Controlling Cheat and Annual Ryegrass in Small Grains Using Novel Crop Harvesting Technologies (LS96-081)

Final Report for AS96-025

Project Type: Research and Education
Funds awarded in 1996: $0.00
Projected End Date: 12/31/1999
Matching Non-Federal Funds: $248,935.00
ACE Funds: $208,624.00
Region: Southern
State: Oklahoma
Principal Investigator:
Thomas F. Peeper
Oklahoma State University
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Project Information


This project has sought to advance grain harvesting technology by including simultaneous collection of weed seed with crop seed during grain harvest. Target species included cheat and Italian ryegrass; major weeds in southern region wheat. Attachments to grain combines were built that removed up to 350 lb/acre of weed seed from wheat fields during harvest. Removing that weed seed did not consistently increase wheat yield or decrease grain dockage the following year.

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(TM) 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 for causing excessive amounts of weed seed to be deposited in the clean grain bin. As a result, 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(TM) 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.

Project Objectives:

a. 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 it.

b. Evaluate the new harvesting procedures as a component of an integrated cultural grassy weed control system in on-farm situations.

c. Determine the economic feasibility of the cultural weed control systems.

d. Disseminate our findings to farmers, agribusiness, and other states.


Literature Review

Very limited research has been conducted on aspects of removing or devitalizing weed seed while harvesting. In Germany, Petsold (29) presented descriptive data on redistribution of weed seeds by the combine and data on terminal velocities of weed seed in the combine cleaning fan airstream. In a paper summarizing German research, Von Wacker and Kahrs (34) suggested that certain weed species could be suppressed by collecting the weed seed with the chaff and removing the materials or adjusting the combine to collect the weed seed with the grain. They also reported that weed seed could be devitalized by damaging the seed with a roller mill. Olfert et al. (27) cited Canadian farmer reports that weed infestations were suppressed when weed seed and chaff were collected behind the grain combine chaffer sieve, removed from the field and used as cattle feed. These practices do not appear to have been widely adopted because farmers in those countries seem to depend on herbicides for weed control rather than adopting new cultural practices.

Published research on seed damage has been directed to minimizing damage to crop seed in order to maximize its germination. However, observations from that research can be applied to intentionally devitalizing weed seed. Brewley and Black (6) reported that cracking or splitting the embryo will nearly guarantee that the seed will not germinate. Bartsch (4) showed that directly impacting the soybean radicle produced the greatest reduction in seed germination and vigor. Increasing the load level on the seed and increasing the size of the cracks also decreased germination (26).

Combine grain recleaners (secondary cleaners) have taken two forms: a stationary cylindrical screen with a segmented auger (2, 3) and pneumatic (30). Stationary cylindrical screen cleaners are used to separate materials with large differences in size. Pneumatic cleaners separate “lighter” materials, materials with lower terminal velocities, and can be designed to clean materials such as grain at high volume flow rates (18). Aspirators such as the Kice unit (19) can easily separate seed of similar size but different terminal velocities. But these units and the dynamic characteristics of materials separated by them have been studied to only a limited extent (1).

Current research on weed control at harvest by the principal investigators. In 1994 we measured the effect of grain combines on cheat distribution in the subsequent crop at harvest in six farmer cooperator’s fields. We used a plot combine to harvest 56-inch wide strips, 30 ft. long on 5 ft. centers, parallel to each other and parallel to the direction the farmers’ combines traveled while harvesting the previous crop. Data showed that their combine harvested the weed seed and deposited it on the ground directly behind the cleaning sieves at the center of the combine (Fig. 1). The next year, wheat yields were reduced in that area and dockage from cheat seed greatly increased.

In 1995, we secured a small grant from the grower-funded Oklahoma Wheat Research Foundation to investigate the effect on the next year’s wheat yield and cheat dockage of collecting the cheat seed during combining and removing the seed from the field. Funds were used to buy a Redekop chaff collector. The collector consisted of a catch pan, cross auger, and blower that mounted directly behind the cleaning sieves. Chaff and weed seed were blown into a trailer towed by the combine. This unit was mounted on a Gleaner M-3 combine donated to OSU for research and demonstration. Experiments were begun on six farmer cooperator’s fields to measure how much cheat could be collected and the effect of collecting that cheat on volunteer wheat and cheat infestation in the following (1995-96) crop. Collecting the weed seed greatly reduced volunteer wheat stand problems after harvest and cheat stands in late summer and fall of 1995. When the cheat was mature at harvest, as it typically is, the reductions were dramatic.

At one location, wheat yield, volunteer wheat density after harvest, and cheat density in the fall with the combine adjusted to minimize dockage were 22 bu/A, 180 plants/ft2, and 11 cheat plants/ft2, respectively. With the combine set to collect all weed seed, wheat yield after recleaning increased to 32 bu/A, volunteer wheat dropped to 1/ft2, and cheat dropped to 1/ft2. Similar results were obtained from the other five locations. We have not had the resources to develop a combine mounted recleaner or to evaluate secondary grain cleaning at another location. In our research to date, secondary cleaning has been done at our laboratory with a grain cleaner used for other research.

