Bàrbara Baraibar

Ecologically sustainable weed management: How do we get from proof‐of‐concept to adoption?

Weed management is a critically important activity on both agricultural and non-agricultural lands, but it is faced with a daunting set of challenges: environmental damage caused by control practices, weed resistance to herbicides, accelerated rates of weed dispersal through global trade, and greater weed impacts due to changes in climate and land use. Broad-scale use of new approaches is needed if weed management is to be successful in the coming era. We examine three approaches likely to prove useful for addressing current and future challenges from weeds: diversifying weed management strategies with multiple complementary tactics, developing crop genotypes for enhanced weed suppression, and tailoring management strategies to better accommodate variability in weed spatial distributions. In all three cases, proof-of-concept has long been demonstrated and considerable scientific innovations have been made, but uptake by farmers and land managers has been extremely limited. Impediments to employing these and other ecologically based approaches include inadequate or inappropriate government policy instruments, a lack of market mechanisms, and a paucity of social infrastructure with which to influence learning, decision-making, and actions by farmers and land managers. We offer examples of how these impediments are being addressed in different parts of the world, but note that there is no clear formula for determining which sets of policies, market mechanisms, and educational activities will be effective in various locations. Implementing new approaches for weed management will require multidisciplinary teams comprised of scientists, engineers, economists, sociologists, educators, farmers, land managers, industry personnel, policy makers, and others willing to focus on weeds within whole farming systems and land management units.

La depredación de semillas de malas hierbas, una función ecológica a conservar y potenciar

Rodriguez Martinez, N., Bordas, P., Pineiro, J., Garcia de Castro, N., Martin, P., Mendez, M. (2013). Meta-analysis of the effects of burnt wood removal on Mediterranean forest regeneration: a step towards an evidence-based management. Ecosistemas 22(1):71-76. Doi.:10.7818/ECOS.2013.22-1.15 Many environmental managers base their decisions on previous field experience, but not on primary scientific literature or advice by academic scientists. Evidence-based management, based on primary scientific literature and meta-analysis, to decide among environmental management options is very infrequent. This paper illustrates this approach using as an example salvage logging in Mediterranean forests. Traditionally, forest management after fire has included salvage logging, i.e., harvest and removal of burnt wood, based on economic, ecological and esthetic grounds. However, salvage logging has also been criticised due to, among other reasons, its potential detrimental effects on forest regeneration. A meta-analysis of the relevant Mediterranean literature suggested no (seedling density and height) or negative (survival) effect of salvage logging on forest regeneration. Although a meta-analysis based on such a small sample size as the one possible in this study does not allow strong conclusions, it suggests that: (1) current management is not consistent with the (scarce) available evidence, at least regarding forest regeneration after fire and (2) stronger evidence should be gathered about this kind of forest management.

Weed Suppression in Cover Crop Monocultures and Mixtures

Interest in planting mixtures of cover crop species has grown in recent years as farmers seek to increase the breadth of ecosystem services cover crops provide. As part of a multidisciplinary project, we quantified the degree to which monocultures and mixtures of cover crops suppress weeds during the fall-to-spring cover crop growing period. Weed-suppressive cover crop stands can limit weed seed rain from summer- and winter-annual species, reducing weed population growth and ultimately weed pressure in future cash crop stands. We established monocultures and mixtures of two legumes (medium red clover and Austrian winter pea), two grasses (cereal rye and oats), and two brassicas (forage radish and canola) in a long fall growing window following winter wheat harvest and in a shorter window following silage corn harvest. In fall of the long window, grass cover crops and mixtures were the most weed suppressive, whereas legume cover crops were the least weed suppressive. All mixtures also effectively suppressed weeds. This was likely primarily due to the presence of fast-growing grass species, which were effective even when they were seeded at only 20% of their monoculture rate. In spring, weed biomass was low in all treatments due to winter kill of summer-annual weeds and low germination of winter annuals. In the short window following silage corn, biomass accumulation by cover crops and weeds in the fall was more than an order of magnitude lower than in the longer window. However, there was substantial weed seed production in the spring in all treatments not containing cereal rye (monoculture or mixture). Our results suggest that cover crop mixtures require only low seeding rates of aggressive grass species to provide weed suppression. This creates an opportunity for other species to deliver additional ecosystem services, though careful species selection may be required to maintain mixture diversity and avoid dominance of winter-hardy cover crop grasses in the spring. Nomenclature: Austrian winter pea, Pisum sativum L.; canola, Brassica napus L.; cereal rye, Secale cereale L., corn, Zea mays L., forage radish, Raphanus sativus L., medium red clover, Trifolium pratense L.; oats, Avena sativa L.; wheat, Triticum aestivum L.

