Atrazine Application Research Articles

Modeling and Prioritizing Interventions Using Pollution Hotspots for Reducing Nutrients, Atrazine and E. coli Concentrations in a Watershed

Excess nutrients and herbicides remain two major causes of waterbody impairment globally. In an attempt to better understand pollutant sources in the Big Sandy Creek Watershed (BSCW) and the prospects for successful remediation, a program was initiated to assist agricultural producers with the implementation of best management practices (BMPs). The objectives were to (1) simulate BMPs within hotspots to determine reductions in pollutant loads and (2) to determine if water-quality standards are met at the watershed outlet. Regression-based load estimator (LOADEST) was used for determining sediment, nutrient and atrazine loads, while artificial neural networks (ANN) were used for determining E. coli concentrations. With respect to reducing sediment, total nitrogen and total phosphorus loads at hotspots with individual BMPs, implementing grassed waterways resulted in average reductions of 97%, 53% and 65% respectively if implemented all over the hotspots. Although reducing atrazine application rate by 50% in all hotspots was the most effective BMP for reducing atrazine concentrations (21%) at the gauging station 06883940, this reduction was still six times higher than the target concentration. Similarly, with grassed waterways established in all hotspots, the 64% reduction in E. coli concentration was not enough to meet the target at the gauging station. With scaled-down acreage based on the proposed implementation plan, filter strip led to more pollutant reductions at the targeted hotspots. Overall, a combination of filter strip, grassed waterway and atrazine rate reduction will most likely yield measureable improvement both in the hotspots (>20% reduction in sediment, total nitrogen and total phosphorus pollution) and at the gauging station. Despite the model’s uncertainties, the results showed a possibility of using Soil and Water Assessment Tool (SWAT) to assess the effectiveness of various BMPs in agricultural watersheds.

Cross-resistance to atrazine and metribuzin in multiple herbicide-resistant kochia accessions: confirmation, mechanism, and management

AbstractKochia accessions (designated as KS-4A and KS-4H) collected from a corn field near Garden City, KS, have previously shown multiple resistance to glyphosate, dicamba, and fluroxypyr. These accessions were also suspected as being resistant to photosystem II (PS II) inhibitors. The main objectives of this research were to 1) confirm the coexistence of cross-resistance to PS II inhibitors (atrazine and metribuzin) applied PRE and POST, 2) investigate the underlying mechanism of PS II-inhibitor resistance, and 3) determine the effectiveness of alternative POST herbicides for control of these multiple herbicide–resistant (MHR) kochia accessions. Results from dose-response experiments revealed that the KS-4A and KS-4H kochia accessions were 23-fold to 48-fold resistant to PRE- and POST-applied atrazine and 13-fold to 18-fold resistant to POST-applied metribuzin compared to a known susceptible kochia accession (KS-SUS). Both accessions also showed putative resistance to PRE-applied metribuzin that needs to be confirmed. Sequence analyses of the psbA gene further revealed that all samples from the KS-4A and KS-4H kochia accessions had a Ser264Gly point mutation. A pretreatment with malathion followed by a POST application of atrazine at 1,120 g ha−1 or metribuzin at 630 g ha−1 did not reverse the resistance phenotypes of these MHR accessions. In a separate greenhouse study, alternative POST herbicides, including bicyclopyrone + bromoxynil; bromoxynil + pyrasulfotole; paraquat alone or in combination with atrazine, metribuzin, 2,4-D, or saflufenacil; and saflufenacil alone or in combination with 2,4-D effectively controlled the KS-4H accession (≥97% injury). To our knowledge, this research reports the first case of kochia accessions with cross-resistance to PRE-applied atrazine and POST-applied metribuzin. Growers should adopt diversified weed control strategies, including the use of competitive crops, cover crops, targeted tillage, and harvest weed seed control along with effective alternative PRE and POST herbicides with multiple sites of action to control MHR kochia seedbanks on their production fields.

