Resumen La biodiversidad de leguminosas forrajeras adaptadas a condiciones semiáridas-áridas es escasa. En la región de transición Pampa-Patagonia de Argentina (PTRA), la precipitación anual es de 440 mm con una evapotranspiración anual de 1690 mm. Solo Vicia villosa Roth muestra adaptación agronómica a dicho ambiente. Se comparó la producción de materia seca de 19 especies de leguminosas seleccionadas con V. villosa (cv. Patagonia INTA) en el primer año de establecimiento durante 2015-2019. Medicago truncatula Gaertn. y Trifolium subterraneum L. (cv. Goulburn) mostraron una alta producción de materia seca invernal, similar a la de V. villosa, pero una pobre producción de biomasa en primavera. La materia seca de primavera aportó ≈ 80% de la biomasa total por año. Los resultados preliminares mostraron que Onobrychis viciifolia Scop. superó al resto de las accesiones evaluadas, excepto a V. villosa. O. viciifolia podría considerarse una especie complementaria a V. villosa, candidata a iniciar un proceso de mejoramiento como nueva leguminosa de pastoreo para ambientes semiáridos-áridos. Este es el primer registro del uso potencial como forrajera de O. viciifolia en la PTRA.

Abstract Biodiversity in forage legumes adapted to semiarid-arid conditions is scarce. In the Pampa-Patagonia transitional region of Argentina (PTRA), the annual rainfall is 440 mm with annual evapotranspiration of 1690 mm. Only Vicia villosa Roth shows agronomic adaptation to such an environment. Dry matter production of 19 selected legume species was compared to V. villosa (cv. Patagonia INTA) in the first year of establishment during 2015-to-2019. Medicago truncatula Gaertn. and Trifolium subterraneum L. (cv. Goulburn) showed high winter dry matter production, similar to V. villosa, but poor biomass production in spring. Spring dry matter contributed ≈ 80% of the total biomass per year. Preliminary results showed that Onobrychis viciifolia Scop. overcame the rest of the accessions evaluated, except for V. villosa. O. viciifolia could be considered a complementary species to V. villosa, a candidate for initiating a process of breeding as a new pasture legume for semiarid-arid environments. This is the first record of the potential use as a pasture of O. viciifolia in the PTRA.

Abstract Lolium multiflorum Lam. (annual ryegrass) is a problematic weed species especially in no-tillage systems of the southern region of Buenos Aires province (Argentina). Increasing herbicide resistance cases have exacerbated the problem, requiring alternative control options based on an Integrated Weed Management approach (IWM). Field experiments were conducted in the south area of Buenos Aires province during 2017-2019 in order to evaluate both the suppressive effect of Viciavillosa (hairy vetch) over annual ryegrass when combined with residual herbicides, and the tolerance of the former to such herbicides. Annual ryegrass stand density and biomass at crop termination were reduced from 2 - 98% in response to combined hairy vetch plus herbicide treatments. Among the best chemical options, pyroxasulfone, acetochlor and S-metolachlor should be mentioned, reaching weed biomass control values of 97, 81 and 76%, respectively. Hairy vetch was partially affected by herbicides with a plant stand reduction ≤ 48%. No significant effect on biomass at crop termination was observed, except for diflufenican and trifluralin. The inclusion of hairy vetch as cover crop combined with residual herbicides could be a practical IWM practice for suppression of annual ryegrass populations resistant to ACCase, ALS and EPSPS inhibitors.

Resumen Lolium multiflorum Lam. (raigrás anual) es una especie de maleza problemática, especialmente en los sistemas de labranza cero en el sur de Buenos Aires (Argentina). El aumento de los casos de resistencia a los herbicidas ha exacerbado el problema, requiriendo opciones de control alternativas basadas en un enfoque de manejo integrado de malezas (MIM). Los experimentos a campo se llevaron a cabo en el área sur de la provincia de Buenos Aires durante 2017-2019 con el fin de evaluar tanto el efecto supresor de Vicia villosa (vicia villosa) sobre raigrás cuando se combinan con herbicidas residuales y la tolerancia de la vicia villosa a tales herbicidas. La densidad de plantas y la biomasa al final del raigrás anual se redujeron del 2 al 98% en respuesta al cultivo de vicia villosa combinado con los tratamientos con herbicidas. Entre las mejores opciones químicas, se debe mencionar a pyroxasulfone, acetochlor y S-metolachlor, alcanzando valores de control de biomasa de raigrás del 97, 81 y 76%, respectivamente. La vicia villosa se vio parcialmente afectada por los herbicidas con una reducción del stand de implantación de ≤ 48%. No se observó ningún efecto significativo sobre la biomasa en el momento de terminación del cultivo, excepto con diflufenican y trifluralina. La inclusión de vicia villosa como cultivo de cobertura combinado con herbicidas residuales podría ser una práctica de MIM para la supresión de poblaciones de raigrás anual resistentes a los inhibidores de ACCase, ALS y EPSPS.

O objetivo deste trabalho foi selecionar herbicidas para otimizar o controle de plantas daninhas e o rendimento da cultura de melão, implantada pela técnica de transplante, nas condições agroecológicas do sul da província de Buneos Aires. Com a finalidade de proteger a cultura durante o período crítico de competição das plantas daninhas, nas primeiras sete semanas , foram utilizados os herbicida trifluralin, pendimethalin , metribuzin, naptalan, butylate, atrazine, linuron e misturas de pendimethalin + linuron, antes do transplante. Os três primeiros herbicidas foram incorporados ao solo de forma mecânica e os demais mediante irrigação. Durante as safras 1992/93 e 1993/94 os herbicidas naptalan, pendimethalin e a mistura controlaram de forma eficiente a comunidade infestante. Os maiores rendimentos da cultura foram obtidos com a aplicação de pendimethalin e com a mistura pendimethalin + linuron, no entanto, o naptalan não trouxe incrementos ao rendimento da cultura em relação a testemunha mantida no mato.

The aim of this study was the selection of herbicides to optimize the weed control and yield of muskmelon crop started through transplanting. Studies were conducted under the agroecological conditions in the South of Buenos Aires Province. In order to protect the crop during the critic period due to weed competition which lasts for the first seven weeks, several herbicides were applicated before transplanting: Trifluralin, Pendimethalin and metribuzin through machanical incorporation, and naptalan, Butylate, Atrazine, Linuron and a mixture of Pendimethalin + Linuron through watering. The best yields were obtained with Pendimethalin and the mixture Pendimethalin + linuron. Naptalan, did not increase the yield of the crop compared with the control with weeds.