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Isoxaflutole and atrazine are representative pesticides for weed control in corn fields. Formulations containing these two pesticides have been registered in China, and their residues may threaten food safety and human health. In this study, a method for simultaneous determination of isoxaflutole, atrazine, and their metabolites in fresh corn, corn kernels, and corn straw was established based on modified QuEChERS pre-treatment and high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS). The linearity of seven compounds was good (R2 ≥ 0.9912), and the matrix effect was 48.5–77.1%. At four spiked levels of 0.01, 0.02, 0.05, and 0.5 mg kg−1, all compounds' average recovery was 76% to 116%, with relative standard deviation (RSD) less than 18.9%. Field experiments were conducted in Liaoning, Heilongjiang, Inner Mongolia, Shanxi, Beijing, and Yunnan provinces to study the terminal residues. The terminal residues of all compounds were below the LOQ (0.01 mg kg−1) in fresh corn and corn kernels, and atrazine residues in corn straw ranged from <0.05 mg kg−1 to 0.17 mg kg−1. Finally, a dietary risk assessment was conducted based on residues from field trials, food consumption, and acceptable daily intake (ADI). For all populations, the chronic dietary risk probability (RQc) of atrazine was between 0.0185% and 0.0739%, while that of isoxaflutole was 0.0074–0.0296%, much lower than 100%. The results may provide scientific guidance for using isoxaflutole and atrazine in corn field ecosystems. [ABSTRACT FROM AUTHOR]

2-Chloro-4-fluoro-N-(N-isopropyl-N-methylsulfamoyl)-5-nitrobenzamide (12) A 50% NaOH aqueous solution (0.48 kg, 6.00 mol) was added dropwise into a stirred solution of B 10 b (0.91 kg, 6.00 mol) and methyltributylammonium chloride (7.7 g, 0.12 mol) in PhCl (6.5 L) at 20 °C. 2-Chloro-4-fluoro-5-nitrobenzoic acid (3) In a 20 L double layer glass reactor, 2-chloro-4-fluorobenzoic acid (1.00 kg, 5.73 mol) was slowly added to stirred concentrated sulfuric acid (4 L, 98%) and a clear solution was obtained. A solution of benzoyl chloride B 11 b (1.19 kg, 5.00 mol) in PhCl (1 L) was slowly added to the reaction solution and stirred at 20 °C for 2 h. [Extracted from the article]

The new triketone herbicide, tembotrione, provides excellent weed control in corn fields. To evaluate its safety, we established a modified QuEChERSpretreatment and ultra-high performance liquid chromatography-mass spectrometry method, using acetonitrile with 2% formic acid as the extractant and C18 as absorbent. The dissipation dynamics of tembotrionein corn straw and the terminal residual levels in all three corn matrices were studied in Henan and Jilin provinces. The linearity was excellent in the range of 0.01 to1 mg L−1, with the determination coefficient (R2) ≥0.9954. The average recovery was between 74% and 117%, with intra-day relative standard deviation less than 18.9 and the inter-day relative standard deviation less than 17.5. The degradation dynamic experiment showed that tembotrione decreased over time and followed the first-order kinetic equation. Our results showed that the regression coefficients of the dynamic equations were 0.9906 and 0.9897, with half-lives of 0.7 and 0.8 d, respectively. The final residue results showed that the maximum residues of tembotrione detected in corn in Jilin and Henan were 0.041 and 0.051 mg kg−1, respectively. The risk quotient (RQ) were calculated as 0.186 and 0.246, both of which were less than 1, which indicated an acceptable risk. [ABSTRACT FROM AUTHOR]

Atrazine (ATZ) is part of a group of herbicides called triazines. ATZ is widely used in agricultural areas of Mexico, commonly used for the selective control of weeds in corn and sorghum crops. The exposure to ATZ can have serious human health effects since its use was associated with the development of cutaneous melanoma in an epidemiological study. The aim of this study was to evaluate the expression of maturation and apoptotic markers in primary skin cultures exposed to ATZ. The primary skin cultures were exposed to 0.1, and 10 µM ATZ with or without ultraviolet (UV) radiation and the expression of maturation and apoptotic markers were evaluated by RT-qPCR. We observed a significant increase in all the melanocyte maturation markers in cells exposed to ATZ with or without UV, with SOX-9 and FAK (melanoblast markers) being the highest. Also, the expression of BCL-2 (anti-apoptotic marker) was the most increased gene in cells exposed to ATZ with or without UV. Low concentrations of ATZ and UV radiation induce genetic changes associated with the development of immature melanocytes and activate mechanisms associated with the inhibition of apoptosis characteristics of malignant cell transformation, which will allow proposing new therapeutic targets and generating new restrictions or care in farmers exposed to pesticides such as the ATZ. [ABSTRACT FROM AUTHOR]

Atrazine is a herbicide widely used in the control of weeds in crops such as corn, sugar cane, and sorghum. It is often found in aquatic environments, where it can potentially endanger nontarget organisms such as microalgae. The present study evaluated atrazine toxicity to seven different species of Chlorophyceae and the tolerance of the species to the herbicide was related to morphological, photosynthetic, chlorophyll‐a content and the activity of the glutathione‐S‐transferase enzyme (GST). The comparison of median effect concentration (EC50) values for growth inhibition indicates higher toxicity of atrazine for Pseudopediastrum boryanum and Desmodesmus communis, intermediate toxicity for Ankistrodesmus densus, Chlamydomonas puliminiorfes, and Raphidocelis subcapitata, and lower toxicity for Kirchneriella lunaris and Ankistrodesmus falcatus (EC50: 38, 42, 66, 103, 248, 1004, and 1585 µg L−1 atrazine, respectively). Principal component analysis (PCA) with algal characteristics suggested that the atrazine‐sensitive algae P. boryanum and D. communis were positively associated with photosynthetic levels and negatively associated with GST activity and chlorophyll‐a concentration. The PCA also suggested that the atrazine‐tolerant algae A. falcatus and K. lunaris were positively associated with morphological parameters, where the larger the cell size, the more tolerant. Although it is difficult to associate a single characteristic of algae as the key factor determining the tolerance to atrazine, results presented in this work indicate that the cell area, the photosynthetic parameters (mainly saturating irradiance), chlorophyll‐a content, and the biotransformation by GST in combination may be potential predictors for the differential tolerance of Chlorophyceae species to the herbicide. Environ Toxicol Chem 2022;41:1675–1685. © 2022 SETAC [ABSTRACT FROM AUTHOR]

