Herbicide Interactions Research Articles

Kinetic study of paraquat adsorption on alginate beads loaded with montmorillonite using shrinking core model

Water contamination by pesticides threatens clean water availability, highlighting the need for advanced sustainable sanitation systems. Adsorption using biopolymers and minerals is prominent. Understanding process kinetics and influencing parameters is crucial for optimizing contaminant-adsorbent contact time for safe water disposal. The adsorption kinetics of Paraquat (PQ) at three initial concentrations (C0 = 19, 38, and 50 ppm) were studied using alginate-montmorillonite (Alg-Mt) beads with varying clay contents and a 30-min gelation time. The beads were characterized by elemental analysis, TG/DTG, FTIR, XRD, SEM, and EDX. The Shrinking Core Model (SCM) was applied to the experimental data to determine if the diffusion of PQ within the beads depended on clay content. The effective diffusion coefficient (Dp) in the adsorbent increased from 7 × 10−12 to 1 × 10−10 m2 s−1 with increasing clay content, suggesting that diffusion into the interior depended on interaction with the mineral.This investigation also demonstrated that the synthesis of beads at different gelation times does not impact either the adsorption capacity or the adsorption rate of the herbicide on the materials. These results indicate that diffusion depends solely on the interaction of the cationic herbicide with the clay encapsulated within the bead hydrogel.

Growth, nutrient uptake and yield ofdirect seeded rice as influenced by weed management practices

A field experiment was conducted during the rainy (Kharif) seasons of 2018 and 2019 at the Kerala Agricultural University, Kerala, to evaluate the effect of herbicides and herbicide combinations on the weed management and growth, nutrient uptake and yield of direct seeded rice (DSR). The experiment was laid out in a randomized block design with three replications. Nine weed control treatments were used, including sole application of three herbicides (cyhalofop butyl @ 80 g/ha, bispyribac sodium @ 25 g/ha, fenoxaprop-p-ethyl@ 60 g/ha), five herbicidal combinations (penoxsulam + cyhalofop butyl commercial formulation @ 150 g/ha, cyhalofop butyl @ 80 g/ha + carfentrazone ethyl @ 200 g/ha, bispyribac sodium @ 25 g/ha + cyhalofop butyl @ 80 g/ha, bispyribac sodium @ 25 g/ha + fenoxaprop-p-ethyl @ 60 g/ha and stale seedbed followed by (fb) glyphosate @ 800 g/ha + oxyfluorfen @ 150 g/ha at 15-20 days after land preparation + cyhalofop butyl @ 80 g/ha + carfentrazone ethyl @ 200 g/ha), and hand weeding twice at 20 and 40 days after sowing. Weeds removed 27.72, 4.61 and 67.95 kg of N, P and K/ha respectively at 45 days after treatment application (DATA) under unweeded conditions in direct seeded rice. Herbicidal treatments enhanced grain yield by 23.89 to 58.84 % and herbicide combinations increased grain yield by 56 to 59 % compared to the unweeded control in direct seeded rice. Tank mix combination of bispyribac sodium @ 25 g/ha + fenoxaprop-p-ethyl @ 60 g/ha and bispyribac sodium @ 25 g/ha + cyhalofop butyl @ 80 g/ha and premix combination of penoxsulam + cyhalofop butyl @ 150 g/ha recorded higher nutrient uptake and grain yields (5.03, 4.76 and 4.79 t/ha, respectively) and were on par to hand weeding twice. Unweeded control recorded the lowest pooled grain yield (2.07 t/ha) and uncontrolled weed competition resulted in 59.95 % reduction in grain yield. Keywords: Crop competition, Herbicide combinations, Herbicide interactions, Nutrient removal, Nutrient uptake, Yield reduction

Understanding the complexities in glyphosate and ametryn interactions: Soil retention and transformation as influenced by their applications alone and mixture