Herbicide programs for control of waterhemp (Amaranthus tuberculatus) resistant to three distinct herbicide sites of action in corn

AbstractControl of waterhemp is becoming more difficult in Ontario because biotypes have evolved resistance to four herbicide sites of action (SOA), including groups 2, 5, 9, and 14. The objective of this study was to compare PRE, POST, and PRE followed by (fb) POST herbicide programs for their effect on control, density, and biomass of multiple-herbicide–resistant (MHR) waterhemp as well as corn injury and grain yield. Two separate field studies, each consisting of five field trials, were conducted over a 2-yr period (2018 and 2019) in fields where corn was grown in Ontario, Canada. The first experiment evaluated MHR waterhemp control with an inhibitor of 4-hydroxyphenyl-pyruvate dioxygenase (HPPD) applied PRE, PRE fb glufosinate applied POST, and glufosinate applied POST. The second experiment evaluated MHR waterhemp control with a non-HPPD inhibitor applied PRE, then PRE fb a POST application of atrazine + mesotrione, and then atrazine + mesotrione applied POST. Atrazine + isoxaflutole caused 3% to 5% corn injury at environment 1 (E1); no corn injury was observed with PRE and POST herbicide programs at environments E2, E3, E4, and E5. In general, atrazine/bicyclopyrone/mesotrione/S-metolachlor and dimethenamid-P/saflufenacil applied PRE controlled MHR waterhemp ≥95% 12 wk after POST application (WAA). A POST application of glufosinate following atrazine + tolpyralate PRE, and a POST application of atrazine + mesotrione following atrazine/dicamba or atrazine/S-metolachlor PRE, improved control at 4, 8, and 12 WAA in most environments. In general, PRE fb POST applications resulted in better control of MHR waterhemp throughout the growing season than single PRE and POST applications (P < 0.05). We conclude that herbicide programs based on multiple effective SOAs may offer effective control of MHR waterhemp where field corn is grown. It is advisable that when choosing an herbicide application program that excellent control of MHR waterhemp should be the goal given its high fecundity and competitive ability.

INTERFERÊNCIA DE HERBICIDAS NO DESENVOLVIMENTO DO MILHETO

O milheto é uma gramínea anual de estação quente que possui porte ereto e alto, usado como fonte de alimento na pecuária e como cobertura de solo no sistema de plantio direto. Por ser uma cultura de baixo valor econômico são raras as informações a seu respeito. O objetivo do trabalho foi verificar a seletividade dos herbicidas atrazine e 2,4-D aplicados isolados ou em associação em diferentes épocas na cultura do milheto. O experimento foi realizado a campo em parcelas de 12 m2 e delineamento de blocos ao acaso, sendo 10 tratamentos e quatro repetições. Os tratamentos foram: 1- testemunha sem capina; 2- testemunha capinada; 3- atrazine em pré-semeadura; 4- atrazine em pós-semeadura; 5- atrazine em V4; 6- 2,4-D em V4; 7- 2,4-D (150% da dose) em V4; 8- atrazine em pré-semeadura + 2,4-D em V4; 9- atrazine em pós-semeadura + 2,4-D em V4, 10- atrazine + 2,4-D em V4. Avaliou-se o número de plantas por metro linear, a fitotoxicidade aos 7, 14, 21 e 28 dias após aplicação, a altura de plantas e a massa seca da parte aérea. Houve redução no estande de plantas com aplicação de atrazine em pré e pós-semeadura. O herbicida 2,4-D apresentou maiores níveis de fitotoxicidade, menor altura de plantas e menor produção de massa seca em todas as avaliações. O herbicida atrazine se apresenta como uma boa alternativa de controle de plantas daninhas na cultura do milheto quando aplicado em V4.