Crop management and herbicide rotation have influenced the sustainability of production systems. The cover crops use and pre-and post-emergence herbicides are important tools that help farmers' strategies and conserve the agricultural system. In this context, the objective of this research was to evaluate the dry matter production of different cover crops before the establishment of corn, the effect on decreasing weed population, and the increase in corn yield. In addition, the influence of pre-and post-emergence herbicides on summer cultivation, observing the behavior concerning weeds, crop injury, and crop yield. The experiment was conducted during the years 2018-2019 in Sertao/RS - Brazil. The experimental arrangement was of randomized blocks with four replications. The treatments used were three different winter cover crops preceding corn cultivation x four pre-emergence herbicides x four post-emergence herbicides, totaling 192 experimental units. Going through the results, atrazine and atrazine + simazine used in pre-emergence had more influence on weed number reduction, and the post-emergence ammonium glufosinate herbicide promoted the highest weed control in post-emergence. Amicarbazone and glyphosate resulted in the best combination for corn yield using in pre-and post-emergence, respectively. Rye + turnip + vetch as cover crop resulted in higher biomass production, more significant weed number reduction, and increase corn yield. [ABSTRACT FROM AUTHOR]

This paper present the results obtained at National Agricultural Research and Development Institute Fundulea, during 2019-2020, according to the new herbicide treatments: Diniro (prosulfuron 40 g/kg + dicamba 400 g/kg + nicosulfuron 100 g/kg) + Trend (adjuvant); Radial 40 (40 g/l nicosulfuron) + Dicopur Top (344 g/l acid 2,4 D from DMA salt and 120 g/l dicamba); Principal plus (50 g/kg dicamba + 92 g/kg nicosulfuron + 23 g/kg rimsulfuron) +Trend (adjuvant); Radial 60 (60 g/l nicosulfuron) + Hudson (fluroxypyr 200 gr/l), postemergently applied - BBCH 14-16, maize 4-6 leaves-, for the annual and perennial weeds controlling from the maize crop. The weather from the experimentation years is representative for the local trend for last decade. The differences (5.64 t/ha in average) between yields of control plots and the yields of treated plots were significant in all years, but the differences within the yields of treated plots were not significant. The herbicides must be correlated with the infestation degree of weed, the spectrum and dominance of weeds, the time of application, the technical potential for efficacy, the local climatic conditions. [ABSTRACT FROM AUTHOR]

Since the commercialization of transgenic glyphosate-tolerant (GT) crops in the mid-1990s, glyphosate has become the dominant herbicide to control weeds in corn, soybean, and other crops in the United States and elsewhere. However, recent public concerns over its potential carcinogenicity in humans have generated calls for glyphosate-restricting policies. Should a policy to restrict glyphosate use, such as a glyphosate tax, be implemented? The decision involves two types of tradeoffs: human health and environmental (HH-E) impacts versus market economic impacts, and the use of glyphosate versus alternative herbicides, where the alternatives potentially have more serious adverse HH-E effects. Accounting for farmers' weed management choices, we provide empirical evaluation of the HH-E welfare and market economic welfare effects of a glyphosate use restriction policy on US corn production. Under a glyphosate tax, farmers would substitute glyphosate for a combination of other herbicides. Should a 10% glyphosate tax be imposed, then the most conservative welfare estimate is a net HH-E welfare gain with a monetized value of US$6 million per annum but also a net market economic loss of US$98 million per annum in the United States, which translates into a net loss in social welfare. This result of overall welfare loss is robust to a wide range of tax rates considered, from 10 to 50%, and to multiple scenarios of glyphosate's HH-E effects, which are the primary sources of uncertainties about glyphosate's effects. [ABSTRACT FROM AUTHOR]

Tolpyralate, a new selective postemergence herbicide developed for the weed control in corn, possesses a unique chemical structure with a 1-alkoxyethyl methyl carbonate group on the N-ethyl pyrazole moiety. This compound shows high herbicidal activity against many weed species, including glyphosate-resistant Amaranthus tuberculatus. Tolpyralate targets 4-hydroxyphenylpyruvate dioxygenase (4-HPPD), which is involved in the tyrosine degradation pathway. Inhibition of the enzyme destroys the chlorophyll, thereby killing the susceptible weeds. Details of tolpyralate discovery, structure optimization, and biological activities are described. [ABSTRACT FROM AUTHOR]

In this study, the control efficacies of nine herbicides against weeds were investigated and their safety in the maize field was evaluated. The efficiencies of nine herbicides at the recommended dosages were carried out using the method of spraying stem and leaves in seed production field for sweet maize. Their risk to sweet maize and post-harvest vegetables (cauliflower and radish) was also studied in the experimental field. The results showed that the control efficiencies of nine herbicides on weed and fresh weight were all above 92% at 25 days after the application. The prevention efficacies and 27% nicosulfuron + mesotrione + atrazine OD (810 g a.i./hm2 ) and 25% mesotrione + atrazine OD (750 g a.i./hm2 ) were the best ones. And that of 20% fluroxypyr EC (180 g a.i./hm2 ) was the lowest one, which showed high degree weed coverage after 50 days. In addition, the tested herbicides were safe and had no negative influence on the growth of sweet maize, and some herbicides could even significantly increase the production. The yield of maize after the treatment by 25% mesotrione + atrazine OD，20% nicosulfuron + bromoxynil octanoate OD (300 g a.i./hm2 )，80% atrazine WP (1 440 g a.i./hm2 ) and 27% nicosulfuron + mesotrione + atrazine OD was higher than that treated by other herbicides. Compared with the control, the yields were increased by 21.03%, 19.26%, 18.74% and 16.84%, respectively. Meanwhile, the treatments of 10% mesotrione SC (150 g a.i./hm2 ), 27% nicosulfuron + mesotrione + atrazine OD, 33.5% mesotrione + propisochlor + atrazine SC (1 005 g a.i./hm2 ) and 30% topramezone SC (27 g a.i./hm2 ) could improve the yield of the post-harvest cauliflower and radish. The increasing rates of yields were 18.05% and 13.68%, 3.37% and 12.67%, 15.45% and 11.06%, and 8.21% and 11.67%, respectively. While the 40 g/L nicosulfuron OD (60 g a.i./hm2) had a negative effect on the yield of cauliflower and radish. The yields were decreased by 9.74% and 3.57% compared with the control. The results could provide scientific basis on selecting and applying effective herbicides to control weeds in sweet corn field. [ABSTRACT FROM AUTHOR]

