M.R. Reis

Avaliação de formulações de glyphosate sobre soja Roundup Ready

This study aimed to evaluate the effects of three glyphosate formulations (Roundup Ready® and R. Transorb® - both with isopropylamine salt and Zapp Qi®, formulated as potassium salt), on transgenic soybean. CD 219RR variety soybean plants displaying the CP4Epsps gene, tolerant to glyphosate, were cultivated. At 25 days after emergence (DAE), when plants showed the second trifolium completely expanded (stadiums V2-V3 ), formulations were applied at 2,000 g ha-1 . Plants intoxication was evaluated 15 days after application as well as the number and dry matter of leaflets, number of radicular nodules and foliar content of N, P, K, S, Ca, Mg, Fe, Cu, Zn, and Mn at flowering and grain yield at the end of the cycle. Soil basal respiration rate, microbial biomass carbon and metabolic quotient were evaluated through soil samples collected during soybean flowering. Isopropylamine salt, present in the Roundup Transorb formulation, was more harmful to the soybean plants, also providing a negative effect on the soil microbiota. Roundup Ready formulation, registered as transgenic soybean, should not be applied on this crop at a higher rate, since it could alter the content of some nutrients, such as N, Ca, Mg, Fe and Cu, besides causing intoxication in the plants.

Persistência de sulfentrazone em Argissolo Vermelho-Amarelo cultivado com cana-de-açúcar

The objective of this study was to evaluate sulfentrazone persistence in Typic Hapludalf and its effect on the microbiota of soil cultivated with sugar-cane. The treatments consisted of herbicide application only in 2003, in 2003 with reapplication in 2004 and control without herbicide. Herbicide distribution in the soil profile (0-10 and 10-20 cm of depth) and persistence in 467/24, 517/74, 550/107 and 640/197 days after application (DAA), were studied in the split-plots and split-split-plots, respectively. Indirect quantification of the residues was accomplished by bioassay and C-CO2 evolution together with microbial biomass (CBM) determination were evaluated in soil collected 640/197 DAA. Reduction of dry mass of the aerial part of Sorghum vulgare was verified during the entire evaluated period when the herbicide was applied in 2003 and reapplied in 2004. Most of the residues were detected at the depth of 010 cm, with their leaching potential in the soil being of little significance under environmental conditions. Sulfentrazone influenced the evolution of C-CO2 and CBM of the soil, with the largest accumulated value of C-CO2 being observed for the treatment without herbicide application. Sulfentrazone presented high persistence in PVA, with a negative effect on soil microorganisms, but without posing leaching risks in its profile.

Atividade microbiana em solo cultivado com cana-de-açúcar após aplicação de herbicidas

The objective of this work was to evaluate the impact of the herbicides ametryn and trifloxysulfuron-sodium, singly or combined, and 2,4-D, on respiratory rate, microbial biomass, and metabolic quotient on sugar cane-cultivated soil. A completely randomized design was adopted in a split-plot scheme with four replications. The effect of the herbicides was evaluated in the plots and the effect of time after herbicide application in the split-plots. The herbicide doses, in kg ha-1, were: 1.30 (2,4-D), 1.00 (ametryn), 0.0225 (trifloxysulfuron-sodium), and 1.463 + 0.0375 for the mixture ametryn + trifloxysulfuron-sodium,, respectively. At 60 days after shoot emergence, the herbicides were sprayed on the sugarcane plants. At 15, 30, 45, and 60 days after herbicide application, rhizospheric and non-rhizospheric soil samples were collected and analyzed for respiratory rate (RR) microbial biomass (MB), metabolic quotient (qCO2), and total C-CO2 evolved from the soil (TCE). Ametryn applied singly or combined with trifloxysulfuron-sodium led to higher RR, while 2,4-D alone had little influence on this variable. Higher TCEs were verified in the soils of the treatments with trifloxysulfuron-sodium, ametryn, and with the compounds combined. Soil MB was reduced in the presence of ametryn applied singly or combined. These treatments resulted in higher values of qCO2 at 45 and 60 days of application, respectively.

Potencial competitivo de biótipos de azevém (Lolium multiflorum)

The objective of this work was to evaluate the competitiveness of ryegrass biotypes resistant and susceptible to glyphosate, as well as their interference in wheat growth at different densities. At harvesting, 50 days after emergence, tillering, height, and leaf area of ryegrass plants were evaluated and shoot and roots of ryegrass and wheat were collected and their root, stalk and leaf dry mass was determined. Based on the data, the following variables were evaluated for ryegrass and wheat: crop growth rate (TCC = MSA/Ndays), with MSA being shoot dry mass and Ndays the number of days between emergence and plant harvesting; specific leaf area (SLA = Af /MSf),with Af being the leaf area and MSf leaf dry mass; and leaf area index (IAF = Af/St), St being soil area, indicating leaf area per soil area. Plant height, dry mass and leaf area of the susceptible ryegrass showed smaller reductions and better phenotypic plasticity, in function of the increasing density per soil area, compared to the resistant one. The susceptible biotype showed to be more competitive and its interference in wheat development was more visible at lower densities. It was concluded that the susceptible ryegrass biotype is more competitive than the resistant one.