Evaluation of pre-emergence herbicides for weed control in maize

Weed management is an ongoing constraint in southern Africa for conventional farming systems and in emerging conservation agriculture systems, which are more heavily reliant on herbicides for primary weed control. The challenge of rising labour costs and decreasing availability creates a greater need to develop effective and efficient weed management methods in key crops such as maize. Field experiments were conducted at Sebele Agricultural Research Station, Botswana in the 2011/12 and 2012/13 cropping seasons to evaluate pre-emergence application of atrazine at 1,000 and 2,000 g a.i. ha-1 and S-metolachlor at 1,440 and 2,880 g a.i. ha-1, and a tank mixture of atrazine at 1,000 and S-metolachlor at 1,440 g a.i. ha-1. Atrazine at either rate alone, effectively controlled annual broadleaf weeds: Acanthospermum hispidum, Datura ferox and Sesamum alatum, but failed to control annual grass weeds (Tragus berteronianus and Urochloa spp.). Conversely, sole application of S-metolachlor at either rate provided complete control of annual grass weeds, but poorly controlled annual broadleaf weeds except small-seeded Amaranthus hybridus and Amaranthus thunbergii. A tank mixture of atrazine and S-metolachlor provided broad-spectrum weed control and successfully controlled both annual broadleaf and grass weeds. Atrazine alone and in tank mixture with S-metolachlor significantly reduced annual broadleaf weed density and biomass and increased maize grain yield by more than 80% when compared with the weedy treatment. High weed density and biomass of annual broadleaf weeds in S-metolachlor treatments significantly reduced maize grain yield to levels similar to the weedy treatment. A pre-mixture of atrazine and S-metolachlor is recommended for broad-spectrum weed control. Using a combination of herbicides with different modes of action may reduce selection pressure for herbicide resistance.

Does diclofenac act like a photosynthetic herbicide on green algae? Chlamydomonas reinhardtii synchronous culture-based study with atrazine as reference

The non-steroidal anti-inflammatory drug diclofenac (DCF) is one of the commonly used and frequently detected drugs in water bodies, and several studies indicate its toxic effect on plants and algae. Studies performed with asynchronous Chlamydomonas reinhardtii cultures indicated that DCF inhibit the growth of population of the algae. Here, a synchronous population of C. reinhardtii, in which all cells are in the same developmental phase, is used. Following changes in cells size, photosynthetic activity and gene expression, we could compare, at the level of single cell, DCF-mediated effects with the effects caused by atrazine, a triazine herbicide that inhibits photosynthesis and triggers oxidative stress. Application of DCF and atrazine at the beginning of the cell cycle allowed us to follow the changes occurring in the cells in the subsequent stages of their development. Synchronized Chlamydomonas reinhardtii cultures (strain CC-1690, wild type) were exposed to diclofenac sodium salt (135 mg/L) or atrazine (77.6 µg/L). The cell suspension was sampled hourly (0–10 h) in the light period of the cell cycle to determine cell number and volume, photosynthetic pigment content, chlorophyll a fluorescence (OJIP test) in vivo, and selected gene expression (real-time qPCR), namely psbA, psaA, FSD1, MSD3 and APX1. The two toxicants differently influenced C. reinhardtii cells. Both substances decreased photosynthetic “vitality” (PI - performance index) of the cells, albeit for different reasons. While atrazine significantly disrupted the photosynthetic electron transport, resulting in excessive production of reactive oxygen species (ROS) and limited cell growth, DCF caused silencing of photosystem II (PSII) reaction centers, transforming them into “heat sinks”, thus preventing significant ROS overproduction. Oxidative stress caused by atrazine was the probable reason for the rapid appearance of phytotoxic action soon after entering the cells, while the effects of DCF could only be seen several hours after treatment. A comparison of DCF-caused effects with the effects caused by atrazine led us to conclude that, although DCF cannot be regarded as typical photosynthetic herbicide, it exhibits an algicidal activity and can be potentially dangerous for aquatic plants and algae.

Suitable weed management practices for dual purpose Sorghum K12 under Irrigated condition

A field experiment was investigated at Agricultural College and Research Institute, Killikulam for evaluating suitable weed management practices for dual purpose sorghum variety K 12 (Sorghum bicolor L.) under irrigated condition during rabi season, 2019-20. The experimental design used for the investigation was Randomized Block Design having three replications and twelve treatments. The weed management practices comprised of pre emergence herbicides namely atrazine @ 0.5 kg ha-1 and pendimethalin @ 0.5 kg ha-1, post emergence herbicides viz., 2,4-D @ 0.5 kg ha-1 and metsulfuron methyl @ 6 g ha-1 with combination of hand weeding and mechanical weeding. Observations on weeds like weed flora, weed dry weight, weed density, weed control efficiency and on growth parameters like plant height, leaf length and breadth and yield parameters like grain and stover yield were documented. The field was infested with all three genera of weeds viz. grasses, broadleaved weeds and sedges. The results obtained from the experiment revealed that the weed density and weed dry weight was higher on the unweeded plot, which produced the lowest grain and stover yield of 1672 kg ha-1 and 5380 kg ha-1, respectively. Application of atrazine @ 0.5 kg ha-1 as pre emergence + one hand weeding at 40 DAS showed a better control over the weeds with a weed control efficiency of 97.0 per cent, which ultimately resulted in higher yield producing 3998 kg ha-1 of grains and 11534 kg ha-1 of stover yield. However, this was on par with weed free check which produced the maximum yield compared to all the other treatments. The weeds accounts around 51.4% and 39.4% of grain and stover yield reduction, respectively.