Limited information exists on the efficacy of pethoxamid for annual grass and broadleaf control in corn and soybean in Ontario. A total of 10 field experiments (5 with corn and 5 with soybean) were conducted during 2015 to 2017 in Ontario, Canada, to compare the weed control efficacy of dimethenamid-P at 544 g·ai·ha−1, pethoxamid at 840 g·ai·ha−1, pyroxasulfone at 100 g·ai·ha−1, and S-metolachlor at 1050 g·ai·ha−1 applied preemergence (PRE). Reduced weed interference with pyroxasulfone and dimethenamid-P resulted in corn yield that was similar to the weed-free control; however, weed interference with pethoxamid and S-metolachlor reduced corn yield 28 and 33%, respectively. Reduced weed interference with pyroxasulfone resulted in soybean yield that was similar to the weed-free control; however, weed interference with pethoxamid, dimethenamid-P, and S-metolachlor reduced soybean yield 27, 27, and 30%, respectively. At 4 and 8 weeks after application (WAA), all VLCFA inhibitor herbicides (Group 15) provided excellent redroot pigweed control (90 to 99%) in corn. There were no differences in common ragweed control, density, and dry weight among the VLCFA inhibitor herbicide evaluated; pyroxasulfone provided highest numeric common ragweed control and lowest numeric density and dry weight. At 4 and 8 WAA, pyroxasulfone provided the best common lambsquarters and wild mustard control and lowest numeric density and dry weight in corn and soybean. At 8 WAA, the VLCFA inhibitor herbicides controlled green foxtail 91 to 96% in corn; dimethenamid-P provided better control of green foxtail than pethoxamid in soybean. There were no differences in barnyard grass control among the VLCFA inhibitor herbicides evaluated. [ABSTRACT FROM AUTHOR]

Summary: A few years ago, a new invasive weed was found in Spanish maize fields grazed by sheep after harvest and identified as a subform of teosinte (Zea mays ssp. mexicana ad int). If teosinte seeds survive digestion, then the weed could spread via sheep manure. The aim of this study was to assess the effect of this process on the emergence and viability of teosinte seeds. In an in sacco study, seeds were introduced into the rumen of fistulised wethers and extracted after 24, 48, 72 and 96 h. Then, seed emergence was recorded and the viability of non‐germinated seeds was analysed. In an 'intake and in vivo' study, lambs were kept in metabolic cages and fed for 6 days with 200 g teosinte seeds and ears. The daily faecal production was individually collected, seeds were recovered and viability was tested (15 days). In the in sacco trials, a decrease in teosinte viability was observed after remaining for 48 h or more in the rumen. In the 'intake and in vivo' trial, between 0.1% and 3% of the ingested seeds that were excreted were viable. Uncoated seeds that lost their exocarp during the mastication and digestion processes were less viable (18%) than intact excreted seeds (74%). The last viable and intact seeds appeared 4 and 6 days after intake respectively. In areas with teosinte infestation, sheep grazing on maize stubble should be avoided and, in case of ingestion, sheep should be kept isolated for 4–6 days to avoid the spread of this invasive weed. [ABSTRACT FROM AUTHOR]

Mexican poppy (Argemone mexicana) is a widespread noxious annual weed associated with crops such as corn (Zea mays L.), and this weed is persistent because it produces a seed bank. This invasive weed species must be controlled even in the dry season because Mexican poppy has a deep-reaching root system, which taps water from deep soil layers. Cases of a human death caused by Mexican poppy seeds in South Africa, India, and other Eastern countries were reported from the early years of the twentieth century. However, when weeds are controlled uniformly instead of site-specific or precision farming method across the spatially variable fields, there are environmental pollution challenges. Site-specific weed control techniques have gained interest in the precision farming community over the last years mainly because of Global Positioning System (GPS) applications, and a controlled measure of herbicides are applied where there are weeds in the field, and areas with more clusters of weeds receive the correct amount of herbicide application. Mexican poppy has prickles and is a nuisance to farmers, and herbicides represent a severe health hazard to humans due to chemical concentrations in water. For that reason, we propose the design of a site-specific weed control plan to use a row-guided robot to detect and identify weeds with accuracy, control speed timeously, and spray herbicides with a high level of precision and automation. These robotics methods are reported to be environmentally conscious, and economically efficient with less labour and management. The proposed method of deep learning neural networks, which use row-guided robots, a machine is trained on multiple images to identify weeds automatically from the main crop, and release a controlled measure of herbicides based on weed location and density, and spray weeds on-the-go upon emergence. [ABSTRACT FROM AUTHOR]

In sugar beet, maize and soybean, weeds are usually controlled by herbicides uniformly applied across the whole field. Due to restrictions in herbicide use and negative side effects, mechanical weeding plays a major role in integrated weed management (IWM). In 2015 and 2016, eight field experiments were conducted to test the efficacy of an OEM Claas 3-D stereo camera® in combination with an Einböck Row-Guard® hoe for controlling weeds. Ducks-foot blades in the inter-row were combined with four different mechanical intra-row weeding elements in sugar beet, maize and soybean and a band sprayer in sugar beet. Average weed densities in the untreated control plots were from 12 to 153 plants m−2 with Chenopodium album, Polygonum convolvulus, Thlapsi arvense being the most abundant weed species. Camera steered hoeing resulted in 78% weed control efficacy compared to 65% using machine hoeing with manual guidance. Mechanical intra-row elements controlled up to 79% of the weeds in the crop rows. Those elements did not cause significant crop damage except for the treatment with a rotary harrow in maize in 2016. Weed control efficacy was highest in the herbicide treatments with almost 100% followed by herbicide band-applications combined with inter-row hoeing. Mechanical weed control treatments increased white sugar yield by 39%, maize biomass yield by 43% and soybean grain yield by 58% compared to the untreated control in both years. However, yield increase was again higher with chemical weed control. In conclusion, camera guided weed hoeing has improved efficacy and selectivity of mechanical weed control in sugar beet, maize and soybean. [ABSTRACT FROM AUTHOR]

