F.C.L. Freitas

Manejo de plantas daninhas no consórcio de milho com capim-braquiária (Brachiaria decumbens)

The objective of this work was to evaluate the effects of nicosulfuron and atrazine mixture on weeds, corn and Brachiaria decumbens intercrops, cultivated under no-tillage and conventional tillage. Six nicosulfuron doses (0, 2, 4, 8, 16 and 24 g ha-1) in mixture with atrazine in the dose of 1.500 g ha-1 were evaluated, plus two controls, represented by both species in monocrop. Seminiferous propagation of the annual weeds was efficiently controlled by applying nicosulfuron in 8 g ha-1 in mixture with atrazine, regardless of the management systems. The perennial species (Artemisia verlotorum and Cyperus rotundus), of vegetative propagation, were not controlled by the herbicide mixture, regardless of the applied dose. Larger infestations of these species were observed under the conventional system. B. decumbens biomass was reduced in the intercrop with corn, when compared to its control in monocrop, presenting a greater reduction when submitted to the largest doses of nicosulfuron, in both planting systems. No difference was observed in the production of grains and corn straw, in function of the treatments studied, under both planting systems.

Comportamento de cultivares de milho no consórcio com Brachiaria brizantha na presença e ausência de foramsulfuron + iodosulfuron-methyl para o manejo da forrageira

O objetivo deste trabalho foi avaliar o comportamento de cultivares de milho no cultivo consorciado com Brachiaria brizantha cv. MG5 Vitoria e o efeito da aplicacao de subdose da mistura dos herbicidas foramsulfuron + iodosulfuron-methyl no manejo de B. brizantha, numa area sem interferencia de plantas daninhas, em sistema de plantio direto. Cinco cultivares de milho foram avaliados: um hibrido simples (AGN 30A00), um hibrido simples modificado (30K75), dois hibridos duplos (RG2A e AGN 25A23) e uma variedade (UFV M100), conduzidos em dois sistemas de manejo de B. brizantha: com e sem aplicacao de 30 g ha-1 da mistura comercial de foramsulfuron + iodosulfuron-methyl (300 + 20 g kg-1). O delineamento experimental foi de blocos ao acaso, em parcelas subdivididas, com quatro repeticoes, sendo os cultivares de milho colocados nas parcelas principais e os sistemas de manejo de B. brizantha nas subparcelas. A aplicacao do herbicida foi realizada aos 30 dias apos a emergencia do milho (DAE). Aos 30, 60, 90 e 120 DAE foram efetuadas avaliacoes da massa seca da parte aerea de B. brizantha. Para cultura do milho, na ocasiao da colheita, que ocorreu aos 120 DAE, avaliaram-se a altura de plantas, o estande final e o rendimento de graos. Verificaram-se maiores valores do rendimento de graos de milho para os cultivares 30K75, AGN 30A00 e RG2A. Os hibridos simples (AGN 30A00) e simples modificado (30K75) foram mais competitivos com a forrageira, reduzindo o acumulo de massa seca, em relacao aos hibridos duplos e a variedade. A aplicacao do foramsulfuron + iodosulfuron-methyl reduziu a taxa de crescimento de B. brizantha, sem, no entanto, afetar o rendimento de graos de milho. Com isso, fica demonstrado que a forrageira nao influenciou o rendimento da cultura, com o consorcio implantado em semeadura simultânea.

Efeitos do trinexapac-ethyl sobre o crescimento e florescimento da grama-batatais

The objective of this work was to evaluate the efficiency of doses and application intervals of trinexapac-ethyl on the vegetative growth and flowering of bahiagrass, to reduce clips and improve lawn quality. The experiment was conducted on the campus of the Federal University of Vicosa, in Vicosa-MG - Brazil, from December 1998 to March 1999, in an established lawn. The experiment was arranged in a randomized complete block design, with 13 treatments and four repetitions, distributed in a factorial scheme (6 x 2 + 1), with six doses of trinexapac-ethyl (0.00; 0.25; 0.50; 0.75; 1.00 and 1.25 kg ha-1), applied two and five days after lawn clipping and a control with clipings every three weeks. Evaluations were made at three, six, nine and twelve weeks after clipping for total dry biomass production, and height and number of seedheads. For all the characteristics studied, a direct relationship was verified between the growth regulator trinexapax-ethyl dose increase and the timing of clipping of vegetative and flowering lawn growth. Thus, lawn clipings were avoided for up to 12 weeks by applying 0.75 kg ha-1 of the growth regulator. No application time or trinexapac-ethyl dose effects were observed on the coloration of the lawn.

