Development and Evaluation of Bio-Cultural Weed Management Systems for Low-Till Grain Production

Final Report for ANC94-023

Project Type: Research and Education
Funds awarded in 1994: $0.00
Projected End Date: 12/31/1997
Matching Non-Federal Funds: $114,322.00
ACE Funds: $58,183.00
Region: North Central
State: Ohio
Project Coordinator:
John Cardina
Ohio State University
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Project Information


[Note to online version: The report for this project includes tables and figures that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact North Central SARE at (402) 472-7081 or [email protected].]

Objectives: The overall goal of this project was to reduce the financial and environmental costs of weed control in corn and soybeans. We targeted conventional growers — those least likely to adopt organic methods and those using the most toxic herbicides. Our first objective was to develop and evaluate weed management practices that satisfy two often conflicting environmental goals: reducing chemical inputs without the increased soil erosion that comes with intensive plowing and cultivation. Next, we tested various alternative weed management practices on cooperating growers’ farms. Our third objective was disseminate results of this research through scientific publications, grower meetings, and a field day.

Methods: To develop weed control practices that minimize herbicides as well as soil erosion, we conducted component studies to determine how to get the most out of cultural practices like cover crops, modified row spacing, and high residue cultivation to control weeds. The specific studies were designed to answer questions asked by grower cooperators, such as: what is the time and seeding rate for hairy vetch?, and how far can herbicide rates be reduced before yields are affected? These and similar questions were studied in replicated, randomized experiments on the university farm so that growers would not have to sacrifice production in treatments that might be ineffective. To test the alternative practices in real farm situations, growers set goals for economic or environmental changes they wanted to make on their farms. Growers were interested in reducing costs and negative environmental impacts of weed control, but were not willing to sacrifice production. Findings were disseminated at an ‘Integrated Crop Production’ field day that addressed the many trade-offs involved in trying to achieve optimal crop productivity without inflicting environmental damage.

Results: We found several effective ways to reduce or eliminate the use of the most toxic herbicides with little increased risk of soil erosion. For growers familiar with herbicides, the easiest way to reduce potential environmental impact was to simply switch to safer products. Further reductions in herbicides were achieved by banding and high residue cultivation. Using this system with reduced rates allowed us to reduce herbicides 85 to 95%. More important than simply decreasing herbicide use was the large reduction in potential environmental impact. A small grains cover crop helped suppress weeds in soybeans, but hairy vetch was less effective in suppressing weeds in corn. Grower cooperators identified the goal of reducing or eliminating high-rate residual herbicides as an environmental as well as an economic decision. Water quality and herbicide drift were important reasons for altering weed control practices.

Impact: The integrated crop management field day was attended by about 50 growers. Results of this project are being used to develop a section on nonchemical weed control methods for the Ohio Weed Control Guide. We are also developing a web page about weeds and weed management in Ohio to address issues about this project as well as a summary of our data. We have prepared a draft manuscript discussing the environmental and health risks and benefits associated with alternative weed management practices. One of the most important results of this project is that the relationship between researchers and growers has continued and we are now exploring low input approaches to management of perennial weeds.


