Methylated seed oil (MSO) is a recommended adjuvant for the newly registered herbicide topramezone in China and also in other countries of the world, but the mechanism of MSO enhancing topramezone ...efficacy is still not clear. Greenhouse and laboratory experiments were conducted to determine the effects of MSO on efficacy, solution property, droplet spread and evaporation, active ingredient deposition, foliar absorption and translocation of topramezone applied to giant foxtail (Setaria faberi Herrm.) and velvetleaf (Abutilon theophrasti Medic.). Experimental results showed that 0.3% MSO enhanced the efficacy of topramezone by 1.5-fold on giant foxtail and by 1.0-fold on velvetleaf. When this herbicide was mixed with MSO, its solution surface tension and leaf contact angle decreased significantly, its spread areas on weed leaf surfaces increased significantly, its wetting time was shortened on giant foxtail but not changed on velvetleaf, and less of its active ingredient crystal was observed on the treated weed leaf surfaces. MSO increased the absorption of topramezone by 68.9% for giant foxtail and by 45.9% for velvetleaf 24 hours after treatment. It also apparently promoted the translocation of this herbicide in these two weeds.
The weed suppressing ability and growth of 17 cover crops and undersown crops was evaluated in eleven pot and laboratory experiments. Weed suppression was greater using mulched cover crops than with ...undersown crops. Mulched cover crops had no effects on biomass of Hordeum vulgare and undersown crops decreased Triticum aestivum biomass in the pot experiments. Biochemical effects of various concentrations of aqueous cover crop root- and shoot-extracts were determined in the laboratory. Observed effects were inhibitory, hormetic, or combined on root growth of Lactuca sativa, Setaria viridis, Amaranthus retroflexus and Zea mays. Nonlinear dose–response functions fitted best to the data; more pronounced inhibitory effects occurred with highly concentrated plant extracts. Festuca rubra, Avena strigosa and Cannabis sativa were the cover crop species with the strongest inhibiting biochemical effect on L. sativa, maize and weeds. Active compounds and mode of action of biochemical are unknown and biochemicals from cover crop residues require research under field conditions.
•Weed suppressing ability of 17 cover crops was evaluated.•Mulched- and undersown cover crops influenced biomass production of cereals.•Shoot/root extracts had inhibitory effects at low doses and hormetic at high doses.•Tested crops can be recommended as cover crops for integrated weed management.•Weed suppression resulted from a combination of competitive and biochemical effects.
•Avena fatua appeared to be a very competitive weed species in winter wheat.•Reduced herbicide dose rates could lower herbicide inputs, for the control of Avena fatua in winter wheat, between 21% and ...59%.•No economic benefit could be found for reduced herbicide dose rates compared to the economic threshold strategy.
Weeds are causing significant yield losses in intensive winter wheat cropping systems worldwide. Prospective weed control strategies aim to reduce herbicide inputs in order to diminish the environmental, food safety and operator risks. The objective of this study is to make a long-term comparison of herbicide saving weed control strategies in intensive winter wheat cropping systems. The herbicide saving weed control strategies are compared with emphasis on herbicide input, crop yield, economic net return and weed population dynamics. The modelling approach is based on existing models for calculation of crop yield loss, herbicide dose-response, weed seed bank development and economic net return. The model is parametrised for wild oat in winter wheat. Field experiments were conducted for model parameter estimation. Three herbicide saving weed control strategies were compared, namely the economic threshold strategy as well as two reduced herbicide dose strategies. The two reduced dose strategies differed in their intensity of dose reduction and thus in their risk for potential efficacy failure. The modelling results could show that, depending on the risk level, reduced dose strategies can decrease herbicide inputs by 21% respectively 59%, compared to the economic threshold method. Differences between the three herbicide saving weed control strategies regarding yield and economic net return were negligible. From the consumer and environmental safety point of view, the high potential for herbicide input reduction makes the reduced herbicide dose methods favourable. However, the benefit for farmers is questionable due to the absence of an actual economic benefit and the enhanced risk of efficacy failure and herbicide resistance development.