Also in 1995, preliminary experiments were conducted to investigate the effects on seedling emergence of processing cheat seed with a roller mill and a hammer mill. Both mills effectively killed the seed by injuring the seed embryo without actually grinding the seed. Crimping by the roller mill reduced cheat emergence 93%. Power requirements were very low. Limited funding prevented us from conducting research to optimize these machines or to develop means for mounting them on a grain combine.

Economic Approaches: Evaluation of alternative farming systems or production techniques can be conducted with traditional tools of economic analysis (9, 16). Young and Painter (37) used standard enterprise budgeting methods, similar to those embedded in the Oklahoma State University Enterprise Budget Generator (20), to evaluate the economics of several cropping systems including crop rotations for Eastern Washington.

The economic-engineering or synthetic-firm approach can be used to build models of hypothetical farm firms (13, 23, 25). For example, a synthetic-firm approach was used to determine the economics of ultranarrow row planting for wheat (11) and the economics of alternative tillage systems (12). Methods have also been developed for evaluating comprehensive farming systems and external costs (33) and for evaluating the importance of timeliness of machine operations (14, 21, 24, 36).

Problem Statement

Problem weeds in cropland are frequently similar to the infested crop in terms of growing season and maturation. Conventional farming practices often benefit weed species that mimic the natural biological cycle of the infested crop. Examples include morning glory in soybeans, barnyardgrass in rice, and cheat and wild oats in wheat.

When a crop is harvested with a combine equipped with a header, biomass including seeds of concurrent weeds, enter the combine. For example, 90% or more of the cheat seed in wheat fields enters the combine at harvest. Some seed flows with the grain into the grain tank and enters the marketing channel as dockage or foreign material. However, grain combines are designed to collect only the crop seed while weed seeds are expelled onto the field. From the flail, to McCormick’s reaper, to modern grain combines, grain harvesting is a classic example of technology solving mankind’s food problems and easing drudgery. This proposed research advances harvesting technology a step further by incorporating weed control into the harvesting process.

Winter wheat is grown continuously on a large portion of the crop acreage in the entire Southern Region of the united States. Attempts to introduce conservation tillage practices have been forestalled by rapidly increasing infestations of weedy cheat (Bromus) and Italian ryegrass (Lolium) species (8, 29). Thus, the USDA recently reported that, in contrast to row crops, the acreage of wheat seeded using conservation tillage systems is relatively small and has failed to increase during the past 5 years (7). Wheat farmers are repeatedly frustrated in attempts to adopt conservation tillage practices and are growing more dependant on herbicides to control these weeds. New cultural practices, including the modification of existing harvesting equipment, are viable alternatives to herbicides for controlling weedy grasses in small grains.

The proposed research and extension project is designed to capitalize on research efforts conducted on a limited scale over the past five years to develop practical grain harvesting equipment for capturing and removing weed seeds from grain fields during harvest. Preliminary on-farm tests have established that: (a) the majority of seeds of major problem weeds pass through grain combines during the harvest of wheat; (b) weed seeds entering the combine are collectable during the time that they are in the combine and before they are expelled to the soil, and; (c) both small and large scale farmers are interested in this technology as an alternative to herbicides for weed control on their farms. Preliminary research also indicates that minor mechanical damage to cheat seeds reduces germination and stimulates their decay in the soil prior to seeding the next wheat crop. This devitalization approach may be an economically viable alternative to collection and removal. Thus, it must also be investigated.

The significance of the proposed project is multifaceted. Most importantly, it completes the link in an integrated seeding-harvesting system for cultural grassy weed control in small grains. Previously, we developed seeding techniques for weed suppression in small grains (11). Farmer acceptance has been wide spread, and they are adopting narrow row spacing wheat seeding (35). However, seeding techniques alone are not adequate to suppress severe infestations of grassy weeds. Removal or devitalization of large amounts of weed seed during harvesting should enable producers to suppress these weeds to levels below economic thresholds without herbicides.

Additional benefits include use of collected cheat and ryegrass seed as high quality livestock feed. Cheat has been found to have the same feed value for dairy cattle as barley (5). Also, problems with volunteer wheat will be greatly reduced which will, in turn, reduce tillage and eliminate the “green bridge” between wheat crops, that shelters crop diseases and insects for possible reinfestation.

