M. Scott Wells

Overcoming weed management challenges in cover crop-based organic rotational no-till soybean production in the Eastern United States

Abstract Cover crop–based organic rotational no-till soybean production has attracted attention from farmers, researchers, and other agricultural professionals because of the ability of this new system to enhance soil conservation, reduce labor requirements, and decrease diesel fuel use compared to traditional organic production. This system is based on the use of cereal rye cover crops that are mechanically terminated with a roller-crimper to create in situ mulch that suppresses weeds and promotes soybean growth. In this paper, we report experiments that were conducted over the past decade in the eastern region of the United States on cover crop–based organic rotational no-till soybean production, and we outline current management strategies and future research needs. Our research has focused on maximizing cereal rye spring ground cover and biomass because of the crucial role this cover crop plays in weed suppression. Soil fertility and cereal rye sowing and termination timing affect biomass production, and these factors can be manipulated to achieve levels greater than 8,000 kg ha−1, a threshold identified for consistent suppression of annual weeds. Manipulating cereal rye seeding rate and seeding method also influences ground cover and weed suppression. In general, weed suppression is species-specific, with early emerging summer annual weeds (e.g., common ragweed), high weed seed bank densities (e.g. > 10,000 seeds m−2), and perennial weeds (e.g., yellow nutsedge) posing the greatest challenges. Due to the challenges with maximizing cereal rye weed suppression potential, we have also found high-residue cultivation to significantly improve weed control. In addition to cover crop and weed management, we have made progress with planting equipment and planting density for establishing soybean into a thick cover crop residue. Our current and future research will focus on integrated multitactic weed management, cultivar selection, insect pest suppression, and nitrogen management as part of a systems approach to advancing this new production system. Nomenclature: Common ragweed, Ambrosia artemisiifolia L.; yellow nutsedge, Cyperus esculentus L.; cereal rye, Secale cereale L.; corn, Zea mays L.; soybean, Glycine max (L). Merr.; wheat, Triticum aestivum L. Resumen La producción orgánica de soya en sistemas de rotación con cero labranza basados en cultivos de cobertura, ha atraído la atención de productores, investigadores y otros profesionales agrícolas por la habilidad de este nuevo sistema de mejorar la conservación del suelo, reducir los requerimientos de mano de obra y disminuir el uso de combustible diesel en comparación con la producción orgánica tradicional. Este sistema está basado en el uso de centeno como cultivo de cobertura el cual es terminado mecánicamente con un rodillo de cuchillas para crear una cobertura de residuos in situ que suprime malezas y promueve el crecimiento de la soya. En este artículo, reportamos experimentos que fueron realizados durante la década pasada en la región este de los Estados Unidos sobre la producción orgánica de soya en sistemas de rotación con cero labranza basados en cultivos de cobertura, y delineamos las estrategias actuales de manejo y las necesidades futuras de investigación. Nuestra investigación se ha enfocado en maximizar la cobertura y la biomasa del centeno de primavera debido al papel crucial que este cultivo de cobertura juega en la supresión de malezas. La fertilidad del suelo y el momento de siembra y término del centeno afectan la producción de biomasa, y estos factores pueden ser manipulados para alcanzar niveles mayores a 8,000 kg ha−1, el cual es el umbral identificado para la supresión consistente de malezas anuales. Manipular la densidad y métodos de siembra también influencia la cobertura del suelo y la supresión de malezas. En general, la supresión de malezas es específica a la especie, siendo las malezas anuales de verano que emergen temprano (e.g. Ambrosia artemisiifolia), los banco de semillas con altas densidades (e.g. >10,000 semillas m−2), y las malezas perennes (e.g. Cyperus esculentus) los mayores retos. Debido a los retos de maximizar el potencial de supresión de malezas del centeno, hemos encontrado que el cultivar con altos residuos también puede mejorar el control de malezas significativamente. Adicionalmente al cultivo de cobertura y el manejo de malezas, hemos progresado con el equipo y la densidad de siembra para el establecimiento de la soya en capas gruesas de residuos de cultivos de cobertura. Nuestra investigación actual y futura se centrará en el manejo integrado de malezas multitáctico, la selección de cultivares, la supresión de plagas insectiles, y el manejo del nitrógeno como parte de un enfoque de sistemas para el avance de este nuevo sistema de producción.

