Atrazine Application Research Articles

Assessing the Effect of Weed Management Practices on Weed Flora, Growth and Yield of Fodder Maize (Zea mays L.)

A field experiment was conducted at Research Farm, AICRP on Forage Crops, Department of Agronomy, JNKVV, Jabalpur (Madhya Pradesh) during of the year 2019. The main objective of the experiment was to find out the effect of different weed control treatments on complex weed flora in fodder maize. Ten treatments were tested in randomized block design with three replications. Treatments consisted of pre-emergence application of atrazine 1000 g/ha, pendimethalin 750 g/ha, atrazine 750 g/ha + pendimethalin 750 g/ha and post emergence application of 2, 4-D 500 g/ha, tembotrione 120 g/ha, topramezone 35 g/ha, tembotrione 120 g/ha + atrazine 250 g/ha, topramezone 35 g/ha + atrazine 250 g/ha, hand weeding twice at 20 and 40 DAS and weedy check. Weed intensity and dry matter accumulation by weeds were recorded species wise and then the effectiveness of weed management and the weed control efficiency were calculated. In maize field, the predominated weeds were Echinochloa colona, Commelina communis, and Digitaria sanguinalis among monocots, Phyllanthus niruri and Eclipta alba among dicots along with a respectable sum of numerous minor weeds. Experimental results indicated that hand wedding has recorded highest weed control efficiency (88.64%) followed by PoE application of topramezone 35 g/ha + atrazine 250 g/ha (74.38%) and tembotrione 120 g/ha + atrazine 250 g/ha (68.31%). All weed control treatments significantly affected the plant height, LAI, stem girth and leaf: stem ratio of crop. Among different herbicidal treatments, topramezone 35 g/ha + atrazine 250 g/ha was found significantly superior and gives highest green fodder yield (47.26 t/ha), dry fodder yield (13.64 t/ha), crude protein yield (1.51 t/ha), net monetary returns (Rs. 44824/ha) and B: C ratio (2.72). Thus, herbicide application of topramezone 35 g/ha + atrazine 250 g/ha was found more reliable to control complex weed flora of fodder maize with higher green fodder yield and net returns.

Effect of Tembotrione on Weed Growth and Productivity of Kharif Maize (Zea mays L.)

A field experiment was conducted in maize (Zea mays L.) during both kharif (June–September, 2014 and 2015) seasons in a randomized block design with nine treatments, including the herbicide tembotrione as early post-emergence at 80, 100 and 120 g ha-1 both as sole and in combination with atrazine at 500 g ha-1, atrazine at 1000 g ha-1, hand-weeding twice at 25 and 40 DAS and unweeded control with three replications. The experimental field was heavily infested with Ludwigia parviflora (Jacq.) Raven, Cynodon dactylon (L.) Pers., Cyperus rotundus (L.) and Fimbristylis miliacea (L.) Vahl. The yield of maize was reduced by around 48% due to weed infestation. From the experiment, it was found that combined application of tembotrione and atrazine was much more effective than sole application of herbicide at any of the levels that were evaluated. Tembotrione at a rate of 80–100 g ha-1+stefesmero surfactant at 733 g ha-1+atrazine at 500 g ha-1 recorded the lowest weed density, weed biomass and weed index; highest values of growth and yield parameters as well as the yield of maize. Therefore, early post–emergence application of tembotrione at 80–100 g ha-1+stefesmero surfactant at 733 g ha-1+atrazine 500 g ha–1 appeared to be the most effective weed management approach for higher weed control efficiency, yield, gross and net return of kharif maize in lateritic soil of West Bengal.

Immediate effects of atrazine application on soil organic carbon and selected macronutrients and amelioration by sawdust biochar pretreatment

