RR soybean seed quality after application of glyphosate in different stages of crop development

In consequence of several studies and speculations concerning the issue of RR transgenic soybean after the application of glyphosate, additional scientific investigations became necessary to clarify the actual viability of the product use when applied in different developmental stages of the soybean crop. Therefore, this study was aimed to evaluate the physiological quality as well as seed health quality of RR soybean subjected to application of the herbicide glyphosate in different phonological stages of the transgenic soybean, cultivar CD 219RR. For this, an experiment with a complete block experimental design with treatments randomly distributed within the block, with four replications, was carried out. The assessed treatments were foliar sprayings of glyphosate in three increasing dosages [0 (control); 1,440 g ha-1; and 2,880 g ha-1] of acid equivalent, applied in two crop developmental stages: vegetative (V6) and reproductive (R2). The variables assessed were: germination; first count of germination; fresh and dry mass of seedlings, lengths of seedling and root; vigor and viability by the tetrazolium test; and seed health quality. Glyphosate application may adversely affect physiological quality of RR soybean seeds, when applied in dosages varying from 1,440 to 2,880 g acid equivalent per hectare at the stages V6 and R2.

Effects of agricultural management practices on earthworm populations and crop yield: validation and application of a mechanistic modelling approach

There is little consensus on how agriculture will meet future food demands sustainably. Soils and their biota play a crucial role by mediating ecosystem services that support agricultural productivity. However, a multitude of site-specific environmental factors and management practices interact to affect the ability of soil biota to perform vital functions, confounding the interpretation of results from experimental approaches. Insights can be gained through models, which integrate the physiological, biological and ecological mechanisms underpinning soil functions. We present a powerful modelling approach for predicting how agricultural management practices (pesticide applications and tillage) affect soil functioning through earthworm populations. By combining energy budgets and individual-based simulation models, and integrating key behavioural and ecological drivers, we accurately predict population responses to pesticide applications in different climatic conditions. We use the model to analyse the ecological consequences of different weed management practices. Our results demonstrate that an important link between agricultural management (herbicide applications and zero, reduced and conventional tillage) and earthworms is the maintenance of soil organic matter (SOM). We show how zero and reduced tillage practices can increase crop yields while preserving natural ecosystem functions. This demonstrates how management practices which aim to sustain agricultural productivity should account for their effects on earthworm populations, as their proliferation stimulates agricultural productivity. Synthesis and applications. Our results indicate that conventional tillage practices have longer term effects on soil biota than pesticide control, if the pesticide has a short dissipation time. The risk of earthworm populations becoming exposed to toxic pesticides will be reduced under dry soil conditions. Similarly, an increase in soil organic matter could increase the recovery rate of earthworm populations. However, effects are not necessarily additive and the impact of different management practices on earthworms depends on their timing and the prevailing environmental conditions. Our model can be used to determine which combinations of crop management practices and climatic conditions pose least overall risk to earthworm populations. Linking our model mechanistically to crop yield models would aid the optimization of crop management systems by exploring the trade-off between different ecosystem services.

Selectivity of the herbicide flazasulfuron applied after postemergence in sugarcane (Saccharum spp. L.) crop

The selectivity of the herbicide flazasulfaron was evaluated when applied at two rates (50 and 100 g/ha) with and without surfactants (Aterbane or Agral at 0.2% v/v). The treatment was applied at early (three leaves) and late (five to six leaves) stages of the postemergence of sugarcane plants (var. RB845257) grown in two soils (sandy and clay) with good moisture status before and after application. Despite the toxicity symptoms, especially at the late stage with the higher rate of application in the sandy soil, the herbicide did not affect the growth nor the stalk yield. The presence of the surfactants had no effect on the toxicity symptoms.

Degradation of the herbicide tebuthiuron using solar photo-Fenton process and ferric citrate complex at circumneutral pH

The influence of pH on the degradation of the herbicide tebuthiuron (TBH) was investigated using in situ generated Fe(III)-citrate complexes (Fe:cit) submitted to the photo-Fenton process under solar irradiation. Using Fe:cit in a wide pH range (2.5-7.5), 100-78% TBH oxidation was achieved respectively from a UV dose of 2.0 J cm(-2) (15 min). Moreover, the oxidation of TBH obtained in the presence of Fe:cit at pH 6.0 was higher than that obtained using Fe(NO3)3 at pH 2.5. A similar behavior is observed for the removal of total organic carbon (TOC) in TBH solutions. In the presence of Fe:cit, 20% and 85% of TOC was removed at pH 7.5 and 2.5, respectively, after 7.5 J cm-2 irradiation, while no mineralization was observed employing Fe(NO3)(3) for the same UV dose. Using Fe(NO3)(3), mineralization was observed only after 11 J cm-2 (8%). A higher mineralization rate was obtained with Fe(NO3)(3) only when a concentration three times higher was employed at pH 2.5. Besides the high efficiency of TBH degradation observed using the ferric citrate complex in the solar photo-Fenton process, it also offers the advantage of application at a pH of up to 7.5. (c) 2007 Elsevier B.V. All rights reserved.