The use of herbicide mixtures is widely adopted by farmers in agriculture worldwide. Glyphosate and ametryn are herbicides commonly applied in tank mixtures, increasing the spectrum of weed control in sugarcane crops. After application, herbicides can reach the soil layer, which is susceptible to retention, transport, and degradation processes. Herbicide interactions in mixtures may affect their bioavailability and persistence in soil, leading to different behavior in the environment compared to when applied alone. This study evaluated the sorption-desorption and transformation of 14C-glyphosate and 14C-ametryn in soil when applied alone or in a tank mixture. The sorption of 14C-ametryn in soil was increased by 25% when mixed with glyphosate (14C-ametryn + glyphosate). This increase in sorption was not evident for 14C-glyphosate when mixed with ametryn (14C-glyphosate + ametryn). The amount desorbed of 14C-ametryn (20%) applied alone was higher than in a mixture (10%). Both herbicide's mineralization half-live time (MT50) was influenced when applied in mixtures. 14C-glyphosate applied alone showed lower MT50 (55 days) compared to 14C-glyphosate + ametryn (119 days). 14C-ametryn also showed lower MT50 when applied alone than when applied with glyphosate (>120 days in both cases). These results suggest that the presence of ametryn in mixture with glyphosate decreases the desorption and mineralization of both herbicides, potentially affecting their bioavailability for weed root absorption and degradation in environment.

Interaction of different chloro-substituted phenylurea herbicides (diuron and chlortoluron) with bovine serum albumin: Insights from multispectral study

In this work, the interaction between different chloro-substituted phenylurea herbicides (diuron (DIU) and chlortoluron (CHL)) and BSA were investigated and compared at three different temperatures (283 K, 298 K and 310 K) adopting UV–vis, fluorescence, and circular dichroism spectra. The quenching mechanism of the interaction was also proposed. The energy transfer between BSA and DIU/CHL was investigated. The binding sites of DIU/CHL and BSA and the variations in the microenvironment of amino acid residues were studied. The changes of the secondary structure of BSA were analyzed. The results indicate that both DIU and CHL can significantly interact with BSA, and the degree of the interaction between DIU/CHL and BSA increases with the increase of the DIU/CHL concentration. The fluorescence quenching of BSA by DIU/CHL results from the combination of static and dynamic quenching. The DIU/CHL has a weak to moderate binding affinity for BSA, and the binding stoichiometry is 1:1. Their binding processes are spontaneous, and hydrophobic interaction, hydrogen bonds and van der Waals forces are the main interaction forces. DIU/CHL has higher affinity for subdomain IIA (Site I) of BSA than subdomain IIIA (Site II), and also interacts with tryptophan more than tyrosine residues. The energy transfer can occur from BSA to DIU/CHL. By comparison, the strength of the interaction of DIU-BSA is always greater than that of CHL-BSA, and DIU can destroy the secondary structure of BSA molecules greater than CHL and thus the potential toxicity of DIU is higher due to DIU with more chlorine substituents than CHL. It is expected that this study on the interaction can offer in-depth insights into the toxicity of phenylurea herbicides, as well as their impact on human and animal health at the molecular level.

Insights into interaction of triazine herbicides with three kinds of different alkyl groups (simetryne, ametryn and terbutryn) with human serum albumin via multi-spectral analysis

