1a. Objectives (from AD-416):
Our overall goal for this project is to develop cover crop-based, reduced-tillage grain production systems that improve farm production sustainability, minimize herbicide resistant weeds, reduce weed-crop competition in organic agriculture, and maximize agro-ecosystem services. Objective 1: Improve the feasibility of using multi-tactic weed management approaches for field cropping systems by developing optimal configurations of cover crops, chemical and cultural weed controls, and soil and crop management. [NP304, Component 2, Problem Statement 2A3] • Sub-objective 1A. Develop cropping systems that integrate multi-tactic weed management practices (physical, chemical, and biological) to address herbicide resistant weeds and weed-crop competition in conventional and organic systems, through optimal combinations of soil management, cover cropping, and at harvest weed seed removal. • Sub-objective 1B. Characterize allelochemicals and nitrogen compounds from living and decomposing cover crops; track their influence on crop: emergence and yield, and weed: emergence, growth rates, and fecundity.
1b. Approach (from AD-416):
Sub-objective 1A. Develop cropping systems that integrate multi-tactic weed management practices (physical, chemical, and biological) to address herbicide resistant weeds and weed-crop competition in organic systems, through optimal combinations of soil management, cover cropping, and at harvest weed seed removal. Experiment 1A.1. Determine individual and combined effects of cover crop mixtures, fertilizer source/rate/placement, and herbicides on weed competitiveness and community assembly in high residue no-till corn production. Experiment 1A.2. Test the impact that harvest weed seed collection (HWSC), herbicides, and cover crops have on weed population dynamics and management of multiple-herbicide resistant weed genotypes in soybean. Sub-objective 1B. Characterize allelochemicals and nitrogen compounds from living decomposing cover crops; track their influence on crop: emergence and yield, and weed: emergence, growth rates, and fecundity. Goal 1B.1. Quantify allelochemical and nitrogenous products released into the soil as a function of cover crop: species, growth stage, and termination method. Experiment 1B.2. Determine the magnitude and duration of weed suppression from cereal rye allelopathic compounds and their interaction with herbicides, and mulch mass on herbicide-resistant weeds.
3. Progress Report:
This is the third year of this project plan. Five of six milestones for the third year of this project were met. The sixth milestone was not met due to the retirement of a support scientist assigned to this aspect of the project plan. We submitted 19 papers over the past year (fourteen of which were accepted) on cover crop-based corn and soybean production, cover crop management for optimal weed and nitrogen management, integrated cover crop and manure management fertility, weed management with high residue cultivators, effects of chemical weed management programs on cover crop performance, allelochemical activity in the soil, cover crop breeding, and influence on crop management on nemotodes. Under Sub-objective 1A, the third year of a long-term multi-tactic weed management cropping systems experiment was continued; all samples were collected and analyzed. Stationary testing of the Harrington Seed Destructor was completed and data is being analyzed. Weed seedbanks and the overall population dynamics of weeds in two long-term cropping system experiments were completed. Under Sub-objective 1B, we used empirical trials to validate and calibrate process-based models that determine nitrogen release from cover crops as well as develop incubation studies to define the decomposition kinetics of cover crops. Cereal rye roots, not shoots, were found to be the primary contributor of phenolic acids to soil. Further, soil phenolic acid concentrations were little affected by tillage or soil depth. Overall, the phenolic acids concentrations increased in soils during the first 3-7 days after cereal rye termination and then decreased to initial concentrations after 56 days. Our research provides insights for future allelopathic research. Specifically, there is a need to understand root release of phenolic acids. Building this body of knowledge is critical to incorporate allelopathy as part of a multi-tactic weed management system. Work on an ARS Area-Wide project directed at developing multi-tactic weed management strategies that address herbicide resistant weeds was continued. For this, the third year of a long-term experiment was completed at three sites (Illinois, Arkansas, and Maryland) to examine the independent and combined effects of cover crops, harvest-time weed seed control, and herbicides on weed control. In addition, all 14 cooperating sites on the Area-Wide project completed the third year of a weed seed rain study to examine which weed species are candidates for control using harvest-time weed seed control tactics. Finally, a cover crop/herbicide interaction study on weed population dynamics entered its second year. We have an accepted manuscript that assesses how the level of cooperation by farmers in addressing herbicide resistance through a shared practice can mitigate frequency of resistance. Further more, we have begun simulations assessing individual and combined effects of numerous weed management tactics (harvest weed seed control, cover crops, tillage, crop rotation, and herbicides). Another round of funding for the Area-Wide project is expected for FY2019 and agreements will be put in place to fund research at cooperating sites next year upon receipt of this funding.
1. Grass/legume mixtures of warm-season summer annual cover crops increase weed suppression in the Northeast. The complementary features of grass-legume species can make combinations of cover crops more competitive against weeds than a single cover crop species by more effectively excluding resources such as nutrients and light from weeds. ARS scientists in Beltsville, Maryland, in collaboration with Cornell University conducted a two-year experiment across the Northeastern U.S. to examine the effects of individual cover crop and cover crop combination treatments on weed suppression. It was found that increasing the number cover crop species increased weed suppression, and that legume cover crops alone were not effective at weed suppression; that mixing legume cover crops with grasses increased their biomass and maximized weed control. This information will be of use to extension and ag-industry personnel who advise farmers on the use of cover crops.