Eficiência no uso da água e interferência de plantas daninhas no meloeiro cultivado nos sistemas de plantio direto e convencional

The objective of this work was to evaluate the effect of the conventional and no-tillage systems and weed management strategies on water use efficiency in melon crop (Cucumis melo). Thus, an experiment was carried out in a randomized block design in split-plots in Mossoro-RN. The plots were constituted of two tillage systems (conventional and no-tillage) and the sub-plots of three weed management systems (plastic mulch, weeding, and no weeding). Density and dry weight of the weeds at 30 days after transplanting, commercial and total yield and daily consumption of water were evaluated. Irrigation management was performed by the characteristic soil water curve for each cropping system at 15 and 30 cm of depth and water control by daily reading a set of tensiometers installed to keep the soil above 75% of field capacity. Water use efficiency (USA), given in kg of fruit per m3, was determined based on the crops yield and water consumption. It was found that the no-tillage system reduced weed density and dry matter in 86.7 and 61%, respectively, compared to conventional tillage, and weed interference reduced commercial yield by 100% under conventional tillage and 36.5% under no-tillage. Soil with plastic mulch under no-tillage and conventional systems, and straw mulching under no-tillage reduced water consumption by 23% (388.8 m3 ha-1), 21% (363.0 m3 ha-1) and 13% (215.0 m3 ha-1), respectively, compared to the weeding treatment under conventional tillage. Soil with plastic mulch under the two tillage systems, or straw mulching under no-tillage increased the efficiency of water use from the ground without cover. In the no-weeding treatment under conventional tillage, weed interference caused total productivity loss and increased water consumption by 9.6%.

Weed interference in carrot yield and quality.

This work aimed to evaluate weed interference in yield and quality of carrots (Daucus carota). An experiment was carried out in a randomized block design, with four replications. The treatments were composed of six periods of weed control (0-12, 0-24, 0-36, 0-48, 0-60 and 0-72 days after emergence (DAE)). The characteristics evaluated were: yield of commercial roots, total soluble solids (TSS), total titratable acidity (TTA), vitamin C, TSS/TTA ratio and pH of roots. The commercial root yields decreased with weed interference, with weed control being required until 36 DAE. Root TSS rates and vitamin C did not vary with weed interference. The presence of weeds for a longer period increased pH and TSS and decreased TSS/TTA ratios.

Eficiência do triclopyr no controle de plantas daninhas em gramado (Paspalum notatum)

Weeds interfere in the formation, quality and aesthetics of the lawn. Desmodium incanum, and Zornia latifolia, when left uncontrolled, can reach infestation levels that would kill the lawn. Herbicide application is one of the most effective ways of handling weeds in lawn; however, information on the use of these products in lawns is scarce. The objective of this work was to evaluate the efficiency of the herbicide triclopyr in controlling Desmodium incanum and Zornia latifolia in the lawn Bahiagrass (Paspalum notatum). The experiment was developed in a lawn area of the campus of the Federal University of Vicosa, in Vicosa-MG, Brazil, from April to May 2000. The treatments were six doses of triclopyr (0.00; 0.24; 0.48; 0.72; 0.96 and 1.20 kg ha-1) and one dose of the 2,4-D + picloram (0.48 + 0.128 kg ha-1), arranged in a randomized complete block design, with four repetitions. The size of each plot was 12 m² (4.0 x 3.0 m), with the treatments applied in a 2.0 m wide strip, with 1.0 m as lateral check to aid in the visual evaluations. Phytotoxicity evaluations were accomplished at 10 and 20 DAT (days after treatment) and the control level at 15 and 30 DAT, both based on the lateral chek. None of the treatments studied showed damage to the quality of the lawn. Starting with doses of 0.48 and 0.66 triclopyr kg ha-1, controls similar or superior to 90% of Desmodium incanum and Zornia latifolia were obtained, respectively. These results were similar to that of the standard treatment (2,4-D + picloram for 0.48 + 0.128 kg ha-1). It was concluded that triclopyr is a selective herbicide for Bahiagrass, providing excellent control of the weeds studied.