Abstract Increasing use of herbicides has contributed immensely to current soil and water degradation in the tropics. Published works on effects of herbicides on soil organic carbon (SOC) – a major indicator for soil health and macronutrients and their enhancement by biochar are scarce for soils in Africa despite heavy herbicide applications every cropping season. This incubation trial evaluated immediate effects of atrazine application on SOC and selected soil macronutrients. The potential of sawdust (SD) biochar to mitigate associated SOC and macronutrients depletion was also assessed. A total of 950 g soil was placed in each leaching column (20 cm length and 7 cm diameter). The experiment was a factorial combination of four SD biochar types: SD + poultry manure (PM) pyrolyzed at 350 °C, SD-PM at 350 °C, SD + PM at 450 °C and SD-PM at 450 °C applied at two rates of 5 and 10 t/ha equivalent to 2.38 and 4.76 g/950 g soil, respectively. Atrazine alone and absolute control (AC) that received neither biochar nor atrazine were included for comparison. The treatments were replicated thrice in completely randomized design. Appropriate biochar was applied within 5 cm soil depth, moistened to field capacity, and left to equilibrate for 2 weeks. Thereafter, 20 mL atrazine solution was applied at 2.5 kg a.i/ha (achieved through 6.75 g atrazine powder/l of distilled water). Basal NPK 15:15:15 fertilizer mixed with urea at 0.1 and 0.03 g/900 g soil, respectively, was applied to mimic farmers’ practice on atrazine treated fields. Maize seeds were thereafter sown in the treated soils and nurtured for 2 weeks. Data taken on soil pH, SOC, exchangeable bases, available phosphorus, and dry biomass weight (DBW) of maize seedlings at the expiration of the trial were subjected to two-way analysis of variance using Genstat Statistical Package with means separated using LSD at 5% probability level. There were significant reductions in soil pH (5.8%), SOC (31%), and Ex. Ca (27%) in atrazine alone soil compared to AC. Contrarily, similar atrazine treated soil pretreated with SD biochar had increased soil pH, SOC, exchangeable Ca, available P, and DBW by 5.6 (in SD + PM@450 °C), 73.6 (SD-PM@450 °C), 84 (SD + PM@450 °C), 2,338.4 (SD + PM@450 °C), and 154.8% (SD + PM@350 °C), respectively, dominantly at 10 t/ha compared to AC. Sole atrazine treated soil was, however, higher in soil available P (23.8 mg/kg) and TDBW (0.56 g) against 5.42 mg/kg and 0.42 g from AC, respectively. Biochar pH and organic carbon were the most influential biochar properties contributing significantly to SOC sequestration and macronutrient enrichment in the atrazine treated soil. Pretreatment of soils with sawdust biochar prior to atrazine application is, therefore, recommended for mitigating associated organic carbon and macronutrient depletion in the soils for enhanced maize production.

Efficacy of Herbicides on Nutrient Uptake of Crop, Weed and Its Impact on Soil Microflora of Irrigated Maize (Zea mays L.)

Aim: Field experiment was conducted to study the suitable weed management methods to check the nutrient depletion by weeds, check the dynamics of microbial population and in relation to improve the biomass stover yield of maize (Zea mays L.).
 Study Design: This experiment laid out in a randomized block design and 8 different weed management treatments with three replications.
 Place and Duration of Study: Field experiment was conducted at Agricultural College and Research Institute, Madurai, Tamil Nadu Agricultural University, Tamil Nadu in kharif 2019.
 Methodology: TNAU maize hybrid CO-6 was used for this experiment. Treatments were application of pre-emergence herbicide atrazine at 0.25 kg/ha or pendimethalin 1 kg/ha applied singly on 3 days after sowing and in combination with post-emergence herbicide tembotrione 120 g/ha or halosulfuron methyl 90 g/ha on 25 DAS, weed free check, unweeded check in maize crop. Weed nutrient depletion and microbial population was analysed in laboratory.
 Results: The application of pre-emergence atrazine 0.25 kg/ha followed by post-emergence tembotrione 120 g/ha effective in controlling of grasses and BLW and enhance the nutrient uptake of maize. The stover maize yield increased with application of herbicides and sequential application of herbicides achieved 88% improved stover yield over unweeded check. Sequential application of herbicides initially reduce the population of soil microflora but the population gradually build up in all the herbicide applied plots at 60 days after application.
 Conclusion: Based on the results of the experiment, it was concluded that pre-emergence atrazine 0.25 kg/ha followed by post emergence tembotrione 120 g/ha effective in controlling of weeds and enhance the nutrient uptake and stover yield of maize without much adverse impact on soil microbial population.

