Fabiane Pinto Lamego

Habilidade competitiva de cultivares de trigo com plantas daninhas

Competitive ability is an important tool for integrated weed management. The objective of this work was to evaluate the potential of wheat cultivars in competing with the weeds Italian ryegrass and wild radish, at different periods of coexistence. The experiment was arranged in a randomized block design, in a factorial scheme 4 x 2 x 3, with three replicates. The following wheat cultivars were allocated in Factor A: BRS Guamirin - short cycle and short plant height; Fundacep Cristalino - short cycle and medium plant height; Fundacep Raizes - medium cycle and medium plant height; and BRS 296 - short cycle and tall plant height. In Factor B, absence or presence of weed control, and in Factor C, weed management time (throughout the crop cycle or until pre-harvest, up to 15 days after seeding and 30 days after seeding - DAS). The Fundacep Cristalino cultivar - short cycle and medium plant height- showed more competitive ability than the Italian ryegrass and wild radish, compared to the other cultivars, in all the periods evaluated. Weed control in wheat must be performed early, especially for cultivars with lower competitive ability.

Manejo de Conyza bonariensis resistente ao glyphosate: coberturas de inverno e herbicidas em pré-semeadura da soja

Conyza bonariensis became the main weed in soybean crop in Southern Brazil, as a consequence of the evolution of resistance to the herbicide glyphosate. The objective of this work was to evaluate the effect of different winter cover crops and the association of burn-down herbicides on the control of glyphosate-resistant C. bonariensis. A field experiment was conducted in the 2010/2011 season. The treatments were arranged in a split-plot scheme, with the winter cover crops lopsided oat, radish, common vetch, Italian ryegrass, wheat, and fallow in the main plots, and in the subplots, the following burn-down treatments: glyphosate (720 g e.a ha-1), glyphosate (720 g e.a ha-1) + 2,4-D (1.050 g e.a ha-1), glyphosate (720 g e.a ha-1) + 2,4-D (1.050 g e.a ha‑1)/paraquat (200 g i.a ha-1) + diuron (100 g i.a ha-1), glyphosate (720 g e.a ha-1) + chlorimuron-ethyl (80 g i.a ha-1), glyphosate (720 g e.a ha-1) + chlorimuron-ethyl (80 g i.a ha-1)/paraquat (200 g i.a ha-1) + diuron (100 g i.a ha-1) and mowing. Radish was the cover crop species that produced the highest amount of shoot dry mass during the winter season, while common vetch had the highest suppressive effect on germination and initial development of C. bonariensis. Associations of glyphosate with 2,4-D or chlorimuron-ethyl, followed by the sequential application of paraquat + diuron, caused the highest reductions in C. bonariensis infestation.

Interceptação da radiação luminosa pelo dossel de espécies florestais e sua relação com o manejo das plantas daninhas

The energy of solar radiation absorbed by the plants is a decisive factor of the photosynthesis tax and it can limit the production, the biomass accumulation and the development of the plants. The objective of the research was to evaluate the interception of the luminous radiation and her relationship with the need of handling undesirable plants through crowning and mowing, in the forest species: Acacia mearnsii De Wild, Eucalyptus grandis W. Hill ex Maiden, Mimosa scabrella Benth e Ateleia glazioviana Baill, submitted at levels spacing: 2,0x1,0m; 2,0x1,5m; 3,0x1,0m and 3,0x1,5m. The measurement of the luminous radiation was accomplished monthly during the period from 0 to 360 days after the planting. The points of samplings were among the plants in the line and in the planting among-line. The crowning and mowing were not necessary when the levels of interception of radiation photosynthesis activate were larger than 60%. However, they became necessary starting from the second month after the planting and with a frequency of 60 days for all the species until the first 180 days. The crowning was spared for the species E. grandis starting from the 210 days and for A. mearnsii and M. scabrella after the 240 days after the transplant. Cleared was given only for the species E. grandis in the spacings 2,0x1,0m and 2,0x1,5m starting from the 210 and 240 days after the planting, respectively.

Plant arrangement and soybean cultivar roles in weed interference results

The use of a soybean cultivar with competitive ability combined with an equidistant plant population distribution can enhance the competitive ability of crops against weeds. Two field experiments were carried out at the Agronomic Experimental Station of the Federal University of Rio Grande do Sul, in Eldorado do Sul-RS, during the 2001/2002 growing season, aiming to characterize the contribution of the cultivar and row spacing to soybean competitiveness against weeds. Experiment 1 tested the competitive conditions expressed by the presence or absence of the soybean cultivar FUNDACEP 33 simulating the weed, row spacing (25 and 50 cm) and six reacting soybean cultivars. Experiment 2 tested the competitiveness conditions expressed by the presence or absence of dicotyledonous weeds, row spacing (25 and 50 cm) and soybean cultivars (IAS 5 and FEPAGRO RS 10). Besides ranking among the best producing cultivars, FEPAGRO RS 10 shows characteristics of a plant able to compete with weeds, especially taller weeds with higher dry matter and foliar mass ratio, providing a better soil coverage. Reduced row spacing allows earlier soybean soil coverage, decreases weed population and dry matter, and maintains or increases soybean grain yield.