Variable dose rate application of herbicides using optical sensors

The aim of this study was to develop and evaluate a variable dose rate application of herbicides using an online electronic control based system with optical sensors for weed detection in forested areas. The proposed concept was to apply a basic dose on 100% of the area (aiming to control small weeds) and to apply a complementary patch-spraying dose only on areas with higher weed infestation. For that purpose, a conventional spray boom was adjusted to apply 40% of the herbicide dose on the full area and the optical sensors were used to control the application of the complementary dose (60%) only on areas with higher infestation. The results showed that the system performed adequately. Field applications presented herbicide savings around 20 to 30%, with a similar weed control performance as compared to the full dose application on 100% of the area.

Phenotypic and biochemical responses of sugarcane cultivars to glyphosate application

Sugarcane cultivars show varying degrees of herbicide susceptibility, with herbicide effects ranging from no injury to total plant eradication. In this study, phenotypic and biochemical responses to glyphosate were evaluated in three sugarcane cultivars. Herbicide tolerance of the three cultivars (IACSP93-3046, IACSP94-4004 and RB72454) was tested in a greenhouse experiment using a completely randomized design. The experiment consisted of four replications of treatments in a factorial arrangement of 3 cultivars × 6 glyphosate dosages (0, 1,440, 2,160, 2,880, 3,600 and 4,320 g a. e. ha-1). Intoxication symptoms, based on a percentage scale ranging from 0 (no injury) to 100 % (total plant death), and total chlorophyll content were recorded at 1, 2, 3, 6, 7, 10, 20 and 34 days after glyphosate application (DAA). Shikimate dehydrogenase and α-esterase isoenzyme assays were performed at 8, 24, 48, 72 and 144 h after application (HAA). Intoxication symptoms observed at 6 DAA ranged from 5 % at the lowest glyphosate dosage (1,440 g a. e. ha-1) to ~30 % at the highest dosage (4,320 g a. e. ha-1) across all cultivars. IACSP94-4004 and IACSP93-3046 were determined to be the most glyphosate-tolerant cultivars. Reduction in chlorophyll content was observed with high dosages of glyphosate at 6 DAA. The shikimate dehydrogenase banding pattern was generally conserved among cultivars and treatments, with the exception of the IACSP94-4004 cultivar, which showed alterations in the banding pattern of α-esterase after glyphosate application. © 2013 Society for Sugar Research & Promotion.

Herbicide selectivity in herbaceous ornamental gardens of tagetes erecta L.

One of the major problems in landscaping in tropics is weed management. The herbaceous ornamental plant, Tagetes erecta L. (Asteraceae), is very popular for its beautiful flowers which can be used in landscape and also as cut flowers. The increase use of this plant and lack of selective herbicides led to the objective of this study to evaluate the herbicide metribuzin selectivity for this ornamental plant. The experimental design was completely randomized using four treatments (herbicide metribuzin doses: 0, 0.5, 1.0 and 1.5 L ha-1, equivalent to 0, 240, 480 and 720 g ha-1) and five replicates. The herbicide was applied over the seedling of T. erecta as pre-emergence of the weed seeds. Evaluations were performed at 7, 14, 21 and 28 days after application (DAA) by visual analysis of the toxicity symptoms over the ornamental, using the European Weed Research Council (EWRC) scale (1 to 9), where 1 is the total absence of symptoms and 9 to death plants. Polynomial regression statistical analysis was used. It was verified that, from the dose of 1.0 L ha-1, T. erecta plants died by 14 DAA, which the most of them had presented a very strong toxicity symptom; for the 0.5 L ha-1 treatment the plants had survived until 28 DAA. However, most of them already exhibited the high toxicity level, dying at 35 DAA. Thus, metribuzin was not suitable for T. erecta even at the lowest rate tested in this study.

