Despite the generally cool weather conditions and lack of heat unit or growing degree day accumulation prevalent in the upper Midwest this summer, soybean is generally developing nicely in most areas of southern Minnesota and northern Iowa.Many fields I observed during the week of Aug 17 – 21 had already reached growth stage R5, and are continuing to progress toward maturity.Soybean development is about 4 - 5 days behind normal as of Aug 31, despite the fact that growing degree day accumulation is generally about 14 – 20 days behind normal as of August 31. Although soybean does respond to heat unit accumulation, it is generally less responsive to temperature than it is to shortening day length.This phenomenon is called photoperiod sensitivity.At the end of August, day length is already considerably shorter than it was at summer solstice, June 21.Soybean senses this shortening day length biochemically through the relative amounts of substances called phytochromes.Consequently, as days become shorter in the summer and fall, the ratio of different forms of phytochrome changes, causing the plant to hasten its advance toward maturity.This is why soybean has the ability to mature even when planted extremely late.
Although corn and soybean are both sensitive to both temperature and photoperiod, corn is generally more sensitive to temperature and heat unit accumulation than to daylength.As of Aug. 31, corn development is generally about 14 – 18 days behind normal.The corn crop looks very good in the upper Midwest, save for localized circumstances of hail or flooding.However it will require some good weather in September and October in order to mature properly.
Harvest Safety
Harvest season is statistically the time period when more on-farm accidents occur than any other time of the year.Farm equipment manufacturers have gone to great lengths over the last 30 years to make equipment safer and more user-friendly.Nevertheless, operator safety around farm equipment requires diligence and thoughtfulness.Everyone, myself included, sometimes gets in a hurry during harvest to get the maximum amount of work done during a limited harvest window.A few safety tips are worth reviewing by you and your employees before harvest starts in a month from now.
Stay rested.This is difficult to do, but extremely important.Operator stress, lack of sleep, and fatigue lead to many accidents during harvest.Establishing priorities and plans that include rest time for the operators will allow harvest to continue safely.
Make sure all harvest equipment is in good repair and operating condition BEFORE harvest starts.Replacement and proper adjustment of worn belts, chains, bearings, etc., will greatly reduce or eliminate the amount of down time during harvest.Reducing down time will reduce operator stress, fatigue, and over-exertion.
Shut down power equipment before making necessary adjustments or repairs.I know far too many people who have lost fingers or limbs or worse simply because they did not stop the power drive on equipment before working on it.
Replace all shields and guards properly before resuming operation.Shields and guards were installed by the manufacturer for operator safety.They are of no use if not in place.
I know all of you can add additional items to this list.Please do so.In fact, I recommend printing your list and posting it in your shop, at your desk, on the refrigerator, in your truck, in your combine, or anywhere else where it can be used as a safety reminder for you and your employees.Please, everyone have a safe and productive harvest!
Combine settings
Adjusting your combine properly for maximum, high quality crop harvest is always important.It is particularly important for harvesting identity-preserved soybean.Adjustments to cylinder speed, concave or rotary clearance, and cleaning fan speed and direction all help to harvest cleaner, higher quality grain with less split seed and damaged seed coat.
With soybean development later than normal this year, if cool weather continues to prevail through harvest, there may be a possibility for uneven ripening and some green pods to occur in soybean fields.Assuming your field is generally at harvestable grain moisture, it can be very tempting to adjust your combine more aggressively to thresh out some of those remaining wet pods that are coming through with the harvested grain.However this can cause excessive damage to the grain that is already dry and more easily threshed.It is relatively easy to clean out a few non-threshed pods from soybean if necessary after the crop is delivered to Rabbe Grain Company.It is much more difficult to remove soybean with damaged seed coats.
Insect Update
Most soybean fields in southern Minnesota and Iowa have developed beyond growth stage R5.5 by now, and thus are not prone to economic loss from aphid feeding.Soybean fields that were treated with an insecticide during the first two weeks of August generally had excellent aphid control.Despite some concern whether one spray treatment would be adequate this year, I neither saw nor heard of anyone needing to treat for aphids more than one time.
Further east in Indiana, Michigan, Ohio, and Illinois, there are a few replant fields or double crop fields planted very late that may still require aphid scouting until the crop reaches growth stage R5.5.
Corn fields scattered throughout Iowa were heavily infested with corn aphids this year.It is not uncommon for low or modest levels of aphid infestation to occur in corn.However this year’s outbreak was significantly larger than normal, and prompted some questions about whether treatment was necessary.There is little information regarding economic threshold levels for aphids in hybrid field corn.Some growers did spray insecticide.It will be interesting to see what kind of results they obtain.Hopefully a few untreated check strips were left for comparison.
Disease Update
There is a significant amount of Sudden Death Syndrome (SDS) showing up in many parts of Iowa in the last week or two.SDS is caused by a soil-borne fungus, Fusarium solani f. sp. glycines, which overwinters as spores on crop residue or freely in the soil.These spores will infect the soybean root as temperatures warm in the spring.Visual foliar symptoms of SDS start with mottling and mosaic of the leaves.Later, the leaf tissue between the major veins will turn yellow and then brown while the tissue near the major veins stays green.
This disease can often be confused with Brown Stem Rot (BSR), which can display similar foliar symptoms.SDS can be distinguished from BSR by splitting open the stem and tap root.SDS-infected plants will display tan or light brown discoloration in the root crown and lower stem while the central portion of the main stem will be white or cream-colored.BSR-infected plants will display a healthy root crown while the central portion of the main stem is discolored.
There is little that can be done to treat for SDS once it has infected a soybean plant.Depending upon the type of soil, any tillage or non-tillage practices that improve soil drainage may reduce the severity of infestation.Use of SDS-resistant varieties is also useful.Selection for genetic resistance to SDS in a breeding program is difficult because the causal organism is difficult to culture.In addition, it is difficult to know beforehand exactly where an outbreak of SDS is going to occur in order to plant a variety test in the outbreak site.Galena Genetics grows yield trials at numerous locations around the Midwest in order to expose our genetic trials to as wide a diversity of environmental conditions, including diseases like SDS, as possible.Wherever SDS symptoms do happen to occur in a given year, resistance ratings are scored and selections are made.