The goal of this research was to reduce the environmental impact of weed management systems without compromising grain production or increasing risk of soil erosion. Studies were conducted on growers' fields and in small plots to develop and evaluate integrated management systems that reduce chemical inputs and costs of weed control. Cover crops, mechanical cultivation, and alternative herbicide technologies were used to reduce residual herbicide and fertilizer inputs. Reduced environmental impact of herbicides was achieved by reducing rates of standard herbicides and use of lower toxicity herbicides at reduced rates. Cover crops and row cultivation were used in and effort achieve effective weed control with reduced herbicide rates. A hairy vetch cover crop contributed significant nitrogen and suppressed early season weed growth. The combination of a cover crop with banded and low-rate herbicide applications reduced herbicide use without resorting to tillage practices that make soil vulnerable to erosion. Obstacles to the use of hairy vetch were the high cost of seed and the need for early establishment. Studies showed that optimum planting dates were from early to late August, and surface sowing was only successful if a rain immediately followed seeding. Although the effectiveness of cover crops for weed control was low and restricted to early season weeds, their value for soil cover and erosion reduction was high. A no-till cultivator was effective when herbicides were banded over the crop row; acceptable weed control was achieved with a reduction in herbicide rates up to 85%. Using an index to compare the environmental impact of various herbicides, the least potential negative impact for corn was for systems that had a hairy vetch cover crop plus banded applications of the herbicide imazethapyr at reduced rates with a no-till cultivator. For soybeans, the lowest potential negative impact was for a system with a small grain cover crop and postemergence applications of a half-rate of theifensulfuron plus chlorimuron plus quizalifop. In soil erosion and water runoff experiments, postemergence herbicide concentrations in surface water were 100 to 300 times less throughout June than concentrations of standard soil applied herbicides. Grower cooperators identified the goal of reducing or eliminating high-rate residual herbicides as an environmental as well as an economic decision. Water quality and herbicide drift were important reasons for altering weed control practices. Economic analysis showed a cost disincentive for reducing environmental risk due to higher prices for lower toxicity herbicides and the need for additional field operations compared with herbicide-only programs. A field day, attended by about 50 growers, addressed environmental and economic trade-offs associated with alternative management strategies, and demonstrated ways to integrate cover crops and rotations systems. Results are being used to prepare a discussion of nonchemical weed control methods for the Ohio Weed Control Guide and for a web page dealing with weeds and weed management in Ohio.

Project Objectives:

Develop and evaluate integrated bio-cultural weed management systems that reduce chemical inputs and costs of weed control in low-till grain production.

Implement a goal-setting approach for on-farm testing and evaluation of alternative weed management systems through a collaboration of producers, researchers, and extension personnel.

Disseminate results of collaborative research through scientific, extension, and popular publications, grower meetings and field days.


Materials and methods:

Component studies. Field experiments were conducted at the Ohio Agricultural Research and Development Center in replicated, randomized blocks to answer fundamental questions about alternative technologies. Experiments were derived from questions asked by grower cooperators to determine, for example: the optimum time, method, and seeding rate for various cover crops; methods of suppressing cover crops in spring; optimum populations for narrow row corn; reduced herbicide rates for banding with no-till cultivation.

Integration of components. Additional studies were conducted to compare integrated systems that use the above approaches in crop rotations to help identify positive interactions. Hairy vetch and winter rye cover crops were planted after wheat and corn, respectively. The hairy vetch cover crop was direct drilled in late August into wheat stubble; corn was planted in May into killed hairy vetch. After corn harvest, a winter rye cover crop was direct drilled into corn residue. The following spring, soybeans were planted or drilled into the killed rye cover crop. Soybeans were sown in narrow (8-inch) rows with a no-till drill and in wide (30-inch) rows with a no-till planter. An adapted corn hybrid was sown with a no-till planter set at a row spacing of 30 in; narrow spacing (15 in) for corn was achieved by doubling back with the planter. The cultivation was accomplished with a high-residue no-till cultivator consisting that left over 95% of residue intact.

Farm trials. Experiments were conducted on four farms in cooperation with growers who are committed to reducing weed control inputs through alternative management systems. Growers set specific goals: some to eliminate most pesticides; others only the most hazardous pesticides. A two-year plan was designed to meet goals and growers defined specific questions in order to implement the plans. Alternative weed management included cover crops, no-till cultivation, narrow rows, or reduced rate herbicide application.

Data analysis and dissemination. All randomized, replicated experiments were analyzed using appropriate statistical procedures including ANOVA and regression following transformation where necessary. Interim results were presented at a field day and have been used in presentations to farmer groups throughout Ohio. Data from component studies are being submitted in refereed publications.

Research results and discussion:

Objective 1: Component studies.
Cover crops: Nitrogen contributions from a hairy vetch cover crop were estimated at 160 lb N per acre; although not all of this will be available the first year, research suggests that N fertilizer rates can be reduced over 50% for corn planted in to hairy vetch. Cover crop biomass production and N fixation depend on timely establishment. In Ohio, optimum planting dates are from early to late August, if soil moisture is adequate. However, the window for establishment may not be sufficient for many continuous corn and corn-soybean rotations. Hairy vetch established best when seeded after small grain harvest. Delaying cover crop kill in the spring increased biomass production but the delay in corn planting also decreased crop productivity. No-till corn seeded into hairy vetch residue had consistently lower weed pressure that corn without hairy vetch. Cultivation or reduced rate postemergence herbicide programs were sometimes more effective under these conditions. If this holds true, it could mean both a savings in cost for the grower and less herbicide being applied to the environment.