A final, and perhaps most far-reaching aspect of the research is that by completing a system for cultural grassy-weed control, we can seriously undertake efforts to convert to conservation tillage-based wheat production systems in the South. Conservation Compliance has increased pressure on small-grains producers in the Southern Region to adopt conservation tillage practices. The pending release of over 4.3 million CRP acres for crop production in the Southern Region creates an immediate need for a major shift toward conservation tillage in small grains. As noted, widespread adoption of conservation tillage for continuous wheat production has been forestalled by cheat, annual ryegrass, and other weedy grass species that quickly overrun these fields. Wheat farmers have been reluctant to accept herbicide dependency as the cost of soil erosion control. Unless new, readily adoptable cultural practices are devised to reduce weedy grass infestations, annual applications of herbicides for weedy grass control in Oklahoma wheat are reasonably expected to increase from under 100,000 acres/yr today, to over 3,000,000 acres/yr by 1999, and new herbicides under development are introduced. Based on current prices, this additional pesticide application would cost $45,000,000/yr, plus the potential costs associated with environmental contamination (27).

Cheat and annual ryegrass have characteristics similar to many grass weeds that plague small grains and other crops. Thus, the results from our work will be applicable to other species. Across the Southern Region, weedy grasses are among the most common and troublesome weeds in small grains and cause serious economic losses (Table 1.) In the Southern Region, the acres of small grains sprayed each year for weed control exceeds any other crop, and the economic losses due to weeds in small grains are second only to soybeans and far exceed corn (Table 2).

Although this discussion has focused on the potential benefits of collecting weed seed in wheat, this approach should be effective for any crop harvested by a combine equipped with a grain header. Crops of importance in the Southern Regional harvested with a header include rice, soybeans, and grain sorghum as well as wheat.

Economic analysis is essential to determine the price ranges over which the evaluated systems would be feasible and suitable for widespread adoption by farmers. For widespread adoption, the alternative system must either increase expected net returns or reduce financial or production risks relative to conventional practices. Also, the adoption rate will depend on the compatibility of the innovation with existing enterprises, managerial skills, available resources, and institutional constraints such as federal commodity program requirements and environmental legislation.


Materials and methods:

Objective 1: Equipment Modification and Development: Three approaches to removing and disposing of cheat and annual ryegrass will be investigated:
1. Combine Mounted Recleaner Approach: Adjust the combine to collect both the grain and weed seed, separate the mixture with a secondary cleaner (recleaner) mounted on the combine, and either collect the weed seed for feed or mechanically damage the weed seed to devitalize it and then return it to the field.
2. Chaff Collector Approach: Collect weed seed and shriveled wheat along with the chaff that is discharged from the combine over the cleaning sieves. Collected material is then removed from the field. It’s value as livestock feed will be determined.
3. Seed Cleaner Approach: Adjust the combine to collect both the grain and weed seed in the clean grain tank, then clean the mixture at the edge of the field, saving the weed seed and shriveled wheat for livestock feed. All approaches will be compared to conventional combine harvesting for impacts on weed densities, grain yields, economics, and constraints.

1. Combine Mounted Recleaner Approach: Combine recleaners were built and marketed as optional or add-on equipment in the 1940-50’s to improve grain cleanliness. They were typically mounted on small pull-type combines and had no capability of handling the high mass flow rates encountered in a modern combine. Also, they offered no place to collect separated weed seed and often it was just returned to the field. Aspiration grain cleaners appear to have the greatest potential for recleaning on a modern self propelled grain combine. Laboratory-scale recleaners with Plexiglas sides will be designed. Grain mass flow rates and grain/weed seed separation characteristics of these designs will be measured. Air speeds and air flow streamlines will be measured with smoke generators, hot-wire anemometers and other air flow measuring instruments. Design variables will be optimized. A prototype cleaner will be constructed and mounted on the OSU Gleaner M-3 combine and evaluated during the summer of 1997.

Weed Seed Devitalization will be incorporated into this system: In our research a roller mill and a hammer mill devitalized cheat seed by damaging the embryo without having to completely crush or grind the seed. However, operating variables of these mills have not been optimized. Other weed seeds such as annual ryegrass have not been tested in these mills. Other mechanisms such as scarifiers have not been investigated to determine their effects on weed germination and growth. Experiments will be conducted to determine the effect of operating variables of existing seed mills on germination of cheat, ryegrass, and shriveled wheat. Variables will include roller gap, teeth/inch of roller circumference, roller speed, hammer mill screen size, hammer and screen clearance, hammer speed, and feed rates and power requirements for both devices. Effects of these variables will be measured in laboratory germinators using standard procedures. Seed will also be germinated in potted soil to measure the effect of the mechanical impedance on weed seedling vigor. Finally, mechanically-treated seed will be planted in fields to germinate and emerge under natural conditions. Treatments tested in the field will be based on laboratory results. The field tests are required to combine the effects of fungal invasion, insect damage, and environmental factors on germination and emergence of the mechanically damaged seed. All experiments will be replicated with appropriate statistical designs. A unique high capacity scarifier will be designed and constructed to damage the seed coats of a wide range of species of weed seed. This device will be tested in the laboratory and field using procedures used to test the hammer and roller mills. Power requirements of all devices will be determined using torque transducers and measuring input shaft speeds.

