{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/140698"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/140698","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"Optimizing Weed Suppression Via Cover Crop and Herbicide Programs in the Mid-Atlantic","abstract":"Many Virginia farmers include cover crops in their corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production due to government subsidies and agronomic benefits. Progressive farmers have optimized cover crop management for specific goals, such as weed suppression and nitrogen fertilizer reductions. Waiting to terminate the cover crop until cash crop planting, so-called \"planting green,\" is often part of the management and is an evolution from the traditional termination timing prior to cash crop planting. To scientifically scrutinize these production systems, three research objectives were developed. These objectives included determining if these systems lead to greater biomass accumulation, increase overall weed suppression, and reduce herbicide inputs. The goal of our first experiment was to determine if a hairy vetch (Vicia villosa R.) and cereal rye (Secale cereale L.) mixture, where the cereal rye was selectively terminated in March, performed better than a hairy vetch monoculture for biomass accumulation and weed suppression. Results indicated that hairy vetch monocultures typically produced greater hairy vetch biomass throughout the season, had greater nitrogen contents, and provided similar weed suppression. Overall, a hairy vetch monoculture cover crop can substitute for a hairy vetch + cereal rye mixture, when the cereal rye is selectively terminated, while providing similar or greater benefits to the following cash crop. Our second objective compared 1-, 2-, and 3-pass herbicide programs initiated either two weeks prior to, or at, corn planting paired with either hairy vetch, hairy vetch + cereal rye, or a winter fallow to determine if herbicide input reductions are possible. We determined a reduction from a 3- pass to a 2- pass herbicide program is possible, however, at least a 2-pass program is needed for season-long weed suppression. Also, herbicide programs that terminated the cover crop at planting (i.e. planted green) tended to provide as good or better weed suppression compared to cover crops terminated prior to planting. While cereal rye is a very popular species for cover cropping, farmers have reported nitrogen immobilization and planting problems because of its extensive biomass and high C:N ratio. Due to this, farmers are interested in substituting black oat (Avena strigosa S.) for cereal rye. Therefore, we conducted two experiments to compare cover crop characteristics. In corn, cereal rye, cereal rye + hairy vetch, black oats, and black oat + hairy vetch were compared while in soybean, black oat and cereal rye treatments were compared. Our results for both experiments indicated that cereal rye and black oat monocultures are similar in terms of lignin content and C:N ratio at cash crop planting. However, black oat treatments typically produced less biomass and suppressed fewer weeds compared to cereal rye treatments. This trend was also seen when comparing the black oat and hairy vetch mixture to the cereal rye and hairy vetch mixture. Ultimately, regardless of cash crop, farmers may still prefer to use a cereal rye monoculture or mixture as their cover crop. Overall, the results of these experiments show that hairy vetch monocultures have the potential to increase weed suppression, nitrogen output, and biomass accumulation compared to hairy vetch and a grass cover crop mixture. However, farmers who include a grass species may lean towards cereal rye because of its benefits over black oats.","abstract_html":"Many Virginia farmers include cover crops in their corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production due to government subsidies and agronomic benefits. Progressive farmers have optimized cover crop management for specific goals, such as weed suppression and nitrogen fertilizer reductions. Waiting to terminate the cover crop until cash crop planting, so-called "planting green," is often part of the management and is an evolution from the traditional termination timing prior to cash crop planting. To scientifically scrutinize these production systems, three research objectives were developed. These objectives included determining if these systems lead to greater biomass accumulation, increase overall weed suppression, and reduce herbicide inputs. The goal of our first experiment was to determine if a hairy vetch (Vicia villosa R.) and cereal rye (Secale cereale L.) mixture, where the cereal rye was selectively terminated in March, performed better than a hairy vetch monoculture for biomass accumulation and weed suppression. Results indicated that hairy vetch monocultures typically produced greater hairy vetch biomass throughout the season, had greater nitrogen contents, and provided similar weed suppression. Overall, a hairy vetch monoculture cover crop can substitute for a hairy vetch + cereal rye mixture, when the cereal rye