AMES, Iowa -- Significant late-August rainfall in some areas creates the possibility of harvesting in wet, muddy fields. It’s a frustrating situation when added to other harvest issues. Combine operators need to accept that harvest likely will not be routine in these areas and recognize that extra time may be required, says Mark Hanna, Iowa State University Extension agricultural engineer.
“Make a careful assessment of the situation prior to harvest,” Hanna said. Potential issues include wet soils and lodged crop from storms or floodwater. Each situation is unique and different combine operators will respond in various ways according to the conditions.”
If discrete soil areas within fields are wetter, additional soil drying is anticipated and the crop is standing well, these areas may be harvested more conveniently later in the season, he said. Traction may be better then and operators may be able to avoid soil compaction by ruts. However, waiting as late as soil freeze-up will not be an option for most situations. Conversely, if wet weather and the advance of colder temperatures limit drying potential, or if stalks are starting to lodge, harvesting these areas earlier in the season may avoid more excessive harvest problems later. Soil compaction potential is greater in wet soils; however, winter freezing of soil moisture may help alleviate this.
Hanna offers the following tips.
Traction can be difficult in wet soils. Check the condition of tires and inflation pressures. Review the operator’s manual section on tires and traction. Check with the dealer or manufacturer on suggested methods of pulling the combine out of mud. Some operators raise the head when drive wheels begin to slip excessively so that the front axle is accessible. Check with the dealer or manufacturer before adding tracks or different tire sizes. If using tracks, tension may need to be adjusted with soil conditions.
If lodging is present, how many acres are lodged? How severe is the lodging? What percentage of the total acres that must be harvested does this represent? Will labor and equipment availability be adequate to handle the situation? Generally, lodged fields should be harvested when they are first ready to avoid increased lodging by further stalk disease development or wind storm.
To evaluate possible changes that may improve crop pick-up, it is important to measure losses in the field behind the combine. Losses at the head are the most common source of machine loss in lodged crops. Each 3/4-lb. corn ear found in a 1/100 of an acre plot equals a loss of one bushel per acre. For example, an operator using an eight-row 30-in. corn head (20 ft. wide) would check an area 21 ft., 9 in. long and eight rows wide behind the combine (area equals 435.6 sq. ft. or 1/100 of an acre). Finding five 3/4-lb. size ears would equal a loss of 5 bushels per acre. For loose grain, two corn kernels or four soybeans per square foot on the ground equals one bushel per acre field loss.
Slowing combine travel speed may reduce the amount of missed crop. Harvesting “against the grain” (e.g., harvesting toward the west in east-leaning stalks) may also reduce losses. Evaluate possible improvements by measuring losses. For corn, make sure ear savers on the corn head are in good condition. Keep gathering snouts as low as practical to pick up downed ears. Gathering chains may need to be more aggressive. Place stripper bars closer together if ear butt-shelling occurs on the stalk rolls. For soybeans, check adjustment of the floating cutterbar and header height control. To adjust clearance between reel pick-up tines and a floating cutterbar, rest the cutterbar on a 4 inch by 4 inch block and adjust the reel so that tines come no closer than 2 inches to the cutterbar.
If many acres of severely lodged crop are present and the window of time for harvest is anticipated to be short, consider procuring a corn head reel and/or crop dividers for corn, and lifters, or a pneumatic air reel for soybeans. Several after-market manufacturers market corn reels that can be mounted over the corn head to help lift and guide stalks into the head. Check availability through dealers or the Internet. Crop dividers mounted on each side of the head help to lift corn ears into the head that might otherwise escape. Lifters help guide soybean plants over the cutterbar. A pneumatic reel blows soybeans and plants on to the grain platform. Even if attachments do not decrease losses, they may allow faster combine travel speed with similar losses, allowing harvest to proceed in a more timely manner.
Grain or soybean size was likely set in many fields prior to damage from standing water. Although narrowing of chaffer and sieve openings in the cleaning shoe won’t be necessary if grain size isn’t reduced, fan speed may need to be lowered slightly if corn test weight is lighter. Increase fan speed until just below the point where losses behind the combine are unacceptable.
Most importantly for a successful and safe harvest, develop the right attitude. Recognize that harvest will not be business as usual, but more time and effort will be required in areas with lodged crop or wet areas with poor traction. Don’t let the inherent safety hazards involved compound field problems with the loss of your time during harvest. Stalk rolls pull in crop at about 12 feet per second, much faster than reaction time to release the grip on a stalk. Do not attempt to unplug plant material from the head before disengaging power to the head and stopping the combine engine. Remove the operator’s key if there is any chance that another person will be in the cab. Attaching a pulling cable to the wrong area on a combine frame can damage equipment and/or injure bystanders. Take the time to have a safe and efficient harvest. Rushing through activities, particularly early in the season before any weather-related pressures have developed, can be counterproductive.
Post-harvest tillage operations
After heavy mid-season rainfall in 1993 an Iowa State University study found no differences in corn or soybean yield following light (field cultivate and plant), intermediate (chisel plow or disk) or deep (subsoil, rip) tillage in fields in southeast Iowa. Although a natural tendency is to want to actively “fix” a current soil problem, tempering of soil by winter field conditions and favorable 1994 weather negated effects of fall 1993 primary tillage. Carefully assess why tillage may be necessary before taking action. Localized tillage to level severe ruts created in a few places may be necessary before planting without tilling the entire field. Beware of creating additional soil compaction and smearing by tilling soil that is too wet at the depth being tilled to fracture properly.