A device to mechanically devitalize weed seed will be purchased or constructed based on the results of these experiments. This device will be mounted on the OSU Gleaner M-3 combine and linked to the grain recleaner. Mounting brackets and power drive trains of the grain cleaner and seed devitalizer will be designed for simplicity and ease of mounting on existing combines. All equipment used will be scale neutral; producers could adopt at least one of the practices, but small producers are less likely to hire transient custom harvesters, thus are more likely to adopt these practices to their own equipment.

2. Chaff Collector Approach: A Redekop chaff collector, tested in 1995, removed the cheat seed but, as configured, too much weed seed entered the grain bin. The deflector which directed the chaff stream into the collector restricted the cleaning fan air flow, causing the weed seed to drop through the cleaning sieve. The chaff collector will be repositioned and the deflector redesigned to minimize its effect on air flow.

3. Seed Cleaner Approach: Grain combines can easily be adjusted to collect almost all the weed seed with the crop grain. But the material collected is unmarketable without recleaning. To conduct a separate recleaning operation, a high capacity cleaner and supporting equipment must be purchased and/or constructed. Mr. Weldon Miller, a small farmer and entrepreneur, has expressed a desire to explore this approach on his farm (see attached letter of support). Since this approach requires cleaning of the weed seed/grain mixture at the edge of the field, Oklahoma State agricultural engineers will work closely with Mr. Miller to design a portable cleaning system that can be operated in the field. We have already tested a KiceR aspirator grain cleaner and found it capable of separating cheat and ryegrass seed from wheat. The cleaner can separate these mixtures at the required mass flow rates. Other grain cleaners will be evaluated, and the best cleaner will be selected. Portable holding tanks will be selected and auger systems designed to efficiently separate the wheat/weed seed mixture.

Objective 2: Field Tests of Equipment and Systems: Replicated field tests will be conducted with the three harvesting systems on farmer cooperator’s fields. The treatments tested and compared to conventional harvesting will include: the Chaff Collector, Combining and Cleaning at a Remote Location, and On-Combine Recleaning with Weed Seed Removal or Devitalization. Each treatment will be replicated a minimum of four times in experiments using a randomized complete block design. Plots will be 200 ft long by 35 ft (two passes with the Gleaner M-3 combine with an 18 ft grain platform (header) with 1 ft of overlap). The entire grain and weed seed mixture collected in the clean grain tank and materials exiting over the sieves will be weighed after each plot is harvested. Samples will be collected for analysis of wheat grain yield, test weight and moisture, yield of weed seed, and crop and weed seed losses. Field efficiency data will be collected by harvesting larger areas. Volunteer wheat growth and weed densities along the centerline of the combine will be determined by counting plants in 2 or more 1/8 m2 quadrants per plot. Wheat grain and weed seed yields will be measured at the next harvest by harvesting parallel 56 inch by 30 ft strips across the entire width of each plot with a plot combine. Graphs of grain and weed seed distribution will be plotted and distributions analyzed as was done for 1994 data (Fig. 1).

OSU researchers will work closely with the farmer-cooperators to select locations with uniform weed populations, to plan post harvest tillage and planting practices for the proposed integrated systems, and to explore possible modifications to the proposed harvesting systems. Cooperators will design their own tillage and seedbed preparation system utilizing their existing equipment while attempting to minimize tillage operations and maximize crop residue cover (Figure 2).

Objective 3: Economic Analysis: Data obtained from the experiments, including those conducted on participants’ fields, will be subjected to economic analysis. The costs and returns of each of the alternative approaches will be determined and compared with the costs and returns of conventional practices used by the cooperating farmers. The ultimate objective of the economic analysis will be to determine the circumstances under which each of the proposed alternatives would be economically feasible. This will be accomplished by evaluating the sensitivity of the costs and returns to alternative wheat prices, weed seed and screening value as feed, harvest time labor rates, timeliness cost of delayed wheat harvest, and capital requirements for the proposed alternatives.

Education and Outreach: Year 1 activities will focus primarily on developing a communication network, data collection, and dissemination of preliminary information. These activities will increase awareness of possible alternatives for cheat and annual ryegrass control while simultaneously arousing interest of wheat producers and related agribusinesses in attending field days planned for the following harvest season.

Within the first month of Year 1, the management team of cooperators, “involved” extension personnel (county and area), and co-PIs will be assembled to reaffirm the goals and objectives of this project and to develop detailed plans-of-action to ensure that all connected with this project know his/her responsibility(s) and to open lines of communications.

Research/demonstration fields will be identified with signs erected to inform the public of the project and planned activities. During harvest (June 1996), wheat production and weed seed reduction data will be collected. Harvest activities will be videotaped for use in news stories and the preparation of educational video(s). A log of field operations will be maintained on each site including volunteer wheat and weed growth prior to wheat seeding and in the crop. OSU personnel will assist cooperators during seeding. Narrow-row seeding will be used to demonstrate a systems concept of reducing the effect of cheat on wheat production. The first year data will be analyzed and compared to preliminary studies. Current report(s) and news releases will be prepared highlighting results and preliminary findings. At the end of Year 1, the entire team will be reassembled to review and discuss results and begin planning for the next harvest.