Influence of spray mixture volume and flight height on herbicide deposition in aerial applications on pastures

The objective of the present study was to analyze the influence of spray mixture volume and flight height on herbicide deposition in aerial applications on pastures. The experimental plots were arranged in a pasture area in the district of Porto Esperidião (Mato Grosso, Brazil). In all of the treatments, the applications contained the herbicides aminopyralid and fluroxypyr (Dominum) at the dose of 2.5 L c.p. ha-1, including the adjuvant mineral oil (Joint Oil) at the dose of 1.0 L and a tracer to determine the deposition by high-performance liquid chromatography (HPLC) (rhodamine at a concentration of 0.6%). The experiment consisted of nine treatments that comprised the combinations of three spray volumes (20, 30 and 50 L ha-1) and three flight heights (10, 30 and 40 m). The results showed that, on average, there was a tendency for larger deposits for the smallest flight heights, with a significant difference between the heights of 10 and 40 m. There was no significant difference among the deposits obtained with the different spray mixture volumes.

Alternative methods for detecting soybean seeds genetically modified for resistance to herbicide glyphosate

The objective of this study was to verify application of two methodologies: substrate moistened with herbicide solution (SM) and immersion of seeds in herbicide solution (IH) for detecting soybean seeds genetically modified. For this, non-transgenic and transgenic soybean seeds, harvested in the 2008/2009 crop seasons were used. The treatments with substrate moistened were: SM1) 0.03% herbicide solution, at 25 ºC, with evaluation in the sixth day (hs -0.03% -25 ºC, 6th d); SM2) HS -0.03% -35 ºC, 5th d; SM3) HS -0.03% - 40 ºC, 5th d; and SM4) hs -0.06% -5 ºC, 5th d. In the methodology of immersion of seeds the following treatments were performed: IH1) seed immersion in a 0.6% herbicide solution, at 25 ºC, for 1 h, (si -0.06% -25 ºC, 1 h; IH2) si -0.06% - 35 ºC, 30 min.; IH3) si -0.06% -40 ºC, 30 min.; IH4) si -0.12% -35 ºC, 30 min.; and IH5) si -0.12% -40 ºC, 30 min. Bioassays allow detecting soybean seeds tolerant to glyphosate herbicide within five days. The seeds of non-genetically modified and genetically modified soybean cultivars may be easily distinguished through the treatments SM2 and SM4 of the moistened substrate methodology; and treatments IH3, IH4, and IH5 of seed immersion methodology. Both methodologies are easily feasible, practical, and applicable in seed analysis laboratories, once do not require special equipments.

Poly(epsilon-caprolactone) nanocapsules carrying the herbicide atrazine: effect of chitosan-coating agent on physico-chemical stability and herbicide release profile

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

FLUXOFENIM USED AS A SAFENER ON SORGHUM SEED FOR S-METOLACHLOR HERBICIDE

This study aimed to evaluate the efficiency of protective fluxofenim seed treatment of sorghum hybrids DKB510 and SCG340, in order to increase the selectivity to the herbicide S-metolachlor applied pre-emergence and to determine the activity of detoxification enzyme glutathione S-transferase (GST). This work was divided into two stages. The first step consisted of field evaluation of the effectiveness of the shield to reduce visual symptoms of plant injury caused by the herbicide and the second determined the activity of GST. It was compared the susceptibility of sorghum seeds to the herbicide by means of visual assessment of injuries at 3, 7, 15 and 30 days after emergence (DAE), root dry weight and shoot at 10 DAE, and determination of activity GST. The treatments were: application of the safener dose at 0 and 40 mL per 100 kg of seed, and spraying of the herbicide S-metolachlor at rates of 1,440 and 2,880 g a.i. ha(-1), and a control without herbicide. The safener use to seed treatment for both sorghum hybrids (DKB510 and SCG340) increased tolerance to the herbicide S-metolachlor in two doses, and the best results were obtained at a dose of 1,440 g ha(-1). The GST enzyme activity showed an increase when using the fluxofenim prior to application of the herbicide S-metolachlor at a dose of 1,440 g ha(-1) for the two hybrids.

Imazapyr herbicide efficacy on floating macrophyte control and ecotoxicology for non-target organisms

the aims of this study were to determine imazapyr efficacy for floating macrophyte control and ecotoxicology for non-target organisms. For the floating macrophyte control efficacy tests were used the doses of 0,5; 1,0; 2,0; 2,5; 3,0; 3,5 and 4,0 L ha(-1) and a control with 10 replicates. The acute toxicology for non-target organisms was estimated by lethal concentration 50% (LC50 and EC50). The floating macrophyte control efficacy was over 90%. Imazapyr was classified as moderately toxic for the following biomarkers: L. minor, H. eques, B. rerio, P. caudimaculatus, P. canaliculata, and P. mesopotamicus and lightly toxic for A. caroliniana. Thus, imazapyr herbicide is a tool with great potential to be used on floating macrophyte control (E. crassipes, P. stratiotes e S. molesta) in Brazil and this practice can be evaluated by the use of application biomarkers.