Effect of Weed Management Practices on Weed Dynamics, Yield Attributes and Yield of Maize

A field experiment was conducted at Research Farm of Agricultural Research Station, Ummedganj, Kota (Agriculture University, Kota), Rajasthan, India during kharif 2019 to find out the most effective herbicide combination for limiting the menace of weeds in maize. Results showed that density of monocot weeds were observed more than dicot weeds during the experimentation. The prominent weeds were Echinochloa colona, Cyperus rotundus, Digera arvensis, Amaranthus viridis, Acalypha indica and Trianthema portulacastrum etc. caused about 58.3% reduction in grain yield as over two hand weeding at 20 and 40 DAS. In general, grassy weeds were better controlled by herbicides than broad leaves weeds. Among herbicides, maximum weed control efficiency (72.18%) was achieved with application of atrazine 500 g a.i. ha-1 (PE) followed by topramezone 25.2 g a.i. ha-1 at 20-25 DAS (72.18%) which is very close to two hand weeding at 20 and 40 DAS. Furthermore, this treatment also produced higher grain (3496 kg ha-1) and stover yield (6460 kg ha-1) which was at par with atrazine 500 g a.i. ha-1 (PE) followed by tembotrione 120.75 g a.i. ha-1 (20-25 DAS) and atrazine 500 g a.i. ha-1 (PE)+hand weeding 30 DAS with in-situ weeds mulching. Thus, pre-emergence application of atrazine 500 g a.i. ha-1 (PE) followed by topramezone 25.2 g a.i. ha-1 at 20-25 DAS is recommended for better weed control and yield of maize.

Nutrients Supplementation through Organic Manures Influence the Growth of Weeds and Maize Productivity.

Declining rate of productivity and environmental sustainability is forcing growers to use organic manures as a source of nutrient supplement in maize farming. However, weed is a major constraint to maize production. A field study was carried out over two seasons to evaluate various integrated nutrient and weed management practices in hybrid maize. The treatment combinations comprised of supplementation of inorganic fertilizer (25% nitrogen) through bulky (Farmyard manure and vermicompost) and concentrated (Brassicaceous seed meal (BSM) and neem cake (NC)) organic manures and different mode of weed management practices like chemical (atrazine 1000 g ha−1) and integrated approach (atrazine 1000 g ha−1 followed by mechanical weeding). Repeated supplementation of nitrogen through concentrated organic manures reduced the density and biomass accumulation of most dominant weed species, Anagalis arvensis by releasing allelochemicals into the soil. But organic manures had no significant impact on restricting the growth of bold seeded weeds like Vicia hirsuta and weed propagated through tubers i.e., Cyperus rotundus in maize. By restricting the weed growth and nutrient removal by most dominating weeds, application of BSM enhanced the growth and yield of maize crop. Repeated addition of organic manures (BSM) enhanced the maize grain yield by 19% over sole chemical fertilizer in the second year of study. Application of atrazine as pre-emergence (PRE) herbicide significantly reduced the density of A. arvensis, whereas integration of mechanical weeding following herbicide controlled those weeds which were not usually controlled with the application of atrazine. As a result, atrazine at PRE followed by mechanical weeding produced the highest maize grain yield 6.81 and 7.10 t/ha in the first year and second year of study, respectively.

