C.O.R.N. Newsletter: 2015-29

Kaylee Port was also a contributor to this article

2015 represents another unique cropping year due to the wet weather conditions during spring planting and persistence through July.  The result has been many fields with highly variable soybeans conditions with a few containing short soybeans.  The variable crop conditions translate into variable harvesting conditions in terms of moisture and height.  Therefore, proper setup and pre-season maintenance along with correct adjustments during combine operation will be important for the 2015 soybean harvest to minimize loss and bean damage. 

Proper combine settings and attention to detail during soybean harvest reduces harvest losses.   Short soybeans are especially difficult to feed into the header and through the combine.  Short beans are difficult to convey into the header because they are often podded lower to the ground which increases the risk of loss.

A few simple combine adjustments can help to prevent grain damage and harvest loss.  Two areas of focus for combine operators in 2015 should be ground speed and combine header settings to keep crop loss to a minimum.  As a combine operator, material fed incorrectly into the header significantly impacts grain quality and loss.  Consider, two important points:

-          4 soybean seeds per square foot equates to a 1-bu/ac loss.  Acceptable harvest loss is 3% or less (approx. 1-2 bu/ac) in soybeans but improperly adjusted combines or an operator not paying attention to details can generate errors of 10% or higher, and

-          80% of harvest loss occurs at the header.

2015 is a year that operators need to focus on details and changing of soybean conditions. Checking harvest loss will be important to keep the combine adjusted properly, especially in short and variable soybeans. Total harvest loss can occur in three areas: 1) pre-harvest soybeans, 2) header and 3) combine. One should check these three areas within different locations in a field.  Checking behind the combine represents total harvest loss but one must check pre-harvest loss before combining an area as well as just in front of the header (header loss).  Combine loss equals the total harvest loss minus the pre-harvest loss.  Checking all three areas determines if and what combine settings must be adjusted, especially header loss. 

One of the first items for the season is to review the owner’s manual and/or consult your local combine dealer for help on proper combine settings specific to the crop and harvest conditions.  The following provides a few suggestions on adjustments and operation factors in variable and short soybeans:

• A floating, flexible cutterbar and automatic header height control can improve the ability to maintain the header low and level to the ground during harvest.

• Take time and slow the combine down.  Slowing up 0.5 to 1.0 mph in areas where harvest loss might be risky. 

• Keep the cutter bar as low as possible for short soybeans and those that are dry.  This point is important in areas with low plant populations and where more pods are on the lower portion of the plant, nearest the ground.

• Shorter soybeans require smaller clearances between the reel, cutter bar, auger and the feed conveyor chain, to ensure stems are feeding through the platform and into the feeder house.

• Check knives, guards, ledger plates and wear plates.  Keep spares handy in 2015.  

• Ensure the sickle is sharp. Dull sickles tend to push stems over rather than cut them cleanly.

• Make sure to properly adjust guards and header to proper engagement angle as outlined in the operator’s manual.

• Check that stems are being cleanly cut across the header.  If not, check for dull blades, improperly set header angle, other incorrect header settings, or reduce your ground speed.

• Keep an eye on reel speed and adjust to match soybean conditions and ground speed within the field.  The rule of thumb is to keep reel speed ~25% faster than ground speed. 

• Make sure the feeder house relative to the header is at the proper adjustment to keep material feed as efficient as possible.

• Importantly, make sure chains and bearings are properly lubricated and serviced on their stated time intervals.  Belts should be tight and checked routinely.

This summer’s weather caused problems with weed control in some areas of the state, and this certainly includes our two major weeds, giant ragweed and marestail.  As we move through harvest and into the season of wheat planting and fall herbicide application, be sure that strategies effectively address marestail since there is an abundance of marestail seed blowing around.  The larger plants evident now in wheat stubble or above the soybean canopy may be producing seed, but these are not the plants that will overwinter and cause problems next spring.  The small marestail plants that have just recently emerged or will emerge yet this fall are a primary target of fall weed control, along with other small, emerged winter annual weeds that can overwinter and have a negative effect on wheat the following spring.  This includes chickweed, deadnettle, annual bluegrass, mustards, etc.  Herbicide treatments at this time can also have considerable activity on biennials (wild carrot, wild hemlock), dandelion, and Canada thistle, although herbicides are often more effective on these weeds later in the fall.  The larger summer annual weeds (ragweeds, marestail larger than rosettes, foxtails, etc) are going to die after the first hard frost, and soybean harvest decimates these weeds to the point that herbicides won’t be effective on them anyway.  Where wheat is planted into a fallow situation, it may be necessary to target the large summer annuals with herbicide in order to ensure that they do not interfere with planting or wheat stand establishment. 

