An ecological future for weed science to sustain crop production and the environment. A review

Sustainable strategies for managing weeds are critical to meeting agriculture's potential to feed the world's population while conserving the ecosystems and biodiversity on which we depend. The dominant paradigm of weed management in developed countries is currently founded on the two principal tools of herbicides and tillage to remove weeds. However, evidence of negative environmental impacts from both tools is growing, and herbicide resistance is increasingly prevalent. These challenges emerge from a lack of attention to how weeds interact with and are regulated by the agroecosystem as a whole. Novel technological tools proposed for weed control, such as new herbicides, gene editing, and seed destructors, do not address these systemic challenges and thus are unlikely to provide truly sustainable solutions. Combining multiple tools and techniques in an Integrated Weed Management strategy is a step forward, but many integrated strategies still remain overly reliant on too few tools. In contrast, advances in weed ecology are revealing a wealth of options to manage weedsat the agroecosystem levelthat, rather than aiming to eradicate weeds, act to regulate populations to limit their negative impacts while conserving diversity. Here, we review the current state of knowledge in weed ecology and identify how this can be translated into practical weed management. The major points are the following: (1) the diversity and type of crops, management actions and limiting resources can be manipulated to limit weed competitiveness while promoting weed diversity; (2) in contrast to technological tools, ecological approaches to weed management tend to be synergistic with other agroecosystem functions; and (3) there are many existing practices compatible with this approach that could be integrated into current systems, alongside new options to explore. Overall, this review demonstrates that integrating systems-level ecological thinking into agronomic decision-making offers the best route to achieving sustainable weed management

Mycorrhizas in South American Anthropic Environments

The agricultural expansion has leaded to increase the irrigated cropland area and the use of fertilizers, resulting in water degradation, increased energy use, and common pollution. Of particular concern is the increased interest to reduce the environmental impacts of high quantities of water dedicated to irrigation by agricultural activities We are now truly recognizing the importance of sustainable measures in agriculture such as conservation of the vegetation cover and management approach to understand surface and deep soil responses to global change. The agroecology management based on key processes from natural ecosystems can help to solve some agricultural difficulties. Increasing studies on the Arbuscular mycorrhizal fungi (AMF) has showed their importance for soil ecology and studies on their biodiversity have spread in some agro-ecosystems such as corn and soybean monocultures. Therefore, it is needed to deeply study the mycorrhizal functions under global change. In this chapter, we examine the major developments and advances on mycorrhizal fungi based on recent research from South American countries. New reports on the occurrence of mycorrhizas in Amazonian dark earth, as well as the inoculum production of arbuscular mycorrhizal fungi native of soils under native forest covers, have resulted in a more detailed understanding of the soil biology from South America. Reports from Amazonian dark earth or “Terra preta do índio” soil has stimulated the use of biochar worldwide as a soil conditioner that can add value to non-harvested agricultural products and promote plant growth. Few reports from Brazil showed that the addition of inorganic fertilizer, compost and chicken manure resulted in increases in plant cover and plant species richness. In this sense, the biochar/mycorrhizae interactions also can be prioritized for sequestration of carbon in soils to contribute to climate change mitigation

Controles ambientales del crecimiento de alfalfa (MedicagosativaL.) a lo largo de un gradiente climático y edáfico