Iron(III) Porphyrin Covalently Supported onto Magnetic Amino-Functionalized Nanospheres as Catalyst for Hydrocarbon and Herbicide Oxidations

This work describes the covalent immobilization of an ironporphyrin, 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin iron(III) chloride (FeTFPP), onto maghemite/silica magnetic nanospheres covered with aminofunctionalized silica. The resulting material (gamma-Fe2O3/SiO2-NHFeP) was characterized by diffuse reflectance infrared spectroscopy (DRIFTS) and UV-Vis absorption spectroscopy. The catalytic activity of this magnetic ironporphyrin was investigated in the oxidation of hydrocarbons (styrene, (Z)-cyclooctene and R-(+)-limonene) and an herbicide (simazine) by hydrogen peroxide or 3-chloroperoxybenzoic acid. Hydrocarbon and simazine oxidation reaction products were analyzed by gas chromatography (GC) and high performance liquid chromatography (HPLC), respectively. This catalytic system proved to be efficient and selective for hydrocarbon oxidation, leading to high product yields from styrene (89%), cyclooctene (71%) and R-(+) -limonene (86%). Simazine oxidation was attained with 100% selectivity for a dechlorinated product (OEAT), while several oxidation products were obtained for the same catalyst in homogeneous media. The catalyst can be easily recovered through application of an external magnetic field and washed after reaction. Catalyst reuse experiments for R-(+)-limonene oxidation have shown that the catalytic activity is kept at 90% after 10 consecutive reactions.

Evaluation of the detection and quantification limits in electroanalysis using two popular methods: application in the case study of paraquat determination

In this work, the reduction reaction of paraquat herbicide was used to obtain analytical signals using electrochemical techniques of differential pulse voltammetry, square wave voltammetry and multiple square wave voltammetry. Analytes were prepared with laboratory purified water and natural water samples (from Mogi-Guacu River, SP). The electrochemical techniques were applied to 1.0 mol L-1 Na2SO4 solutions, at pH 5.5, and containing different concentrations of paraquat, in the range of 1 to 10 mu mol L-1, using a gold ultramicroelectrode. 5 replicate experiments were conducted and in each the mean value for peak currents obtained -0.70 V vs. Ag/AgCl yielded excellent linear relationships with pesticide concentrations. The slope values for the calibration plots (method sensitivity) were 4.06 x 10(-3), 1.07 x 10(-2) and 2.95 x 10(-2) A mol(-1) L for purified water by differential pulse voltammetry, square wave voltammetry and multiple square wave voltammetry, respectively. For river water samples, the slope values were 2.60 x 10(-3), 1.06 x 10(-2) and 3.35 x 10(-2) A mol(-1) L, respectively, showing a small interference from the natural matrix components in paraquat determinations. The detection limits for paraquat determinations were calculated by two distinct methodologies, i.e., as proposed by IUPAC and a statistical method. The values obtained with multiple square waves voltammetry were 0.002 and 0.12 mu mol L-1, respectively, for pure water electrolytes. The detection limit from IUPAC recommendations, when inserted in the calibration curve equation, an analytical signal (oxidation current) is smaller than the one experimentally observed for the blank solution under the same experimental conditions. This is inconsistent with the definition of detection limit, thus the IUPAC methodology requires further discussion. The same conclusion can be drawn by the analyses of detection limits obtained with the other techniques studied.

Application of Polysaccharide Hydrogels in Adsorption and Controlled-Extended Release of Fertilizers Processes

This article studied the applicability of poly(acrylamide) and methylcellulose (PAAm-MC) hydrogels as potential delivery vehicle for the controlled-extended release of ammonium sulfate (NH(4))(2)SO(4) and potassium phosphate (KH(2)PO(4)) fertilizers. PAAm-MC hydrogels with different acrylamide (AAm) and MC concentrations were prepared by a free radical polymerization method. The adsorption and desorption kinetics of fertilizers were determined using conductivity measurements based on previously built analytical curve. The addition of MC in the PAAm chains increased the quantities of (NH(4))(2)SO(4) and KH(2)PO(4) loaded and extended the time and quantities of fertilizers released. Coherently, both loading and releasing processes were strongly influenced by hydrophilic properties of hydrogels (AAm/MC mass proportion). The best sorption (124.0 mg KH(2)PO(4)/g hydrogel and 58.0 mg (NH(4))(2)SO(4)/g hydrogel) and desorption (54.9 mg KH(2)PO(4)/g hydrogel and 49.5 mg (NH(4))(2)SO(4)/g hydrogel) properties were observed for 6.0% AAm-1.0% MC hydrogels (AAm/MC mass proportion equal 6), indicating that these hydrogels are potentially viable to be used in controlled-extended release of fertilizers systems. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2291-2298, 2012