Part 24, Number 10,
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A study was carried out for 2 years (2002/2003 and 2003/2004) on a private farm in Alentejo (Évora), in southern Portugal, where wheat was sown with rain after the start of the winter rainy season. A no-tillage wheat crop was used, as this technology provides the necessary soil capacity for post-emergence at different stages of weed development. A mixture of diclofop-methyl+fenoxaprop-p-ethyl+mefenepir-diethyl was used in three doses at two times with three different application volumes.
The results indicate that lower herbicide concentrations with higher water application volumes reduced weed control efficiency at both weed developmental stages. In each treatment, the first weed development stage (starter shoot) resulted in a higherharvest grainyield. At this stage, both the weed and the crop are more sensitive to the herbicide, and as a result, the higher weed control efficiency was not reflected in higher grain yield due to some crop toxicity caused by the herbicide as the concentration increased.
Weed recurrence was low for both application times, suggesting that lower than recommended herbicide rates (2.5-31 ha)−1) or usually used by Portuguese farmers (21ha−1) can be used for satisfactory control ofA stiff lollipopG. In winter wheat, postemergence treatments can reduce rates when combined with adequate application volumes and early application times. When herbicide application was delayed (complete seeding), higher herbicide rates were required to achieve the highest crop yield.
Economic aspects, negative effects of pesticides on the environment and risk of food contamination have led to a reduction in the use of agricultural chemicals, including herbicides, in recent years. Widespread concern about the environmental side effects of herbicides, combined with public health fears, has led to several herbicides being banned in some countries and increased pressure on farmers to reduce herbicide use (Matteson, 1995). However, herbicides have been the predominant means of weed control in the developed world for over 40 years (Gill and Holmes, 1997).
Recent studies strongly advocate two directions for developing cropping systems with a reduced reliance on herbicides (Sterrenberg and Brandt, 1996; Lotz et al., 1997). One, called chemical refinement, focuses on reducing the use of herbicides through the development and improvement of curative tactics based on technological solutions, such as improved application technology, improved application time, factor-adjusted dosages and the development of herbicides with low environmental impact. effect (Bastiaans et al., 2000).
Today, the goal of weed control is to keep the weed community at acceptable levels rather than keeping the crop completely weed free. Satisfactory weed control can often be achieved when herbicides are used at doses lower than those normally recommended (Zhang et al., 2000; Boström and Fogelfors, 2002) and thus maintain satisfactory crop yields (Steckel et al., 1990; Hamill and Zhang, 1995b). Lower dose herbicides are often sufficient to control weed densities at or below threshold levels, and sublabeled herbicide doses combined with some mechanical weed control have been shown to be an effective way to reduce herbicide inputs in agricultural systems (Hamill and Zhang, 1995a).
To facilitate the decision of what is an appropriate dose in a particular field, the farmer needs support (Boström and Fogelfors, 2002) and a number of different types of decision support systems are currently available to help crop advisors and farmers to choose optimal herbicide. . dose (Forcella et al., 1996; Stigliane et al., 1996; Buhler et al., 1997; Shaw et al., 1998).
To ensure satisfactory weed control even under unfavorable field conditions, producers often recommend higher doses than necessary. Knowledge of the effects of various factors that influence herbicide effectiveness, e.g. weed species present, growth stage (Bruce et al., 1996), crop competitiveness, variety and weather conditions (Xie et al., 1997; Skuterud et al., 1998; Tottman et al. al., 1998), increases the possibility of using a herbicide dose that is lower than the recommended dose, while achieving sufficient weed control and an acceptable crop yield (Fogelfors, 1990; Salonen, 1992a, Salonen, 1992b). Zhang et al. (2000), based on several studies in different crops and under different environmental conditions, found considerable variations in weed control efficiency with different herbicide doses. In a few studies at the recommended rate, they achieved a weed control efficiency of only 20-40%, while a weed control efficiency of 70% or higher was achieved in 50% of the studies with herbicide doses as low as 20% of the recommended rate. . . The same authors found that weed control efficiency was usually lower and varied more at lower doses than at the recommended dose, but remained within the 60-100% range in over 90% of cases. For cereals, greater than 70% weed control was maintained in over 90% of cases with rates between 30% and 60% of recommended rates.