In this study, the interaction of triazine herbicides with three kinds of different alkyl groups (simetryne, ametryn and terbutryn) with human serum albumin (HSA) are investigated through UV–vis, fluorescence, and circular dichroism (CD) spectra. The mechanisms on the fluorescence quenching of HSA initiated by triazine herbicides are obtained using Stern-Volmer, Lineweaver-Burk and Double logarithm equations. The quenching rate constant (Kq), Stern-Volmer quenching constant (Ksv), binding constant (KA), thermodynamic parameters such as enthalpy change (∆H), entropy change (∆S) and Gibbs free energy (∆G) and number of binding site (n) are calculated and compared. The variations in the microenvironment of amino acid residues are studied by synchronous fluorescence spectroscopy. The binding sites and subdomains are identified using warfarin and ibuprofen as site probes. The conformational changes of HSA are measured using CD spectra. The results reveal that the triazine herbicides with different alkyl groups can interact with HSA by static quenching. The combination of the three herbicides and HSA are equally proportional, and the binding processes are spontaneous. Hydrophobic interaction forces play important roles in simetryne-HSA and ametryn-HSA, while the interaction of terbutryn-HSA is Van der Waals forces and hydrogen bonding. Moreover, the three herbicides can bind to HSA at site I (sub-domain IIA) more than site II (subdomain IIIA), and combine with tryptophan (Trp) more easily than tyrosine (Tyr) residues, respectively. By comparison, the order of interaction strength is terbutryn-HSA > ametryn-HSA > simetryne-HSA. Terbutryn can destroy the secondary structure of HSA more than simetryne and ametryn, and the potential toxicity of terbutryn is higher. It is expected that the interactions of triazine herbicides with HSA via multi-spectral analysis can offer some valuable information for studying the toxicity and the harm of triazine herbicides on human health at molecular level in life science.

Role of glutathione S-transferases in the mode of action of herbicides that inhibit amino acid synthesis in Amaranthus palmeri

Acetolactate synthase inhibitors (ALS inhibitors) and glyphosate are two classes of herbicides that act by inhibiting an enzyme in the biosynthetic pathway of branched-chain or aromatic amino acids, respectively. Besides amino acid synthesis inhibition, both herbicides trigger similar physiological effects in plants. The main aim of this study was to evaluate the role of glutathione metabolism, with special emphasis on glutathione S-transferases (GSTs), in the mode of action of glyphosate and ALS inhibitors in Amaranthus palmeri. For that purpose, plants belonging to a glyphosate-sensitive (GLS) and a glyphosate-resistant (GLR) population were treated with different doses of glyphosate, and plants belonging to an ALS-inhibitor sensitive (AIS) and an ALS-inhibitor resistant (AIR) population were treated with different doses of the ALS inhibitor nicosulfuron. Glutathione-related contents, GST activity, and related gene expressions (glutamate-cysteine ligase, glutathione reductase, Phi GST and Tau GST) were analysed in leaves. According to the results of the analytical determinations, there were virtually no basal differences between GLS and GLR plants or between AIS and AIR plants. Glutathione synthesis and turnover did not follow a clear pattern in response to herbicides, but GST activity and gene expression (especially Phi GSTs) increased with both herbicides in treated sensitive plants, possibly related to the rocketing H2O2 accumulation. As GSTs offered the clearest results, these were further investigated with a multiple resistant (MR) population, compressing target-site resistance to both glyphosate and the ALS inhibitor pyrithiobac. As in single-resistant plants, measured parameters in the MR population were unaffected by herbicides, meaning that the increase in GST activity and expression occurs due to herbicide interactions with the target enzymes.

Toxic interaction of glyphosate herbicide and tau-fluvalinate insecticide on pheasant embryos

Toxic interaction of glyphosate herbicide and tau-fluvalinate insecticide on pheasant embryos

Study on the toxicity prediction model ofacetolactate synthase inhibitor herbicides based on human serum albumin and superoxide dismutase binding information

Toxicity significantly influences the successful development of drugs. Based on the toxicity prediction method (carrier protein binding information-toxicity relationship) previously established by the our group, this paper introduces information on the interaction between pesticides and environmental markers (SOD) into the model for the first time, so that the toxicity prediction model can not only predict the toxicity of pesticides to humans and animals, but also predict the toxicity of pesticides to the environment. Firstly, the interaction of acetolactate synthase inhibitor herbicides (ALS inhibitor herbicides) with human serum albumin (HSA) and superoxide dismutase (SOD) was investigated systematically from theory combined with experiments by spectroscopy methods and molecular docking, and important fluorescence parameters were obtained. Then, the fluorescence parameters, pesticides acute toxicity LD50 and structural splitting information were used to construct predictive modeling of ALS inhibitor herbicides based on the carrier protein binding information (R2 = 0.977) and the predictive modeling of drug acute toxicity based on carrier protein binding information and conformational relationship (R2 = 0.991), which had effectively predicted pesticides toxicity in humans and animals. To predict potential environmental toxicity, the predictive modeling of drug acute toxicity based on superoxide dismutase binding information was established (R2 = 0.883) by ALS inhibitor herbicides-SOD binding information, which has a good predictive ability in the potential toxicity of pesticides to the environment. This study lays the foundation for developing low toxicity pesticides.