Crescimento de cultivares de café arábica submetidos a doses do glyphosate

This study evaluated the effects of glyphosate on the growth of three arabica coffee cultivars. A factorial (3xa0xxa05) was arranged in a randomized block design with four replications, with treatments consisting of three coffee varieties: Catucai Amarelo (2xa0SL), Oeiras (MG-6851) and Topazio (MG-1190) and five glyphosate doses (0, 57.6, 115.2, 230.4 and 460.8xa0 gxa0 ha-1 ). The herbicide was applied when the coffee plants reached 21xa0pairs of leaves, before reaching their upper third ones. At 45 and 120 days after glyphosate application (DAA), increase in leaf area, stem diameter, number of leaves and plagiotropic branches was evaluated, being initially measured on the day the herbicide was applied, and plant intoxication rate at 10, 45 and 120xa0DAA. Dry matter of leaves, roots and stem, and root length and density were measured at 120xa0DAA. Symptoms of coffee plant intoxication caused by glyphosate were similar in different cultivars, being characterized by chlorosis and leaf narrowing. Increase in the number of leaves, plagiotropic branches and stem diameter, regardless of the cultivar, was not affected by glyphosate. Cultivar Topazio was the most sensitive to glyphosate, in terms of accumulation of leaf area, root dry matter and root density.

Dinâmica de nutrientes em tecidos foliares de cana-de-açúcar após aplicação de herbicidas

The objective of this work was to evaluate the impact of the herbicides ametryn and trifloxysulfuron-sodium, alone or combined, and 2,4-D, on mineral nutrition and growth in sugar cane plants. Sugar cane plants with three to four fully expanded leaves were sprayed with ametryn, trifloxysulfuron-sodium, and ametryn + trifloxysulfuron-sodium at the doses of 1.30; 1.00; 0.0225, and 1.463 + 0.0375 Kg ha-1, respectively. A completely randomized design was adopted in a split-plot scheme with four replications. Herbicide effect was evaluated in the whole plots and the effect of time after application in the split-plots. At 15, 30, 45, and 60 days after spraying (DAA), leaf tissue samples were collected and analyzed for height and dry mass of the shoots, number of leaves and tillers, and foliar concentrations of macro and micronutrients of sugar cane plants. The leaf concentrations of N, P and Mg were not affected by herbicide use. After herbicide spraying, increase in the accumulation rate (coefficient b0) of the cationic nutrients Ca, Mg and K, was observed in the plants treated with ametryn + trifloxysulfuron-sodium. When 2,4-D was applied, a reduction in the accumulation rate of the S and alteration in the dynamics of the nutrients Mg, Ca and K were verified in relation to the other treatments. The herbicides reduced the iron concentration in sugar cane plants to 15 DAA, in the following order: ametryn+trifloxysulfuron-sodium > ametryn > trifloxysulfuron-sodium > 2,4-D. At 60 DAS, trifloxysulfuron-sodium led to increase of 22.10% in biomass accumulation of the sugar cane shoots in comparison to the control treatment without herbicide application. The number of tillers plants treated with trifloxysulfuron-sodium was double in relation that of those treated with ametryn, evidencing negative effect ametryn. This work evidences herbicide effects on the concentration of leaf nutrients and growth of sugar cane plants.

Ação de herbicidas sobre microrganismos solubilizadores de fosfato inorgânico em solo rizosférico de cana-de-açúcar

The objective of this work was to evaluate the impact of the herbicides ametryn and trifloxysulfuron-sodium, singly or combined, and 2,4-D, on the activity of inorganic phosphate-solubilizing microorganisms and the populational density of fungi and bacteria in sugarcane rhizosphere. Sugarcane plants with three to four fully expanded leaves and fungi were sprayed with ametryn, trifloxysulfuron-sodium, and ametryn + trifloxysulfuron-sodium at the doses of 1.30, 1.00, 0.0225 and 1.463 + 0.0375 kg ha-1, respectively. A completely randomized design was adopted in a split plot scheme with four replications. The effect of the herbicides was evaluated in the whole plots and the effect of time after application in the split-plots. At 15, 30, 45, and 60 days after spraying (DAS), rhizospheric and non-rhizospheric soil samples were collected and immediately analyzed for the populational densities of bacteria and fungi and the potential and relative inorganic phosphate solubilization activity in the soil. 2,4-D reduced the bacterial density in the soil for all the evaluation times, densities of bacterial populations in the rhizosphere for all periods of time showing a higher sensitivity of this group to this compound. At 15 DAS, all herbicides tested reduced the number of fungi in the soil. Trifloxysulfuron-sodium and 2,4-D led to higher inorganic phosphate solubilization at 15, 30, and 45 DAS, and 15 and 30 DAS, respectively, without affecting microbial biomass. The highest relative inorganic phosphate solubilization was observed in the soils treated with ametryn + trifloxysulfuron-sodium. This work showed that herbicide application on sugarcane shoots affects the number of microorganisms and phosphate solubilization activity in the rhizosphere.