Herbicide options for burndown of existing weeds prior to planting of no-till wheat include glyphosate, Gramoxone, Sharpen, and dicamba.  Among these, the combination of glyphosate and Sharpen probably provides the best combination of efficacy on marestail, flexibility in application timing and residual control.  Dicamba labels have the following restriction on preplant applications – “allow 10 days between application and planting for each 0.25 lb ai/A used”.  A rate of 0.5 lb ai/A would therefore need to be applied at least 20 days before planting.  We do not know of any 2,4-D product labels that support the use of 2,4-D prior to or at the time wheat planting.  There is some risk of stand reduction and injury to wheat from applications of 2,4-D too close to the time of planting.  Liberty and other glufosinate products are also not labeled for use as a burndown treatment for wheat.  Sharpen should provide limited residual control of winter annuals that emerge after herbicide application, and the rate can be increased from 1 to 2 oz/A to improve the length of residual.  Gramoxone should also effectively control small seedlings of marestail and other winter annuals.  Be sure to use the appropriate adjuvants with any of these, and increase spray volume to 15 to 20 gpa to ensure adequate coverage with Sharpen or Gramoxone.

There are several effective postemergence herbicide treatments for wheat that can be applied in November to control these weeds, in fields where preplant burndown treatments are not used.  The most effective postemergence treatments include Huskie or mixtures of dicamba with Peak, tribenuron (Express etc), or a tribenuron/thifensulfuron premix (Harmony Xtra etc).  We discourage application of 2,4-D to emerged wheat in the fall due to the risk of injury and yield reduction.

Excessive rainfall (which contributed to N loss and poor root development) followed by late season drought had a major impact on ear and kernel formation in many Ohio corn fields this year. Poor ear and kernel development is associated with variability in plant growth within fields that is related to differences in the timing and duration of soil saturation.   In some areas within fields subject to protracted saturated soil conditions, ears are absent (“barren”) or severely reduced in size with a few scattered kernels (nubbin ears). Affected plants often appear stunted and yellow due to N loss and restricted shallow root systems. Where the impact of excessive moisture was less pronounced and plant height and color look normal or near normal, ear cob size may be normal but kernel number is markedly reduced. No kernels may be evident on the last two or more inches of the ear tip. Several factors may cause this problem. The ovules at the tip of the ear are the last to be pollinated, and under the stress conditions only a limited amount of pollen was available to germinate late emerging silks. Pollen shed was complete or nearly complete before the silks associated with the tip ovules emerge. As a result, no kernels formed at the ear tip. Uneven soil conditions and plant development within fields may have magnified this problem. Pollen feeding and silk clipping by corn rootworm beetles and Japanese beetles can also contribute to pollination problems resulting in poorly filled tips and ears.

Incomplete ear fill may also be related to kernel abortion. If plant nutrients (sugars and proteins) are limited during the early stages of kernel development, then kernels at the tip of the ear may abort. Kernels at the tip of the ear are the last to be pollinated and cannot compete as effectively for nutrients as kernels formed earlier. Although we usually associate this problem with drought conditions, the stress conditions that occurred this year, such as N deficiency, excessive soil moisture and foliar disease damage, may cause a shortage of nutrients that lead to kernel abortion. Periods of cloudy weather following pollination, or the mutual shading from very high plant populations can also contribute to kernel abortion. Some agronomists and farmers characterize the kernel abortion that occurs at the end of the ear as “tip dieback”, “tip-back”, or “nosing back”, although poor pollination is also usually a factor affecting poor kernel set at the tip. Kernel abortion may be distinguished from poor pollination of tip kernels by color. Aborted kernels and ovules not fertilized will both appear dried up and shrunken; however aborted kernels often have a slight yellowish color.

Zipper ears are another ear development problem evident in some fields. Zipper ears exhibit missing kernel rows (often on the side of the cob away from the stalk that give sort of a zippering look on the ears”).  The zippering is due to kernels that are poorly developed and/or ovules that have aborted and/or not pollinated. Zippering often extends most of the cob’s length and is often associated with a curvature of the cob, to such an extent that zipper ears are also referred to as "banana ears". For more on these ear development problems and others ear abnormalities, check the following: “Troubleshooting Abnormal Corn Ears” available online athttp://u.osu.edu/mastercorn/