Predicting atrazine concentrations in waterbodies across the contiguous United States: The importance of land use, hydrology, and water physicochemistry

AbstractAtrazine contamination is ubiquitous in North American surface waters, but the dependency of the herbicide's distribution on landscape and within‐lake processes is currently poorly known. We sought to identify novel predictors of atrazine and to build a coherent framework to model its concentration in waterbodies through the development of binomial‐gamma hurdle models and LASSO regression models. We constructed models for over 900 waterbodies in the contiguous United States using data from the 2012 U.S. EPA National Lake Assessment, the 2012 U.S. Department of Agriculture CropScape and the Global HydroLAB HydroLAKES databases. Atrazine was detected in 32% of U.S. waterbodies, with a mean concentration of 0.17 μg L−1 when detected. The two‐part hurdle model explained as much as 75% of the variance in atrazine across a spatially and temporally heterogeneous landscape. Three predictors explained 31% of the variability in atrazine detection in U.S. waterbodies, where the proportion of corn + soy cultures in the watershed was the most important variable. Once atrazine was detected, our models explained an additional 29% of the variability in atrazine concentrations, where the estimated areal weight of atrazine application (kg atrazine km2) in the watershed was the most important predictor. Spatially, water quality variables associated with eutrophication were linked to increased levels of atrazine contamination while cooler water temperatures and natural lakes and landscapes were associated with decreased levels of contamination. Our results suggest that changes in land‐use practices may be the most effective way to mitigate atrazine contamination in waterbodies.

English

A two-year investigation into the effects of weed management practices, sowing dates and maize varieties was made in a Striga endemic field at Minna, Nigeria. The treatment was a factorial combination of variety (SAMMAZ 15, 17, 37, 40 and SUWAN-1-SR-Y), weed management practices (weedy check, two hoe weeding (HW) at 3 + 6 weeks after sowing (WAS), pre-emergence (PE) Atrazine at 2.4 kg a.i ha-1 + 1 HW at 6 WAS and PE Atrazine at 2.4 kg ha-1 + post-emergence (POE) Nicosulfuron at 0.06 kg ha-1 at 6 WAS) and sowing dates: early (28th May), mid-season  (18th June) and late-season (9th July) in 2018 and early-season (26th May), mid-season (16th June) and late-season  (7th July) in 2019 laid in a split plot arranged in a randomized complete block with three replications. Maize variety and weed management practices were combined as the main plot and sowing dates constituted the subplot. Delayed Striga shoot emergence and reduced shoot density were observed in SAMMAZ 15 and 40 and higher grain yield with SAMMAZ 17 in 2018 and 2019. Application of Atrazine plus Nicosulfuron significantly delayed Striga shoot emergence, reduced shoot density and higher maize grain yield in both years. Sowing in May significantly delayed Striga shoot emergence and reduced shoot density in both years. Sowing in June significantly increased maize grain yield in 2018 and 2019. These results suggest that SAMMAZ 15 and 40 in combination with PE Atrazine at 2.4 kg a.i ha-1 and POE Nicosulfuron at 0.06 kg a.i ha-1 and sowing in May effectively reduced Striga infestation. SAMMAZ 17 in combination with PE Atrazine at 2.4 kg a.i ha-1 and POE Nicosulfuron at 0.06 kg a.i ha-1 and sowing in June increased maize grain yield. Key words: Maize variety, sowing date, Striga, weed management. &nbsp

Atrazine residues in flooded and nonflooded soil and effects on soybean

AbstractAtrazine applied at planting is commonly used for weed control in corn. With global climate change causing an increase in river flooding in the United States over the past decade, producers need information to determine the best course of action in flooded fields treated with atrazine into which they wish to immediately plant soybean. Studies were designed to understand the effect of flooding on atrazine residual activity including atrazine concentration, soybean injury, and soybean yield. In 2012, soybean yield in flooded treatments was reduced by prior atrazine application. In 2014, soybean injury was <10% in all plots, and nonflooded, atrazine-treated soils had yields equal to the nontreated. Findings from this research indicated that it is possible for producers to consider replanting soybean after atrazine application, with appropriate changes to product labeling.

Effects of tall fescue biochar on the adsorption and desorption of atrazine in different types of soil.