From Soil to Spectrum: Decoding the Impact of Nutrient Management Practices and Herbicides using FTIR

Background: FTIR spectroscopy is the instrumental technique used in science for studying soil constituents and their variations rapidly. Being a non-extraction technique, FTIR could also be used to study the interaction of soil composition with the applied external inputs like fertilizer nutrients through organic and inorganic sources and herbicides by assessing the variations in spectral patterns. This will also reveal the type of interaction and changes taking place in soil swiftly. Hence, the current study was carried out to investigate the interaction of herbicides with soil components under various fertilizer nutrient management practices. Methods: Three herbicides (glyphosate, pendimethalin, metribuzin) were applied to the sandy loam soil treated with soil inorganic fertilizer (NPK+MN) and organic fertilizer (NPK+FYM). Treated soils along with control, were collected, processed and subjected to FTIR analysis. Based on the intensity of absorption changes, the type of interactions and changes that occurred in the soil were assessed. Result: Results of the study reveal that the application of herbicides (glyphosate, pendimethalin and metribuzin) to soil and NPK + micronutrients and NPK + FYM resulted in complex interactions and changes in FTIR absorption intensities, notably in fingerprint regions (1200-400 cm-1). Shift in the peaks at different wave numbers occurred due to the interaction of soil constituents with the herbicides and organic matter as FYM. The study highlights that a deeper understanding of these complex interactions is crucial for optimizing the use and time of application of fertilizer nutrients and herbicides, minimising environmental impacts and promoting sustainable agricultural practices that preserve soil health and productivity.

Growing Season Fires and Herbicide May not Be the Silver Bullet to Lespedeza cuneata Management

Invasive species are generally managed across rangelands to achieve livestock productivity and biodiversity maintenance objectives. The invasive legume Lespedeza cuneata (Dum. Cours.) G. Don. is managed across much of the Great Plains with aerially applied herbicides that target broadleaf forbs and dormant season (late March−early April) fire. It is hypothesized that altering fire timing to the growing season or integrating late-season herbicide into fire management may lead to more successful reduction of L. cuneata without negatively affecting rangeland plant communities. However, most of the literature outlining the effects of L. cuneata and its management is limited to small scale (< 100 m2), highly controlled studies that are not transferrable to large working rangelands. We manipulated eight large (333−766 ha) pastures managed with fire and grazing (i.e., pyric herbivory) to assess whether growing and dormant season fires, herbicide application, or the interactive effect of fire timing and herbicide reduced L. cuneata without negatively affecting broad rangeland plant composition (i.e., functional group cover) from 2019 to 2021. Our study was performed at two scales relevant to rangeland management: the pasture and burn patch scales. None of our treatments (i.e., fire timing, herbicide application, or the interaction of fire timing and herbicide) had a significant effect on L. cuneata canopy cover at either the pasture or patch scale. Our treatments also did not affect forb or shrub cover at the pasture or patch scales. Grass and sedge cover was significantly increased post herbicide at the patch scale, but not at the pasture scale. Grass and sedge cover was unaffected by any other treatment at both scales considered in this study. Our results add to nearly two decades of research, conducted elsewhere, that pyric herbivory alone may be sufficient to manage L. cuneata and promote rangeland biodiversity in the tallgrass prairie.

