Substitution of Cultural Practices for Herbicides to Control Annual Rye Grass and Cheat in Small Grains
Winter wheat is grown continuously on a large portion of the acreage dedicated to crop production in the entire Southern Region of the United States. Attempts to introduce conservation tillage practices have always led to rapidly increasing infestations of weedy Bromus, Lolium, and Hordeum species. Farmers are increasingly abandoning conservation tillage practices or are turning to herbicides to control these weeds. The introduction of new cultural practices including the modification of existing harvesting and planting equipment is a viable alternative to herbicides for controlling light seeded weedy grasses in small grains.
The proposed research and extension project continues and expands a one-year low-input sustainable agriculture project to develop and demonstrate quickly adoptable cultural methods with substantial potential for preventing pandemic infestations of cheat and annual rye grass, two of the most common grassy weeds found in the Southern Region. Practices include: (1) preventing the return of annual rye grass and cheat seeds to fields during harvesting, (2) increasing the natural ability of wheat to compete against annual rye grass and cheat by using new seeding techniques, and (3) identifying wheat cultivars with greater natural abilities to compete against weedy grasses. A complete economic analysis will be performed to evaluate the economic feasibility of the proposed practices. Farmers have been included in the planning, research and on-farm demonstration phases of the project.
Preliminary tests were conducted in 1989 to evaluate the potential of collecting chaff and straw from a harvesting wheat. Results were positive, but the volume of straw collected was so great that we decided to separate the weed seed from the straw.
During the spring of 1990, we designed and constructed a pneumatic collector and conveying system and mounted it on a Gleaner M-2 combine. This device collected weed seed, chaff, and shriveled wheat discharged over the combine shoe and conveyed the material to a trailing wagon, a separator in the wagon to remove the chaff. The modified silage wagon could hold all material collected while harvesting two combine bins of clean grain.
We established experiments in seven farmers’ fields containing moderate to severe infestations of annual ryegrass or cheat. The weed seed collector worked as designed. The collector removed up to 410 lbs/ac of annual ryegrass seed and 180 lbs/ac of cheat. At two locations, we used the ultranarrow row grain drill to plant wheat. Seeding rates were 75 and 120 lbs/ac, and row spacings were 3, 6, and 9 inches. There were no significant problems with the weed seed collector.
Field tests, that summer, showed the collector-separator worked and would be practical with some modifications. However, the Southern Region Low Input Sustainable Agriculture Research and Education Program failed to fund the final year of the project, and the principal investigator for this objective took a position at another institution. Consequently, we elected to concentrate our efforts on the other objectives. Work was halted on this objective.
In addition to the LISA grants, the principal investigators were able to secure major funding from several sources to expand and continue research outlined in Objective 2. Research on the objective was initiated in 1988 with a one time grant from the Oklahoma Wheat Research Foundation. Subsequent research was funded in part by the Oklahoma Center for the Advancement of Science and Technology, Oklahoma Wheat Commission and the Southern Region Pesticide Impact Assessment Program. Results are summarized by year, below:
In 1988, averaged over area research locations, ultranarrow row seeding practices increased yields of cheat infested wheat by over 11% and decreased cheat seed production by up to 25%. Results of these experiments were used to plan field experiments under the LISA project initiated in the fall of 1989. Experiments were established at three locations to more completely define the interactions among wheat row spacing, seeding rate, and date of planting on cheat suppression and wheat yield. Experiments were also established at two locations to investigate the influence of the severity of cheat infestation on the benefits derived from manipulating row spacing and wheat seeding rate. Additional experiments were established on farmer participant fields to investigate and demonstrate the benefit of 3 inch row spacing and higher seeding rates on annual ryegrass and cheat suppression and wheat grain yield. It was apparent, based on 1988 research, that water injection was not a practical method for stimulating germination. Subsequent attempts to prime wheat seed failed to improve stands.
In the fall of 1989, five major experiments were established to determine the effects of row spacing, wheat seeding rate, weed seed density, and date of planting on wheat grain yield and weed seed yield. Results of these experiments, harvested in June 1990, showed that narrowing row spacing significantly increased grain yield and could reduce by half the dockage attributable to weed seed. Grain yield increases were as great as 455 lbs/ac in weed free treatments and 410 lbs/ac in weed infested treatments when row spacing was reduced from 9 to 3 inches. Increasing wheat seeding rate in weed infested fields will generally reduce weed seed and significantly increase grain yield. These benefits occur independent of the weed seed (cheat) density at planting. Grain yield increased as date of planting is delayed.
Experiments were conducted at three locations in 1990-91 to investigate the interaction of row spacing, seeding rate, and herbicide treatment on cheat control. Treatments consisted of the herbicides metribuzin and Finesse (a chlorsulfuron and metsulfuron premix) applied at two rates plus an untreated check; three row spacings 3, 6, and 9 inches; two seeding rates and cheat and weed free plots. At one location the combination of metribuzin and reduced row spacing increased wheat yield. At the second location decreasing row spacing increased wheat yield for all herbicide treatments and the check. The Finesse treatments increased wheat yield. At the third location, all herbicide treatments increased yield. Seeding at the higher rate increased yield. At one location the three way interaction of low rate of Finesse, reduced row spacing and increased seeding rate reduced cheat seed yield. At two locations, the combination of increased seeding rate and reduced herbicide rate decreased cheat seed yield. The experiments showed that the combination of planting in narrow spaced rows, increasing wheat seeding rates, and applying reduced rates on herbicides can increase wheat yields and reduce the amount of weed seed harvested.