The Effects of Atrazine, Diuron, Fluazifop-P-butyl, Haloxyfop-P-methyl, and Pendimethalin on Soil Microbial Activity and Diversity

Understanding the impacts of herbicides on soil microbial communities is important, as these organisms mediate a wide range of ecosystem services. Here, we investigated whether the diversity and function of soil microbial communities were significantly influenced by one-off applications of atrazine, diuron, fluazifop-P-butyl, haloxyfop-P-methyl and pendimethalin as pure compounds at their recommended doses over multiple time points (1, 3, 7, 14, 30 and 60 days). Phylogenetic marker gene sequencing revealed that none of the herbicides influenced the numbers of bacterial and archaeal taxa or the evenness of their abundances. Similarly, none of the herbicides influenced the composition of bacterial and archaeal communities, except for diuron, fluazifop-P-methyl and pendimethalin, which were associated with larger relative abundances of a small number of OTUs on day 30 only. Functionally, none of the herbicides significantly influenced fluorescein diacetate hydrolysis (FDA) and beta-glucosidase activities or the induced respiratory responses of soil microbial communities to a range of substrates. These data indicate that the active herbicide ingredients tested may have minimal non-target effects when applied once at their recommended dose. Given their frequent use, it is important to next consider whether these herbicides have more pronounced effects at higher doses and application frequencies.

Weed control in maize with herbicides and its effect on grain yield

Competition posed by weeds is a major challenge in crop production as weeds cause severe reduction in yield by competing with crop plants for limited resources like light, space applied nutrients and water also. Several researchers and eminent investigators observed that diverse weed flora causes huge losses in maize yield and if the weeds are not managed at right time then it results in huge yield penalty. Among weed management treatments, hand weeding at 15-21 days after sowing and 30-42 days after sowing and integration of pre-emergence application of atrazine 1.5 kg ha-1, pendimethalin at 1.50 kg ha-1, pendimethalin + atrazine both at 0.5 kg ha-1 as pre-emergence spray, atrazine + alachlor at 0.75 + 1.25 kg ha-1, or alachlor at 1.5 kg ha-1fb hand weeding at 30 days after sowing and tembotrione 125 g ha-1+surfactant applied on 20 DAS were proved more effective. In case of sequential treatments, pre-emergence application of atrazine at 1.25 kg ha-1 or pendimethalin at 1.5 kg ha-1 fbparaquat at 0.6 kg ha-1at 3 weeks after sowing or pre-emergence application of atrazine at 1.0 kg ha-1 followed by topramazone at 0.030 kg ha-1 at 30 days after sowing gave higher gross returns, net returns and benefit cost ratio, thus proved more economical.

Efficacy of p-hydroxy-phenyl-pyruvate dioxygenase (HPPD) enzyme-inhibitive tembotrione and topramezone herbicides for weed-management in rainy season grain sorghum (Sorghum bicolor)

A field experiment was conducted during the rainy season (kharif) of 2019 and 2020 at Maharana Pratap University of Agriculture and Technology, Udaipur, Rajasthan, to ascertain the weed-management efficacy of postemergence (PoE) tembotrione and topramezone at 25 days after sowing following pre-emergence (PE) atrazine in the kharif grain sorghum [Sorghum bicolor (L.) Moench]. Eight treatments (6 herbicidal along with weed-free and weedy check) were evaluated in randomized block design (RBD) with 3 replications. Results showed that, uncontrolled weeds have inflicted a grain, stover yield and net income penalty of 63.7, 55.5 and 69% over weed-free check (3.47, 12.34 t/ha and `135,216). Pre-emergence (PE) application of atrazine @ 0.5 kg a.i./ha was found to be the most promising herbicide in terms of benefit: cost ratio (5.76) despite having 12.4, 6.2, and 6.71% lower grain, stover and net income than weed-free treatment (5.03). Both PE and PoE application of atrazine did not bring any yield and profit gains over its PE application. Topramezone and tembotrione (PoE) controlled weeds as effective as weed-free treatment and their impacts persisted up to crop maturity. However, on account of crop phytotoxicity that is dependent on dose (2.83–5.17) severe yield losses (60 and 51.9% grain and stover) were recorded. Both tembotrione and topramezone at their higher dose (0.0242 and 0.0363 kg a.i./ha) resulted in at par grain yield (1.18 t/ha) as weedy check (1.26 t/ha).