Year 2 activities will emphasize education and outreach using: (1) formal and informal field days at cooperators’ farms where producers can witness alternative cheat and annual ryegrass collection and utilization systems; (2) dissemination of information through written materials (i.e. news releases, fact sheets, and journal articles), radio tapes, and television (i.e. OSU Sun-Up, a 15 minute farm program broadcast daily on the Public Broadcasting Television network); (3) producing a 20-30 minute educational video tape; and (4) coordinating and conducting a nation-wide teleconference. In addition, university personnel will cooperate with the Cooperative Extension Services in all other states in the Southern Region to disseminate information.

Research results and discussion:

1. On-farm tests
The on-farms tests were conducted to determine if alternative harvesting systems would provide larger net returns than the traditional procedure. The treatments considered in this research were a conventional system and six experimental strategies. The alternative methods used a field portable, trailer mounted Kice aspirator grain cleaner, with appropriate supporting equipment a prototype combine mounted (bin-unit) aspirator cleaner, or neither, with various combine separator fan air settings.

Method__Description = Name
(1)__Normal Combine Settings with Bin-Unit Cleaner = Normal Bin-Unit
(2)__Low Combine Air Settings = Low Air
(3)__Low Combine Air Settings with Kice Cleaner = Low Air with Kice
(4)__Low Combine Air Settings with bin-Unit Cleaner = Low Air with bin-Unit
(5)__High Combine Air Settings = High Air
(6)__High Combine Air Settings with Kice
Cleaner = High Air with Kice

These methods were evaluated in field trials during the 1997 wheat harvest. The studies were conducted on farmer-participant fields near Red Rock, Marland, Billings, and Hunter, Oklahoma. Net returns above operating (OC) and cleaning costs (CC) for the treatments were determined by subtracting OC and CC from the total gross revenue from wheat and expected cheat sales. Returns were calculated for three representative farm sizes; a low, medium, and high cleaner cost scenario; and two estimated cheat prices. After returns were established for the alternatives, they were compared to the net returns from the Conventional system to determine if any benefits existed. If a net existed, then the required yield increase for the subsequent year was estimated. If an analysis of variance indicated a significant difference across treatments, then a Duncan=s multiple range test was performed to compare the treatment means.

Location Conclusions

The Red Rock location had the largest cheat infestation of this study. The most profitable treatment at Red Rock was the High Air with Kice method. The net benefit offered over the Conventional system was between $34 and $15 per acre (/ac) for the various farm sizes, cheat prices, and cost options. The benefit was the additional returns above operating costs and cleaner related costs. This was a very unexpected outcome. The High Air with Kice treatment was anticipated as having better grades and less yield than the Conventional. Its wheat price after discounts was significantly larger due to enhanced grades and lower dockage, but the yield after dockage was not significantly higher than the base system. Despite the large benefits from the High Air with Kice method, there was only a statistical difference in returns between it and the Conventional system for the 1,500 acre farm with the $0.06 per pound cheat price, and low cost estimation. With the 17 other combinations of cheat prices, cost options, and farm sizes, the null hypothesis of no difference in net returns between the High Air with Kice and the Conventional could not be rejected. It could be concluded that, even though the High Air with Kice treatment consistently improved returns, it was not to the point of statistical significance at the 5% level. Therefore, an unambiguous recommendation of this alternative over the Conventional system could not be made.

The Marland site had the second worst cheat infestation of the four locations, although it was much smaller than Red Rock. The most profitable treatment was the Low Air with Bin-Unit and Conventional treatments could not be rejected at the 5% level. It was determined that none of the alternatives significantly improved returns.

The Billings field studies had the second smallest cheat population. With the $0.06 per pound cheat price, the Low Air with Bin-Unit method generated the greatest net returns. However, when cheat price was lowered, the High Air alternative proved to be the most effective method. This outcome stood true at each farm size and for the varied cost options at Billings. The results from this location demonstrate the importance of the cheat market and price. The Low Air with bin-Unit procedure relied on selling its cleanings to be effective, while the High Air tactic was profitable based on an improved price and a higher yield, which was unexpected. However, despite the benefits offered by the alternatives there was never a significant difference between either of the two treatments and the Conventional at the 5% level for Billings. Across the three farm sizes, three cost estimates, and two cheat prices, none of the treatments were statistically different from any of the other treatments.

Cheat infestation at the Hunter location was slight at best. It had the lowest average dockage level of the four sites. For comparison purposes there were only two alternatives to the Conventional system. However, the most profitable treatment was the Conventional system at every cost option and cheat price. At a majority of the cost and cheat price combinations the Low Air with Kice treatment was even significantly lower than the Conventional. This was the anticipated outcome at a site with such a small cheat population.