is selectively terminated, while providing similar or greater benefits to the following cash crop. Our second objective compared 1-, 2-, and 3-pass herbicide programs initiated either two weeks prior to, or at, corn planting paired with either hairy vetch, hairy vetch + cereal rye, or a winter fallow to determine if herbicide input reductions are possible. We determined a reduction from a 3- pass to a 2- pass herbicide program is possible, however, at least a 2-pass program is needed for season-long weed suppression. Also, herbicide programs that terminated the cover crop at planting (i.e. planted green) tended to provide as good or better weed suppression compared to cover crops terminated prior to planting. While cereal rye is a very popular species for cover cropping, farmers have reported nitrogen immobilization and planting problems because of its extensive biomass and high C:N ratio. Due to this, farmers are interested in substituting black oat (Avena strigosa S.) for cereal rye. Therefore, we conducted two experiments to compare cover crop characteristics. In corn, cereal rye, cereal rye + hairy vetch, black oats, and black oat + hairy vetch were compared while in soybean, black oat and cereal rye treatments were compared. Our results for both experiments indicated that cereal rye and black oat monocultures are similar in terms of lignin content and C:N ratio at cash crop planting. However, black oat treatments typically produced less biomass and suppressed fewer weeds compared to cereal rye treatments. This trend was also seen when comparing the black oat and hairy vetch mixture to the cereal rye and hairy vetch mixture. Ultimately, regardless of cash crop, farmers may still prefer to use a cereal rye monoculture or mixture as their cover crop. Overall, the results of these experiments show that hairy vetch monocultures have the potential to increase weed suppression, nitrogen output, and biomass accumulation compared to hairy vetch and a grass cover crop mixture. However, farmers who include a grass species may lean towards cereal rye because of its benefits over black oats.","abstract_has_math":false,"creators":["Beville, Jenna Elizabeth"],"institution":"Virginia Tech","degree_name":"Master of Science in Life Sciences","degree_level":"masters","degree_discipline":"Plant Pathology, Physiology and Weed Science","degree_department":"Plant Pathology, Physiology and Weed Science","school":null,"contributors":[],"advisors":[],"committee_chairs":["Flessner, Michael L."],"committee_members":["Askew, Shawn D.","Frame, W. Hunter"],"year":2026,"date_issued":"2026-01-08","date_published":"2026-01-08","updated_at":"2026-07-22T22:20:35Z","subjects":["Biomass accumulation","weed suppression","herbicide reduction","hairy vetch (Vicia villosa R.)","cereal rye (Secale cereale L.)","black oat (Avena strigosa S.)"],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45616"],"render_values":[{"text":"vt_gsexam:45616","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/140698","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Flessner, Michael L."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Askew, Shawn D.","Frame, W. Hunter"]},{"key":"dc:contributor.department","label":"Department","values":["Plant Pathology, Physiology and Weed Science"]},{"key":"dc:creator","label":"Author","values":["Beville, Jenna Elizabeth"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-01-09T09:02:06Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-01-09T09:02:06Z"]},{"key":"dc:date.issued","label":"Date","values":["2026-01-08"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Plant Pathology, Physiology and Weed Science"]},{"key":"thesis:degree_level","label":"Degree Level","values":["masters"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science in Life Sciences"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Biomass accumulation","weed suppression","herbicide reduction","hairy vetch (Vicia villosa R.)","cereal rye (Secale cereale L.)","black oat (Avena strigosa S.)"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45616"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/140698"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Many Virginia farmers include cover crops in their corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production due to government subsidies and agronomic benefits. Progressive farmers have optimized cover crop management for specific goals, such as weed suppression and nitrogen fertilizer reductions. Waiting to terminate the cover crop until cash crop planting, so-called \"planting green,\" is often part of the management and is an evolution from the traditional termination timing prior to cash crop planting. To scientifically scrutinize these production systems, three research objectives were developed. These objectives included determining if these systems lead to greater biomass accumulation, increase overall weed suppression, and reduce herbicide inputs. The goal of our first experiment was to determine if a hairy vetch (Vicia villosa R.) and cereal rye (Secale cereale L.) mixture, where the cereal rye was