Field experiments were conducted in 2010 and 2011 in a typical location of North China Plain to evaluate weed control efficacy of four post-emergence herbicides nicosulfuron, mesotrione, topramezone ...and the combination of mesotrione/nicosulfuron when they were applied at reduced doses at different weed growth stages. Experimental results showed that nicosulfuron, topramezone and the combination of mesotrione/nicosulfuron provided better weed control efficacy than mesotrione when they were applied at their label recommended doses at the 2- to 3-leaf and 4- to 5-leaf stages of weeds; nicosulfuron and mesotrione/nicosulfuron could at least be reduced by 33% and topramezone reduced by 67% without sacrificing total weed control efficacy and maize grain yield. Nicosulfuron and its combination with mesotrione could effectively control broadleaved and grass weeds when their doses were reduced by 67% and by 33%, respectively. Topramezone could effectively control broadleaved and grass weeds when its dose was reduced by 67%. The efficacy of mesotrione in controlling grass weeds was bad even at the label recommended dose. All four herbicides tested did not affect the maize grain yield.
•Higher nicosulfuron, topramezone, mesotrione/nicosulfuron efficacy than mesotrione.•Nicosulfuron and mesotrione/nicosulfuron could be reduced by 33% for weed control.•Topramezone could be reduced by 67% for broadleaved and grass weed control.
Japanese bindweed was found to be one of the most abundant and most difficult-to-control weed species during a 2-yr weed survey in more than 100 winter wheat fields in the North China Plain region. ...Multivariate data analysis showed that Japanese bindweed is most abundant at sites with comparative low nitrogen (N) fertilization intensities and low crop densities. To gain deeper insights into the biology of Japanese bindweed under various N fertilization intensities, winter wheat seeding rates, herbicide treatments, and their interactions, a 2-yr field experiment was performed. In nonfertilized plots, a herbicide efficacy (based on density reduction) of 22% for 2,4-D, and of 25% for tribenuron-methyl was found. The maximum herbicide efficacy in Nmin-fertilized plots (target N value based on expected crop yield minus soil mineral nitrogen content,) was 32% for 2,4-D and 34% for tribenuron-methyl. In plots fertilized according to the farmer's practices, a maximum herbicide efficacy of 72% for 2,4-D and of 64% for tribenuron-methyl could be observed. Furthermore, medium and high seeding rates improved the herbicide efficacy by at least 39% for tribenuron-methyl and 44% for 2,4-D compared to the low seeding rate. Winter wheat yield was not significantly affected by seeding rate itself, whereas at low and medium seeding rates, Nmin fertilization was decreasing winter wheat yield significantly compared to the farmer's usual fertilization practice. At the highest seeding rate, Nmin fertilization resulted in equal yields compared to the farmer's practices of fertilization. Nomenclature: 2,4-D; tribenuron-methyl; Japanese bindweed; Calystegia hederacea Wallich CAGHE; wheat; Triticum aestivum L. Se encontró que Calystegia hederacea fue una de las especies de malezas más abundantes y más difíciles de controlar en un estudio observacional de 2 años de duración en más de 100 campos de trigo de invierno en la región de las Planicies del Norte de China. Análisis multivariado de datos mostró que C. hederacea es más abundante en sitios con niveles comparativos bajos de intensidad de fertilización con nitrógeno (N) y densidades de cultivo bajas. Para ganar un mayor conocimiento sobre la biología de C. hederacea bajo intensidades variables de N, densidades de siembra de trigo de invierno, tratamientos con herbicidas, y sus interacciones, se realizó un experimento de campo durante 2 años. En parcelas sin fertilización, se encontró una eficacia del herbicida (basada en reducción de la densidad de la maleza) de 22% con 2,4-D, y de 25% con tribenuron-methyl. La eficacia máxima de herbicidas, en parcelas fertilizadas usando el método Nmin, fue 32% con 2,4-D y 34% con tribenuron-methyl. En las parcelas fertilizadas de acuerdo a las prácticas de los productores, la eficacia máxima del herbicida observada fue 72% para 2,4-D y 64% para tribenuron-methyl. Además, densidades de siembra medias y altas mejoraron la eficacia del herbicida en al menos 39% con tribenuron-methyl y 44% con 2,4-D al comparase con la densidad de siembra baja. El rendimiento del trigo de invierno no fue afectado significativamente por la densidad de siembra, mientras que en las densidades de siembra baja y media, la fertilización Nmin disminuyó el rendimiento del trigo de invierno significativamente, al compararse con las prácticas de fertilización usuales de los productores. En la densidad de siembra alta, la fertilización Nmin resultó en rendimientos iguales en comparación con las prácticas de fertilización de los productores.
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