@article{ramanathan_gannon_locke_everman_2023, title={Characterizing atrazine, mesosulfuron-methyl, and topramezone bioavailability in North Carolina soils using greenhouse bioassays}, volume={6}, ISSN={2639-6696}, url={http://dx.doi.org/10.1002/agg2.20371}, DOI={10.1002/agg2.20371}, abstractNote={Abstract Herbicide carryover injury to rotational crops can vary in severity depending on the influence of soil properties on herbicide bioavailability. Greenhouse bioassays were conducted with soybean, radish, and canola to evaluate differences in the bioavailability of three herbicides with carryover risk, atrazine, mesosulfuron‐methyl, and topramezone. Bioassays were conducted in three varying regional soil types with nine herbicide treatment rates including a control. Plant visual injury was evaluated weekly, and aboveground dry biomass was weighed after harvest of soybean 28 days after emergence (DAE) and radish and canola 21 DAE. A log‐logistic dose–response regression model was used to quantify herbicide‐effective concentrations for 30% (EC 30 ), 50% (EC 50 ), and 80% (EC 80 ) visual injury and aboveground dry biomass reduction in each soil type. Relative herbicide‐soil bioavailability was determined through comparisons of herbicide‐effective concentrations among soil types. Pearson correlation revealed that atrazine, mesosulfuron‐methyl, and topramezone EC 30 for all species were positively correlated to soil organic matter (OM) content ( r = 0.56, 0.48, and 0.40, respectively) and cation exchange capacity (CEC) ( r = 0.43, 0.41, and 0.45). Topramezone EC 80 for soybean and radish was positively correlated to soil clay content ( r = 0.51) and silt content ( r = 0.51) and negatively correlated to sand content ( r = −0.51) and pH ( r = −0.52). Decreased atrazine, mesosulfuron‐methyl, and topramezone bioavailability in soil with high OM and CEC, decreased topramezone bioavailability in coarse‐textured soil and at high soil pH, and differential herbicide sensitivity of crop species can inform grower decisions on herbicide selections and rotational crop plans.}, number={2}, journal={AGROSYSTEMS GEOSCIENCES & ENVIRONMENT}, publisher={Wiley}, author={Ramanathan, Shwetha S. and Gannon, Travis W. and Locke, Anna M. and Everman, Wesley J.}, year={2023}, month={Jun} }
 @article{ramanathan_gannon_maxwell_2023, title={Dose-response of five weed species to indaziflam and oxadiazon}, volume={6}, ISSN={["1550-2740"]}, url={https://doi.org/10.1017/wet.2023.39}, DOI={10.1017/wet.2023.39}, abstractNote={Abstract Indaziflam and oxadiazon are efficacious preemergence herbicides used in warm-season turfgrass because of their persistence and residual activity. It is beneficial to quantify effective concentrations for preemergence control of summer annual weeds and determine whether these concentrations are maintained throughout weed emergence periods. Therefore, greenhouse bioassays were conducted with barnyardgrass, broadleaf signalgrass, doveweed, large crabgrass, and purple nutsedge. Treatments included indaziflam at 0, 4, 8, 12, 17, 21, 25, 29, 33, and 37 g ai ha-1 or oxadiazon at 0, 420, 841, 1,260, 1,681, 2,102, 2,354, 2,942, 3,363, and 3,783 g ha-1. Although preemergence herbicides are not used to control perennial weeds, purple nutsedge was included to investigate the effect of selected herbicides on its growth. Herbicide EC50, EC80, and EC90 for seedling emergence inhibition and shoot and root mass reduction were quantified from log-logistic dose–response curves. Herbicide concentration that remains from a preemergence application during the regional species-specific periodicity of emergence was predicted using first-order kinetics equations. Indaziflam and oxadiazon controlled seedling emergence 14 d after treatment (DAT) in the evaluated annual weeds and shoot and root mass in all species 84 DAT. Indaziflam applied in mid-March at 33 g ha-1 may provide up to 90% seedling emergence inhibition in large crabgrass and signalgrass; up to 80% in barnyardgrass; and up to 50% in doveweed. Oxadiazon applied in mid-March at 3,363 g ha-1 may provide up to 80% seedling emergence inhibition in all species. Indaziflam and oxadiazon may control up to 80% shoot mass and up to 50% root mass, respectively, in purple nutsedge and 80% to 90% shoot or root mass in other species. Such information is useful in evaluating adequacy of herbicide management practices for season-long weed control, and it aids turfgrass managers in applying preemergence herbicides at optimal timing based on target weed species. Nomenclature: Indaziflam; oxadiazon; barnyardgrass; Echinochloa crus-galli (L.) P. Beauv.; broadleaf signalgrass; Bracharia platyphylla (Griseb.) Nash; doveweed; Murdannia nudiflora (L.) Brenan; large crabgrass; Digitaria sanguinalis (L.) Scop.; purple nutsedge, Cyperus rotundus L.}, journal={WEED TECHNOLOGY}, author={Ramanathan, Shwetha S. and Gannon, Travis W. and Maxwell, Patrick J.}, year={2023}, month={Jun} }
 @article{ramanathan_gannon_everman_locke_2022, title={Atrazine, mesosulfuron‐methyl, and topramezone persistence in North Carolina soils}, volume={114}, ISSN={0002-1962 1435-0645}, url={http://dx.doi.org/10.1002/agj2.21041}, DOI={10.1002/agj2.21041}, abstractNote={Abstract Investigating the effects of soil properties on herbicide persistence can aid in evaluating the carryover potential of herbicides in soil and the consequent injury risk to rotational crops. Laboratory incubation experiments were conducted to quantify the persistence of atrazine, mesosulfuron‐methyl, and topramezone in five regional soils under aerobic conditions at 23 °C. Additionally, mesosulfuron‐methyl persistence was tested at 7 °C, which is representative of regional average winter soil temperature. Herbicide half‐life was calculated with the logarithmic form of first‐order rate of degradation using linear regression and was correlated with soil properties. Half‐lives of atrazine (37–73 d) and topramezone (15–19 d) varied among soil types at 23 °C. Mesosulfuron‐methyl half‐life varied among soils at 7 °C (8.8–9.8 d) and 23 °C (5.4–5.8 d) and between temperatures. Atrazine and topramezone half‐lives were shortest in Candor sand (4% clay, 1.8% organic matter [OM], pH 5.1) and longest in Portsmouth sandy loam (13% clay, 5.3% OM, pH 4.3). Mesosulfuron‐methyl half‐life was longer at lower soil temperature. Half‐lives of atrazine, mesosulfuron‐methyl, and topramezone were correlated with soil OM content ( r = .83, −.53, and .63, respectively) and pH ( r = −.86, .55, and −.57). Additionally, atrazine and topramezone half‐lives were positively correlated with soil clay content ( r = .83 and .71), and mesosulfuron‐methyl half‐life was negatively correlated with temperature ( r = −.97). Correlations between soil OM content, clay content, and pH among soil types may have influenced herbicide persistence.}, note={title = {Atrazine, mesosulfuron-methyl, and topramezone persistence in North Carolina soils}, journal = {Agronomy Journal}}, number={2}, journal={Agronomy Journal}, publisher={Wiley}, author={Ramanathan, Shwetha S. and Gannon, Travis W. and Everman, Wesley J. and Locke, Anna M.}, year={2022}, month={Mar}, pages={1068–1079} }