E.A. Ferreira

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.

Sensibilidade de cultivares de cana-de-açúcar à mistura trifloxysulfuron-sodium + ametryn

The objective of this study was to evaluate the sensitivity of 11 cultivars (SP801842, SP79-1011, SP81-3250, SP80-1816, RB855113, RB835486, RB845210, RB867515, RB928064, RB72454 and RB855536) and four clones (RB947643, RB855002, RB957712 and RB957689) of sugarcane to the pre-formulated mixture of the herbicides trifloxysulfuron-sodium (18.5 g kg-1) + ametryn (731.5 g kg-1), termed Krismat®. Cultivars and clones were cultivated in vases under non-protected environment. In both assays, the herbicide mixture was applied at 60 days after sprouting. In assay 1, the herbicide mixture was applied at a single rate of 2.00 kg ha-1 on all the cultivars and clones, while in assay 2 it was applied at rates of 1.00; 2.00; and 6.00 kg ha-1 on cultivars RB855113 and RB867515. After herbicide application and harvest at 45 days after treatment (DAT), weekly evaluations of phytotoxicity (%),and dry matter were conducted as well. The variables plant height, leaf number, leaf area and dry matter of the aerial part and stalk were evaluated only in the second assay. RB855113 cultivar showed the highest sensitivity to the herbicide mixture; the genotypes SP80-1842, SP80-1816, SP79-1011 and RB957689 showed medium sensitivity and the clones presented good tolerance. For the RB855113 cultivar, the highest toxicity index was observed from 20 to 27 DAT. Reduction of plant height, leaf number, foliar area and dry matter of the aerial part and stalk was observed during this period due to the increase of the product doses. Cultivar RB867515 was tolerant at the lowest herbicide doses. However, it was found to be sensitive, at the highest tested dose.

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.

Densidades de plantas daninhas e épocas de controle sobre os componentes de produção da soja

This work aimed to evaluate the effects of different weed densities on the yield components of soybean grain, cv. BRS 243 RR. The experimental design was arranged in completely randomized blocks, and the treatments consisted of increasing periods of control and three weed densities (low, medium and high). The initial periods of control were: 0, 0-5, 0-10, 0-15, 0-21, 0-28, 0-35, 0-42, 0-49 and 0-125 (harvesting). In low infestation areas, the weed community was composed mainly of Brachiaria plantaginea, Ipomoea nil, Euphorbia heterophylla and others. In medium and high infestation areas, the outstanding weeds were Brachiaria plantaginea, Ipomoea nil, Digitaria horizontalis, Cyperus rotundus and others. B. plantaginea was responsible for the highest dry matter accumulation in all levels of infestation. Regarding the crop yield components, number of pods per plant was the most severely affected by competition, reduced at about 58% in the low infestation area, 71% in the medium infestation area and 78% in the high infestation area. Number of seeds per pod and weight of 1000 grains were less influenced by competition; however, these parameters were reduced, indicating a relation between weed control periods and infestation level with soybean yield component.

Período anterior à interferência na cultura da soja-RR em condições de baixa, média e alta infestação

The aim of this study was to evaluate the period before weed interference in soybean culture, cv. BRS 243-RR, under low, medium and high weed density. The experimental design was arranged in complete randomized blocks, and the treatments consisted of increasing periods of weed control (0, 0-5, 0-10, 0-15, 0-21, 0-28, 0-35, 0-42, 0-49 and 0-125 days). In low weed infestation area the main weed species were: Brachiaria plantaginea,Ipomoea nil,Euphorbia heterophylla. In medium and high infestation areas, Brachiaria plantaginea,Ipomoea nil,Digitaria horizontalis and Cyperus rotundus were the most frequent weeds. Considering 5% and 10% of tolerance of soybean grain yield reduction, it was concluded that the period before interference was 17 and 24 days after emergence (DAE) in low infestation, area 11 and 15 DAE in medium infestation area and 11 and 16 DAE in high infestation area. Weed interference during the full crop cycle reduced soybean grain yield in 73%, 82% and 92%, for low, medium and high weed density, respectively.

Leaf blade quantitative anatomy of sugarcane cultivars and clones

The objective of this study was to make a quantitative assess of the anatomic characteristics of leaf blade of the sugarcane cultivars RB855113, SP80-1842, SP80-1816, RB867515 and clone RB957689 presenting different sensitivity to the mixture of sodium trifloxysulfuron + ametryn herbicides. Compared to the other cultivars assessed, RB855113 cultivar, considered more sensitive to the herbicide mixture, presented relevant differences such as greater proportion of bulliform cells, greater tissue proportion in the transverse section of the leaf blade, greater stomata and trichome density on both surfaces, thinner epidermis on the adaxial surface and length of stomata on both surfaces. The external paraclinal wall of the bulliform cells was thinner than in the common epidermis cells in all the genotypes on the adaxial and abaxial surfaces. Multivariate analysis of the data on the variables considered most relevant to explain the herbicide penetration singled out the sensitive RB855113 from the other materials. Such characteristics can explain the greater penetration, and consequently, greater sensitivity of this cultivar to the sodium trifloxysulfuron + ametryn mixture.