Direct toxicity and emigration: evaluation of herbicide interactions with a biological control agent for Brazilian peppertree (Schinus terebinthifolia)

Direct toxicity and emigration: evaluation of herbicide interactions with a biological control agent for Brazilian peppertree (Schinus terebinthifolia)

Herbicides versus Nitrogen Cycle: Assessing the Trade-Offs for Soil Integrity and Crop Yield—An In-Depth Systematic Review

The interaction of herbicides in the nitrogen cycle and their consequences on soil health and agricultural production are essential topics in agronomic research. In this systematic review article, we have synthesized recent studies on this subject. The results revealed that the indiscriminate use of herbicides can have negative effects on vital processes in the nitrogen cycle, such as reduced enzymatic activity and microbial respiration. Moreover, herbicides alter the soil microbial composition, affecting nitrogen cycling-related activities. Symbiotic nitrogen fixation is also impaired, resulting in a reduction in the population of nitrogen-fixing bacteria and a decrease in the availability of this nutrient in the soil. These effects compromise soil fertility and the release of nitrogen to plants. Therefore, sustainable agricultural practices must be adopted, considering nitrogen cycling efficiency and the preservation of soil and natural resources. This understanding is crucial for guiding appropriate management strategies aimed at minimizing the negative effects of herbicides on the nitrogen cycle and ensuring soil health and agricultural productivity.

Interaction of herbicides with mepiquat chloride and prohexadione calcium in winter wheat

Interaction of herbicides with mepiquat chloride and prohexadione calcium in winter wheat

New Insights into the Interactions between Herbicides: Trends from Recent Studies.

The use of herbicide combinations is a common practice in modern agriculture. However, unexpected results may be observed due to herbicide and weed diversity, therefore, highlighting the need for a predictive strategy. To this end, a data set was made based on recent studies. This data set included herbicide attributes, such as active ingredient, chemical family, and mode of action, and weed attributes, namely, species, clade, type of leaves, family, and lifespan. Globally, additive interactions (46.30%) were more frequent than antagonistic (29.09%) and synergistic (24.61%) ones. The occurrence of these herbicide interactions with regard to herbicide and weed features is also discussed. Moreover, mesotrione and glyphosate have been, respectively, identified as the most promising or inadequate herbicides in predicting beneficial mixtures. The resulting global trend could guide farmers in their choice of beneficial herbicide companions.

EFFECT OF PALM POLLEN,PUMPKIN EXTRACT, NANO FERTILIZER AND THEIR INTERACTIONS WITH WHEAT HERBICIDES

This experiment was aimed to study the effect of the interaction of herbicides and varieties with different types of foliar nutrition in production the highest yield for three wheat varieties. A field experiment was carried out at the College of Agricultural Engineering Sciences - University of Baghdad / Jadiriyah for two seasons, as the seeds of the first season were sown on 13/12/2018 and harvested on 15/5/2019, and the seeds of the second season were sown on 4/12/2019 and harvested on 10/5/2020. The randomized complete block design (RCBD) was used in the arrangement of split plots, the nutrition included the main plots, while the varieties with herbicides treatments occupied the secondary plots with three replications. The treatment of V3H3 was significantly superior in achieving the highest average in the grain yield value 4.75 and 5.10 ton h-1 for the two seasons, respectively. As for the nutrition, treatment F3 gave the highest average in the grain yield amounted to 4.74 and 4.69 ton ha-1 for the two seasons, respectively. It could be concluded that V3H3 the best treatment to compete with the weeds by giving it the highest yield. Also, It is noted that the leaves feeding treatments all led to a significant increases in the yield and some of its components despite the normal fertilization treatment was the best treatment by giving it the highest grain yield and a significant increases in two of the yield components.