To gain validity of commercial situations, these treatments were conducted at privately owned farms instead of university research stations. Performing research in this manner is very precarious, and unfortunately the weed control effects for the subsequent year could not be evaluated. The agronomic effects of the methods studied in this report could hold the key to discovering an alternative to the Conventional wheat harvesting method that consistently and significantly improves returns.

An additional limitation to this study was the small amount of source data. With only three or four replications for each treatment, there may not have been enough power in the statistical analysis. If more data were available, some of the alternatives that indicated improvements in net returns might be proved to be significantly different than the Conventional.

The estimated cheat market was also a sensitive area in the research. Attempting to predict a price for an unknown market was very difficult. Even by using two price estimates, the revenue from the expected sale of cheat and cleaning was still questionable. Especially when a portion of net benefits was due to this anticipated revenue increase.


A change in the traditional procedure could benefit not only farmers and producers, but the wheat industry in general, by providing cleaner wheat for the marketing channel. A need for additional research can be seen in the areas of aspirator cleaner design, the possible marketing of cheat and cleanings as a feed stuff, and the feasibility of additional cleaning equipment on modern grain combines.

Since the four locations had varying cheat problems, important information was gained from this study. If a severe problem exists, such as the one at Red Rock, there are several alternatives to the Conventional system of harvest that may increase returns. However, at lower levels of cheat infestation the economics of the alternatives are less promising. Based on the results presented in the study, there was not an alternative procedure of harvest that consistently and significantly improved net returns at any level of cheat infestation.

Experiment Station Tests

Experiment station tests were established in the fall of 1997 to overcome a major limitation noted above, i.e. our inability to predict harvesting method effects on the subsequent crop. In the first such experiment in an Italian ryegrass infested field at Chickasha, OK, we evaluated the benefits of reduced separation air to prevent blowing the weed seed back onto the field simultaneously using the on-board aspirator to clean up the grain. Reducing the combine=s separator air to the medium-low or low levels greatly increased the volume of material collected in the grain bin (Table E1). This was expected since the material was not being blown out of the combine back onto the field. As was expected, the amount of material removed by the aspirator increased as the amount of weed seed collected with the grain increased. The aspirator successfully collected 31 or 32 lb/A of Italian ryegrass seed. However, recleaning the grain that entered the bin after it passed through the aspirator revealed that another 93ƒp15 lb/A of ryegrass seed was not removed by the aspirator. Thus, we concluded that the capacity of the aspirator was too small. The on-board aspirator removed only 1 to 3 lb/A of wheat, which was a very small loss compared to conventional seed cleaning operations.

The subsequent year, there was a significant increase in wheat yield as a result of low-air harvesting the previous year. However, the Italian ryegrass infestations remained very heavy and wheat yields were lower than the previous year.

At site two at Chickasha, normal and low separator air settings were compared in a cheat infested field, with and without simultaneous use of the on-board aspirator. As planned, reducing the air flow increased the volume of harvested material (Table E2). The on-board aspirator removed much of the total material and thus reduced the volume of the cheat and other materials entering the grain bin. With the low air setting, the combine collected over 330 total pounds per acre of cheat seed. However, the quantities and the bulky nature of the chaff, wheat, and weed seed collected again overloaded the aspirator to where it only removed about 10% of the cheat collected by the combine.

The medium low fan setting did not significantly increase the volume of material collected by the combine, but did increase the total material removed by the aspirator, and the total grass weed seed retained by the combine (Table E3). However, the next year Italian ryegrass increased tremendously, reducing wheat yields to about half those of the previous year. Weed seed content of the grain harvested in 1999 was over 440 lb/A and was not affected by harvesting method used the previous year.

Participation Summary

Educational & Outreach Activities

Participation Summary

Education/outreach description:


Hauhouot, Marilyne. 1998. Mechanically devitalizing cheat (Bromus secalinus L.) seed to reduce germination. Ph.D. dissertation. Stillwater, Okla.: Oklahoma State University.

Dunn, Jeffry Wayne. 1998. Economics of alternative wheat harvesting methods for weed-infested Oklahoma fields. M.S. thesis. Stillwater, Okla.: Oklahoma State University.

Refereed Journal Articles:

Slagell-Gossen, R.R., M. Hauhouot, T.F. Peeper, R.L. Claypool, and J.B. Solie. 1998. Effects of mechanical damage on cheat (Bromus secalinus) caryopsis anatomy and germination. Weed Sci. 46:249-257.

Hauhouot, M., J.B. Solie, G.H. Brusewitz, and T.F. Peeper. 1998. Roller and hammer milling cheat to reduce germination as an alternative method for weed control. Trans. ASAE. 41(4):973-980.