Cultivation: A no-till cultivator sliced weeds off beneath crop residue, leaving residue to protect the soil from erosion. This cultivation was most effective when herbicides were applied in bands over the crop row. Under these conditions, acceptable weed control was achieved when the amount of active ingredient applied was reduced by 50% compared to broadcast applications of full labeled rates. Depending on weed pressure and herbicide used, the application of conventional herbicides could be reduced up to 85% in these systems. Substitution of new herbicides at reduced rates allowed us to reduce the amount of herbicide applied by over 90%. Because of greatly increased environmental safety of some newer herbicides, no-till cultivation systems resulted in large reductions in potential environmental impact compared to standard management systems. Weed control with no-till cultivation was better in systems with a small grain cover crops in soybeans, but was not improved by hairy vetch cover crops in corn.

Alternative herbicide technologies: Because grower cooperators were not interested in total elimination of herbicides, we sought to develop management systems that used the least amount of the most offensive herbicides, and to evaluate efficacy, economics, and potential environmental impact of alternatives. In soil erosion and water runoff studies, postemergence herbicide concentrations in surface water were 100 to 300 times less throughout June than concentrations of atrazine + alachlor. In addition, the postemergence herbicides were detected for only a short time, whereas atrazine + alachlor persisted into fall. Risks associated with atrazine + alachlor were user safety, water quality and weed resistance, but costs were low. Postemergence programs were considered to have lower user and environmental hazards, but higher risk of non-performance, higher costs, and potential resistance development. No-herbicide systems had lower input costs, higher labor costs, and different risks for users and the environment. We conclude that growers should be aware of relative risks associated with alternative management practices.

Objective 2. On farm integration of components.
The most important benefit from this project cannot be measured in dollars or bushels of corn; it is getting growers and researchers to consider the many trade-offs associated with all aspects of weed and crop management. We have also come to appreciate the complexity and difficulty in attempting to weigh benefits and risks of various management systems. This project focuses on "conventional" growers because they are the ones applying most of the herbicides and therefore the potential to reduce herbicide use resides with them. These growers are not likely to convert to "organic" production methods, so the alternative approaches they try will still include some herbicide(s). Therefore, one way to evaluate potential benefits is in terms of herbicide use reduction. Table 1 shows conservative estimates of anticipated reductions in herbicide use where alternative technologies are adopted. Use of cover crops will also improve soil structure, fertility, and biological diversity, resulting in less soil erosion, lower fertilizer inputs, and a more favorable balance between pests and predators, but these factors are difficult to quantify.

Table 2 shows results of monthly water runoff from tilled plots compared with no-till plots with no cover, corn residue, and hairy vetch cover crop. These data document higher water infiltration in no-till compared to conventional tillage, and suggest a benefit in yearly infiltration with the cover crop. All the growers we are working with have significant acreage of highly erodible land. Moldboard plowing and cultivation are not viable options for them for weed management. Therefore, one of the factors they must weigh in developing alternative management practices is potential for increased erosion. We have collected surface water runoff data from soil erosion studies with different management practices in an effort to aid this evaluation.

Energy inputs were a concern of most grower cooperators. Using growers' figures for time and fuel consumption together with published data on energy consumed in production of herbicides, we compared energy inputs in various systems (Table 3). The highest energy input was for the system with conventional tillage plus herbicides, whereas the lowest was for a no-till system with reduced rates of herbicides banded with no-till cultivation. The estimate of energy input in the organic system is conservative because only one cultivation is included; furthermore, the data are not adjusted for variation in crop productivity.