Cultural strategies for managing weeds and soil moisture in cover crop based no-till soybean production

Abstract A four site-year study was conducted in North Carolina to evaluate the effects of soybean planting timing and row spacing on soil moisture, weed density, soybean lodging, and yield in a cover crop-based no-till organic soybean production system. Soybean planting timing included roll-kill/planting and roll-kill/delayed planting where soybean planting occurred either on the same day or approximately 2 wk later, respectively. Soybean row spacing included 19, 38, and 76 cm, and all treatments included a weedy check and weed-free treatment. Rye biomass production averaged above 10,000 kg ha−1 dry matter, which resulted in good weed control across all sites. Despite having good weed control throughout all treatments, weed coverage was highest in the 76-cm row-space treatment when compared to both the 19-cm and 38-cm row spacing in two of the four site-years. Soybean lodging is a potential consequence of no-till planting of soybeans in high residue mulches, and of the three row spacings, the 19-cm spacing exhibited the greatest incidence of lodging. Row spacing also influenced soybean yield; the 19- and 38-cm row spacing out yielded the 76-cm spacing by 10%. Soil volumetric water content (VWC) was higher in the cereal rye mulch treatments compared to the no rye checks. Furthermore, delaying soybean planting lowered soil water evaporation. However, the increased soil VWC in the rolled-rye treatment did not translate into increased soybean yield. The rolled-rye treatment exhibited significant (P < 0.01) increases in soil VWC when compared to the no-rye treatment at three of the four site-years. These results highlight planting date flexibility and potential risk to lodging that producers face when no-till planting organic soybeans. Nomenclature: Glyphosate; s-metolachlor; imazethapyr; redroot pigweed, Amaranthus retroflexus L.; cereal rye, Secale cereal L.; DM, dry matter.

Weed suppression and soybean yield in a no-till cover-crop mulched system as influenced by six rye cultivars

Cover crop mulches have been successful in reducing weed severity in organic soybeans. This study examined six rye cultivars (SRCs) used as cover crops to determine which were most adapted for use with a roller–crimper in the southeastern U.S. To be an effective mulch, a rye cultivar must produce high biomass and reach reproductive growth stage to facilitate mechanical termination via the roller–crimper prior to soybean planting. Rye cultivars were planted at three locations in North Carolina over the 2009 and 2010 growing seasons. Each rye cultivar was mechanically terminated via a roller–crimper implement. Rye cover crops were terminated on two dates and soybeans were immediately no-till planted into the mulch. In 2009, all rye cultivars produced greater than 9000 kg ha −1 rye biomass dry matter (DM) with the exception of Rymin at Plymouth (2009), but in 2010 only the early flowering cultivars produced in excess of 9000 kg ha −1 DM. There were no detectable soybean yield differences between the SRCs and the weed-free checks, and weed control was excellent across all SRCs at both Plymouth and Salisbury (2009). After an unseasonably cold and wet winter in 2010, the late flowering rye cultivars were not fully controlled by the early termination date due to delayed maturation (less than 65% control at 2 WAP) whereas the early flowering cultivars were fully controlled (100% control at 2 WAP). Rye biomass production was below 9000 kg ha −1 DM for the late flowering and dough development rye cultivars. The early-terminated rye plots had greater weed coverage across all SRCs than those from the late termination date ( P

Glucose and Insulin Response of Horses Grazing Alfalfa, Perennial Cool-Season Grass, and Teff Across Seasons

Abstract Elevated nonstructural carbohydrate (NSC) values in pasture forages can cause adverse health effects in some horses (Equus caballus L.). The objectives of this study were to determine the impact of different forage species on blood glucose and insulin concentrations of horses throughout the grazing season. Research was conducted in July (summer) and September (fall) in St. Paul, MN. Alfalfa (Medicago sativa L.), mixed perennial cool‐season grasses (CSG), and teff (Eragrostis tef [Zucc.] Trotter) pastures were grazed by six horses (24 ± 2 years) that were randomly assigned to one of three forage types in a replicated Latin‐square design. Jugular catheters were inserted 1 hour before the start of grazing and horses had access to pasture each day from 08:00 to 16:00 hours. Jugular venous blood samples were collected from each horse before being turned out (0 hours) and then at 2‐hour intervals following turnout. Plasma and serum samples were collected and analyzed for glucose and insulin, respectively. Corresponding forage samples were taken by hand harvest. Seasons were analyzed separately and data were analyzed using the MIXED procedure in SAS with P ≤ .05. Teff generally had lower (P ≤ .05) equine digestible energy, crude protein, and NSC compared to the other forages. Differences in peak insulin were observed between horses grazing CSG and teff during the fall grazing (P ≤ .05). These results suggest grazing teff could lower the glucose and insulin response of some horses. HighlightsTeff consistently had higher fiber and lower digestible energy values.Horses grazing teff had a tendency for a lower insulinemic response in the fall.Teff has potential to be used as alternative forage for overweight horses.