2. Tolerance of interseeded annual ryegrass and red clover cover crops to residual herbicides. Relatively few farmers grow cover crops due to the difficulty in getting adequate cover crop growth before winter. Planting cover crops earlier in the growing season when corn is less than two feet tall using specialized interseeder planting equipment holds promise, but remnant herbicides applied to the corn cash crop may damage cover crops. ARS scientists in Beltsville, Maryland, in collaboration with Penn State and Cornell University examined the impact of herbicides on annual ryegrass and red clover cover crops. We found that most herbicidies damaged annual ryegrass and that mesotrione caused significant damage to red clover. Herbicides saflufenacil, rimsulfuron, and atrazine did not cause significant damage to either cover crop. This research promotes the use of cover crops by demonstrating compatability of certain cover crop-herbicide combinations that can be used by farmers who wish to establish cover crops via interseeding.
3. Planting drill for interseeding cover crops into corn. Relatively few farmers in the mid-Atlantic region grow cover crops due to inadequate cover crop growth before winter. ARS scientists in Beltsville, Maryland, in collaboration with Penn State and Cornell University designed a cover crop interseeder drill that plants cover crop seed prior to corn harvest to lengthen the cover crop growing season and enhance cover crop establishment before winter. Interseeded cover crops planted with this drill did not affect grain yields of the corn cash crop when planted at corn growth stage V5 about 18 inches in height. Our results highlight the viability of this novel drill for interseeding cover crops.
Wayman, S., Kucek, L.K., Mirsky, S.B., Ackroyd, V., Cordeau, S., Ryan, M.R. 2016. Organic and conventional farmers differ in their perspective on cover crop use and breeding. Renewable Agriculture and Food Systems. 32:376-385.
Melkonian, J., Poffenbarger, H.J., Mirsky, S.B., Ryan, M.R., Moebius-Clune, B.N. 2017. Estimating nitrogen mineralization from cover crop mixtures using the Precision Nitrogen Management model. Agronomy Journal. 109:1944-1959.
Vann, R.A., Reberg-Horton, S., Mirsky, S.B., Poffenbarger, H.J., Zinati, G.M., Moyer, J.B. 2017. Starter fertilizer for managing cover crop-based organic corn. Agronomy Journal. 109:2214-2222.
Mirsky, S.B., Ackroyd, V.J., Cordeau, S., Curran, W.S., Hashemi, M., Reberg-Horton, S., Ryan, M., Spargo, J.T. 2017. Hairy vetch biomass across the eastern United States: Effects of latitude, seeding rate and date, and termination timing. Agronomy Journal. 109:1510-1519.
Hoffman, E., Cavigelli, M.A., Gustavo, C., Matthew, R., Ackroyd, V.J., Richard, T.L., Mirsky, S.B. 2018. Energy use and greenhouse gas emissions in organic and conventional grain crop production: accounting for nutrient inflows. Agriculture Ecosystems and the Environment. 162:89-96.
Curran, W.S., Hoover, R.J., Mirsky, S.B., Roth, G.W., Ryan, M.R., Ackroyd, V.J., Wallace, J.M., Dempsey, M.A., Pelzer, C.J. 2018. Evaluation of cover crops drill interseeded into corn across the mid-Atlantic region. Agronomy Journal. 110:435-443. https://doi.org/10.2134/agronj2017.07.0395.
Mirsky, S.B., Spargo, J.T., Curran, W.S., Reberg-Horton, S., Ryan, M., Schomberg, H.H., Ackroyd, V.J. 2017. Characterizing cereal rye biomass and allometric relationships across a range of fall available nitrogen rates in the eastern United States. Agronomy Journal. 109:1520-1531.
Bybee-Finley, A., Mirsky, S.B., Ryan, M. 2017. Crop biomass not species richness drives weed suppression in warm-season annual grass-legume intercrops in the Northeast. Weed Science. 65:669-680.
Wallace, J.M., Curran, W.S., Mirsky, S.B., Ryan, M.R. 2017. Tolerance of interseeded annual ryegrass and red clover cover crops to residual herbicides in Mid-Atlantic corn cropping systems. Weed Technology. 31:641-650.
Wallace, J.M., Keene, C.L., Curran, W.S., Mirsky, S.B., Ryan, M.R., Van Gessel, M.J. 2018. Integrated weed management strategies in cover crop-based, organic rotational no-till corn and soybean in the mid-Atlantic region. Weed Science. 66:94-108.
Teasdale, J.R., Mirsky, S.B., Cavigelli, M.A. 2018. Meteorological and management factors influencing weed abundance during 18 years of organic crop rotations. Weed Science. 1:8. https://doi.org/10.1017/wsc.2018.15.