Glyphosate sprayed on the pre-existing vegetation reduces seedling emergence and growth of forage species

Seeding pastures or forage crops by no-tillage methods usually involves the spray of glyphosate to suppress the existing vegetation. While  many studies found detrimentaleffects of glyphosate on seed germination and seedling growth of the subsequent crop, others found negligible effects. This study aimed to evaluate the effect of glyphosate spraying on germination, seedling emergence and seedling growth of four forage species: Trifolium repens, Lotus tenuis, Festuca arundinacea and Paspalum dilatatum. The experiment was carried out spraying glyphosate on the pre-existing vegetation and on bare soil 1, 30, 60 and 90 days before sowing, and a control  treatmentsprayed with water. Glyphosate sprayed on pre-existing vegetation 1 to 60 days before seeding reduced emergence, while sprayed 1 to 30 or 1 to 60 days before seeding reduced seedlings belowground biomass and root length of all species and aboveground biomass of legumes respect to sprayed 90 days before seeding, sprayed on bare soil, and control treatment. This herbicide would remain active in the soil environment for at least 60 days after spraying when it was previously absorbed by plants, causing a severe damage to seedlings emergence and growth. Highlights: Glyphosate sprayed on pre-existing vegetation 1 to 60 days before seeding reduced seedling emergence of Trifolium repens, Lotus tenuis, Festuca arundinacea and Paspalum dilatatum. Glyphosate sprayed on pre-existing vegetation 1-30 or 1-60 days before seeding reduced seedlings belowground biomass and root length of all species and aboveground biomass of legumes Gyphosate sprayed 90 days before seeding or sprayed on bare soil did not affect seggling emergence and growth. Gyphosate would remain active in the soil environment for at least 60 days after spraying when it was previously absorbed by plants.Seeding pastures or forage crops by no-tillage methods usually involves the spray of glyphosate to suppress the existing vegetation. While  many studies found detrimentaleffects of glyphosate on seed germination and seedling growth of the subsequent crop, others found negligible effects. This study aimed to evaluate the effect of glyphosate spraying on germination, seedling emergence and seedling growth of four forage species: Trifolium repens, Lotus tenuis, Festuca arundinacea and Paspalum dilatatum. The experiment was carried out spraying glyphosate on the pre-existing vegetation and on bare soil 1, 30, 60 and 90 days before sowing, and a control  treatmentsprayed with water. Glyphosate sprayed on pre-existing vegetation 1 to 60 days before seeding reduced emergence, while sprayed 1 to 30 or 1 to 60 days before seeding reduced seedlings belowground biomass and root length of all species and aboveground biomass of legumes respect to sprayed 90 days before seeding, sprayed on bare soil, and control treatment. This herbicide would remain active in the soil environment for at least 60 days after spraying when it was previously absorbed by plants, causing a severe damage to seedlings emergence and growth. Highlights: Glyphosate sprayed on pre-existing vegetation 1 to 60 days before seeding reduced seedling emergence of Trifolium repens, Lotus tenuis, Festuca arundinacea and Paspalum dilatatum. Glyphosate sprayed on pre-existing vegetation 1-30 or 1-60 days before seeding reduced seedlings belowground biomass and root length of all species and aboveground biomass of legumes Gyphosate sprayed 90 days before seeding or sprayed on bare soil did not affect seggling emergence and growth. Gyphosate would remain active in the soil environment for at least 60 days after spraying when it was previously absorbed by plants

Taller virtual de extensión sobre prácticas de manejo sustentable del pastoreo en cría

Agricultural extension implies a complex process of interaction between agricultural education and research, and farmers. MAS-PASTO (FAUBA) is an extension project based on the participative discussion as regards knowledge between professor-researchers, producers and professionals. The virtual workshop in 2020 aimed to help producers, who had previously participated in in-presence workshops with the group, consolidate their knowledge through practice on their own farm. For this, each farmer worked on one of the following topics: 1) sowing of pastures and annual forage; 2) management and improvement of grasslands and 3) design of forage circuits. All farmers calculated their farm meat production, regardless of the topic chosen. For 6 months, cooperative work was performed between producers, professors and a young professional agronomist. The work as regards the chosen topic was performed individually.  Finally, a meeting in which each farmer shared its work, difficulties and  findings with  their peers was carried out through a virtual platform. The workshop was assessed through surveys to participants and a SWOT analysis. The results showed that the workshop allowed them to put prior knowledge into practice and to incorporate them into their farms management. It also consolidated an effective as well as replicable method, for the generation and transference of process technologies from FAUBA to the productive sector.La extensión agropecuaria implica un proceso complejo de interacción entre la educación e investigación agropecuaria y los productores. El proyecto de extensión MAS-PASTO de la Facultad de Agronomía de la Universidad de Buenos Aires (FAUBA), es un proyecto basado en la discusión participativa de conocimientos entre docentes-investigadores, productores y profesionales. El taller 2020 (virtual) tuvo como objetivo que productores, que habían participado en talleres anteriores del grupo (presenciales), afiancen los conocimientos a través de la práctica en establecimientos propios. Para esto cada productor trabajó en alguno de los siguientes ejes temáticos: 1) siembra de pasturas y verdeos; 2) manejo y mejoramiento de pastizales naturales y 3) diseño de circuitos forrajeros. Todos los productores abordaron el cálculo de la producción de carne para sus establecimientos, independientemente del eje temático elegido. Durante 6 meses, se realizó un trabajo conjunto entre productores, docentes y un joven profesional agrónomo. Se trabajó individualmente sobre la aplicación del tema elegido y, al finalizar el trabajo individual, se llevó adelante una jornada conjunta de intercambio donde cada productor presentó a sus pares en forma virtual el trabajo realizado, sus dificultades y resultados obtenidos. El taller se evaluó mediante encuestas a los participantes y la elaboración de un análisis FODA. Los resultados mostraron que el taller permitió a los productores practicar los conceptos presentados previamente e incorporarlos al manejo de sus establecimientos. A su vez, permitió consolidar un método efectivo y replicable para la generación y transferencia de tecnologías de procesos desde la FAUBA hacia el sector productivo