Maize producers transitioning to an organic cropping system must grow crops organically without price premiums for 36 months before certification. We evaluated conventional and organic maize with recommended and high seeding and N rates in New York to identify the best organic management practices during the transition. Conventional versus organic maize management differences included a treated (fungicide/insecticide) Genetically Modified (GM) hybrid versus a non-treated non-GM isoline; side-dressed synthetic N versus pre-plow composted manure; and Glyphosate versus mechanical weed control, respectively. Organic versus conventional maize yielded 32% lower as the entry crop (no previous green manure crop). GrainN%and weed densities explained 72% of yield variability. Organic and conventional maize, following wheat/red clover in the second year, yielded similarly. Organic maize with high inputs following wheat/red clover and conventional maize with high inputs following soybean in the third year yielded the highest. Grain N% and maize densities explained 54% of yield variability. Grain crop producers in the Northeast USA who do not have on-farm manure and forage equipment should plant maize after wheat/red clover with additional N (~56 kg N/ha) at higher seeding rates (~7%) during the transition to insure adequate N status and to offset maize density reductions from mechanical weed control. [ABSTRACT FROM AUTHOR]

This paper proposes a new machine vision system, focused on crop row detection with three main goals: (1) to achieve a correct orientation at the starting point in the field for each path; (2) to achieve a precise guidance during path following and (3) to determine the weed density and overlapping. The vision system is designed to be installed onboard a mobile agricultural vehicle, i.e. submitted to turns, vibrations and undesired movements. The images are captured under image perspective projection, being affected by the above undesired effects. To achieve the above goals, we have designed an image processing strategy comprising two main modules: (a) crop rows detection with precise adjustment and (b) data extraction for determining weeds densities for site specific-treatments, guidance and the overlapping of the area where the treatment is to be applied. Both modules form a full process, and each module contains different processes, some of them coming from existing approaches (image segmentation and crop row estimation with adjustment) and other specifically designed for the proposed approach (exposure time control, position and orientation of the tractor and weeds density matrix computation with overlapping control). The proposed strategy has been conveniently tested and also the different processes defining each module, verifying their performances in terms of accuracies and processing times. Comparative analyses have also been carried out against some existing processes, also with acceptable performances. [ABSTRACT FROM AUTHOR]

Efficiency of crop production system is usually influenced by management of weeds. Weeds make a strong competition influence to the growing plants, especially when herbicides are not properly applied. In order to support crop growth, the optimal level of resources and nutrients is also needed. The aim of the investigation was to evaluate the effect of nitrogen form, maize row spacing and herbicide treatment on 1. Weed biomass, 2. Herbicide efficacy and 3. Maize biomass production. The investigations were conducted in Maize Research Institute Zemun Polje, Belgrade, during 2014-2016. Field experiment was settled as a split-split-plot block design with four replications. Maize was planted with application of standard and slow-realize form of urea. Within each N source, maize was grown into two inter-row spacing (50 cm and 70 cm) and with following weed control treatments: without herbicide application, application of pre-emergence (S-metolachlor + mesotrione) and post-emergence (nicosulfuron + mesotrione) herbicides mix. Maize hybrid ZPSC 388 was sown in the second decade of April, 2014, 2015 and 2016. Six weeks after herbicide application, the fresh biomass of uprooted weeds from 1 m² was measured and coefficient of efficacy was calculated. At the same time, aboveground biomass of whole crop plants was evaluated. Results show that weed biomass was slightly higher in 70 cm than in 50 cm row distance but it was significantly lower on treatments than on untreated control. Pre-emergence mixture of S-metolachlor + mesotrione provided good control and at the higher extent when it was applied after slow-realising urea. The best efficacy was observed in post-emergence treatment with mesotrione + nicosulfuron in 50 cm row distance and standard urea application (96.65%). Chemical control of weeds significantly increased biomass of maize plants, while row spacing and nitrogen form, didn't show greater influence. Maize biomass at the developmental stage of 22-24 leaves was the highest in the herbicide treatments, application of standard urea and 50 cm inter-row distance which indicates that space between maize rows could be decreased from standard 70 cm. [ABSTRACT FROM AUTHOR]

Two field trials were performed at Tamiya Experimental Station, Fayoum Govemorate Egypt , during 2012 and 2013 seasons , to study the competitive ability of some maize hybrids in associated weeds by modification of crop density .The experiment included: Three hill distances (25,30and 35 cm apart) on one side of ridge at approximately 28000,23333 and 20000 plants I fed ,Three weed control treatments, one hand hoeing ,hand hoeing twice and the unweeded (control) and Three maize hybrids , i.e. , T.W.C.310, T.W.C.1100 and T.W.C. Nefertiti 3. Results showed that all weeded treatments significantly depressed weed growth comparing to the unweeded one .application of hoeing caused significant increases in plant height, ear height ,number of ear /plant , all ear characters , and grain yield I feddan . Moreover, two hoeing superiored one hoeing in all characters. Each increases in hill distances resulted in increasing - total weed dry weight, ear height, number of ear /plant ,ear length ,ear diameter, grain number I ear ,ear weight, grain weight /ear, 100- grain weight and grain yield I feddan .Neffertiti 3 surpassed other hybrids in all grain characters and grain yield I feddan .While T W C 1100 recorded the lowest values. [ABSTRACT FROM AUTHOR]