Efficiency of post-emergence herbicides for enhancing growth and yield of hybrid maize (Zea mays) in Kandahar, Afghanistan

A field experiment was conducted at research farm of the Afghanistan National Agricultural Science and Technology University (ANASTU), Kandahar, Afghanistan, in randomized complete- block (RCBD) design during summer 2017, to evaluate the effect of post-emergence (PoE) herbicides in maize (Zea mays L.). Results revealed that sequential application of atrazine @ 1,500 g/ha as pre-emergence followed by (fb) tembotrione @ 120 g/ha as post emergence (PoE) 25 days after sowing (DAS) recorded significantly higher plant height and leaf-area index at 60 and 90 days after sowing (DAS), while dry-matter accumulation and the yield attributes as grains/row, grain/cob and grain weight/cob at harvesting stages. Weed infestation in hybrid maize caused 35.8% yield loss compared to weed-free control. Application of the weed-management treatments increased the maize yield by 35.2% (11.6 – 51.2) over unweeded check. Significantly higher grain yield (6.50 t/ha) was recorded with sequential application of atrazine (1,500 g/ha) as pre-emergence followed by tembotrione (120 g/ha) at 25 DAS, which was at par with pendimethalin (1,000 ml/ha) as pre-emergence followed by atrazine (750 g/ha) + 2,4-D amine (400 g/ha) at 25 DAS as PoE (6.21.3 t/ha) and atrazine (1,500 g/ha) as pre-emergence fb 2,4-D amine (400 g/ha) at 25 DAS (6.12 t/ha). Therefore, the sequential application of pre-and post-emergence herbicides could be opted for enhancing growth and yield and weed control of hybrid maize in Afghanistan and similar ecologies.

Comparative study of bacterial community dynamics in different soils following application of the herbicide atrazine

Microbial communities in cultivated soils control the fate of pollutants associated with agricultural practice. The present study was designed to explore the response of bacterial communities to the application of the widely-used herbicide atrazine in three different crop fields that differ significantly in their physicochemical structure and nutritional content: the nutrient-rich (with relatively high carbon and nitrogen content) Newe Yaar (NY) and Ha-Ogen (HO) soils and the nutrient-poor, sandy Sde-Eliyahu (SE) soil. The 16 S rRNA gene amplicon sequencing revealed the nutrient poor HO soil differs in its response to atrazine in comparison to the two nutrient-rich soils both in the shortest persistence of atrazine and its effect on community structure and composition. Potential reported bacterial degraders of atrazine such as Pseudomonas, Clostridium and Bacillus were more abundant in contaminated sandy/poor soils (HO) whereas bacteria known for nitrogen cycling such as Azospirillum, Sinorhizobium, Nitrospira and Azohydromonas were significantly more abundant in the nutrient rich contaminated SE soils. No significant increase of potential indigenous degrader Arthrobacter was detected in SE and NY soils whereas a significant increase was recorded with HO soils. An overall shift in bacterial community composition following atrazine application was observed only in the nutrient poor soil. Understanding atrazine persistence and microbiome response to its application of in dependence with soil types serve the design of precision application strategies.

Managing the efficiencies of three different bacterial isolates for removing atrazine from wastewater

Three individual bacterial isolates previously isolated from two types of soil with a different history of atrazine applications were chosen, purified, and subjected to subsequent work. Identification of the individual bacterial isolates was conducted using molecular methods 16S rRNA and then tested for their atrazine degradation potentials. Effects of different parameters like mixing, starvation, UV exposure, and sodium citrate for enhancing the atrazine bioremediation process by identified bacteria were also studied. The molecular method identified individual bacterial isolates as Stenotrophomonas sp. strain SD2 (strain SD2), Bacillus cereus strain BC3 (strain BC3), and Paenarthrobacter ureafaciens strain AD3 (strain AD3). The bacterial isolate strain AD3 was able to degrade 47.95% of atrazine after 28 days. Mixing strain AD3 with strain BC3 showed almost doubled of atrazine degradation percentage (61.39%) of using strain BC3 as an individual isolate (36.59%). The atrazine degradation efficacy for Stenotrophomonas sp. strain SD2, Bacillus cereus strain BC3, and Paenarthrobacter ureafaciens strain AD3 was increased between 1.28 and 4.32 folds after the starvation process. The UV exposure enhanced the efficiencies of the tested isolates either individual or mixtures (from 1.08 to 4.63-fold). Adding sodium citrate as a stimulator to the media of growing the tested isolates enhanced their potential for atrazine degradation.