The excessive application of atrazine in agriculture has resulted in serious environmental contamination. The addition of biochar could reduce the bioavailability and mobility of atrazine in soil through adsorption-desorption processes. In this study, tall fescue biochar was prepared at 500 °C, and its effect on the adsorption-desorption behavior of atrazine in red soil, brown soil, and black soil was investigated. The tall fescue biochar with the pH value of 9.64 had a developed porous structure and large specific area that contained abundant surface functional groups. The element composition of the tall fescue biochar was C (50.46%), O (15.01%), N (4.54%), H (2.56%), and S (1.47%). The adsorption process of atrazine in the three soil types with and without biochar addition was divided into a fast stage, slow stage, and equilibrium stage. A pseudo second-order kinetic model was suitable for fitting the adsorption process of atrazine, and the determination coefficient (R2) ranged from 0.985 to 0.999. The adsorption-desorption processes of atrazine were described accurately by the Freundlich model (R2 of 0.967-0.999). The adsorption capacity of the three soil types for atrazine increased significantly with the addition of biochar, whereby the equilibrium adsorption amount increased from an initial range of 3.968 to 5.902 μg g-1 to a final range of 21.397 to 21.968 μg g-1. The desorption of atrazine was also inhibited as the hysteresis coefficient (HI) increased from an initial range of 0.451 to 0.586 to a final range of 0.916 to 0.941. The adsorption capacity of the red soil improved more than did the brown soil or black soil. Moreover, spontaneous adsorption of atrazine by the biochar-soil system occurred more easily at 35 °C than at 15 °C and 25 °C. Overall, tall fescue biochar was a prospective soil amendment material.

Control of Italian ryegrass and Alexandergrass in corn using different corn sowing date, pre- and post-emergent herbicides

Glyphosate-resistant (GR) Italian ryegrass (LOLMU) and Alexandergrass (URPLA) are troublesome weeds in corn cropping systems in Southern Brazil. The emergence pattern of those weeds is not uniform and may change according to the season’s environmental characteristics. Also, herbicide resistance has been diminishing the success of the weed control programs. The objectives of this study were to evaluate the influence of corn-sowing date on LOLMU and URPLA densities and their control provided by pre- and post-emergent herbicides. Field trials were conducted in two crop seasons in Southern Brazil consisting of three corn sowing date (August, September, and October) and the application of atrazine + S-metolachlor (residual) in corn pre-emergence in different post-emergence weed control programs with glyphosate, ammonium-glufosinate, nicosulfuron, and atrazine. The results indicated that the sowing date had a significant influence on LOLMU and URPLA densities. Corn sown in the earliest period was exposed to a higher LOLMU density, whereas corn sown in the latest period had a higher density of URPLA. Also, the application of residual herbicide at corn pre-emergence reduced both weed species densities and decreased the pressure for the control of glyphosate-resistant LOLMU for the post-emergence herbicides. The use of residual herbicides in corn pre-emergence is an efficient strategy to be considered in the LOLMU and URPLA control programs, followed by post-emergence application of glyphosate, ammonium-glufosinate, atrazine, and nicosulfuron.

Time-of-day effect on weed control efficacy with tolpyralate plus atrazine

AbstractTolpyralate is a new 4-hydroxyphenyl-pyruvate dioxygenase (HPPD)–inhibiting herbicide for weed control in corn. Previous research has reported efficacy of tolpyralate + atrazine on several annual grass and broadleaf weed species; however, no studies have evaluated weed control of tolpyralate + atrazine depending on time-of-day (TOD) of application. Six field experiments were conducted over a 2-yr period (2018, 2019) near Ridgetown, ON, to determine if there is an effect of TOD of application on tolpyralate + atrazine efficacy on common annual grass and broadleaf weeds. An application was made at 3-h intervals beginning at 06:00 h with the last application at 24:00 h. There was a slight TOD effect on velvetleaf, pigweed species, and common ragweed control with tolpyralate + atrazine; however, the magnitude of change throughout the day was ≤3% at 2, 4, or 8 wk after application (WAA). There was no effect of TOD of tolpyralate + atrazine on the control of lambsquarters, barnyardgrass, and green foxtail. All weed species were controlled ≥88% at 8 WAA. There was no effect of TOD of tolpyralate + atrazine application on corn yield. Results of this study show no evidence of a TOD effect on weed control efficacy with tolpyralate + atrazine.