Striga hermonthica and drought are the major stresses limiting maize yields in sub-Saharan Africa. The search for diverse maize lines' tolerance to drought and resistance to S. hermonthica ( DTSTHR) is very crucial for yield improvement in areas affected by the two stresses. Understanding the genetic diversity among the lines is important to develop cultivars resistant to S. hermonthica and tolerant to drought. The lines were developed from biparental crosses of drought-tolerant and Striga-resistant lines. A total of 128 DTSTHR maize lines were characterized using single-nucleotide polymorphism ( SNP) markers. Results of the cluster analysis based on 3297 SNP markers showed four distinct groups consistent with the pedigrees of the lines. Furthermore, model-based analysis also formed the same groups of the DTSTHR lines. Integrating the pedigree information with combining ability and the SNP analyses may provide defined heterotic groups for maize improvement work in West and Central Africa. These results also help breeders to utilize DTSTHR lines present at IITA for developing biparental crosses without disrupting the heterotic groups they have established in their breeding programmes. [ABSTRACT FROM AUTHOR]

Based on the previous finding that a substitution at 5-position of the benzene ring is favorable to enhance the degradation rates of sulfonylurea herbicides, a total of 16 novel 2,5-disubsituted sulfonylurea compounds were chemically synthesized and fully characterized by means of 1H NMR, 13C NMR, HRMS and X-ray diffraction. By using HPLC analysis, the degradation behavior of M03 , a compound belonging to this family, was studied and confirmed that chlorsulfuron itself is not a degraded product of the 2,5-disubstituted sulfonylureas. Inhibition constants against plant acetohydroxyacid synthase (AHAS) were determined for selected compounds, among which SU3 showed seven times stronger activity against the mutant W574L enzyme than chlorsulfuron. Molecular docking suggested that the substituted group at 5-position of benzene ring is likely to interact with the surrounding residues Met200 and Asp376 of At AHAS. From the greenhouse herbicidal assay and crop safety test, SU5 and SU6 are considered as herbicide candidates to control dicotyledon weeds in corn, while SU3 is likely to be a promising candidate to control dicotyledon weed species and barnyard grass in wheat. The present research has therefore provided some new insights to understand the structure-activity relationships of herbicidal sulfonylureas with di-substitutions at benzene ring. [Display omitted] • A total of 16 novel 2,5-disubsituted sulfonylurea compounds were synthesized. • The degradation behavior of M03 was studied for the first time. • SU3 showed stronger inhibition against W574L than chlorsulfuron. • Binding mode of SU3 with plant AHAS was predicted via molecular docking. • SU3 , SU5 and SU6 are promising leads for the development of selective herbicides. [ABSTRACT FROM AUTHOR]

Deficiencies of metal micronutrients are common in some calcareous soils. Samples of aerial parts of maize and five common weeds and also soil beneath these plants were collected and analyzed to investigate the status and relationships of metal micronutrients in soil, crop, and common weeds of maize field trials at two sites. Results showed that Fe concentration in five studied weeds was higher than that of maize; the highest Fe concentration was found inConvolvolus arvensisandEchinochloa crus-galli(first site) and inConvolvolus arvensistissues (second site). At both sites, the highest Mn concentration was observed in aboveground parts ofEchinochloa crus-galli. The concentration of Mn (both sites) and Fe and Cu (second site) were remarkably higher inEchinochloa crus-gallitissues in comparison with maize. Also the concentrations of Fe (both sites) and Cu (second site) were considerably higher inConvolvolus arvensistissues in comparison with maize. Available Fe was the highest in the soil beneathConvolvolus arvensisandPortulaca oleracea(first site) and beneathConvolvolus arvensisandCenopodium album(second site). The high value of available Fe in the soil beneathConvolvolus arvensismay explain why Fe concentration was the highest in aerial parts of this weed species. [ABSTRACT FROM AUTHOR]

Recent development of site-specific weed management strategies suggests patch application of herbicides to avoid their excessive use in crops. The estimation of infestation of weeds and control thresholds are important components for taking spray decisions. If weed pressure is below a certain level in some parts of the field and if late germinating weeds do not affect yield, it may not be necessary the spray such places from an economic point of view. Consequently, it makes sense to develop weed control thresholds for patch spraying, based on weed cover early in the growing season. In Danish maize field experiments conducted from 2010 to 2012, we estimated competitive ability parameters and control thresholds of naturally established weed populations in the context of decision-making for patch spraying. The most frequent weed was Chenopodium album, accompanied by Capsella bursa-pastoris, Cirsium arvense, Lamium amplexicaule, Tripleurospermum inodorum, Poa annua, Polygonum aviculare, Polygonum persicaria, Stellaria media and Veronica persica. Relative leaf cover of weeds was estimated using an image analysis method. The relation between relative weed leaf cover and yield loss was analysed by nonlinear regression models. The competitive ability parameters and economic thresholds were estimated from the regression models. The competitive ability of weed mixtures was influenced by the increasing proportion of large size weeds in the mixtures. There was no significant effect of weeds which survived or established after the first herbicide application, indicating that early image analysis was robust for use under these conditions. [ABSTRACT FROM AUTHOR]

A field experiment was carried out to study the influence of nitrogen (N), phosphorus (P), and potassium (K) nutrient supply on weed flora in maize. The investigations were conducted in a long-term fertilization experiment launched in 2003 on a loamy chernozem soil with lime deposits, in Fejér County, Hungary. The composition, biomass weight, and density of weeds were determined in relation to different nutrient supplies. Seventy-five percent of weeds consisted of three species: Ambrosia artemisiifolia L., Datura stramonium L., and Helianthus annuus L. Density of weeds varied relative to the different nutrient treatments, with a range of 82–131 plants m−2. The total weed density was significantly lower by 19.9–37.8 percent in the N-containing treatments (NP, NPK) than in non-N treatments. The density of the nitrophilD. stramoniumL.,Chenopodium albumL.,Chenopodium hybridumL., andAmaranthus blitoidesS. Watson was higher when N supply was greater. [ABSTRACT FROM PUBLISHER]