Currently, the majority of Portuguese farmers still rely on the conventional tillage system based on the body plough, disc harrow and/or tooth harrow to establish crops with the main purpose of seed bed preparation and initial weed control. However, due to the reversal of soil layers, weed seeds are buried, mixed and carried back to soil layers, from which they emerge and become established in the next crop. The need for additional chemical weed control with other economic and environmental disadvantages of conventional tillage is leading more and more farmers to use alternative tillage systems such as shallow tillage and direct seeding. The use of these tillage systems changes the distribution of weed seeds in the surface layer of the soil and the timing of weed emergence. In Mediterranean conditions, high initial weed growth can be expected after the first rainfall, as most weed seeds remain at or near the soil surface. For example, spraying before sowing removes a significant proportion of potential weeds and subsequently reduces weed pressure in the established crop.
Both the reduced weed pressure and the benefit of much better tillering capacity, which allows better timing of application, especially in direct seeding, should allow adequate weed control at lower herbicide rates. Earlier application dates will not only bring the weed to a more sensitive stage, but may also allow the use of lower application rates to ensure adequate crop penetration and contact with the weed leaves. In addition, as shown by O'Donovan et al. (1985), early weed removal is important to prevent crop yield reduction.
The increasing interest of Portuguese farmers in the application of conservation tillage systems was a goal to investigate the possibility of reducing the use of herbicides in winter wheat grown without tillage. In addition, it enabled the verification of the effect of different application volumes and times on the weed control efficiency of lower herbicide doses.
Materials and methods
In 2002/2003, a trial was carried out to investigate the effect of three doses of a post-emergence herbicide to control Lolium rigidum G. in winter wheat (Triticum aestivum L.) in interaction with three different application volumes and two weed development stages. and 2003/2004, on a private farm near Évora/southern Portugal. The herbicide used was a commercial mixture of 250 µl−1of 22.73% (w/w) diclofop-methyl+20 gl−1of 1.82% (w/w) fenoxaprop-p-ethyl+40 gl−1of 3.64% mefenpyr-diethyl. Your
Lolium control showed no significant differences between the different herbicide doses and application volumes or for their interaction. However, there was a trend toward a decrease in Lolium control as application volume was increased (Table 5) for all herbicide rates and weed developmental stages. In the first weed development phase (the beginning of the run), the effectiveness of all herbicide doses was higher for the lowest application volume (V1). In second weed development phase
Other authors (Zhang et al., 2000; Boström and Fogelfors, 2002) reported that satisfactory weed control can be achieved with lower doses than normally recommended. The results obtained in these trials show that the success of lower doses of herbicides depends on the early time of application when the weeds are more sensitive (O'Donovan et al., 1985).
The tillage system (direct seeding) used in this study seems to contribute in two different ways to the possibility of reducing the amount
The control of Lolium rigidum G. as the main grass weed problem in winter wheat under Mediterranean conditions is a major contributor to the total cost of weed control.
The results of this study show that it is possible to reduce the dose from 2.5 to 31 ha−1of the diclofop-methyl+fenoxaprop-p-ethyl+mefenepir-diethyl herbicide mixture recommended by the manufacturer and even the dose normally used by the Portuguese farmers (21ha−1) to achieve sufficient Lolium control efficiency for
The authors would like to thank the University of Évora, which supported these experiments.
- R.Skuterudet al.
Effect of herbicides applied at different times of the day
- K.S.Gillet al.
Early growth period weed flora of spring crops under conventional, reduced and no-till systems on clay soils in northern Alberta, Canada
Land preparation Res.
Type and timing of autumn tillage with and without herbicides at reduced doses in southern Sweden. 1. Yield and quantity of weeds
Land preparation Res.
