properly treated, over time Lyme disease becomes chronic and can manifest in autoimmunity or a number of other degenerative, debilitating health issues. Sign up for the summit by going to https://chroniclymediseasesummit4.com/.
Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143 or www.CentralIowaAg.com.