The determination of the critical period of competition between the weeds and the economic cultivation is the only efficient road to only establish methods of weeds handling during the time that the cultivation requires it and this way to facilitate the coexistence interespecific economic weeds-cultivation. To achieve that objective, it was carried out an investigation during two years (2007-2008) in the National Institute of Agriculture Science, where it was evaluated at random by means of a design of blocks, with treatments at the 16, 24, 32, 40, 48 and 54 days after the germination with and without weeds, and two witness, with and without handling during the whole cycle of the corn. The dominant weeds in the system, was Cyperus rotundus and Rottboellia exaltata attributable to the chemical methods of handling precedents. In accordance with the carried out statistical analyses the critical period of competition of the weeds with the cultivation of the corn was in the period that lapses from 24 to 40 days after having germinated the cultivation, period during which the works of handling of the weeds cannot miss the cultivation, preferably in a mechanical way, to guarantee high yields and ecological balance in the productive system. Corn yields were higher when the crop was treated at the critical period reaching values between 11 and 12 t.ha-1 .Work before and after this alone period they contribute to elevate the energy expenses and to unbalance the agroecosystem. [ABSTRACT FROM AUTHOR]

Abstract: LiDAR (Light Detection And Ranging) is a remote-sensing technique for the measurement of the distance between the sensor and a target. A LiDAR-based detection procedure was tested for characterisation of the weed vegetation present in the inter-row area of a maize field. This procedure was based on the hypothesis that weed species with different heights can be precisely detected and discriminated using non-contact ranging sensors such as LiDAR. The sensor was placed in the front of an all-terrain vehicle, scanning downwards in a vertical plane, perpendicular to the ground, in order to detect the profile of the vegetation (crop and weeds) above the ground. Measurements were taken on a maize field on 3m wide (0.45m2) plots at the time of post-emergence herbicide treatments. Four replications were assessed for each of the four major weed species: Sorghum halepense, Cyperus rotundus, Datura ferox and Xanthium strumarium. The sensor readings were correlated with actual, manually determined, height values (r 2 =0.88). With canonical discriminant analysis the high capabilities of the system to discriminate tall weeds (S. halepense) from shorter ones were quantified. The classification table showed 77.7% of the original grouped cases (i.e., 4800 sampling units) correctly classified for S. halepense. These results indicate that LiDAR sensors are a promising tool for weed detection and discrimination, presenting significant advantages over other types of non-contact ranging sensors such as a higher sampling resolution and its ability to scan at high sampling rates. [Copyright &y& Elsevier]

Abstract: Landscape effects on arable weed communities have mainly been studied in areas dominated by intensive agricultural land use, while less attention has been paid to the same effects in cultivated fields close to the rural–urban interface. Our objective was to assess the effects of ongoing agricultural land abandonment and urban sprawl on arable weed communities since this is a widespread phenomena in Mediterranean landscapes. Weeds were sampled at three different distances (5, 10, 15m) from the field margin in 21 maize fields located within a 75km2 area in Liguria and Tuscany, Italy. Species were aggregated in functional response groups based on chorological categories, Raunkiær life forms and CSR plant strategies. Landscape surrounding each field was assessed in four circular buffers of radii ranging from 250 to 1500m. Attributes characterising fields and field margins were also considered. Community composition and diversity of weed communities were affected by field and landscape characteristics. Old and new abandonment increased species richness and weed diversity but had an opposite effect on the Raunkiær functional response groups. Urban sprawl was positively correlated with abundance of geophytes, competitive and cosmopolite species and negatively correlated with therophytes and competitive-ruderals. Most landscape parameters had stronger effect at the smallest scale. The effect of landscape parameters was clearer when weeds were classified by functional response trait than by taxonomy. [Copyright &y& Elsevier]

In the years 2000 - 2011 (12 years) was conducted weed survey on the farms in conventional farming system. The goal was to detect the most harmful weeds, as important biotic, environmental stress factor, on the farms in the canopies of maize for grain in maize, sugar beet and potato production regions of the Slovak Republic. The fields were selected in all production regions of Slovakia. An actual weed infestation was evaluated before preemergence application of herbicides. Screening of each field was made on 1 m2 area with four replications. The four randomly established sample quadrants were situated minimally 20 m from field margin and apart from each other, respectively. The level of infestation was evaluated according to average density of weeds per square meter. Obtained data from farms was statistically analyzed by correlation analysis in Statistica 7.0. According to the obtained data and results of weed survey the most troublesome weeds with the heaviest weed infestation level of maize for grain stands were in maize production region Chenopodium spp., Amaranthus spp. and Echinochloa crus galli (L.) P. Beauv.; in sugar beet production region Persicaria spp., Atriplex spp. and Echinochloa crus galli (L.) P. Beauv.; in potato production region Atriplex spp., Chenopodium spp. and Elytrigia repens (L.) P. Beauv. An actual weed infestation depends on production region. After herbicides control the significant changes in weed flora were noted in term of abundance and share of some weed species on total weed community. The dynamics of actual weed infestation depend on climate conditions of maize, sugar beet and potato production region, forecrop and canopy health condition. Weeds are always a problem in maize for grain stands. They can rapidly reduced the yield of maize, but management and control may be considered necessary to safeguard crop quality and yield. The originality of result is in mapping the weed species and its actual weed infestation in cultural crops (maize for grain stands). [ABSTRACT FROM AUTHOR]

