A 7-year multi-criteria analysis of sugarcane intercropping compared to conventional cropping systems

Effect of crop management and climatic factors on weed control in sugarcane intercropping systems

Conservation tillage systems, such as no-tillage, are ecologically advantageous because they reduce soil erosion; however, they rely heavily on herbicide use. Our goal was to determine how weed communities of no-tillage systems are affected when the system is modified to reduce herbicide use through a combination of banded herbicides and interrow cultivation. To this end, we conducted a 9-yr study in a no-tillage corn–soybean–winter wheat rotation. All management systems had a preplant application of glyphosate, followed by either broadcast PRE herbicides (conventional no-tillage), interrow cultivation with banded PRE herbicides, or interrow cultivation alone. Aboveground weed densities were assessed each year and data were grouped into early (1991 to 1993) and late (1996 to 1998) time periods. Over time, weed communities became more distinct, showing a strong response to management and crop. In the early years, weed communities separated more in response to management than crop. In the late years, this was reversed. Weed communities in systems with interrow cultivation were more diverse than those in conventional no-tillage. The response to weed management system and crop was species specific. For example, the abundance of yellow foxtail was higher when interrow cultivation was employed, but abundance was equal in all crops. Dandelion was more abundant in conventional no-tillage of corn and soybean; however, it was equally abundant in all management systems in wheat. Seed bank species richness increased over time and was highest in systems with interrow cultivation. Herbicide use can be reduced in a modified no-tillage corn–soybean–wheat rotation by incorporating interrow cultivation, with or without banded herbicides, into the management plan. The weed community trajectory changes, and the weed community becomes more diverse. A more diverse weed community will not necessarily alter how we manage weeds.

Intensification of crop rotation affecting weed communities and the use of herbicides in the rolling Pampa

Separating the confounding effects of farming practices on weeds and winter wheat production using path modelling

Effects of reduced nitrogen input on productivity and N 2 O emissions in a sugarcane/soybean intercropping system

Regulation of cover crops and weeds using a roll-chopper for herbicide reduction in no-tillage winter wheat

Do European Agri-environment Measures Help Reduce Herbicide Use? Evidence From Viticulture in France

Based on a workshop held at the German Weed Science Conference in February 2024, this paper explores strategies for reducing herbicide use in arable cropping systems to enhance weed diversity. Although potentially detrimental to crop yields, weeds play a vital role in supporting ecosystem functions such as pollination, nutrient cycling, and microbial diversity. The reduction of herbicide use is regarded as an important management strategy for preserving weed biodiversity, which has been declining in Europe. Three strategies for reducing herbicide use are discussed: site-specific herbicide application, species-specific herbicide dose rates, and the use of selective herbicides with narrow target spectra. Each strategy is evaluated for its technical feasibility, agronomic risks, and potential benefits for weed diversity. While challenges such as high investment costs, technical limitations, and the need for precise weed distribution data remain, emerging technologies like AI-driven weed detection and autonomous robots offer promising solutions. The paper emphasizes the importance of combining reduced herbicide use with other management practices, such as crop rotation and mechanical weeding, to achieve sustainable and ecologically beneficial weed control. A shift in farmers’ perspectives on “clean fields” and more comprehensive guidance on the ecological value of weeds is essential for the widespread adoption of these strategies.

Práticas de manejo que favoreçam o estabelecimento precoce de plantas cultivadas em relação às plantas daninhas são importantes no manejo dessas e, em conseqüência, na redução do uso de herbicidas. A redução do intervalo de tempo entre a dessecação das coberturas de inverno e a semeadura de milho é um dos manejos que podem reduzir a infestação de plantas daninhas estivais, devido ao atraso de estabelecimento das plantas daninhas. O objetivo desse trabalho foi avaliar o efeito de épocas de dessecação de duas coberturas do solo de inverno, em relação à semeadura do milho, sobre a infestação de plantas daninhas e sobre a produtividade da cultura. Para tanto, foi conduzido um experimento em Canoinhas, SC, na safra 2004/05. Avaliaram-se duas culturas de cobertura: azevém e consórcio entre azevém, aveia preta, centeio, ervilhaca comum e nabo forrageiro. Essas culturas foram manejadas quimicamente em cinco épocas: 30, 20, 10, 5 e 1 dia antes da semeadura do milho em delineamento fatorial 2 x 5. O manejo das coberturas de inverno próximo à semeadura da cultura de milho reduziu a densidade e o acúmulo de massa pelas plantas daninhas, conferindo maiores produtividades de grãos.

