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Cooperative Extension Service |
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Agricultural
Experiment Station |
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Aquaculture
Dale Bumpers College
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Wheat Production in Arkansas
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Sample Moisture Discount (% of wheat weight) |
Wheat Harvest Moisture Range for Equal Market Value |
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3.0% for wheat at 15% m.c. |
15% 12% |
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5.5% for wheat at 16% m.c. |
16% 10% |
Standing wheat is one of the easiest crops to harvest. Adjust header height to minimize the straw gathered with the grain. Watching a yield monitor or loss monitor highlights how important it is to readjust cutting height as the wheat height varies. The combine performs at peak efficiency when a uniform flow of grain/straw enters the combine. This uniform feeding and the draper header’s ability to harvest any crop are reasons for purchasing a draper (triple conveyor belt) header. Erratic crop feed into the combine complicates threshing and separating, increasing field loss and, possibly, kernel damage.
Stripper headers minimize material other than grain entering the combine. This increases the threshing and separating capacity or the potential for increasing forward speed. Properly setting the stripper requires careful attention to the "hood" height, header height and stripping rotor speed. The grain is removed from the head and gathered into the combine in one step. Make one adjustment at a time while monitoring gathering loss, kernels remaining on the standing grain, sieve and walker loss and the foreign matter reaching the grain tank. Smooth fields are essential for maximum utilization of stripper harvesters because rough ground can limit forward speed to well below the threshing and cleaning capacity of today’s large combines.
Combines need to be adjusted for the wheat moisture content, the amount of straw that is gathered, grain weight (heavy or light heads) and the amount of weeds in the field. Check the initial thresher, concave, sieve and fan settings in your Operator’s Manual. Operators should use the slowest rotor or cylinder speed and the widest concave spacing possible. These settings should be only aggressive enough to separate the grain from the stalk. Operator’s Manuals generally provide a good initial setting. Consult the Operator’s Manual for your stripper to obtain threshing and cleaning settings and the proper options because they typically vary from the combine manufacturer’s suggestions. Applying experience and judgment to field conditions helps improve or "fine-tune" the combine adjustments, ensuring an excellent job.
Rotary combines do an excellent job in wheat, and the same basic principles apply to them. Research indicates they may cause slightly less kernel damage.
Adjust threshing speed or aggressiveness for field conditions. Changing moisture contents and different wheat varieties often affect the ease of kernel removal. Generally, the following principles apply:
Thresher Speed – Faster than soybeans and sorghum; slightly faster than rice; about the same as oats.
Concave Spacing – Not as critical with the spike-tooth as the rasp bar, but generally about like rice and narrower than soybeans.
Sieve Openings – Initial chaffer sieve opening doesn’t vary much from other crops but cleaning sieve generally should be closed down.
These are general guidelines. With the spike-tooth cylinder, some "hulled" or damaged kernels will appear in the bin, even before all the grain is threshed out of the heads. Be careful not to use excessive threshing cylinder speed if wheat is to be harvested for seed. Judge threshing performance by three keys:
1. Damaged kernels
2. Kernels remaining in the heads
3. How pulverized straw is before going through a chopper
With uniform feeding, good threshing and separating shouldn’t be difficult. Total field losses due to the combine shouldn’t exceed 1 bushel per acre. If wheat losses were spread uniformly over an acre, approximately:
21 seeds per square foot = 1 bushel per acre
Not using enough air or enough fan speed is a common failure. A good blast of air is necessary to "tumble" chaff at the front of the chaffer. A good air pattern keeps chaff bouncing nearly to the back of the chaffer, permitting wheat to drop through. Open the sieve until some foreign matter appears in the bin. Then, increase the air speed or aim the baffles or reduce the covering on the fan intake. If a little clean grain appears in the tailings, adjustments are about right. If more wheat appears on the ground behind the machine, you have blown some over. Reduce air accordingly.
The following flow chart is a good step-by-step method of diagnosing harvest losses and correcting them in the field.
Grain loss monitors are helpful for optimizing operating adjustments and combine forward speed. The sensors must be properly installed in the straw and chaff discharge to intercept wheat that leaves the combine. The sensitivity may have to be set to assure that only grain and not straw segments are triggering the sensors. Calibrate the monitor for wheat by occasionally checking the ground behind the combine to verify that observed harvest losses are proportional to the signal in the cab.
Temporary monitor fluctuations can be overlooked. However, observing a monitor and the field conditions will quickly highlight conditions that increase field separation loss. An alert operator "fine-tunes" thresher speed and forward speed to use the combine’s capacity while reducing wheat loss.
Always make only one adjustment at a time. Then check the combine performance under normal load. Count losses in the field, evaluate the bin sample and monitor the tailings throughout the harvest day.
Yield monitors basically provide actual dry weight yield, based on a moisture sensor and a grain flow sensor that are electronically calibrated to estimate yield at every point in the field. The bushel per acre information they provide has and helped growers to identify the benefits of good drainage, superior varieties and evaluate various fertility treatments or pesticide applications. New uses continue to develop.
Yield monitors have been very accurate and trouble-free in standing wheat. Both the global positioning system (G P S) with mapping capability and the non-recording, instantaneous, non - G P S models provide valuable management data. It is essential to cut a constant width (near full header width) to get accurate yield per acre data. This is the only source of error that should exceed 1 or 2 percent. Occasionally, light rain or heavy dew on the surface of the kernel will bias the actual average moisture content and consequently the field yield. (Computer adjustment of the weight based on surface moisture may bias the yield, typically showing yields much lower than actual when the surface of the kernel is damp.)
Soybeans are typically seeded after wheat. They can be no-tilled immediately behind the combine if the combine discharge isn’t concentrated. Chaff spreaders distribute the discharge from the shoe and strawchoppers distribute the discharge from the strawwalkers/rotor. For Case combines, an inexpensive chaff spreader attaches to the bottom of the straw spreaders. Growers with several other combines may need a hydraulic-drive chaff spreader. With a good chaff spreader, residue from top-yielding wheat doesn’t hamper a good no-till seeding rig, if the combine isn’t temporarily stopped while threshing. Strawchoppers are effective, but typically increase operation cost.
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University of Arkansas • Division of Agriculture |
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