During the 1991-92 crop year experiments were established to determine the effects of row spacing, seeding rate and herbicide treatment on annual ryegrass control. Treatments consisted of the herbicides; three row spacings 3, 6, and 9 inches, two seeding rates. Herbicides were required to improve wheat yields. However, reducing row spacing and increasing seeding rate enabled reduction of the herbicide application rate at one location.
Experiments were begun to investigate the effects of wheat cultivars, and row spacing on wheat vegetative growth (for cattle grazing) and grain yield in cheat free and cheat infested fields. The combination of dry weather followed by hail storms produced atypical results.
In the fall of 1992, the second year of the two year experiment to determine if the effect of wheat cultivar, row spacing, and weed infestation was begun. Experiments were initiated at three locations to determine the effect of row spacing on suppression of broadleaf weed, primarily wild buckwheat. Results of these tests will be reported in late 1993.
In addition to the LISA grants, the principal investigators were able to secure major funding from the sources listed in Objective 2 for Objective 3. In addition, they received contributions of equipment and components from Great Plains Manufacturing Company and John Deere Company to expand and continue research outlined in Objective 3. Results are summarized below:
During the first two years of the project, we used ultranarrow row plot drills built at the Agricultural Engineering shop to plant experiments. Only one U.S. manufacturer built a grain drill capable of seeding cereal grains at ultranarrow row spacings. This grain drill was complicated, expensive and was not accepted by farmers. Consequently, we embarked on a program to design grain drill openers that were acceptable to farmers.
During 1990, we designed and tested two grain drill openers capable of placing seed in three inch rows while operating successfully in a wide range of tillage conditions. The opener designs were based on distinctly different concepts. Twenty-four units of each design were constructed and mounted on grain drills designed for the specific opener. These grain drills were extensively field tested on six farmer cooperator fields in the fall of 1990.
One of the designs met the initial design criteria: it could be operated in a wide range of tillage systems, it is simple, and it should be less expensive than conventional grain drill openers. This design used a floating knife opener and spring loaded press wheel to place seed in newly tilled soil. Precision of seed placement depth is similar to current designs. The opener could handle large amounts of crop residue. The grain drill, constructed in 1990, used an air seeder metering unit.
This grain drill was tested at 7 locations including four farmer cooperators’ fields. The grain drill successfully planted a wide range of conditions including crop residue. The grain drill plots produced higher grain yields than those planted by a conventional row spacing double disc grain drill at a majority of the locations.
Analysis of previous years’ data showed that grain yields were near optimum when planted in 3 inch spaced rows. Planting in 3 inch spaced rows frequently reduced weed seed yield. Yield data from 1990-91 experiments supported these findings. The new ultranarrow row (3 inch) grain drill opener will enable farmers to take advantage of these results.
Major equipment manufacturers, although interested in our research, were unwilling to build ultranarrow row grain drills. They did not believe ultranarrow row planting was compatible with the Conservation Compliance Program. Specifically, they did not think a 3 inch row spacing grain drill could plant in high levels of crop residue. In the fall of 1992, we modified a 7 inch spacing John Deere 9450 press wheel hoe drill to plant in 3, 4, 3, 4…inch row spacing. This grain drill proved capable of planting wheat in high levels of residue and could be operated at high speed. Experiments were established at 8 locations to compare performance of the grain drill with a conventional grain drill and the ultranarrow grain drill described previously. These experiments will be harvested in June 1993.
During 1989-1991 we collected data for economic analysis of the proposed cultural practices, including cooperating farmer surveys. We made economic assessments based on the data collected and developed mathematical models to assist in these analyses.
An analysis of the potential economic returns for planting in ultranarrow rows was conducted. Enterprise budgets were computed for farm sizes of 300 to 1000 acres using the representative farm approach. Use of an ultranarrow row grain drill will increase returns $6.79/ac for the 1000 acre farm, and the grain drill will increase returns $6.03/ac for the 300 acre farm. All data are being presented in a format compatible with the Planetor/Budgetor budget generator. Further analyses are being completed at this time.
Results of five years of research clearly show there are significant agronomic and economic advantages to seeding wheat in ultranarrow rows. In the presence of cheat and in clean tilled fields decreasing row spacing to 3 inches consistently increased grain yield an average of 3 bushels per acre. Weed seed yield was frequently significantly reduced. Increasing wheat seeding had an additive effect on grain yield and weed seed suppression. When herbicides were required, adoption of these practices will often enable the reduction of herbicide application. Grain drill modifications were developed to enable farmers to plant at this spacing in heavy crop residues. Estimated cost of this conversion was less than $1,000 per 10 foot grain drill. Economic analyses showed clearly the advantage to adopting these practices.
(1) Use 1988-1989 and 1989-1990 research results to demonstrate the advantages of using more competitive wheat cultivars, increased seeding rates, and ultranarrow row spacing for annual rye grass and cheat suppression in wheat, and continue research to optimize the competitiveness of more competitive cultivars.
(2) Refine the ultranarrow row grain drill opener, designed and tested in 1989, to improve seeding depth uniformity and clod and crop residue clearance.
(3) Provide on-farm demonstrations of the decreases in cheat and annual rye grass populations attainable by catching and removing material discharged from the chaffer (lower cleaning unit) of small grains combines.
(4) Estimate the impact of the alternative weed control methods on per unit production costs, family resource use, machinery investment and net return to a representative farm family, and compare results with corresponding estimates for farming systems which rely on conventional methods.