EFFECT OF WEED CONTROL TREATMENTS, SOWING DATE AND SOWING METHOD ON GROWTH AND YIELD OF FINGER MILLET (Eleusine coracana (L.) Gaertn) IN SUDAN SAVANNA OF NIGERIA

Field experiment was conducted during 2016, 2017 and 2018 rainy seasons at the Research Farm of National Institute for Horticultural Research (NIHORT) Bagauda (Latitude 11̊ 33ꞌ N and Longitude 8̊ 23ꞌ E, 481m above sea level) Kano, in the Sudan savanna of Nigeria. The aim of the study was to evaluate the effect of weed control treatments, sowing dates and methods on the growth and yield of finger millet (Eleusine coracana (L.) Gaertn.). The experiment consisted of three (3) sowing date (late June, early July and late July), three (3) sowing methods (broadcasting, drilling and dibbling) and six weed control treatment (atrazine at 0.8 or 1.2kg a.i.ha-1, 2,4-D at 0.5 or 0.75kg a.i. ha-1, two hoe weeding at 3 and 6 weeks after sowing (WAS) and weedy check). These were laid out in a split-split-plot design and replicated three (3) times. Sowing dates were assigned to main plot, sowing methods to subplot while weed control to sub-sub plots. The results revealed that sowing on late June and early July produced significantly taller plant and higher grain yield. Broadcasting produced higher number of tillers (m-2) and grain yield in 2016 (887.3kg ha-1), 2017 (1230.0kg ha-1) and 2018 (1255.0kgha-1). Furthermore, two hoe weeding produced significantly higher grain yield (kgha-1) in all the seasons which were statistically similar with plots treated with atrazine at 1.2kg a.i. ha-1 and those treated with 2,4-D at 0.5 and 0.75kg a.i. ha-1. Based on these findings, it can be concluded that finger millet should be sown between late June to early July by broadcasting method and application of either atrazine at 1.2 kg a.i. ha-1 pre-emergence or 2,4-D at 0.5kg a.i. ha-1 post-emergence for higher grain yield (kgha-1).

Short-term response of soil enzyme activities and bacterial communities in black soil to a herbicide mixture: Atrazine and Acetochlor

Combined application of atrazine (ATZ) and acetochlor (ACE) was used as an emerging herbicidal method in black soil zone of northeastern China recently. However, the interaction toxic effect of the two herbicides on the soil biological characteristics has not been investigated yet. In this study, the alterations of soil enzyme activities and bacterial communities in black soil were assayed during a short term (28 days) exposure period by spiking ATZ, ACE or ATZ + ACE (1:1, w: w) at 0×, 1×, 2×, 5× and 10× the recommended dose in a microcosm experiment conducted under greenhouse condition. The results showed that ATZ and ACE had synergistic inhibitory effects on soil enzymes activities. Higher inhibition rates of urease, acid phosphatase, sucrase and catalase were observed in ATZ + ACE, and the enzyme activities could not recover to the level without herbicide application after 28 days. The higher IBRv2 value of ATZ + ACE also indicated that the comprehensive toxicity was stronger than that of ATZ or ACE. The microbial community structure was affected differently by ATZ, ACE and ATZ + ACE as the PLFAs analysis displayed, and ATZ + ACE was more harmful to bacteria than ATZ or ACE. The decrease in relative abundance of Proteobacteria was more sensitive to ATZ, and the decrease of Acidobacteriota was more sensitive to ACE, and the relative abundance of these two phyla decreased more obviously in ATZ + ACE. In addition, the PICRUSt analysis showed that the functions of the replication and repair, energy metabolism, cell motility and cellular processes and signaling were inhibited by ATZ and ACE, especially in the ATZ + ACE treatment. This means that combined application of ATZ and ACE has a greater potential risk on soil microbes and consequently the nutrient cycling process.

Removal of atrazine from submerged soil using vetiver grass (Chrysopogon zizanioides L.)