Lucerne is one of the most valuable forage species because of its high productivity and nutritional traits. However, the knowledge of spatio-temporal variability and environmental controls of its growth generated from the simultaneous study of several sites and throughout several years is extremely scarce. Five-year biomass data were analyzed from four rain fed sites located across a climatic and edaphic gradient in Argentina. The aims proposed were to characterize annual and seasonal lucerne growth, to analyze environmental controls of spatial and emporal growth, and to compare water use efficiency (WUE) among sites. Annual growth differed significantly among sites, ranging between 7,514 and 14,262 kg DM/ha. This range at the spatial scale was mainly explained by variations in annual rainfall and WUE among sites. Seasonal growth depended on incident radiation and actual evapotranspiration.  Interannual variability of lucerne growth was explained by precipitation occurred during the growing season in the driest sites, on sandy soils with less water retention capacity. Knowing the sources of variability of lucerne growth, would allow developing more efficient livestock management due to less uncertainty on the forage production dynamics.La alfalfa es una de las especies forrajeras más valoradas por su alta productividad y características nutritivas. Sin embargo, el conocimiento de la variabilidad espacio-temporal y los controles ambientales del crecimiento generado a partir del estudio simultáneo de varios sitios y años es extremadamenteescaso.En este trabajo se analizaron cinco años de datos de biomasa de cuatro sitios de secano ubicados a lo largo de un gradiente climático y edáfico en Argentina. Los objetivos propuestos fueron: caracterizar el crecimiento anual y estacional de la alfalfa, analizar los controles ambientales del crecimiento a escala espacial y temporal y comparar la eficiencia en el uso del agua (EUA) entre sitios. El crecimiento anual difirió espacialmente, oscilando entre 7.514 y 14.262 kgMS/ha. Esta variabilidad fue principalmente explicada por variaciones en las precipitaciones anuales y la EUA. El crecimiento estacional dependió de la radiación incidente y la evapotranspiración real. La variabilidad interanual del crecimiento fue explicada por la precipitación ocurrida durante la estación de crecimiento en los sitios secos, con suelos arenosos de baja capacidad de retención hídrica. Conocer las fuentes de variación en el crecimiento de alfalfa permitirá el desarrollo de prácticas de manejo ganadero más eficientes debido a la menor incertidumbre en la dinámica de producción forrajera

Respuesta de hongos benéficos del suelo asociados a Lootus tenuis a la aplicación de glifosato

En los últimos años se está adoptando la práctica de promoción de Lotus tenuis a través de la aplicación de glifosato en pastizales de La Pampa Deprimida debido a su importante aporte en cantidad y calidad d e forraje. Sin embargo, diversos estudios han demostrado que el uso de este herbicida puede ocasionar efectos no deseados en microorganismos benéficos del suelo. El objetivo de este trabajo fue evaluar el efecto de la aplicación de glifosato sobre los hongos micorrícicos arbusculares y hongos septados oscuros asociados a L. tenuis . En una pastura de L. tenuis se establecieron dos tratamientos: Lotus tenuis promovido y Lotus tenuis establecido. En el primer caso, la pastura se pulverizó en invierno (fines de agosto) con 3,5 l/ha de glifosato, mientras en el segundo tratamiento la pastura de L. tenuis no recibió la aplicación del herbicida. Los resulta- dos demuestran que el número de esporas viables de hongos micorrícicos arbusculares fue un 52% menor, y el porcentaje de arbúsculos en plantas de L. tenuis un 40% menor, en el tratamiento Lotus tenuis promovido en relación con el tratamiento Lotus tenuis establecido. La colonización radical por hongos septados oscuros no fue afectada por la aplicación de glifosato. La pérdida de funcionalidad de la simbiosis micorrícica podría en el mediano plazo afectar no solo la producción de biomasa de L. tenuis , sino también la diversidad y producti- vidad de todas las especies presentes en la comunidad vegetal. La información generada en este trabajo será de utilidad para rediseñar prácticas de manejo que permitan la producción de alimento con un uso sustentable de los recursos

Glyphosate vulnerability explains changes in root-symbionts propagules viability in pampean grasslands

Research into the impact of agricultural practices on plant symbionts is essential for understanding the factors that modulate plant community productivity and diversity. Although glyphosate is used worldwide as an herbicide, its effects on root symbionts under natural conditions have not been sufficiently studied. We performed a field experiment to evaluate the influence of glyphosate, used for promoting winter forage production, on the viability of arbuscular mycorrhizal fungi (AMF) and rhizobium propagules and other ecosystem traits in native grasslands. The number of viable propagules was strongly reduced with a single application at the recommended dose. Spore viability reduction was dependent on AMF species. Furthermore, changes in plant community composition and soil salinity were detected, which may eventually influence these symbionts in the future. Considering the low nutrient availability and high root-symbiont dependency of several species with forage value, repeated applications might lead to a loss in the grassland diversity and productivity, decreasing livestock production. Application of sublethal doses of this herbicide could avoid these damages, although success in increasing winter forage production would be less. Our results are relevant for understanding the effects of glyphosate on non-target species and designing sustainable land management systems.nada para comenta