Glyphosate no controle de biótipos de azevém e impacto na microbiota do solo

This study aimed to evaluate the resistance Italian ryegrass (L. multiflorum) against glyphosate and the impact of the control of these biotypes on soil respiration and microbial biomass. Two essays were conducted: the first evaluated intoxication and dry mass of the plants of biotypes of three Italian ryegrass population (population 1 - resistant; population 2 - intermediary resistance; and population 3 - sensitive to glyphosate) submitted to different glyphosate rates. The second assay evaluated dry matter of the aereal part, plant height, number of leaves and respiration and microbial mass of the soil cultivated with the resistant and sensitive biotypes, with and without glyphosate application (480 g ha-1). At 14 DAA, death of the susceptible biotype was observed, when treated with rates starting from 200 g ha-1 of glyphosate. The resistant ad intermediate resistant biotypes showed glyphosate phytotoxicity of 85% at the highest rate evaluated. The resistant biotype presented the highest dry matter production of the aerial part at 42 DAA and during sprouting, at 72 DAA, compared to the intermediary biotype. The sensitive biotype presented higher plant height, number of leaves and dry mass of the aerial part, to the resistant biotype, without glyphosate. No difference was observed in the microbial activity in the soil among the treatments.

Effect of herbicides on raw the matter quality of sugarcane genotypes

The objective of this study was to evaluate the effects of ametryn, trifloxysulfuron-sodium and ametryn + trifloxysulfuron-sodium mix on the raw matter quality of sugarcane genotypes. The experiment was conducted in the field, in a Paleudult, using a split-plot design with fourxa0replications. The herbicides ametryn (2.000 g ha-1), trifloxysulfuron-sodium (22.5 g ha-1) and the commercial mixture of ametryn + trifloxysulfuron-sodium (1.463 + 37,0 g ha-1), applied in post initial emergence of the crop, plus a hoed control, were allocated in the plots. Ten sugarcane genotypes were arranged in the split-plots: RB72454, RB835486, RB855113, RB855156, RB867515, RB925211, RB925345, RB937570, RB947520 and SP80-1816. A harvest time, 430xa0 days after planting, the following characteristics were assessed: total soluble-solids (Brix), broth purity, fiber, apparent sucrose and sugar and stem productivity, regarding the raw matter quality of the genotypes. To facilitate interpretation of the results, all the evaluated characteristics were converted into percentages in relation with the hoed control (no herbicide). Different herbicide effects on the genotypes were observed, with RB855156 and RB835486 presenting the lowest stem and sugar yield. Among the herbicides, trifloxysulfuron-sodium had the greatest influence on these characteristics. There was a decrease in stem and sugar yield in genotype RB855113 treated with the mixture (ametryn + trifloxysulfuron-sodium). None of the genotypes was affected by the herbicide ametryn, when applied alone.

Distribuição de glyphosate e acúmulo de nutrientes em biótipos de azevém

This work aimed to evaluate nutrient accumulation and glyphosate translocation in ryegrass biotypes. Two trials were conducted: in the first, 10 uL of 14C-glyphosate ware applied on the upper side of the first leaf showing completely visible ligule, with ryegrass plants at the three-tiller stage. The amount of glyphosate absorbed, translocated and exudated was evaluated 64 hours after application, by using a liquid scintillation spectrometer. Glyphosate was quantified in the leaf it had been applied, in the tillers, roots and in the nutritive solution the plants were grown. In the second trial, glyphosate was applied on the resistant and the susceptible biotypes at the rate of 480 g L-1. Ten days after application, the shoot and roots were collected and oven-dried and the levels of macronutrients were determined. In the first trial, root exudation was observed in both biotypes, in which the amount of exudated glyphosate was similar and not greater than 5% of the absorbed glyphosate. In the main tiller of the susceptible biotype, a higher concentration of 14C-glyphosate was observed, compared to the resistant one. The resistant biotype showed more glyphosate accumulation in the leaf it had been applied and in the susceptible biotype; most 14-C glyphosate was found in the root system. In the second trial, the susceptible biotype showed less P accumulation than the resistant one. Both the resistant and susceptible biotypes tended to accumulate more total N and inorganic N in the shoot and in the whole plant in the absence of glyphosate, compared to the applied treatments. Both biotypes presented the same absorption capacity and macronutrients accumulation in the absence of the glyphosate.