- L.Bastianet al.
Designing weed management systems with a reduced reliance on herbicides poses new challenges and prerequisites for modeling crop-weed interactions
Field Crops Res.
- U.Bostromet al.
Weed and crop yield response to guidelines supporting herbicide dose decisions
- J.A.Bruceet al.
Effect of growth stage and environment on foliar absorption, translocation, metabolism and activity of nicosulfuron in quackgrass (Elytrigia repens)
- DDBuhleret al.
Perennial weed populations after 14 years of variable tillage and cultivation
- DDBuhleret al.
Field evaluation of a bioeconomic model for weed control in soybean (Glycine max)
- Fogelfors, H., 1990. Different doses of herbicide for weed control in cereals - final report of long-term...
- F.Forket al.
Multi-year validation of a decision aid for integrated weed control in row crops
Weeds in agricultural crops 1. Life forms and occurrence under Swedish conditions
Swedish J. Agri. Res.
Reduction of herbicides in metribuzin-based weed control programs in corn
Kan. J. Plant Sci.
Quackgrass control with glyphosate and SC-0224 in corn and soybeans
Kan. J. Plant Sci.
Integrating reduced-rate soil herbicides with physical control for weed control in fennel (Foeniculum vulgareMill.)
2014, Plant protection
Yousefi et al. (2012) found that the optimal dose of imazethapyr for control of Amaranthus reroflexus was always significantly lower than the recommended dose. Indeed, reduced herbicides are often sufficient to control weed densities at or below threshold levels, and lower herbicide rates combined with some mechanical weed control have been shown to be an effective way to reduce herbicide input in agricultural systems (Barros et al. ., 2005). The combination of management practices, such as cutting back herbicides, could improve weed control efficiency at reduced rates (Zhang et al., 2000).
Fennel is widely used in traditional medicine for its antimicrobial effects. Because fennel is a perennial crop and has slow initial growth, weed control is essential. Experiments were conducted over two consecutive seasons to evaluate the effectiveness of soil-applied herbicides at reduced rates in combination with physical control for weed management and fennel yield optimization. The treatments were herbicide type (trifluralin and pendimethalin), application rate (recommended rate (R), 75% R, 50% R and 0% R) and physical weed control (none, one manual weeding 50 days after planting (DAP) ), mulch of wheat straw). A weed-free control was also included in each year. The results showed that the use of soil-applied herbicides resulted in reduced weed biomass, but did not provide season-long weed control without additional physical control. In both seasons, pendimethalin gave better weed control than trifluralin. Reduced herbicides were found to be more effective when the herbicides were applied followed by hand weeding than when they were used alone or in combination with mulch. Experimental results also showed that a one-time increase in herbicides increased seed yield by 17.5 and 7.5% in 2012 and by 16.5 and 6.3% in 2013, when manual weeding and mowing, respectively, were used as additional controls. In general, 75% of the label recommended rate of herbicides followed by one manual weeding at 50 DAP produced consistently high yields and reduced weed biomass, reflecting both superior weed control and crop safety.
Weed Control and Wheat (Triticum aestivum L.) Yield Using 2,4-D Plus Carfentrazone Ethyl and Florasulam Plus Flumetsulam: Efficacy Evaluation
2007, Plant protection
Three field experiments were conducted in the research areas of Plant Protection Research Institute, Iran, at different locations in 2004–2005 to investigate the effectiveness of different broadleaf herbicides for weed control in wheat. Treatments included hand-weeded and weed-infested controls throughout the season and post-emergence applications of florasulam plus flumetsulam at 8.75, 10.50 and 12.25 ga.i./ha, 2,4-D plus carfentrazone-ethyl at 210, 245, 280 and 490 ga.i./ha, bromoxynil plus MCPA at 75, 100 and 150 ga.i./ha, 2,4-D at 560, 720 and 1120 ga.i./ha, tribenuron methyl and 2,4 -D plus MCPA. Herbicides were applied during wheat germination. Naturally occurring broadleaf weed populations were used in experiments. The results showed that bromoxynil plus MCPA at 150 ga.i./ha, 2,4-D plus MCPA, and 2,4-D plus carfentrazone-ethyl at 490 ga.i./ha were the best options for weed control. Bromoxynil plus MCPA at 150 ga.i./ha and 2,4-D plus MCPA also resulted in the highest wheat yield. Overall, it can be concluded that alternative application of bromoxynil plus MCPA at 150 ga.i./ha, 2,4-D plus MCPA and 2,4-D plus carfentrazone-ethyl at 490 ga.i./ha is the best would be. possibility of achieving satisfactory weed control, high grain yield and prevention of weed-resistant weed development.