Rapid necrosis: Implications of environmental conditions and plant growth stage on 2,4-D resistance and effect of other auxinic herbicides in Sumatran fleabane (Conyza sumatrensis)

AbstractResistant plants of Sumatran fleabane with unusual rapid necrosis (RN) symptoms after application of 2,4-D were characterized in previous studies. Field observations indicated variability in the occurrence of the RN caused by 2,4-D, but the causes of the variation are unknown. This study aimed to investigate the effect of environmental conditions, plant growth stage, and simultaneous and sequential herbicide mixtures with other auxin mimics on the occurrence of RN caused by 2,4-D. Application at temperature of 12 C delayed the symptoms and decreased the intensity of the RN but still resulted in plant survival to 2,4-D. The absence of light after herbicide application caused a slight delay in the symptoms, but the production of hydrogen peroxide and the size of the necrosed area were not affected by the light treatments before and after 2,4-D application. Changes in plant photosynthesis through inhibiting photosystem II do not prevent the occurrence of RN symptoms. The auxinic herbicides dicamba, triclopyr, and halauxifen-methyl do not cause RN symptoms and are effective at controlling the resistant biotype when applied without 2,4-D, but the effectiveness of these herbicides was reduced when sprayed on the resistant biotype either together, 4 h, or 24 h after 2,4-D. The RN phenotype does not occur for dicamba and triclopyr, even in advanced plant growth stages and high doses on the resistant biotype. The herbicides dicamba and triclopyr effectively controlled resistant plants, especially when sprayed at the initial growth stages. The results of this study identify environmental effects, plant development effects, and herbicide interactions that interfere with the occurrence of RN symptoms caused by 2,4-D in Sumatran fleabane. These data provide insights about the mechanisms behind the RN symptoms caused by 2,4-D and are important for identifying the causes of variability of the herbicide symptomology and performance under experimental and field conditions.

Synergistic and Antagonistic Herbicide Interactions for Control of Volunteer Corn in Glyphosate/Glufosinate/2,4-D-Resistant Soybean

Weed interference from glyphosate/glufosinate-resistant (GGR) volunteer corn can reduce soybean yield and quality. The recent release of glyphosate/glufosinate/2,4-D choline (GG2)-resistant soybean will allow for expanded POST herbicide mixture options for broad-spectrum weed control. Herbicide antagonism between ACCase-inhibiting graminicides and synthetic auxin herbicides has been confirmed for various grass weed species, including volunteer corn. Field experiments (total of 4) were carried out in 2021 and 2022 in southwestern Ontario to assess volunteer corn control with combinations of glufosinate, 2,4-D choline, or dicamba plus clethodim or quizalofop-p-ethyl applied POST to GG2-resistant soybean. Quizalofop-p-ethyl and quizalofop-p-ethyl + glufosinate controlled GGR volunteer corn 95 and 98%, respectively, 6 weeks after application (WAA); adding 2,4-D choline or dicamba to quizalofop-p-ethyl reduced control to &amp;le; 15%. Clethodim controlled GGR volunteer corn 81%, and the addition of glufosinate increased control to 97%; the co-application of 2,4-D choline or dicamba with clethodim reduced GGR volunteer corn control to 58 and 45%, respectively at 6 WAA. ACCase-inhibiting herbicides co-applied with glufosinate resulted in a synergistic improvement in GGR volunteer corn control while co-applications with synthetic auxin herbicides resulted in an antagonistic decrease in GGR volunteer corn control. Greater antagonism occurred when the synthetic auxin herbicides were co-applied with quizalofop-p-ethyl than clethodim. All mixtures of quizalofop-p-ethyl or clethodim with 2,4-D or dicamba resulted in unacceptable control of GGR volunteer corn.

4-Hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides: past, present, and future