selectively terminated in March, performed better than a hairy vetch monoculture for biomass accumulation and weed suppression. Results indicated that hairy vetch monocultures typically produced greater hairy vetch biomass throughout the season, had greater nitrogen contents, and provided similar weed suppression. Overall, a hairy vetch monoculture cover crop can substitute for a hairy vetch + cereal rye mixture, when the cereal rye is selectively terminated, while providing similar or greater benefits to the following cash crop. Our second objective compared 1-, 2-, and 3-pass herbicide programs initiated either two weeks prior to, or at, corn planting paired with either hairy vetch, hairy vetch + cereal rye, or a winter fallow to determine if herbicide input reductions are possible. We determined a reduction from a 3- pass to a 2- pass herbicide program is possible, however, at least a 2-pass program is needed for season-long weed suppression. Also, herbicide programs that terminated the cover crop at planting (i.e. planted green) tended to provide as good or better weed suppression compared to cover crops terminated prior to planting. While cereal rye is a very popular species for cover cropping, farmers have reported nitrogen immobilization and planting problems because of its extensive biomass and high C:N ratio. Due to this, farmers are interested in substituting black oat (Avena strigosa S.) for cereal rye. Therefore, we conducted two experiments to compare cover crop characteristics. In corn, cereal rye, cereal rye + hairy vetch, black oats, and black oat + hairy vetch were compared while in soybean, black oat and cereal rye treatments were compared. Our results for both experiments indicated that cereal rye and black oat monocultures are similar in terms of lignin content and C:N ratio at cash crop planting. However, black oat treatments typically produced less biomass and suppressed fewer weeds compared to cereal rye treatments. This trend was also seen when comparing the black oat and hairy vetch mixture to the cereal rye and hairy vetch mixture. Ultimately, regardless of cash crop, farmers may still prefer to use a cereal rye monoculture or mixture as their cover crop. Overall, the results of these experiments show that hairy vetch monocultures have the potential to increase weed suppression, nitrogen output, and biomass accumulation compared to hairy vetch and a grass cover crop mixture. However, farmers who include a grass species may lean towards cereal rye because of its benefits over black oats."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["Cover crops are plants that are grown during the off seasons of main crops, such as corn (Zea mays L.) or soybean (Glycine max (L.) Merr.). These crops are not grown for profit, but rather because of benefits for crop production like weed suppression or nutrient output. Government subsidies associated with certain cover crops have also helped them gain popularity in Virginia. Recently, more Virginia farmers have started using specific cover crops to achieve certain outcomes such as reducing the need for fertilizer and/or herbicides. To try to capitalize on these benefits, farmers often wait to kill their cover crops until cash crop planting, also known as \"planting green.\" This timing differs from the traditional management when cover crops are killed prior to cash crop planting. Many corn farmers in Virginia have opted to use either hairy vetch (Vicia villosa R.) alone or a hairy vetch and cereal rye (Secale cereale L.) mixture as a cover crop. Currently, little research has been done on the impact of planting green into hairy vetch monocultures or mixtures in Virginia. Therefore, to better characterize these practices, experiments were conducted. Progressive corn farmers who plant a hairy vetch and cereal rye mixture cover crop and terminate only the cereal rye in March which leaves the hairy vetch to keep growing until corn planting. This method allows the farmer to maximize the benefits from the hairy vetch such as weed suppression and nitrogen output while avoiding issues associated with cereal rye. Our analysis of this system found that hairy vetch alone produced larger amounts of hairy vetch biomass throughout the season, had more potential fertilizer reductions, and could provide similar weed suppression compared to the hairy vetch and cereal rye mixture. Thus, we determined that hairy vetch alone could be a substitute for the hairy vetch and cereal rye mixture, when the cereal rye is selectively terminated, and still provide similar if not better benefits to the following corn crop. Many corn farmers in Virginia have reported being able to reduce herbicide use due to the weed suppression provided by cover crops. Thus, our second experiment was comparing 1-, 2-, and a 3- pass herbicide programs in either no cover crop, hairy vetch only, or a hairy vetch and cereal rye mixture to determine if reducing herbicide inputs is possible. A reduction from a 3-pass to a 2-pass can be possible without a loss of weed control. We also saw that herbicide programs that enable the corn to be