Evaluation of some newly registered herbicides for weed control in wheat (Triticum aestivum L.) in Iran
2007, Plant protection
Field experiments were conducted in the research fields of the Plant Protection Research Institute, Iran, at six sites in 2005–2006 to investigate the weed control performance of some newly registered herbicides in wheat compared to some current herbicides. Treatments consisted of post-emergence applications of chlorsulfuron at 10.5 and 15 ga.i./ha, metsulfuron methyl plus sulfosulfuron at 32 and 36 ga.i./ha, both as dual-purpose herbicides, pinoxads at 45 and 60 ga. i./ha as grass weed herbicide, pinoxaden at 45ga.i./ha plus nonionic surfactant at 0.2% (v/v), tribenuron-methyl at 18.75ga.i./ha plus clodinafop propargyl at 64ga.i./ha , clodinafop propargyl, bromoxynil plus MCPA, bromoxynil plus MCPA at 600ga.i./ha plus clodinafop propargyl at 64ga.i./ha, prespiration applications of dual herbicide prosulfocarb at 2400 and .i weed/ha and . management. Post-emergence herbicides were used in wheat milling. The results showed that metsulfuron methyl plus sulfosulfuron at 36ga.i./ha is a suitable option for post-emergence control of broadleaf and grass weeds in wheat. This treatment also resulted in nearly the highest grain yield in several locations. The results also showed the importance of different wheat cultivars and environmental conditions on herbicide effectiveness; which is the best control option may vary based on variety and location. Chlorsulfuron and prosulfocarb also did not have significant priority over older herbicides in these trials, so further research is needed to investigate their effectiveness.
Broadleaf weed control in winter wheat (Triticum aestivum L.) with postemergence herbicides in Iran
2007, Plant protection
Field experiments were conducted in 2004–2005 at five locations in wheat growing areas of Iran to study weed control and winter wheat response to post-germination applications of diflufenican plus MCPA at 0.5, 1 and 1.5 l/ha, clopyralid plus 2.4 - D and fluroxypyr both at 1.5, 2 and 2.5 l/ha, tribenuronmethyl, 2,4-D plus MCPA, bromoxynil plus MCPA and dicloprop-p plus mecoprop-p plus MCPA. The post-emergence application of diflufenican plus MCPA, clopyralid plus 2,4-D and fluroxypyr improved broadleaf weed control compared to other herbicides. The data show that fluroxypyr at 2.5 L/ha caused the greatest reduction in weed populations and biomass in most cases. The efficacy of bromoxynil plus MCPA was generally better than tribenuron-methyl, 2,4-D plus MCPA, and dicloprop-p plus mecoprop-p plus MCPA, although it varied between sites and weed species. The application of diflufenican plus MCPA, clopyralid plus 2,4-D and fluroxypyr resulted in the highest wheat yield of all treatments.