In the years 2000 - 2011 (12 years) was conducted weed survey on the farms in conventional farming system. The goal was to detect the most harmful weeds, as important biotic, environmental stress factor, on the farms in the canopies of pea for grain in maize, sugar beet and potato production regions of the Slovak Republic. The fields were selected in all production regions of Slovakia. An actual weed infestation was evaluated before preemergence application of herbicides. Screening of each field was made on 1 m2 area with four replications. The four randomly established sample quadrants were situated minimally 20 m from field margin and apart from each other, respectively. The level of infestation was evaluated according to average density of weeds per square meter. Obtained data from farms was statistically analyzed by correlation analysis in Statistica 7.0. In the pea for grain canopies 10 most dangerous weed species were detected, the most problematic were: perennial weeds Cirsium arvense (L.) Scop. and Elytrigia repens (L.) DESV and annual weeds Atriplex spp., Avena fatua L., Amaranthus spp., Anthemis spp., Chenopodium spp., Tripleurospermum perforatum (Mérat) M. Lainz, Echinochloa crus galli (L.) P. Beauv and Datura stramonium (L.). Temporal dynamic of actual weed infestation depends on production region. After herbicides control the significant changes in weed flora were noted in term of abundance and share of some weed species on total weed community. Temporal dynamics of actual weed infestation depend on climate conditions of maize, sugar beet and potato production region, forecrop and pea stand health condition. Spring and perennial weeds are always a problem in pea for grain stands, because pea plants are not so competitive, but control may be considered necessary to safeguard crop quality and yield. The originality of result is in mapping the weed species and its actual weed infestation in cultural crops (pea for grain stands). [ABSTRACT FROM AUTHOR]

Dose-response experiments were conducted under controlled conditions to determine the effective minimum rates (ED90) of foramsulfuron for 11 weed species that occur in maize growing areas in Turkey. Annual weeds were collected from maize fields in the cotyledon stage and transferred to pots containing a mixture of soil-turf (1:1 ratio). Perennial weeds were grown from rhizome pieces collected from infested fields. Weeds were then treated with different rates of foramsulfuron to determine the effective minimum rate (ED90) for each weed species via dose-response experiments. Results showed that ED90 rates were lower than the recommended herbicide rate for most weed species. Weeds were grouped with respect to their sensitivities into 5 different groups: ED90 < 25%, ED90 between 25% and 50%, ED90 between 50% and 75%, ED90 between 75% and 100%, and ED90 > 100% of the recommended herbicide rate. In additional field experiments the performance of these rates applied alone or in combination with ammonium-sulphate on weed and maize grain yield was evaluated, and ED90 rates were determined for some weed species. The results show that 25% of the herbicide rate alone insufficiently controlled weeds; however, the addition of AS improved the effect of this rate. In general, the 50% rate was as efficient as the recommended rate and provided similar maize yield as obtained from plots treated with higher rates or from weed-free control plots. As compared to the ED90 rates determined under controlled conditions, effective minimum rates observed under field conditions were similar for some weed species, but higher for some others. In the case of total weeds the ED90 rate of the herbicide corresponded to 54% of the recommended herbicide rate. Results of these experiments suggest that weed control in maize can be effectively achieved with about half the recommended rate of foramsulfuron, without a loss in yield. [ABSTRACT FROM AUTHOR]

Abstract: Despite the availability of modern hybrids and better agronomic practices, there existed large gaps between attainable yield of maize (Zea mays L.) grown with recommended practices and producers’ harvest yields in the humid temperate regions of eastern Canada. A field experiment was conducted for 3 years in Ottawa, Canada, to determine the most important management yield-limiting factor(s) on rainfed maize grain production. A package of recommended practices (RP) was composed with the recommended levels of nitrogen (N), phosphorus (P), potassium (K), micronutrients, chemical weed control, and plant population density (PPD). Each factor was modified from the RP, making a total of 11 treatments. Under the low occurrence of diseases or insects, weed infestation was the most important yield-limiting factor, which reduced grain yield by 27–38%. While lack of preplant N application (100kgha−1) reduced yield by 10–22%, there was no yield increment with additional sidedressing N (50kgNha−1). Grain yield was reduced by 8–13% with low PPD (60,000plantsha−1) in all years, whereas increasing PPD to 90,000plantsha−1 did not improve yield, compared with the RP. Withhold P application did not affect yield in all years, but yield was reduced by up to 13% in the absence of K, and by 10% and 12% without Zn or Mn, respectively, in 1 year. Our results indicated that lack of weed control (i.e. herbicide use) was the major yield-limiting factor followed by fertilizer N and PPD. The responses of grain yield to K, Zn, and Mn were site and/or year specific. Our study provided experimental data and an insight understanding of yield gap between genotype''s yield potential achievable with recommended practices and yields with producers’ practices. [Copyright &y& Elsevier]

Sorghum allelopathy has been utilized as an economical and natural technique for controlling Weeds in some field crops like wheat (Triticum aestivum L.), maize (Zea mays L.), rice (Oryza sativa L.), mungbean (Vigna radiata L.) and Brassica (Brassica juncea L.). It can be used as sorgaab (water extract of mature sorghum plants), sorghum mulch, sorghum soil incorporation or included in crop rotation. Two field experiments were conducted for two years in the summer of 1997 and 1998. In Experiment 1, the response of maize (Zea mays L.) and summer weeds to foliar applications of sorgaab, hand weeding and herbicide spray was studied. In Experiment 2, the comparative efficacy of sorgaab at 15, 30 and 45 days after sowing (DAS) and sorghum mulch for controlling weeds were studied. Sorgaab foliar spraying controlled from 18–50% weeds and increased maize grain yield by 11–44%. Mature and chaffed sorghum herb- age (10–15 Mg ha-1) surface applied at sowing controlled up to 26–37% weeds and increased maize yield by 36–40%. Three foliar sprays of sorgaab at 15, 30 and 45 days alter sowing was the most economical method for controlling weeds in maize as compared with hand weeding, chemical herbicides and sorghum mulch. Weed control through hand weeding and/ or chemical herbicides was found to be economically impractical due to higher costs involved in both cases. Sorgaab can be used as a natural weed inhibitor in maize. [ABSTRACT FROM AUTHOR]

Knowledge of the long-term effects of tillage on weed flora will provide useful information to improve weed management in agroecosystems. Field studies were conducted from 1991 to 1997 to evaluate the effects of tillage systems on weed density and species composition before control methods in rotations including wheat (Triticum aestivum L.), soyabean [Glycine max (L.) Merr.] and maize (Zea mays L.). In wheat, annual broad-leaved species showed higher populations in conventional tillage in 4 out of 6 years, and grassy annuals and perennial species showed an erratic response with tillage systems. In summer crops, broad-leaved populations were higher under conventional tillage than non-tillage for the last 5 years in the wheat/soyabean rotation and for the last 4 years in the maize/soyabean rotation. The weed spectrum changed rapidly in non-tillage plots. With time, in the absence of tillage, grassy annual populations increased in the maize/soyabean rotation, and wind-dispersed weed populations increased in the wheat/soyabean rotation. Perennial weeds showed an inconsistent behaviour in relation to tillage systems in the maize/soyabean rotation. [ABSTRACT FROM AUTHOR]

Focuses on research on Cyperus rotundus L. weeds. Investigation of the effect of maize, cotton and groundnut canopies on the suppression of the weed; Study of C. rotundus growth and development under a constant maize population planted in isometric and rectangular stands; Effectiveness of the maize canopy in suppressing the spread and regenerative capacity of C. rotundus early in the season; Discussion of the implications for integrated control of the weed.