planted green tended to result in greater weed control compared to cover crops terminated prior to planting. While cereal rye is a popular cover crop in Virginia, farmers have reported planting issues and potential increases in fertilizer needs. Black oats (Avena strigosa S.) is a potential substitute for addressing these issues. Thus, we compared black oat, cereal rye, and then either paired with hairy vetch in corn and black oats and cereal rye alone in soybean. Cereal rye and black oats alone tended to have similar chemical compositions at cash crop planting. We also saw that black oats typically produced lesser amounts of biomass and suppressed fewer weeds compared to cereal rye. Similar results were seen with treatments containing hairy vetch. Overall, farmers in Virginia may still favor cereal rye alone or within a mixture over black oats, regardless of the following cash crop. Ultimately, our research concluded that a cover crop of hairy vetch alone typically leads to greater biomass accumulation, nitrogen accumulation, and weed suppression compared to a hairy vetch and grass species mixture. However, if farmers intend to add a grass species, cereal rye may be more favorable due to its greater benefits compared to black oats. Farmers may want to add a grass cover crop to increase the overall cover crop's biomass, reduce soil erosion, and offset costs due to associated government subsidies."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Master of Science in Life Sciences"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["Optimizing Weed Suppression Via Cover Crop and Herbicide Programs in the Mid-Atlantic"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Flessner, Michael L."],"dc:contributor.committeemember":["Askew, Shawn D.","Frame, W. Hunter"],"dc:contributor.department":["Plant Pathology, Physiology and Weed Science"],"dc:creator":["Beville, Jenna Elizabeth"],"dc:date.accessioned":["2026-01-09T09:02:06Z"],"dc:date.available":["2026-01-09T09:02:06Z"],"dc:date.issued":["2026-01-08"],"dc:description.abstract":["Many Virginia farmers include cover crops in their corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) production due to government subsidies and agronomic benefits. Progressive farmers have optimized cover crop management for specific goals, such as weed suppression and nitrogen fertilizer reductions. Waiting to terminate the cover crop until cash crop planting, so-called \"planting green,\" is often part of the management and is an evolution from the traditional termination timing prior to cash crop planting. To scientifically scrutinize these production systems, three research objectives were developed. These objectives included determining if these systems lead to greater biomass accumulation, increase overall weed suppression, and reduce herbicide inputs. The goal of our first experiment was to determine if a hairy vetch (Vicia villosa R.) and cereal rye (Secale cereale L.) mixture, where the cereal rye was selectively terminated in March, performed better than a hairy vetch monoculture for biomass accumulation and weed suppression. Results indicated that hairy vetch monocultures typically produced greater hairy vetch biomass throughout the season, had greater nitrogen contents, and provided similar weed suppression. Overall, a hairy vetch monoculture cover crop can substitute for a hairy vetch + cereal rye mixture, when the cereal rye is selectively terminated, while providing similar or greater benefits to the following cash crop. Our second objective compared 1-, 2-, and 3-pass herbicide programs initiated either two weeks prior to, or at, corn planting paired with either hairy vetch, hairy vetch + cereal rye, or a winter fallow to determine if herbicide input reductions are possible. We determined a reduction from a 3- pass to a 2- pass herbicide program is possible, however, at least a 2-pass program is needed for season-long weed suppression. Also, herbicide programs that terminated the cover crop at planting (i.e. planted green) tended to provide as good or better weed suppression compared to cover crops terminated prior to planting. While cereal rye is a very popular species for cover cropping, farmers have reported nitrogen immobilization and planting problems because of its extensive biomass and high C:N ratio. Due to this, farmers are interested in substituting black oat (Avena strigosa S.) for cereal rye. Therefore, we conducted two experiments to compare cover crop characteristics. In corn, cereal rye, cereal rye + hairy vetch, black oats, and black oat + hairy vetch were compared while in soybean, black oat and cereal rye treatments were compared. Our results for both experiments indicated that cereal rye and black oat monocultures are similar in terms of lignin content and C:N ratio at cash crop planting. However, black oat treatments typically produced less biomass and suppressed fewer weeds compared to cereal rye treatments. This trend was also seen when comparing the black oat and hairy vetch mixture to the cereal rye and hairy vetch mixture. Ultimately, regardless of cash crop, farmers may still