AbstractThe herbicides that inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD) are primarily used for weed control in corn, barley, oat, rice, sorghum, sugarcane, and wheat production fields in the United States. The objectives of this review were to summarize 1) the history of HPPD-inhibitor herbicides and their use in the United States; 2) HPPD-inhibitor resistant weeds, their mechanism of resistance, and management; 3) interaction of HPPD-inhibitor herbicides with other herbicides; and 4) the future of HPPD-inhibitor-resistant crops. As of 2022, three broadleaf weeds (Palmer amaranth, waterhemp, and wild radish) have evolved resistance to the HPPD inhibitor. The predominance of metabolic resistance to HPPD inhibitor was found in aforementioned three weed species. Management of HPPD-inhibitor-resistant weeds can be accomplished using alternate herbicides such as glyphosate, glufosinate, 2,4-D, or dicamba; however, metabolic resistance poses a serious challenge, because the weeds may be cross-resistant to other herbicide sites of action, leading to limited herbicide options. An HPPD-inhibitor herbicide is commonly applied with a photosystem II (PS II) inhibitor to increase efficacy and weed control spectrum. The synergism with an HPPD inhibitor arises from depletion of plastoquinones, which allows increased binding of a PS II inhibitor to the D1 protein. New HPPD inhibitors from the azole carboxamides class are in development and expected to be available in the near future. HPPD-inhibitor-resistant crops have been developed through overexpression of a resistant bacterial HPPD enzyme in plants and the overexpression of transgenes for HPPD and a microbial gene that enhances the production of the HPPD substrate. Isoxaflutole-resistant soybean is commercially available, and it is expected that soybean resistant to other HPPD inhibitor herbicides such as mesotrione, stacked with resistance to other herbicides, will be available in the near future.

Smutgrass (Sporobolus indicus) control in bahiagrass is improved with applications of herbicide and fertilizer

AbstractSmutgrass is an invasive weed species that can quickly outcompete bahiagrass because of its aggressive growth, prolific seed production, and rhizomatous nature. Total renovation of bahiagrass pastures or hayfields is generally not a feasible or economically viable option for most producers. Therefore, controlling the continual spread of smutgrass will require an integrated weed management (IWM) plan that incorporates multiple strategies. The objective of this study was to test the interactions of herbicides and fertilizers on smutgrass control in bahiagrass and determine the most efficacious and economical IWM plan for low-input bahiagrass systems. This research was conducted on a mixture of ‘Tifton 9’ and ‘Pensacola’ bahiagrass at the Alapaha Beef Station in Alapaha, GA. The study design was a randomized complete block with a three-by-four factorial treatment arrangement with six replications. Fertility treatments included 56 kg N ha–1 (ammonium nitrate, 34% N) + 56 kg K2O ha–1, 56 kg N ha–1, and an unfertilized control. Smutgrass was reduced to &lt;15% ground coverage when a postemergent herbicide was applied. The addition of a preemergent herbicide and/or fertilizer further reduced the coverage of smutgrass (P &lt; 0.01). As smutgrass declined, the bahiagrass ground coverage increased; other vegetation and dead material did not differ by treatment. Generally, herbage accumulation and crude protein were only affected following the second N application (P &lt; 0.01). Treatments that included preemergent (indaziflam) and postemergent (hexazinone) herbicides in addition to N and K2O resulted in an improved bahiagrass stand as timely weed suppression removed competition, while fertilizer provided essential nutrients for optimum growth to fill in the gaps. Combining herbicide and fertilizer is a more economical option for producers when compared to a complete bahiagrass renovation.

Leaching of saflufenacil in soils with different organic matter contents

Saflufenacil is a herbicide recommended for use in the main agricultural crops in Brazil to control eudicotyledonous weeds. However, the application of saflufenacil has been carried out without previous knowledge of this herbicide interactions with soil colloids, which may increase environmental contamination risks. In this study, the leaching of saflufenacil in soil samples was estimated with different organic matter contents. Therefore, PVC columns were filled with samples of Xanthic Ferralsol (XF) and Ferralsol (F), with different physical and chemical attributes. Twelve hours after herbicide (70 g i.a. ha-1) application, the PVC columns were subjected to a rainfall of 60 mm. For the evaluation of saflufenacil leaching, the columns were sectioned in ten parts with 5-cm each. Saflufenacil leached up to 50 and 40 cm deep in the samples, with the lowest contents of organic matter of XF and F, respectively. The increase in organic matter content of Ferralsol and Xanthic Ferralsol samples reduced saflufenacil leaching and the symptoms of intoxication in the indicator species. There was an inverse relation between the content of organic matter and the leaching of the herbicide in both soils studied. It was observed that the application of saflufenacil in soils with low organic matter contents may represent a significant environmental contamination risk of soils and watercourses.