Assessment of tribenuron methyl soil residue on crop germination properties
2022, Healthy plants
Herbicide weed control in plum orchards
2021, Magazine for Horticulture
Strong temporal variation in methane fluxes from natural gas well soils
Atmospheric Pollution Research, bind 11, udgave 8, 2020, s. 1386-1395
We measured methane and carbon dioxide fluxes at natural gas wells and undisturbed soils in the Rocky Mountain and Gulf Coast regions of the United States, including production and gas storage wells. We collected both short-term (15 min) and multi-day (between 3 and 8), continuous measurements at 47 well pads and two undisturbed sites. Methane fluxes varied by more than an order of magnitude over periods as short as 30 min (eg, 19–593 mgm)−2H−1in one case), and diurnal and seasonal variation was also significant (e.g. change from spring to autumn from 509 to 14174 mgm−2H−1). We hypothesize that short-term flux variability was caused by a pulsed flow of methane during its migration through the subsurface. Barometric pressure and well conditions likely affected the fluxes, but we found only weak evidence for this. Bacterial methanotrophy appeared to affect the magnitude and variability of the methane flux. We injected methane into the subsurface at a well, and we found that although the methane and carbon dioxide fluxes and combustible soil gas concentrations increased in response to the injection, the response was not uniform and the fluxes showed high hourly variations despite a constant injection rate. Methane fluxes were generally higher at well bottoms compared to background bottoms (often much higher), and fluxes tended to be higher at wellway locations closer to the wellhead.
Assessment of growth, leaf N concentration and chlorophyll content in sweet sorghum using canopy reflectance
Field Crop Research, Volume 209, 2017, pp. 47-57
Remote estimation of leaf nitrogen (N) or pigments using hyperspectral reflectance allows for non-destructive diagnosis of plant N status. Two cultivars of sweet sorghum (Sorghum bicolor [L.] Moench) (Top 76-6 and Dale) were grown at 0, 56, 112, 168 and 224 kgNha−1in 2009 and 2010. Reflectance measurements were linked to plant height, number of nodes in the main stem, leaf N concentration and total chlorophyll content to determine the relationship between these characteristics and crown reflectivity. Canopy reflectance was most sensitive to N-state in the visible region, especially near green (595 nm) and red (701 nm) wavebands. Spectral models with a simple ratio consisting of visible wavebands or wavebands from the visible and near-infrared regions performed better than models developed with only the most sensitive single waveband. Based on cross-validation of spectral models between data from two years and two cultivars, the models predicted with a simple ratio consisting of reflectance (R) ratio at 595 nm vs. 1676nm and 595nm vs. 508 nm, leaf N concentration and chlorophyll content with the greatest accuracy (highest r2and lowest relative error, RE). These simple ratio models were used to develop general spectral models to derive coefficients for estimating leaf N concentration (−66.63 × R595/R1676+34,14; R20.52; RE 16.8%) and chlorophyll content (-49.12×R595/R508+107,47; R20.64; RE 17%). The identified spectral models can be used to assess growth, diagnose sweet sorghum N status, and can be useful in making N management decisions for site-specific fertilization applications.
Glyphosate-resistant populations Lolium multiflorum and Lolium perenne from New Zealand are also resistant to glufosinate and amitrole
Plant protection, volume 78, 2015, pp. 1-4
This study investigated whether glyphosate-resistant populations of Lolium multiflorum and Lolium perenne from some New Zealand vineyards were still susceptible to glufosinate and amitrole. The plant response of a glyphosate-resistant population of L. multiflorum, population A, and two glyphosate-resistant L. perenne populations, populations J and O, to glufosinate and amitrole were evaluated and compared with susceptible populations in two dose-response experiments. Based on the herbicides that provide 50% growth reduction (GR50values), populations A, J and O were 3.9, 4.5 and 3.8 times more resistant to glufosinate, respectively, compared to the susceptible populations in a glufosinate dose-response experiment. Populations A, J, and O were also found to be 2.9, 5.0, and 13.1 times more resistant to amitrole, respectively, in an amitrole dose-response experiment. Very similar results were obtained when both dose-response experiments were repeated. This is the first confirmed report of weed species that have developed multiple resistances to glyphosate, glufosinate and amitrole. These are the three main herbicides currently used for weed control in New Zealand vineyards.