prefer to use a cereal rye monoculture or mixture as their cover crop. Overall, the results of these experiments show that hairy vetch monocultures have the potential to increase weed suppression, nitrogen output, and biomass accumulation compared to hairy vetch and a grass cover crop mixture. However, farmers who include a grass species may lean towards cereal rye because of its benefits over black oats."],"dc:description.abstractgeneral":["Cover crops are plants that are grown during the off seasons of main crops, such as corn (Zea mays L.) or soybean (Glycine max (L.) Merr.). These crops are not grown for profit, but rather because of benefits for crop production like weed suppression or nutrient output. Government subsidies associated with certain cover crops have also helped them gain popularity in Virginia. Recently, more Virginia farmers have started using specific cover crops to achieve certain outcomes such as reducing the need for fertilizer and/or herbicides. To try to capitalize on these benefits, farmers often wait to kill their cover crops until cash crop planting, also known as \"planting green.\" This timing differs from the traditional management when cover crops are killed prior to cash crop planting. Many corn farmers in Virginia have opted to use either hairy vetch (Vicia villosa R.) alone or a hairy vetch and cereal rye (Secale cereale L.) mixture as a cover crop. Currently, little research has been done on the impact of planting green into hairy vetch monocultures or mixtures in Virginia. Therefore, to better characterize these practices, experiments were conducted. Progressive corn farmers who plant a hairy vetch and cereal rye mixture cover crop and terminate only the cereal rye in March which leaves the hairy vetch to keep growing until corn planting. This method allows the farmer to maximize the benefits from the hairy vetch such as weed suppression and nitrogen output while avoiding issues associated with cereal rye. Our analysis of this system found that hairy vetch alone produced larger amounts of hairy vetch biomass throughout the season, had more potential fertilizer reductions, and could provide similar weed suppression compared to the hairy vetch and cereal rye mixture. Thus, we determined that hairy vetch alone could be a substitute for the hairy vetch and cereal rye mixture, when the cereal rye is selectively terminated, and still provide similar if not better benefits to the following corn crop. Many corn farmers in Virginia have reported being able to reduce herbicide use due to the weed suppression provided by cover crops. Thus, our second experiment was comparing 1-, 2-, and a 3- pass herbicide programs in either no cover crop, hairy vetch only, or a hairy vetch and cereal rye mixture to determine if reducing herbicide inputs is possible. A reduction from a 3-pass to a 2-pass can be possible without a loss of weed control. We also saw that herbicide programs that enable the corn to be planted green tended to result in greater weed control compared to cover crops terminated prior to planting. While cereal rye is a popular cover crop in Virginia, farmers have reported planting issues and potential increases in fertilizer needs. Black oats (Avena strigosa S.) is a potential substitute for addressing these issues. Thus, we compared black oat, cereal rye, and then either paired with hairy vetch in corn and black oats and cereal rye alone in soybean. Cereal rye and black oats alone tended to have similar chemical compositions at cash crop planting. We also saw that black oats typically produced lesser amounts of biomass and suppressed fewer weeds compared to cereal rye. Similar results were seen with treatments containing hairy vetch. Overall, farmers in Virginia may still favor cereal rye alone or within a mixture over black oats, regardless of the following cash crop. Ultimately, our research concluded that a cover crop of hairy vetch alone typically leads to greater biomass accumulation, nitrogen accumulation, and weed suppression compared to a hairy vetch and grass species mixture. However, if farmers intend to add a grass species, cereal rye may be more favorable due to its greater benefits compared to black oats. Farmers may want to add a grass cover crop to increase the overall cover crop's biomass, reduce soil erosion, and offset costs due to associated government subsidies."],"dc:description.degree":["Master of Science in Life Sciences"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:45616"],"dc:identifier.uri":["https://hdl.handle.net/10919/140698"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["Biomass accumulation","weed suppression","herbicide reduction","hairy vetch (Vicia villosa R.)","cereal rye (Secale cereale L.)","black oat (Avena strigosa S.)"],"dc:title":["Optimizing Weed Suppression Via Cover Crop and Herbicide Programs in the Mid-Atlantic"],"dc:type":["Thesis"],"thesis:degree_discipline":["Plant Pathology, Physiology and Weed Science"],"thesis:degree_level":["masters"],"thesis:degree_name":["Master of Science in Life Sciences"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:20:35Z"}