Another issue of interest is environmental impact associated with management alternatives. This is a very complicated issue because of contrasting risks involved in all management strategies. Acute and chronic hazards associated with non-herbicidal methods of weed control include hearing loss and exhaust inhalation from additional time on tractors, and silicosis from inhalation of silica dust during multiple tillage operations. Non-herbicidal methods involve more tillage, which exposes soil to wind and water erosion, and is a hazard to wildlife. Risks associated with herbicide use depend on many factors. Herbicides vary in toxicity, and many chemical, physical, and biological factors determine how they behave in the environment. We used the "Environmental Impact Quotient" method developed at Cornell to evaluate relative risk of alternative weed management strategies involving herbicides. Unfortunately, this system does not include relative risk of non-chemical methods. Nevertheless, some results are shown in Table 4, showing the relative cost of weed management and the principal hazards. In the non-organic systems, the highest environmental impact is for systems using standard no-till or a combination of tillage and herbicides. These were also among the most expensive. However, in the alternative systems that were developed and studied in this project, the relative environmental impact was reduced significantly by switching herbicides, using reduced rates, and banding with no-till cultivation. As the data for the alternative no-till systems indicate, there is also a cost associated with reducing environmental impact where herbicides are used. In organic systems, the cost of reducing environmental impact is borne by rotation to crops with lower returns, such as wheat and hay.

Objective 3. Dissemination of results.
Results of experiment station and on-farm studies continue to be disseminated through scientific publications, popular publications, and field days. Publications focus not only on biological and economic data and will generate a discussion on evaluating sustainability of management systems as well as the use of the goal setting approach to adopting alternative management. Research plots and collaborating farms were part of the annual Ohio Cover Crops Field Day and other alternative agriculture oriented tours.

A Field Day was held in mid-summer at the research center and at participating farms with tours, handouts, workshops and posters. Publicity was provided by growers and by IFO coordinators. Growers, university researchers, and extension personnel provided information to the public about the trials, their scientific validity, economic risks, performance issues, and interpretation of production and economic data. One important feature of this project was the support and cooperation of extension personnel, who lend their expertise and state-wide contacts to make field days a success.

Participation Summary

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

The following publications are in print, press, or preparation:

Gallagher R. S & Cardina J. Row cultivation for modified no-till corn system. To be submitted to Weed Science.

Gallagher R. S. & Cardina J. Integrating row spacing, cover crops, and reduced herbicide rates for weed management in no-till corn and soybean. To be submitted to Agronomy Journal.

Gallagher R. S., Cardina J., & Webster T. Optimizing hairy vetch planting dates and seeding rates for vetch biomass production and weed suppression in no-till corn. To be submitted to Weed Technology.

Gallagher R. S., Cardina J., & Harrison S. H. Crop residue and tillage effects on surface water quality parameters. To be submitted to Agronomy Journal.

Gallagher R. S. & Cardina J. Evaluation criteria for integrated crop management systems. To be submitted to Journal of Alternative Agriculture.

Gallagher R. S. & Cardina J. (1994). Integrated Crop Management Systems for No-till Corn and Soybean Production. ASA Annual Meeting, Nov. 13-18, Seattle, WA, p. 91.

Gallagher R. S., Cardina J., & Harrison S. H. (1994). Alternative management for no-till crop production. Proc. Clean Water - Clean Environment - 21st Century. 3:105-107.

Project Outcomes

Project outcomes:

Farmer Adoption

The number of growers directly involved with this research was four. One grower went out of business during the project, a testimony to the economic difficulties farmers are facing. The number of growers attending field days was about 50. Because we targeted 'conventional' growers, our audience was perhaps more skeptical than the alternative farm community might have been. However, growers were aware of many risks and benefits of various management practices, but short-term economic impacts tend to drive many management decisions. Therefore, changes in practice may be slow for "conventional" growers.

Specific recommendations are to consider all aspects of environmental, energy, time, and economic impacts of management systems, and attempt to adopt those that are appropriate for the local soil and site conditions. Too often, there is a focus on the latest environmental issue that is has received coverage in the press. But issues like soil erosion, that have little public appeal, can be more significant for long term sustainability than other issues that receive greater attention. Secondly, growers should consider that the most effective way to reduce hazards associated with herbicides is to use less by switching chemistry, banding, or lowering rates; however, as growers move away from standard approaches, costs and risk of non-performance may increase.


Areas needing additional study

There is a strong need for more integrative studies on weed biology and ecology, with special attention to seed dispersal and survival in soil seedbanks. Long-term crop/weed management studies are needed to understand how species shifts occur. In addition, growers need information on when and where weeds of different species are likely to occur with respect to landscape dictated soil properties.

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.