Reviewing research priorities in weed ecology, evolution and management : a horizon scan

Summary Weedy plants pose a major threat to food security, biodiversity, ecosystem services and consequently to human health and wellbeing. However, many currently used weed management approaches are increasingly unsustainable. To address this knowledge and practice gap, in June 2014, 35 weed and invasion ecologists, weed scientists, evolutionary biologists and social scientists convened a workshop to explore current and future perspectives and approaches in weed ecology and management. A horizon scanning exercise ranked a list of 124 pre‐submitted questions to identify a priority list of 30 questions. These questions are discussed under seven themed headings that represent areas for renewed and emerging focus for the disciplines of weed research and practice. The themed areas considered the need for transdisciplinarity, increased adoption of integrated weed management and agroecological approaches, better understanding of weed evolution, climate change, weed invasiveness and finally, disciplinary challenges for weed science. Almost all the challenges identified rested on the need for continued efforts to diversify and integrate agroecological, socio‐economic and technological approaches in weed management. These challenges are not newly conceived, though their continued prominence as research priorities highlights an ongoing intransigence that must be addressed through a more system‐oriented and transdisciplinary research agenda that seeks an embedded integration of public and private research approaches. This horizon scanning exercise thus set out the building blocks needed for future weed management research and practice; however, the challenge ahead is to identify effective ways in which sufficient research and implementation efforts can be directed towards these needs.

Weed Seed Fate during Summer Fallow: The Importance of Seed Predation and Seed Burial

Maximizing weed seed exposure to seed predators by delaying post-harvest tillage has been suggested as a way to increase weed seed loss to predation in arable fields. However, in some areas of northeastern Spain, fields are still tilled promptly after cereal harvest. Tillage usually places seeds in a safer environment compared to the soil surface, but it can also increase seed mortality through seed decay and fatal germination. By burying the seeds, tillage also prevents weed seed predation. Weed seed fate in a tilled vs. a no-till environment was investigated during the summer fallow months in three cereal fields in semi-arid northeastern Spain. Rigid ryegrass and catchweed bedstraw seeds were used. Predation rates were measured in a no-till area within each field in 48-h periods every 3 wk, and long-term predation rates were estimated. Fate of buried seeds was measured by burying 20 nylon bags with 30 seeds of each weed species from July to September at a depth of 6 cm in a tilled area contiguous to the no-till area. Predation rates over the entire summer were 62% and 49% for rigid ryegrass and catchweed bedstraw, respectively. High availability of crop seeds (preferred by ants) on the soil surface may have decreased predation of weed seeds early in the season. Seed loss due to burial was 54% and 33% for rigid ryegrass and catchweed bedstraw, respectively. Unusual above-average precipitation probably prompted higher than normal weed germination rates (fatal germination) in some fields, and thus led to higher seed mortality rates compared with an average year. These results suggest that leaving the fields untilled after harvest may be the optimum strategy to reduce inputs to the weed seedbank during the summer fallow period in semi-arid systems. Nomenclature: Catchweed bedstraw, Galium aparine L; Rigid ryegrass, Lolium rigidum Gaudin.