A survey was conducted in southern and central Finland from 1982 to 1984 to determine the main weed species affecting spring cereal production. The weed flora was dominated by broad-leaved species. The most common broad-leaved weeds were Chenopodium album L., Galeopsis L. spp., Viola arvensis Murr. and Stellaria media (L.) Vili., and the most common grass weed was Elymus repens (L.) Gould. The density of weeds averaged 170 plants m-2 (median 124), and the dry weight 320 kg ha-1 (median 183). Ordination analyses revealed that the species composition of weed populations varied regionally and was affected by soil characteristics and crop management practices, particularly by long-term use of herbicides. An additional aspect studied in the survey was herbicide efficacy in farmers’ fields. Phenoxy acid herbicides, MCPA, dichlorprop and mecoprop, were the most common active ingredients used in the 252 spring cereal fields surveyed. MCPA alone gave only a moderate control of 65%, determined as a reduction of weed biomass, whereas the efficacy of herbicide mixtures containing MCPA averaged 83%. Inadequate control was in most cases due to a wrong choice of active ingredient for the prevailing weed population. Reduction in the use of herbicides by applying lower doses than recommended was studied in field experiments. Herbicide formulations of MCPA/dichlorprop, MCPA/mecoprop and MCPA/fluroxypyr were screened in spring barley (Hordeum vulgäre L.) and spring wheat (Triticum aestivum L.) fields. The efficacy of herbicides, applied at the lowest recommended dose, averaged 85%. At a 30% lower dose the efficacy still reached 79%. Even lower herbicide doses were often adequate, depending on the herbicide, weed species and the crop. The production of weed biomass was adequately suppressed with reduced doses since the most common and aggressive species, such as Chenopodium album and Galeopsis spp., were efficiently controlled with low doses. Use of reduced herbicide doses for three years in the same field caused neither an increase in the subsequent weed infestation nor changes in the species composition of weed populations compared with the treatments at recommended rates of application. The percentage emergence of weeds averaged 70-75% at the time of herbicide application when the crop was at the 3-4 leaf growth stage. However, spraying during the early growth stages of those weeds that emerge in the main flush is recommended since the competitive ability of the crop is normally sufficient to suppress the growth of late-emerging weed seedlings. At harvest the proportion of weed biomass in unsprayed plots, as a proportion of the total vegetative biomass, averaged 3.1% in barley fields and 3.6% in wheat fields. The growth of weeds was more efficiently suppressed with reduced herbicide doses than by increasing the seeding rate of the crop. The mean yield gain remained below 5% at all rates of herbicide application. No reliable density-based threshold for chemical weed control was established. Instead, site-specific dose adjustment based on the composition and infestation level of the prevailing weed populations is suggested to reduce the total use of herbicides and to maintain the current low levels of weed infestation. Consequently, annual reductions of 30% in use of cereal herbicides are expected. Such a reduction corresponds to monetary savings of approximately FIM 20 million per annum at the national level.

Reducing herbicide use and leaching in agronomically performant maize-based cropping systems: An 8-year study

The use of underseeded red clover (Trifolium pratense L.) as a cover crop in winter wheat has been declining because of poor clover establishment during dry growing seasons, the lack of selective herbicides for weed control in clover, and the difficulty in using burn-down herbicides to remove the clover before planting no-till corn. During 1990–1992, we conducted on-farm trials on silt loam no-till and sandy ridge-till fields in southern Ontario to evaluate the establishment and growth of alternative stubble-seeded cover crops following wheat and their effects on subsequent weed and volunteer wheat growth. In general, oats (Avena sativa L.), oilseed radish (Raphanus sativus L.), and barley (Hordeum vulgare L.) produced more biomass than the other stubble-seeded cover crops, hairy vetch (Vicia villosa Roth.), red clover, and buckwheat (Fagopyrum esculentum L.). In comparison, winter-hardy underseeded hairy vetch and red clover produced the most biomass and provided better weed control; however, any reduction in herbicide use is offset by the need to burn down these cover crops. An evaluation of cover-crop effects on post-wheat-harvest weed growth was not possible because of sparse and variable weed growth, which occurred even in the absence of a cover crop. However, volunteer wheat biomass was inversely correlated with cover-crop biomass. At the no-till site, cover-crop response to straw baling and the subsequent effects on weed and volunteer wheat growth and corn performance also were evaluated. Straw baling had minimal effects on cover-crop growth; however, volunteer wheat growth doubled. No-till corn was not adversely affected by the amounts of residue present where cover crops were established the previous year. Importantly, reducing the amount of wheat straw by baling increased early-season growth rates and corn grain yield by 0.91 Mg ha−1. We conclude that alternative stubble-seeded cover crops, such as oats, barley and oilseed radish, are suitable for no-till corn. At present, cover crops augment weed management but are not a substitute for herbicides, as burn-down herbicides are required to remove existing weeds or winter-hardy cover crops. Key words: Underseeded, stubble seeded, baling, volunteer wheat