Avaliação agroeconômica das culturas da beterraba e coentro em função da época de estabelecimento do consórcio

Intercropping is a cropping practice widely used in the production of vegetables, and that greatly influences the productivity of these crops, and generates multiple agroeconomic benefits. The aim of this study was to evaluate the yield of sugar beet (Beta vulgaris L.) and coriander (Coriandrum sativum L.) depending on the time of intercropping establishment between these crops. The work was conducted at the Universidade Federal Rural do Semi-arid, Mossoro, RN, during the period from July 2006 to September 2006. The experimental design was of randomized complete blocks with seven treatments and four replications. The treatments consisted of the intercropping of coriander and beet planted at 0, 7 and 14 days after sowing of beet (Treatments 1; 2 and 3), sole crop of beet (Treatment 4) and the sole crops of coriander planted at the same times of intercropping establishment (Treatments 5; 6 and 7). The intercropping of sugar beet with coriander is agronomically feasible, and that this should be planted simultaneously or with the planting of coriander at seven days after sowing of beets, when were also obtained higher values of land equivalent ratio.

Leaching of Sulfentrazone in Soils from the Sugarcane Region in the Northeast Region of Brazil

Sulfentrazone leaching potential is dependent on soil properties such as strength and type of clay, organic matter content and pH, and may result in ineffectiveness of the product and contamination of groundwater. The objective of this study was to evaluate sulfentrazone leaching in five soils of the sugarcane region in the Northeast Region of Brazil, with different physical and chemical properties, by means of bioassay and high-performance liquid chromatography (HPLC) resolution. The experiment was conducted in a split plot in a completely randomized design. The plots had PVC columns with a 10 cm diameter and being 50 cm deep, filled with five different soil classes (quartzarenic neosol, haplic cambisol, yellowish-red latosol, yellowish-red acrisol, and haplic gleysol), and subplots for 10 depths in columns, 5 cm intervals. On top of the columns, sulfentrazone application was conducted and 12 hours later there was a simulated rainfall of 60 mm. After 72 hours, the columns were horizontally placed and longitudinally open, divided into sections of 5.0 cm. In the center of each section of the columns, soil samples were collected for chromatographic analyses and sorghum sowing was carried out as an indicator plant. The bioassay method was more sensitive to detect the presence of sulfentrazone in an assessment for chromatography soil, having provided greater herbicide mobility in quartzarenic neosol and yellowish-red latosol, whose presence was detected by the indicator plant to a depth of 45 and 35 cm, respectively. In the other soils, sulfentrazone was detected up to 20 cm deep. The intense mobility of sulfentrazone in quartzarenic neosol may result in herbicide efficiency loss in the soil because the symptoms of intoxication and the amount of herbicide detected via silica were highest between 15 cm and 35 cm depth regarding the soil surface layer (0-10 cm), indicating that sulfentrazone should be avoided in soils with such characteristics.

Validation and application of a QuEChERS based method for estimation of half-life of imidazolinone herbicides in soils by LC-ESI-MS/MS

A modified QuEChERS (quick, easy, cheap, effective, rugged and safe) method was validated and applied for the estimation of half-lives of two imidazolinone group herbicides, imazethapyr and imazapic, in the Dystric Plinthosol (FX) and Ferralsol (LVA) agricultural soils using liquid chromatography tandem mass spectrometry. The solutions were prepared in a matrix extract to avoid matrix effects. The analytical method showed satisfactory specificity, selectivity, linearity (R2 > 0.99), recoveries (range 85.0-117.0%), with RSD between 6.7% and 16.6%, and precision (range 94.7-108.5%), with RSD between 6.0% and 11.9%. The limit of detections for imazethapyr and imazapic in the soils were 2.2 µg kg-1 and 2.0 µg kg-1, and the limit of quantifications were 6.6 µg kg-1 and 6.1 µg kg-1. The half-lives of imazethapyr (35.7 and 97.9 days) and imazapic (40.4 and 64.4 days), in the FX and LVA soils, respectively, indicate that they are medium-persistence herbicides with possibility of leaching into groundwater. In addition, high concentrations of imazethapyr and imazapic were found in the soil samples after the time of application, meaning that there is a potential for prolonged soil residual activity due to carryover.

Efeito de coberturas do solo sobre a podridão cinzenta do caule em Vigna unguiculata

Universidade Federal Rural do Semiárido UFERSA, Centro de Ciências Agrárias, Campus Mossoró, 59625-900, Mossotró, RN, Brasil. Universidade Federal de Viçosa, Departamento de Fitotecnia, Campus Viçosa, 36570-900, Viçosa, MG, Brasil. Autor para correspondência: Cheyla Magdala de Sousa Linhares (cheyla_magdala@hotmail.com) Data de chegada: 26/04/2017. Aceito para publicação em: 02/01/2018. 10.1590/0100-5405/174041