The long-term widespread application of atrazine poses significant threats to the eco-environment and human health. To investigate the potential of vetiver (Chrysopogon zizanioides L.) for phytoremediation of the environmental media contaminated by atrazine, an indoor incubation experiment was conducted in submerged soil over 30 days. Results showed that the chlorophyll level of the vetiver was not significantly affected by exposure to atrazine. Vetiver could take up and accumulate atrazine from submerged soil and peaked around the 20th day with a concentration of 1.0 mg kg−1 in leaf. The metabolites Hydroxyatrazine (HA), deethylatrazine (DEA), Deisopropylatrazine (DIA), and didealkylatrazine (DDA) were detected in the leaf on the 30th day, indicating vetiver could degrade atrazine inside the leaf tissue. The atrazine removal rate in the vetiver planted and unplanted jars were 69.72 and 60.29%, respectively, indicating that 9.43% higher atrazine removal was achieved in the presence of vetiver (p < 0.05). The atrazine dissipation in the submerged soil followed first-order kinetics, the degradation constant was 0.066, and the half-life of atrazine dissipation was shortened by 6.86 days in the presence of vetiver. The present study suggests that vetiver can take up atrazine from submerged soil and accumulate in the leaf, which could then degrade in the leaf. Novelty statement: Although the fate of atrazine in agricultural soils has been extensively investigated through various experiments, little is known about the effect of vetiver grass on atrazine dissipation from submerged soil. With the identification of soil-leaf transportation and four metabolites in vetiver leaf and soils, significantly accelerated atrazine dissipation from the submerged soil was achieved in the presence of vetiver. Particularly, the formation of less toxic dealkylated products in the leaf indicated vetiver is a promising grass for atrazine removal from submerged soil.

Detection of Atrazine and its metabolites by photonic molecularly imprinted polymers in aqueous solutions

Water contamination caused by atrazine (ATZ) application in agriculture is a risk to the environment and human health. Common analytical methods are expensive and complex. A sensor for low-cost and simple detection of ATZ and its metabolites, deethylatrazine (DEA) and deisopropylatrazine (DIA), in aqueous solutions was developed by combining colloidal crystal with molecular imprinting technique. The sensor is formed by 3D interconnected macroporous structure with numerous nanocavities derived from ATZ and its metabolites imprinting in a thin polymeric film. Molecularly Imprinted Polymers (MIPs) were characterized by Fourier Transform Infrared spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) and were incubated in solutions at variable concentrations. Target molecules were specifically absorbed in nanocavities and caused swelling in the polymer resulting in changes of Bragg diffraction peak wavelength. Kinetic tests showed that rebinding equilibrium was reached within 20 minutes. The sensor had a dynamic range of 0.1 to 10 ppb for quantifying target analytes in aqueous solutions with limit of detection of 0.1, 0.2, and 0.3 ppb, and limit of quantification of 0.33, 0.66, and 1 ppb for ATZ, DEA, and DIA, respectively. Cross-reactivity tests were conducted in 1 and 5 ppb solutions combining all three targets and showed absence of positive interference effects and low probability of false positives given by individual sensors. MIPs were examined in natural waters containing ATZ and its metabolites contamination, showing good agreement with real concentrations of targets. The MIP yields rapid and efficient detection of target molecules in aqueous solutions close to environmentally relevant concentrations.

Identification and Comprehensive Evaluation of Resistant Weeds Using Unmanned Aerial Vehicle-Based Multispectral Imagery.

Atrazine is one of the most widely used herbicides in weed management. However, the widespread use of atrazine has concurrently accelerated the evolution of weed resistance mechanisms. Resistant weeds were identified early to contribute to crop protection in precision agriculture before visible symptoms of atrazine application to weeds in actual field environments. New developments in unmanned aerial vehicle (UAV) platforms and sensor technologies promote cost-effective data collection by collecting multi-modal data at very high spatial and spectral resolution. In this study, we obtained multispectral and RGB images using UAVs, increased available information with the help of image fusion technology, and developed a weed spectral resistance index, WSRI = (RE-R)/(RE-B), based on the difference between susceptible and resistant weed biotypes. A deep convolutional neural network (DCNN) was applied to evaluate the potential for identifying resistant weeds in the field. Comparing the WSRI introduced in this study with previously published vegetation indices (VIs) shows that the WSRI is better at classifying susceptible and resistant weed biotypes. Fusing multispectral and RGB images improved the resistance identification accuracy, and the DCNN achieved high field accuracies of 81.1% for barnyardgrass and 92.4% for velvetleaf. Time series and weed density influenced the study of weed resistance, with 4 days after application (4DAA) identified as a watershed timeframe in the study of weed resistance, while different weed densities resulted in changes in classification accuracy. Multispectral and deep learning proved to be effective phenotypic techniques that can thoroughly analyze weed resistance dynamic response and provide valuable methods for high-throughput phenotyping and accurate field management of resistant weeds.

Impacts of Future Climate Variability on Atrazine Accumulation and Transport in Corn Production Areas in the Midwestern United States.