Hauhouot-O’Hara, M., J.B. Solie, R.W. Whitney, T.F. Peeper, and G.H. Brusewitz. 1999. Effect of hammer mill an roller mill variables on cheat (Bromus secalinus L.) seed germination. Appl’d Engr. Agr. 15:139-145.

Professional Papers and Abstracts:

Hauhouot, M., J.B. Solie, G.H. Brusewitz, and T.F. Peeper. 1998. Roller and hammer milling cheat to reduce germination as an alternative method for weed control. ASAE Paper No. 97-1002. ASAE, St. Joseph, MI 49085-9659.

Hauhouot-O’Hara, M., J.B. Solie, R.W. Whitney, T.F. Peeper, and G.H. Brusewitz. 1998. Effect of hammer mill an roller mill variables on cheat (Bromus secalinus L.) seed germination. ASAE Paper No. 98-1039. ASAE, St. Joseph, MI 49085-9659.

Dunn, Jerry W. and Francis M. Epplin. 1999. Economics of Alternative Harvesting Methods and On-Farm Cleaning for Weed-Infested Wheat. J. Agric. Applied Economics 30:In press.

Education and Outreach

The majority of the educational and outreach activities of this project were conducted in the first two years. Plans to disseminate our findings on a wider basis were stymied by our inability to demonstrate a consistent economic benefit associated with the alternatives harvesting methods.


1. Al-Yahya, S.A., C.J. Bern, and C.R. Hurburgh, Jr. 1991. Aspirator separation of corn-fines mixtures. Trans. ASAE. 34(3):944-949.

2. Anonymous. 1959. Dealer parts catalog: special attachments for “60” series all crop harvesters. Allis-Chalmers Mfg., Co. Milwaukee. WI.

3. Anonymous. 1971. Parts catalog: F series combines. Allis-Chalmers Mfg., Co. Milwaukee, WI.

4. Bartsch. J.A., C.G. Haugh, K.L. Athow, and R.M. Peart. 1986. Impact damage to soybean seed. Trans. ASAE. 29(2):582-586.

5. Berry, M.H., K.L. Turk, and L.A. Moire. 1944. The feeding value of cheat for dairy cows. J. Dairy Sci. 27:627-628.

6. Bewley, J.D. and M. Black. 1994. Seeds: physiology of development and germination. Plenum Press. New York, NY.

7. Conservation Technology Information Center. 1995. Conservation Impact. 11(6):2-3.

8. Davidson, J.M. and P.W. Santelmann. 1973. An evaluation of various tillage systems for wheat. Okla. Agric. Expt. Stn. Bulletin B-711. 17 pp.

9. Dobbs, T.L., M.G. Leddy, and J.D. Smolik. 1988. “Factors influencing the economic potential for alternative farming systems: Case analyses in South Dakota.” Amer. J. Alternative Agric. 3:26-34.

10. Driver, J.E., T.F. Peeper, and J.A. Koscelny. 1993. Cheat (Bromus Secalinus) control in winter wheat (Triticum aestivum) with sulfonylurea herbicides. Weed Technol. 7:851-854.

11. Epplin, F.M., V.A. Allread, J.B. Solie, T.F. Peeper, and J.A. Koscelny. 1992. Economics of ultranarrow row planting for hard red winter wheat production in Oklahoma. J. Production Agric. 5:427-431.

12. Epplin, E.M., D.E. Beck, E.G. Krenzer, Jr., and W.F. Heer. 1993. Effects of alternative planting dates and tillage systems on the economics of hard red winter wheat production in Oklahoma. J. Production Agric. 6-1:7-8, 57-62.

13. Epplin, F.M. and R.T. Ervin. 1982. “Evaluating the use of an alternative breed type as a pest management strategy.” North Central J. Agric. Econ. 10:225-232.

14. Epplin, F.M., T.F. Tice, A.E. Baquet, and S.J. Handke. 1982. “Impacts of Reduce Tillage on Operating Inputs and Machinery Requirements.” Amer. J. Agric. Econ. 64:1039-1046.

15. Ferreira, K.L., T.F. Peeper, and F.M. Epplin. 1990. Economic returns from cheat (Bromus secalinus) control in winter wheat (Triticum aestivum). Weed Technol. 4:306-313.

16. Goldstein, W.A. and D.L. Young. 1987. “An agronomic and economic comparison of a conventional and a low-input cropping system in the Palouse.” Amer. J. Alternative Agric. 2:51-56.

17. Griffin, J.L. 1986. Ryegrass (Lolium multiflorum) control in winter wheat. Weed Sci. 34:98-100.

18. Grochowicz, J. 1980. Machines for Cleaning and sorting of Seeds. Translated from Polish for the USDA and NSF, Wash. D.C., by the Foreign Sci. Pub. Dept. of the Nat. Ctr. for Sci., Technical, and Economic Info., Warsaw, Poland. 374p.

