Controlling Cheat and Annual Ryegrass in Small Grains Using Novel Crop Harvesting Technologies (AS96-025)
Since McCormick first invented his reaper about 150 years ago, the age old drudgery of grain harvesting has slowly yielded to mechanization. After decades of gradual improvements, the grain binders and stationery threshing machines were finally joined together into machines known as “combined reaper-threshers” and later called combines. Over the past 75 years, the primary function of grain combines has remained the same—collect the grain crop and return everything else to the field. An advantage of the old grain binder plus stationery thresher harvesting system was that weed seeds were carried off the field with the bound shocks of grain. Our project goal was to regain this advantage by advancing grain harvesting technology to include separate collection of the seeds of weedy grasses, particularly cheat and Italian ryegrass, that now pass through a combine and return to the field.
1. Investigate three distinct modifications to conventional grain harvesting procedures designed to either
remove cheat and annual ryegrass seed from the field during the wheat harvesting process or devitalize
2. Evaluate the new harvesting procedures as a component of an integrated cultural grassy weed control
3. Determine the economic feasibility.
4. Disseminate our findings.
A series of field experiments were conducted to evaluate the performance of harvesting equipment attachments whose functions was to retain weed seed as wheat was harvested, in contrast to discharging the weed seed back onto the field. A Redekop® chaff collector, purchased from the Canadian manufacturer, was a well designed machine wheat gave no mechanical problems. It did a very good job of collecting chaff and weed seed discharged over the cleaning sloe.
However, the collector choked the air flow from the combine separator causing excessive amounts of weed seed to be deposited in the clean grain bin. Subsequent research focused on readjusting the combine separator air fan flow, to deliberately collect the weed seed with the harvested wheat, and removing the weed seed with a field portable aspirator cleaner before the wheat seed was delivered to the grain buyer.
A Kice® aspirator and appropriate drives and a grain holding tank were mounted on a tandem trailer and evaluated in on-farm tests. The aspirator was highly efficient and reduced dockage of cheat infected wheat from about 25% to less than 1%. Disadvantages to this approach were the cost of the field portable cleaning unit, and the extra labor and time required for conducting the in-field recleaning operation.
To overcome these problems of the field-portable aspirator cleaner system, an on-board aspirator cleaner was designed and installed on the Gleaner M2 combine. To overcome the requirement for separate storage of the weed seed removed by the on-board aspirator-cleaner, a hammer mill was designed, tested, and installed on the combine. Materials removed from the wheat grain flowed through the hammer mill, which effectively destroyed the weed seed, which was then returned to the field. The design also allowed collection of the aspirator material rather than passing it through the hammer mill, in order to inspect and quantify the materials removed from the wheat grain.
In Italian ryegrass infested wheat, reducing the air flow across the separator fan increased material removed by the on-board aspirator from 12 to 149 lb/a. However, the on-board aspirator was of inadequate capacity to effectively clean the wheat. In one experiment, recleaning the wheat cleaned by the on-board aspirator revealed that up to 108 lb/a of Italian ryegrass seed remained in the wheat.
At another site, the on-board aspirator removed up to 219 lb/A of materials from the grain before it entered the combine grain bin. However, another 308 lb/A of cheat seed remained in the wheat. Despite removing such large quantities of weed seed during the harvesting process, the weed seed content of the succeeding wheat crop was not affected by such removal. This was attributed to plasticity of the weed population which allowed a smaller number of weeds to produce the same amount of seed as a larger number would have. At one site, removing Italian ryegrass seed during harvesting did increase the yield of the succeeding crop 3 bushels/A indicating a very positive benefit of weed seed removal.