Forage Plant Ecophysiology under Different Stress Conditions

Forage production often occurs in fragile environments with low fertility and various limitations [...

Role of Grazing Intensity on Shaping Arbuscular Mycorrhizal Fungi Communities in Patagonian Semiarid Steppes

Arbuscular mycorrhizal fungi (AMF) are vital for maintaining ecosystem structure and functioning and can be affected by complex interactions between plants and herbivores. Information found in the literature about how ungulate grazing affects AMF is in general contradictory but might be caused by differences in grazing intensities (GIs) among studies. Hence we studied how different GIs affect the composition, diversity, and abundance of AMF communities in a semiarid steppe of Patagonia. We predicted that 1) total AMF spore abundance (TSA) and diversity would decrease only under intense-grazing levels and 2) AMF species spore abundance would depend on their life-history strategies and on the GI. To test our predictions, we compared AMF communities among nongrazed (NG), moderately grazed (MG, 0.1–0.3 sheep ha1), and intensely grazed sites (IG, > 0.3 sheep ha1). GI was the most important factor driving changes in TSA and diversity, regardless of host plant identity. TSA, diversity, and evenness significantly decreased in IG sites but were not affected by MG. AMF species spore abundance varied depending on their life-history strategies and GI. Families with high growth rates like Glomeraceae and probably Pacisporaceae showed the highest spore abundance in all sites but decreased under IG. Species with higher carbon demands like Gigasporaceae showed low spore abundance and frequency in NG and MG sites and were absent in IG sites. In contrast, species with low growth rates, but efficient carbon usage, like Acaulosporaceae, showed low spore abundance in all sites but increased in IG sites compared with NG or MG sites. We conclude that intensification of grazing reduces AMF diversity and abundance, with the likely loss of AMF benefits for plants, such as improved nutrient and water uptake and soil aggregation. Therefore, sustainable grazing systems should be designed to improve or restore AMF communities, particularly in degraded rangelands, like the Patagonian steppes.Instituto de Botánica "Dr. Carlos Spegazzini"Facultad de Ciencias Agrarias y Forestale

High Recovery from Either Waterlogging or Drought Overrides Any Beneficial Acclimation of Chloris gayana Facing a Subsequent Round of Stress

Climate models predict that plants will face extreme fluctuations in water availability in future global change scenarios. Then, forage production will be more frequently subjected to the destabilizing pressure of sequentially occurring waterlogging and drought events. While the isolated effects of drought (D) and waterlogging (WL) are well characterized, little is known about the consequences when both stresses occur sequentially. We hypothesized that plants sequentially subjected to opposite water scenarios (D followed by WL or vice versa) are less stress tolerant than plants experiencing repetitions of the same type of water stress (i.e., D + D or WL + WL) due to contrasting acclimation and allocation to either shoots (WL) or roots (D). Chloris gayana (a tropical forage grass capable of tolerating either D and WL) plants were randomly assigned to nine treatments (a sequence of two stress rounds—WL or D—each followed by a recovery phase at field capacity). Relative growth rates and allometric responses were measured after each stress round and recovery period. In the first round of stress, both WL and D reduced plant RGR similarly, despite their allocation being opposite—prioritizing shoots or roots under WL and D, respectively. The high recovery displayed after either WL or D overrode any possible acclimation of the plants facing a second round of water stress. We conclude that the tolerance of C. gayana to sequential water stress (either for WL or D) is likely to depend more heavily on its recovery ability than on its previous adjustment to any stress scenario that may evoke memory responses. Knowledge like this could help improve forage grass breeding and the selection of cultivars for poorly drained soils subject to sequential stress events