19. Kice, J. 1985. Skilled air manual for milling and other industries. Kice Metal products, Co. Wichita, KS.

20. Kletke, D. Operation of the Enterprise Budget Generator. Rpt. P-790. Oklahoma Agricultural Experiment Station, Stillwater. 1979.

21. Kletke, D. and R. Sestak. 1980. “A Decision Aid for Evaluating Alternative Farm Machinery Complements – MACHSEL.” Current Farm Economics. 63:3-14.

22. Kodayari, K., R.E. Frans and F.C. Collins. 1983. Diclofop – a selective herbicide for Italian ryegrass (Lolium multiflorum) control in winter wheat. Weed Sci. 31:436-438.

23. Madden, J.P. 1967. Economies of size in farming. Agri. Econ. Rpt. 107. Economic Research Service, U.S. Dept. Agr., Washington, D.C. 83pp.

24. Misra, S.K. and S.R. Spurlock. 1991. “Incorporating the Impacts of Uncertain Fieldwork Time on Whole-Farm Risk-Return Levels: A target MORTAD Approach.” Southern J. Agric. Econ. 23-2:9-17.

25. Moore, C.V. and H.O. Carter. 1984. Methodological and empirical issues in economies of size studies in Proc. Economies of Size Studies. Center for Agricultural and Rural Development, Iowa State University, Ames. 220pp.

26. Nikolenko, V.F. and D.I. Alexeeva. 1994. CIGR XII World Congress on Agricultural Engineering Proceedings. Volume 2.

27. Olfert, M.R., M. Stumborg, W. Craig, and R.A. Schoney. 1991. The economics of collecting chaff. Amer. J. Alternative Agric. 6(4):154-160.

28. Peeper, T.F. 1984. Chemical and biological control of downy brome (Bromus tectorum) in wheat and alfalfa in North America. Weed Sci. 32(Supp. 1):18-25.

29. Petzold, K. 1955. Combine Harvesting and Weeds. Land Technik 10(11):468-470.

30. Quick, G. and W. Buchele. 1978. The grain harvesters. American Society of Agricultural Engineering. St. Joseph, MI.

31. Runyan, T. 1980. Cultural control of Bromus species in Winter Wheat. M.S. Thesis, Oklahoma State University, Stillwater. 66 pp.

32. Stanger, C.E., and A.P. Appleby. 1989. Italian ryegrass (Lolium multiflorum) accessions Tolerant to diclofop. Weed Sci. 37:350-352.

33. Teague, M.L., D.J. Bernardo, and H.P. Mapp. 1995. “Farm-level economic analysis incorporating stochastic environmental risk assessment.” Amer. J. Agric. Econ. 77-1:8-19.

34. Von Wacker, P. and J. Kahrs. 1993. Unkaut schon bei der Getreideernte bekampfer? (Should weeds be controlled at harvest?) Pflanzenschute – Praixis 0:18-20.

35. Watson, S. 1995. Production notes. The Wheat Farmer. August, 1995, p7-8.

36. Williams, J.R., R.V. Llewelyn, and G.A. Barnaby. 1990. “Risk Analysis of Tillage Alternatives with Government Programs.” Amer. J. Agric. Econ. 72:172-181.

Project Outcomes

Project outcomes:

1. The research and development efforts documented the potential benefits and problems with the harvesting methods explored. These extensive efforts will define the direction of future research in this area.

2. The research defined the potential for using novel harvesting approaches for farmers interested in exploring Italian ryegrass seed production as a companion crop to their wheat.

3. This project has impacted research by harvesting equipment manufacturers in Canada and Australia, where herbicide resistant weeds are a greater problem than they are here in the US.

4. The biggest impact of this project may take a few years to unfold. There is not a lot of grain harvesting research conducted at universities or elsewhere because of the time, expense, and resources required. Here at OSU, 18 graduate research assistants are or were directly involved with the project. Of that number, 13 were agricultural engineers. Of the 8 engineers that have completed their graduate programs to date, five are employed by companies who build grain harvesting equipment or attachments for such equipment, including Case, John Deere, Kincaid Equipment Manufacturing, and Bliss.

Another Ph.D. agricultural engineer returned to her native country, Ivory Coast, and is working with that government’s Agricultural Research Branch. One student finished her M.S. in Botany, and is currently teaching at the Red Plains Junior College in west-central Oklahoma. Other students involved are currently pursuing degrees in their chosen fields of Agricultural Economics, Agricultural Engineering, and Plant and Soil Sciences both here and at other universities. We are confident that changes will come in the designs of grain combines, that center on incorporating weed seed collection into the wheat harvesting process. It will be very interesting to see whether the innovations are developed in other major grain producing counties before they are developed in the USA.

It will also be interesting to see whether the smaller companies introduce innovations sooner than John Deere and Case. We know that a great deal of grain harvesting research is now underway in industry. As a result of the recent buy-out of Case by New Holland, John Deere successfully recruited an entire group of grain harvesting equipment engineers from Case, including some of our former students. What is going on? Only time will tell.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.