Dessecação pré-colheita e efeitos sobre a produtividade e qualidade fisiológica de sementes de soja

The anticipation of soybean harvest is possible with the use of pre-harvest burn-down practice, which reduces the time of permanence of seeds in the field, after reaching physiological maturation. The objective of this work was to evaluate the effect of time of application of the herbicide paraquat as burn-down during soybean pre harvest on yield and physiological quality of the seeds. The work consisted of two steps: one field experiment, conducted in Jaboticaba-RS, in 2010/2011 and the analysis of the physiological quality of seeds. The treatments consisted of three times of paraquat (240 g a.i. ha-1) application, R6, R7.1 and R7.3, as well as one untreated (without burn‑down). Yield grains and yield components were evaluated. Seed quality analysis was conducted at the Seed Production and Technology Laboratory of UFSM, Campus of Frederico Westphalen, RS, where the following evaluations were carried out : germination, first germination count, root and shoot weight, shoot dry mass of seedlings, accelerated aging, electrical conductivity, field emergence and emergence velocity index. Paraquat application as burn-down practice in soybean pre harvest, at the R6 and R7.1 soybean stages, causes high yield loss in soybean crop. Burn-down without potential yield loss is only viable after R7.3 soybean growth stage. Seeds originated from plants which received paraquat application in R6 and R7.1, show a superior percentile of germination and a higher germination velocity. However, seeds from plants which received paraquat at stage R6 have less seed vigor.

Vinhaça como fonte de potássio: resposta da sucessão aveia-preta/milho silagem/milho safrinha e alterações químicas do solo na Região Noroeste do Rio Grande do Sul

A vinhaca, residuo do processo de destilacao do alcool e rica em potassio (K) e sua aplicacao ao solo pode aumentar a disponibilidade do nutriente, mas tambem provocar alteracoes nas propriedades quimicas do solo. O trabalho objetivou avaliar a viabilidade tecnica da utilizacao da vinhaca como fonte alternativa de K na sucessao aveia preta/milho silagem/milho safrinha, alem de possiveis alteracoes em atributos quimicos do solo na camada de 0-10cm. O experimento foi conduzido no Municipio de Ajuricaba (RS), no periodo 04/2010 a 06/2011. Os tratamentos utilizados foram: T1) adubacao mineral NPK; T2) N + P sem vinhaca; T3) N+P+50m3 ha-1 de vinhaca; T4) N+P+100m3 ha-1 de vinhaca; T5) N+P+150m3 ha-1 de vinhaca; e T6) N+P+200m3 ha-1 de vinhaca. Na aveia preta, foram avaliados os teores totais foliares de P, K e o acumulo de materia seca. No milho silagem, a altura de plantas, altura de insercao da espiga e a produtividade de forragem e, no milho safrinha, o peso de mil sementes e a produtividade de graos. Quanto aos atributos quimicos do solo, foi avaliado o pH, os teores de P, K, Ca, Mg e a capacidade de troca cationica. Na aveia-preta, as maiores doses de vinhaca proporcionaram os menores acumulos de materia seca, sendo 100m3 ha-1 a melhor dose observada. Para a cultura do milho, a dose de 100m3 ha-1 de vinhaca proporcionou produtividade de silagem semelhante a adubacao mineral e foi capaz de suprir a necessidade de potassio tambem para o cultivo do milho safrinha. Em relacao aos atributos quimicos do solo, nao se observaram alteracoes significativas na camada avaliada (0-10cm). A utilizacao da vinhaca como fonte de potassio mostrou-se uma alternativa tecnicamente viavel e a sua utilizacao em nivel de lavoura uma forma de descarte desse residuo.

Épocas e parcelamentos da adubação nitrogenada aplicada em cobertura na cultura do feijoeiro, grupo comercial preto e carioca, em semeadura direta

The research had as objective to evaluate what is the better time of N application and what is the partition of nitrogen fertilization to be used in no tillage system, in bean cultivars of black and carioca commercial groups. The experiment was conducted in Jaboticaba city - RS. The treatments were N application, using urea as nitrogen source, in one dose (100%) in the time: seedling emergence, at 7, 14, 21, 28 and 35 days after emergence (DAE) and according to the following partition combinations: 50%+50%, 30%+70 and 70%+30% of the dose in each time, totalizing 36 treatments. The variables evaluated were: plant height (cm); number of nodes of principal stem; number of nodes m-2; number of pods plant-1; number of pods m-2; number of grains pod-1; base height of the first pod from the soil; insertion height of the first pod; and 100 grains mass and productivity. It is concluded that the better time of application and partition was 30% of the dose at 7DAE + 70% at 35DAE differing of the suggestions proposed by the actual N recommendations for bean crop. And that the application of 100% of the N dose, at the seedlings emergence, presented the lowest productivity does not showing be promising to the bean groups studied.

Teste rápido de imersão foliar de Euphorbia heterophylla para confirmação de resistência a herbicidas inibidores da Protox e da ALS

Tests to verify resistance (R) vary according to time of execution and degree of complexity, and the efficacy of rapid and simple methods to confirm weed resistance to herbicides must be determined. Two experiments were simultaneously carried out in a completely randomized design, under laboratory conditions, by submerging leaves of E. heterophylla susceptible and with multiple resistance to ALS-and PPO inhibitors in herbicide solutions. The aerial part of the plants was submerged in herbicide solution at different concentrations of imazethapyr, imazapyr, and nicosulfuron (ALS inhibitors), and fomesafen, lactofen and carfentrazone (PPO inhibitors). S biotype control increased with time and commercial ratings of ALS and PROTOX inhibitors had an effective control. The R biotype showed different levels of resistance as a function of the herbicide and variable evaluated. The results confirm that leaf immersion technique is adequate to discriminate S biotypes from those with multiple resistance to ALS and PPO inhibitors. The technique proved to be quick enough for early detection of resistance, allowing the adoption of measures to deal with resistance during the same season.