Physiochemical assessment of environmental behaviors of herbicide atrazine in soils associated with its degradation and bioavailability to weeds

Atrazine residue in soil is one of the serious environmental problems and continues to risk ecosystem and human health. To address the environmental behaviors and dissipation of atrazine and better manage the application of atrazine in reality, we comprehensively investigated the adsorption and desorption, migration ability, and vanishing of atrazine in three distinct soils in China including Jiangxi (JX, pH 5.45, TOC 0.54%), Nanjing (NJ, pH 6.15, TOC 2.13%), and Yancheng (YC, pH 8.60, TOC 0.58%) soils. The atrazine adsorptive capacity to the soils was arranged in the order of NJ > YC > JX. The leaching assay with profiles of the soils showed strong migration, suggesting it had a high bioavailability to weeds and potential for underground water contamination. We further investigated the effects of environmental factors such as soil moisture, microbial activity and photolysis on atrazine degradation and showed that the degradation of atrazine in the soil mainly underwent the abiotic process, most likely through hydrolysis and photolysis-mediated mechanisms, and to less extend through soil microbial catabolism. Using HRLC-Q-TOF-MS/MS and by comparing the measured and theoretical m/z values and fragmentation data, ten metabolites comprising eight degraded products and two conjugates were characterized. Atrazine existing in the soils and sprayed coordinately blocked the growth of three common weeds, which prompted us to use the minimal atrazine in practice to control the waste of the pesticide and its impact on the environment. Overall, our work provided an insight into the mechanisms for the degradation of atrazine residues in the soils and contributed to the environmental risk assessment of the pesticide and management in its application control in the crop rotation and safe production.

Effective weed management strategy for maize (Zea mays) under rainfed condition of southern Rajasthan

A field experiment was conducted during the rainy season of 2015 and 2016 at Agricultural Research Station (MPUAT), Banswara, Rajasthan to find out effective weed management strategy for enhancing productivity and economic return of maize (Zea mays L.) under rain-fed condition of southern Rajasthan. Ten treatment combinations of pre-emergence (atrazine and pendimethalin), post-emergence (2,4-D amine, halosulfuron and tembotrione) herbicides with weed free and weedy check were laid out in randomized block design with three replications. The result revealed that application of atrazine 50WP @1.5 kg/ha PE fb tembotrione 42SC @286 g/ha POE at 25 DAS significantly reduced weed density and weed dry weight with increased weed control efficiency and weed control index at 50 DAS as compared to other herbicidal treatments. The weed free treatment gave significantly higher plant height, yield attributes, grain yield (6.31 and 6.86 t/ha) and stover yield (6.87 and 8.15 t/ha), HEI (67.51%) and gross return (₹ 88363/ha) followed by application of atrazine as PE fb tembotrione as POE at 25 DAS over rest of the treatments. While, net return (₹ 55498/ha) and B:C ratio (2.05) recorded highest with application of atrazine PE fb tembotrione POE at 25 DAS than weed free and rest of the treatments. Hence, sequential application of atrazine 50WP @1.5 kg/ha PE fb tembotrione 42SC @286 g/ha POE at 25 DAS may be recommended for enhancing productivity and economic return through effective weed management in maize under rainfed condition of southern Rajasthan.

Effect of weed control on weeds, grain yield and its components of maize (Zea mays L)

The present study entitled “effect of weed control on weeds, grain yield and its components of maize (Zea mays L.) cv. Single cross-10 was carried out at the Agricultural and Experiments Research Station at Giza, Faculty of Agriculture, Cairo University, Egypt. The experiment was conducted in the summer 2017 and was repeated in 2018 on the same piece of land to conform previous findings. The experiment design was Randomized Complete Block design (RCBD) having three replications. Six treatments include atrazine (1.0 kg/ha), glyphosate (0.8 kg/ha). atrazine + glyphosate, one hand hoeing after three weeks, hand hoeing twice after three and five weeks from sowing and weedy chick as control were used. Results indicated that glyphosate was found superior to atrazine for all studied characters. Moreover, lower weed dry matter accumulation and higher weed control % as well as higher values of ear characters ( ear length, ear diameter, grain weight/ear and shilling %) and grain yield per unit area were recorded in tank mix application of atrazine + glyphosate followed by hand hoeing twice.