Presents a survey of four patches of Abutilon theophrasti seedlings in two continuous maize production fields during the period of 1995-97. Description of the spatial patterns of the weeds; Indication that autocorrelation coefficients decreased at a greater rate across crop rows than parallel to crop rows; Consideration of factors affecting patch-level processes of spatial aggregation, stability, and edge dynamics; Proposal of demographic- and patch-level processes important for patchiness in agricultural fields.

• The study was carried out for silt loam, clay loam, silty clay loam and clay soils. • EMI is effective for identifying surface soil clay content at the field scale. • Cross-correlation shows atrazine transport parameter is strongly correlated with clay content, thus correlated with EMI. • HYDRUS 2D provides different atrazine movement simulations along the corn field. • Combining EMI with HYDRUS-2D provides atrazine spatial distribution helping the development of best management practices. Atrazine is an herbicide commonly used to control weeds in corn crop. Atrazine becomes an environmental concern when it moves off-site to surface and ground waters. Understanding how atrazine moves in the field is important for developing management controls. Electromagnetic induction (EMI) has been used to map certain contaminant transport at the field scale. This study was developed to evaluate the efficacy of EMI technology for identifying surface soil atrazine concentration in a corn crop field. The research was conducted in a corn silage field with silt, clay and loam soils at the U.S. Meat Animal Research Center (USMARC), Clay Center, NE – USA, and it was divided in three stages; i) EMI data collection and a response surface sampling design for collection of bulk soils and soil core samples, ii) atrazine transport parameters were obtained by Breakthrough Curves using the bulk soil and numerical adjustments using STANMOD (HYDRUS package), and iii) Modeling atrazine parameters through EMI signal data with posterior atrazine's movement simulations through the soil using HYDRUS 2D. Atrazine's retardation factor, partition coefficient, and transfer coefficient were strongly correlated with EMI signal exhibiting a strong correlation with apparent electrical conductivity (EC a). The low values for RMSE and RRMSE and the high values for Willmott and Pearson coefficients indicate EMI technology can be used to predict atrazine movement parameters. HYDRUS 2D quantitatively simulates the atrazine concentration leaching and how the temporal scale of this contamination would be. Combining EMI technology with HYDRUS 2D modeling provides researcher with additional information for developing better management practices for controlling atrazine movement to surface water; however, further studies are needed determine the effectiveness of this approach for other soil types. [ABSTRACT FROM AUTHOR]

Dicamba is a moderately volatile herbicide used for post-emergent control of broadleaf weeds in corn, soybean, and a number of other crops. With increased use of dicamba due to the release of dicamba-resistant cotton and soybean varieties, growing controversy over the effects of spray drift and volatilization on non-target crops has increased the need for quantifying dicamba collected from water and air sampling. Therefore, this study was designed to evaluate stable isotope-based direct quantification of dicamba from air and water samples using single-quadrupole liquid chromatography–mass spectrometry (LC–MS). The sample preparation protocols developed in this study utilize a simple solid-phase extraction (SPE) protocol for water samples and a single-step concentration protocol for air samples. The LC–MS detection method achieves sensitive detection of dicamba based on selected ion monitoring (SIM) of precursor and fragment ions and relies on the use of an isotopically labeled internal standard (IS) (D3-dicamba), which allows for calculating recoveries and quantification using a relative response factor (RRF). Analyte recoveries of 106–128% from water and 88–124% from air were attained, with limits of detection (LODs) of 0.1 ng mL−1 and 1 ng mL−1, respectively. The LC–MS detection method does not require sample pretreatment such as ion-pairing or derivatization to achieve sensitivity. Moreover, this study reveals matrix effects associated with sorbent resin used in air sample collection and demonstrates how the use of an isotopically labeled IS with RRF-based analysis can account for ion suppression. The LC–MS method is easily transferrable and offers a robust alternative to methods relying on more expensive tandem LC–MS/MS-based options. [ABSTRACT FROM AUTHOR]

Weeds present important challenges to both conventional farmers who rely on herbicides and organic farmers who rely on cultivation. Data from field experiments indicate that diversifying crop sequences with additional species can improve weed suppression when either herbicides or cultivation serve as primary control tactics. Here, we report the results of modeling analyses that investigated how cropping system diversification would affect the population dynamics of giant ragweed (Ambrosia trifida L.), an annual dicotyledonous species that is problematic in the central U.S. for both conventional and organic farmers. We found that to prevent an increase in giant ragweed density, the minimum control efficacy needed from herbicides or cultivation used in corn (Zea mays L.) and soybean (Glycine max (L.) Merr.) would be 99.0% in a 2-year corn–soybean system, but 91.4% in a 5-year corn–soybean–rye (Secale cereale L.)–alfalfa (Medicago sativa L.) system. Thus, the diversified rotation would be better buffered against less-than-perfect weed control during corn and soybean phases. Further modeling analyses indicated that the weed suppression effect associated with greater rotation length was attributable not only to increased crop species richness but also to greater temporal variation in planting dates. A planting interval variation index (PIVI), calculated as the coefficient of variation in months between planting activities, was strongly associated with the weed suppressive ability of the rotations we modeled and may be a useful metric for designing other cropping systems. Overall, our results indicate that diversified rotation systems that include both annual and perennial crops are likely to be valuable for managing problematic weed species. [ABSTRACT FROM AUTHOR]