Modeling spatial and interannual variations of nitrous oxide emissions from UK cropland and grassland using DailyDayCent
Agriculture, ecosystems and environment, volume 250, 2017, pp. 1-11
Agricultural land is the main source of nitrous oxide emissions from management practices, including fertilizer application. While the amount of fertilizer is one of the main drivers of nitrous oxide emissions, emissions also depend on other variables, such as climate and soil properties. To understand the spatial and interannual variations in emission rate, simulations of N2O2 emissions were made from 2000 to 2010 for grass and cropland in the UK. In addition, the sensitivity of these emissions to soil and climate inputs was also tested. Emissions between 0.3 and 3.5 kgNha−1jr−1a 0.7-7 kgNha−1jr−1were simulated in UK cropland and grassland respectively. Although interannual variations can be attributed to climate forcing, the main cause of spatial variations in emissions was soil clay content. However, when testing the sensitivity of nitrous oxide emissions to soil clay content alone, it was not always the best predictor of emissions when soil texture changes outside the normal range used as input to the model from various databases.
Structural equation modeling reveals complex relationships in mixed sods
Plant Protection, Volume 78, 2015, pp. 106-113
The relationships between vegetation components in perennial pastures are complex, especially those involving grasses, weeds, legumes, and other forbs. When herbicides are used for broadleaf weed control, there may be a trade-off between the benefits of weed removal and the loss of legumes. Few studies distinguish between the contribution of different vegetation components to total forage yield, both before and after spraying. Herein, we use Structural Equation Modeling (SEM) to quantify relationships between grasses, legumes (Medicago sativa L. or Trifolium spp.), a common noxious weed (Cirsium arvense (L.) Scop) and other forbs at two sites within the Parkland -region of central Alberta, Canada. After clearing broadleaf vegetation with herbicide, we quantified changes in forage relative yield ratios (RYR) over two years. The SEM approach revealed clear differences in the ratio of grass components between sites. At the more mesic site, abundant thistle biomass had little influence on other turf components, and no benefit was observed in weed removal after spraying. In contrast, even low levels of thistle biomass suppressed grass and legume biomass at the more extreme site, and response after spraying revealed weed removal benefits. Unexpectedly, legumes were found to suppress grass biomass at both sites, suggesting strong interspecific competition between forage species. Subsequent removal of legumes appeared to release grass biomass from competition within sprayed plots, as illustrated by increased forage yield two years after spraying. These results highlight the complexities within temperate perennial pastures and illuminate the potential short-term effects of weeds and legumes on overall sod dynamics and forage production.
Field trial results of straw yield with different harvesting methods and modeled effects on soil organic carbon. A case study from southern Finland
Biomass and bioenergy, volume 95, 2016, pp. 8-18
We have estimated the effect of different cutting heights and harvesting strategies on the amount of harvestable residual biomass and allocation of residual biomass in the soil. A case study has been carried out on regional sources of straw biomass with the different crops currently grown in Varsinais-Suomi (southern Finland) (average from 2003-2012) and in the predicted future warmer climate (scenario RCP 4.5, year 2055) . We also estimated, using the Yasso07 model, the effects of different residual uptake intensities on soil organic carbon (SOC) at present and in the future warmer climate. The results indicated that the cutting height has a significant influence on the amount of straw biomass incorporated into the soil and the subsequent change in SOC. The impact depended on crop type and variety. When collecting and using straw, e.g. in energy production, harvesting methods that create greater stubble heights can help maintain soil fertility. The Yasso07 model suggests that in the predicted future warmer conditions, more straw could be collected without lowering SOC, as SOC mineralization in the warmer climate is expected to increase less than organic carbon changes caused by higher crop and root biomasses. Collecting and using straw as a renewable energy source always lowers greenhouse gas (GHG) emissions compared to fossil fuels. However, collecting straw every other year instead of every year, even with taller stubble, would reduce field traffic and compact the soil, saving the farmer extra work, while also significantly reducing greenhouse gas emissions.
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