Evolution of target and non-target based multiple herbicide resistance in a single Palmer amaranth (Amaranthus palmeri) population from Kansas

AbstractThe evolution of resistance to multiple herbicides in Palmer amaranth is a major challenge for its management. In this study, a Palmer amaranth population from Hutchinson, Kansas (HMR), was characterized for resistance to inhibitors of photosystem II (PSII) (e.g., atrazine), acetolactate synthase (ALS) (e.g., chlorsulfuron), and EPSP synthase (EPSPS) (e.g., glyphosate), and this resistance was investigated. About 100 HMR plants were treated with field-recommended doses (1×) of atrazine, chlorsulfuron, and glyphosate, separately along with Hutchinson multiple-herbicide (atrazine, chlorsulfuron, and glyphosate)–susceptible (HMS) Palmer amaranth as control. The mechanism of resistance to these herbicides was investigated by sequencing or amplifying the psbA, ALS, and EPSPS genes, the molecular targets of atrazine, chlorsulfuron, and glyphosate, respectively. Fifty-two percent of plants survived a 1× (2,240 g ai ha−1) atrazine application with no known psbA gene mutation, indicating the predominance of a non–target site resistance mechanism to this herbicide. Forty-two percent of plants survived a 1× (18 g ai ha−1) dose of chlorsulfuron with proline197serine, proline197threonine, proline197alanine, and proline197asparagine, or tryptophan574leucine mutations in the ALS gene. About 40% of the plants survived a 1× (840 g ae ha−1) dose of glyphosate with no known mutations in the EPSPS gene. Quantitative PCR results revealed increased EPSPS copy number (50 to 140) as the mechanism of glyphosate resistance in the survivors. The most important finding of this study was the evolution of resistance to at least two sites of action (SOAs) (~50% of plants) and to all three herbicides due to target site as well as non–target site mechanisms. The high incidence of individual plants with resistance to multiple SOAs poses a challenge for effective management of this weed.

Influence of weed management practices on weed control efficiency, growth and productivity of hybrid maize

A field experiment was conducted during Kharif 2015 at Arkabahal Farm, Bhawanipatana Odisha, India to find out the most efficient and effective method of weed management in hybrid maize under rainfed condition. The treatments comprised of intercropping of maize + cowpea (1:1), maize + cowpea(1:1) with pre emergence application of pendimethalin @ 1 kg/ ha, pre emergence application of atrazine @ 1 kg/ ha either alone or with hand weeding at 30 days after sowing(DAS), pre emergence application of atrazine + pendimethalin @ (0.5 + 0.5) kg/ha followed by hand weeding at 30 DAS, hand weeding at 15 DAS and twice hand weeding at 15 and 30 DAS were compared with un weeded control. The results of experiment revealed that dry matter production of weeds, crop growth of hybrid maize in terms of plant height, number of leaves/plant, leaf area index and dry matter production along with yield attributes and yield were significantly influenced by the weed management treatments. The integrated use of pre-emergence application of herbicide combination of atrazine + pendimethalin (0.5 + 0.5) kg/ha and atrazine @ 1kg/ha with supplemented with hand weeding at 30 DAS in sole maize along with pendimethalin @ 1 kg/ha in intercropping of maize with cowpea remarkably reduced the weed dry matter accumulation and enhanced the weed control efficiency and crop growth parameters in terms of plant height, number of leaves/plant, leaf area index and dry matter production. The highest maize grain (5.67 t/ha) and stover yield (6.57 t/ha) were recorded in pre-emergence application of herbicide mixture of atrazine + pendimethalin (0. 5 + 0.5) kg/ha supplemented with hand weeding practice at 30 DAS. It remained at par with pre-emergence application of atrazine @ 0.5kg/ ha with hand weeding at 30 DAS in sole maize and pendimethalin @ 1 kg/ha in intercropping of maize + cowpea. The uninterrupted growth of weeds reduced the grain yield of maize to an extent of 68.11%.