Glyphosate translocation in hairy fleabane (Conyza bonariensis) biotypes

The objective of this work was to evaluate the translocation of glyphosate in C. bonariensis plants resistant and susceptible to that herbicide. The 14C-glyphosate was mixed with commercial gyhphosate (800 g ha-1) and applied on the center of the adaxial face of a third node leaf, using a micro syringe, and adding 10 µL of a solution with specific activity of 1,400 Bq, 45 days after plant emergence. The concentration of the glyphosate translocated in the plant was evaluated at time intervals of 6, 12, 36 and 72 hours after being applied on the application leaf, stem, roots and leaves. Ten hours after treatment application, the distribution of the product in the application leaf, divided into base, center and apex, was also evaluated by measuring the radiation emitted by 14C-glyphosate in a liquid scintillation spectrometer. Greater glyphosate retention was observed in the resistant biotype leaf, approximately 90% of the total absorbed up to 72 hours. In the susceptible biotype, this value was close to 70% in the same period. Susceptible biotype leaves, stem and roots showed greater concentration of glyphosate, indicating greater translocation efficiency in this biotype. In the resistant biotype, the herbicide accumulated in greater quantity at the apex and center of the application leaf, while in the susceptible biotype greater accumulation was observed at the base and center leaf. Thus, it can be stated that the resistance mechanism is related to the differential translocation of this herbicide in the biotypes.

Interferência de plantas daninhas em diferentes densidades no crescimento da soja

Este trabalho foi realizado com o objetivo de avaliar os efeitos de densidades de plantas daninhas (baixa, media e alta infestacao) sobre as variaveis de crescimento da soja, cv. BRS 243RR. O delineamento experimental foi de blocos ao acaso, sendo os tratamentos constituidos por dez periodos de convivencia das plantas daninhas com a cultura (0, 0-5, 0-10, 0-15, 0-21, 0-28, 0-35, 0-42, 0-49 e 0-125 dias). As variaveis estudadas foram altura de plantas, massa seca dos ramos desprovidos de folha, massa seca das folhas, numero de folhas e area foliar da soja. As avaliacoes foram determinadas no final do periodo de interferencia, juntamente com a avaliacao de densidade e acumulo de fitomassa da comunidade infestante. Na area onde a soja foi cultivada sob baixa infestacao de plantas daninhas, observou-se aumento da densidade das infestantes em funcao do tempo apos a emergencia da soja. Todavia, o contrario foi observado nas areas de media e alta infestacao; nelas verificou-se reducao da densidade das plantas daninhas ao longo do periodo de avaliacao. A altura e area foliar das plantas de soja foram influenciadas pelo nivel de infestacao, o que nao foi observado para massa seca e numero de folhas. Conclui-se que o nivel de infestacao afeta de maneira diferenciada as variaveis que definem o crescimento da soja.

Translocação do glyphosate em biótipos de azevém (Lolium multiflorum)

This work evaluated foliar absorption and glyphosate translocation in Italian ryegrass (Lolium multiflorum) susceptible and resistant biotypes, 14C-glyphosate was applied by using a precision micro syringe, and adding 10 µL of solution on the adaxial side of the first leaf with ligule totally visible, when Italian ryegrass plants showed 3 tillers. The quantity of glyphosate absorbed and translocated was evaluated through a liquid scintilation spectrometer by measuring radiation emitted by 14C-glyphosate at 2, 4, 8, 16, 32 and 64 hours after application. The roots and aerial part were analyzed as well as the leaf where application was performed and the solution used to wash the leaf. Glyphosate absorption speed was similar in both Italian ryegrass biotypes, with over 50% of herbicide absorption in the first 8 hours after application. Up to 64 hours, higher retention (81.64%)of glyphosate was observed in the resistant biotype, while only 55% was retained in the susceptible biotype. In the remaining aerial part and roots, a higher amount of glyphosate was absorbed by the susceptible biotype, indicating higher capacity of its translocation. After 64 hours of application, only 6%, of glyphosate was found in the plants, on average indicating that most of the product could be exuded. It could be concluded that Italian ryegrass sensitivity to glyphosate can be attributed to higher translocation capacity of this herbicide by susceptible biotypes.