Atrazine is one of the most prevalent herbicides that has been widely applied to agricultural lands in the U.S. Understanding the transport and accumulation of atrazine in the subsurface under future climate scenarios is essential for future agriculture and water management. Here, we predict atrazine transport and accumulation under an intensive corn production land based on 20 projected global climate model (GCM) realizations, while considering uncertainties of transport parameters. Our study predicted continuous groundwater table declination and atrazine mass accumulation on the study site. We show that atrazine mass accumulation in corn production areas is subject to total precipitation in the atrazine application season, whereas atrazine plume movement is controlled by the sequence of annual precipitation. Atrazine mass transport and accumulation are more sensitive to climate variation on the field sites with low sorption and atrazine degradation rate. Under the extreme condition, the atrazine plume can migrate as far as five meters from the ground surface in only three years. While annual mean precipitation in the Midwestern U.S. is projected to increase in the future, groundwater vulnerability to atrazine and associated water quality impacts may rise in the U.S. Corn Belt, especially in sites with low atrazine degradation and sorption.

CONTROL EFFICACY AND PHYTOSOCIOLOGICAL CHARACTERIZATION OF WEEDS AS A FUNCTION OF POST-EMERGENCE HERBICIDES APPLIED TO MAIZE

S Studies evaluating the effectiveness of herbicides on weed control, coupled with the sustainability of the weed management system, are of great importance. The present study aims to evaluate the efficacy of post-emergence herbicides applied to maize while inferring the sustainability of the treatments employing an ecological approach. The experiment was installed in a randomized block design with four replications. The treatments consisted of the application of atrazine at the dose of 1500 g ha-1; atrazine + mesotrione at 1500 + 72 g ha-1; atrazine + tembotrione at 1500 + 100.8 g ha-1; atrazine + nicosulfuron at 1500 + 22.5 g ha-1; atrazine + glyphosate at 1500 g ha-1 + 792.5 g ha-1, in addition to weeded and infested control treatments. The herbicides were applied at the 4 leaf stage of maize. The phytotoxicity and control efficacy was assessed 7, 14, 21, and 28 days after applying treatments (DAT). In addition, a phytosociological survey of all plots was carried out in the last assessment. Herbicides did not cause phytotoxicity symptoms to the crop. However, associations of atrazine with glyphosate and atrazine with tembotrione promoted the greater effectiveness of weed control. Despite being classified as one of the treatments with better effectiveness, the association between glyphosate and atrazine, caused a more significant reduction in the diversity of the plant community, and alternative weed management practices should be applied to maize cropping fields to avoid weed selection.

Physiological and agronomic responses to the application of post-emergence herbicides on sweet potato cultivar selected for its potential as biofuel feedstock

Sweet potato exhibits a prostrate growth habit, which makes weed management to be manually performed or conducted through the application of selective herbicides. Considering the absence of registered herbicides for the selective control of broad leaf weeds on the sweet potato crop, we investigated the physiological and agronomic responses of the sweet potato cultivar Duda, selected for its great potential in biofuel production, to different post-emergence herbicides. Two experiments, one conducted under field conditions and the other under controlled (potted plants) conditions, were performed under a randomized complete block design, with four replicates each. Four different herbicides, atrazine and S-metolachlor (3,5 L.ha-1), carfentrazone-ethyl (0,75 L.ha-1), fomesafen and fluazifop-P-butyl (1,8 L.ha-1) and nicosulfuron (1,25 L.ha-1), were used and the experiments were composed by five treatments with the control (no herbicide application) treatment,. Physiological indicators, including carbon assimilation, stomatal conductance, leaf transpiration rate, internal CO2 concentration, and water-use efficiency were monitored at 24 h, 48 h and 15 d after herbicides application, while agronomic evaluations were performed at 30 and 152 days from herbicide application. Application of atrazine (inhibitor of photosystem II) together with S-metolachlor (inhibitor of cell division/elongation) led to reductions on the physiological indices soon after treatment imposition but it had no effect on dry matter accumulation in the shoot, nor on the roots, not affecting the starch content, storage root productivity, and estimated ethanol production as well. In contrast, application of carfentrazone-ethyl, a protoporphyrinogen oxidase inhibitor, exerted significant negative physiological and agronomic effects, decreasing root productivity and estimated ethanol yield. We conclude that the use of atrazine in a mixture with S-metolachlor represents a suitable selective approach for the control of broad leaf weeds in sweet potato crops.