Herbicides are the most common method for weed control in berry crops, although the evolution of herbicide resistance, worker and crop safety concerns, and regulatory challenges associated with the prevention of off-target movement are driving interest in alternative weed management technologies. Optically guided, targeted spray systems show promise for reducing herbicide use, minimizing crop damage, and expanding weed control options in perennial crops. In 2021 and 2022, field trials were conducted in New Jersey to evaluate the impact of conventional banded and targeted (WEED-IT™ system) herbicide applications on weed control and crop outcomes. Control of common groundsel, horseweed, and common purslane was influenced by herbicide type and application strategy but not by their interaction. Fluroxypyr applied at 280 and 560 g a.e./ha provided similar or better control of common groundsel and common purslane (>90%) compared with the 2,4-D choline and glufosinate (71% to 92%) standards. Similarly, horseweed control with florpyrauxifen-benzyl applied at 30 and 60 g a.e./ha (80% to 91%) matched or exceeded the suppression provided by 2,4-D and glufosinate (62% to 87%). Herbicide applications using the WEED-IT™ system reduced herbicide use by approximately 50% but provided less weed control than the traditional banded method; results likely reflect the effects of crop size and density on spray coverage. Crop injury was primarily observed on new canes, with targeted applications causing slightly more damage than the banded treatments across all observation timings. Stunting of new blueberry canes exceeded 8% at 1 week after application and decreased to less than 1% by 4 weeks after application, compared with a maximum of 3% stunting from banded applications. The greater levels of observed crop damage probably result from the system’s inability to distinguish between crops and weeds. Despite the potential of targeted spraying technologies to reduce herbicide use, their effectiveness and safety in perennial crops warrant further research, particularly regarding integration into comprehensive weed-management programs.

Photo by Edwin Remsberg and USDA-SARE Research on the effects of cover crops seems to be everywhere these days—from use in organic farming to home gardens and to traditional row crop systems. The studies seek to determine how cover crops influence erosion, soil compaction, microbial communities, weeds, and soil nutrients to name a few. However, like many topics, there is not a clear consensus about the effects of cover crops. Results that are positive, neutral, and negative have been published, making it difficult for those who may be interested in using cover crops to determine if they are an appropriate tool. This lack of consensus was noticed by weed scientist O. Adewale Osipitan when he attended a workshop where the topic of cover crops to reduce weeds was presented. Coming away from the workshop with more questions than answers, Osipitan, who is currently a post-doctoral researcher at the University of Nebraska–Lincoln, says, “I felt the answers to these questions required collection and analysis of broad-based data from different contradictory findings to arrive at a quantitatively summarized answer.” Because of this, he decided to conduct a meta-analysis. Being new to this approach, he consulted with colleagues who had experience in it and decided to focus on the effect cover crops have on weed biomass and the yield of the main crop grown after the cover crop. An initial search of the literature turned up 894 papers, and based on pre-selected inclusion criteria, 46 were included in the analysis. Osipitan points out the importance of having pre-selected criteria, which makes it easy to determine what papers should be included. From this analysis, Osipitan and co-authors, Anita Dille, Yared Asefa, and Stevan Knezevic determined that cover crops can provide effective weed suppression. This will come as no surprise to many, but what is more interesting is that in addition to providing weed suppression, this analysis demonstrated that there was either no effect or a positive effect on the yield of the main crop. The main crops, or cash crop that followed the cover crop, were categorized as grains or vegetables. There was a positive yield benefit of cover crops for vegetable crop yields and no impact on grain crop yields. Although this approach provides evidence that cover crops will have no effect or a positive effect on the cash crops growers depend on, it is important to note the potential for a bias toward positive results in this approach. Osipitan mentions that there is the potential for publication bias to influence the results of a meta-analysis. Researchers often rely on peer-reviewed publications to determine what data to include, and peer-reviewed publications are less likely to include non-significant or negative results. It may be beneficial to include unpublished data from graduate student theses and dissertations, which are often unpublished because the results are non-significant, to strengthen the analysis. This meta-analysis may aid in giving farmers interested in using cover crops some peace of mind that they will not have to sacrifice yields. “A take home for farmers is that if cover crops are properly selected and properly managed, there would be weed suppression benefits comparable to what tillage or herbicide could provide, particularly during the early part of the main crop's growing season, after cover crop termination,” Osipitan says. There are additional environmental benefits to reducing herbicide use too as herbicides often run off and impact non-target organisms like aquatic vegetation, amphibians, and fish and can lead to herbicide-resistant weeds. View the open access article in Agronomy Journal, “Cover Crop for Early Season Weed Suppression in Crops: Systematic Review and Meta-Analysis,” at: https://doi.org/10.2134/agronj2017.12.0752. A second meta-analysis by Osipitan and colleagues in Crop Science looks at how management of cover crops and main crops influence cover crop weed suppression. See https://doi.org/10.2135/cropsci2018.09.0589.

Weed suppression by cover crops grown during the winter fallow period in continuous corn may lead to a reduction in herbicide use. Rye, crimson clover, and subterranean clover cover crops were compared with corn stubble under a conventional management system (CS) that included plowing and use of preemergence residual herbicides and a low-input management system (LIS) that included no-tillage and use of a presowing nonresidual herbicide for three consecutive years (1994–1996). Cover crop and above-ground weed biomass prior to desiccation were not influenced by management system. Cover crop biomass ranged from 1,420 to 5,657 kg ha−1 for rye, from 563 to 4,217 kg ha−1 for crimson clover, and from 563 to 4,248 kg ha−1 for subterranean clover. At crop planting, rye reduced weed biomass from 54 to 99%, crimson clover from 22 to 46% (with a negative value in 1995), and subterranean clover from 21 to 67%. Weed growth suppression was usually higher in years when cover crop biomass was higher. There were n...