Additive and synergistic interactions of 4-hydroxyphenylpyruvate dioxygenase (HPPD) and photosystem II (PSII) inhibitors for the control of glyphosate-resistant horseweed (Conyza canadensis) in corn

AbstractGlyphosate-resistant (GR) horseweed [Conyza canadensis (L.) Cronquist; syn.: Erigeron canadensis L.] interference can substantially reduce corn (Zea mays L.) yield. The complementary activity of 4-hydroxyphenylpyruvate dioxygenase (HPPD) and photosystem II (PSII) inhibitors has been investigated for the control of several weed species, and in many cases has been synergistic; however, there is little information on the interaction of HPPD- and PSII-inhibiting herbicides for postemergence control of GR C. canadensis in corn. Four field trials were studied over 2 yr (2019, 2020) in Ontario, Canada, in commercial corn fields with natural infestations of GR C. canadensis to evaluate the level of GR C. canadensis control with three HPPD-inhibiting herbicides (mesotrione, tolpyralate, and topramezone) and three PSII-inhibiting herbicides (atrazine, bromoxynil, and bentazon) applied individually and in tank-mix combinations, and to document the interaction of the three HPPD inhibitors tank mixed with the three PSII inhibitors. Mesotrione, tolpyralate, and topramezone controlled GR C. canadensis 83%, 84%, and 72%, respectively, at 8 wk after application (WAA). Bromoxynil and bentazon controlled GR C. canadensis 71% and 79%, respectively, while atrazine provided only 31% control at 8 WAA. The joint application of atrazine, bromoxynil, or bentazon with mesotrione increased GR C. canadensis control from 83% to 100% at 8 WAA. Tolpyralate tank mixed with atrazine, bromoxynil, or bentazon controlled GR C. canadensis 96%, 98%, and 98%, respectively, which was comparable to the mesotrione tank mixes at 8 WAA. Topramezone plus atrazine, bromoxynil, or bentazon controlled GR C. canadensis 91%, 93%, and 95%, respectively, at 8 WAA. Interactions between HPPD and PSII inhibitors were synergistic for all combinations of mesotrione or tolpyralate with atrazine, bromoxynil, or bentazon. The interaction between topramezone and PSII inhibitors was additive. All nine tank mixes controlled GR C. canadensis &gt;90%. This study concludes that bromoxynil or bentazon, instead of atrazine, can be co-applied with mesotrione, tolpyralate, or topramezone without compromising GR C. canadensis control in corn.

Integrated weed management in pearl millet [Pennisetum glaucum (L.) R. Br.

The scarcity of labour in agriculture and change in behaviour, weed management in rain fed pearl millet is very difficult. Further, to improve/ fine tune the existing recommendation of weed management in pearl millet, this experiment was planned. A field experiment was carried out during the rainy (Kharif) seasons of 2012 to 2014 in sandy loam soils at ICAR-All India Coordinated Research Project on Pearl Millet, Research Farm, Agricultural Research Station, Mandor, Jodhpur (Agriculture University, Jodhpur), to evaluate the effect of integrated weed management in rainfed pearl millet (Pennisetum glaucum L.) with pre-emergence application of atrazine 0.5 kg/ha + 1 HW at 35 DAS, four levels of post-emergence application of atrazine (0.1, 0.2, 0.3 and 0.4 kg/ ha) along with one hand weeding at 35 DAS, two hand weeding and hoeing (at 20 and 40 DAS). Eight treatment combinations were laid out in randomized block design in four replications. All weed management practices caused significant improvement in grain and dry fodder yield of pearl millet compared to the weedy check (1943 kg/ha and 30.86 q/ha). The best treatment was found weed free and it was followed by post emergence application of Atrazine @ 0.4 kg/ha. In comparison to the weed dry matter recorded at harvest with weedy check (547.1 kg/ha), all weed management practices recorded quite lower dry matter of weeds and were found to be at par in managing weeds compared to the weed free plot. Efficiency of post emergence application of Atrazine @ 0.2,0.3 and 0.4 kg/ha was found more better in controlling weeds than the recommended practice of managing weeds by pre emergence application of Atrazine. Weed control efficiency were also found higher in weed free and it was followed by two hand weeding and post emergence application of Atrazine @ 0.4 kg treatments, respectively.