Growth inhibition of sourgrass as a function of period of darkness after diquat application

Photosystem-inhibiting herbicides, such as diquat, act by inducing oxidative stress. However, oxidative damage impairs translocation, resulting in regrowth of the plants. The aim was to evaluate the effectiveness of diquat in controlling the growth of sourgrass exposed to different periods of darkness after application of the herbicide, as well as to evaluate the photosynthetic activity and the production of reactive oxygen species. Two experiments (field and greenhouse) were conducted by applying diquat (200 g a.i. ha-1) on sourgrass plants at the 3 to 4 tiller stage. The treated plants were subjected to different periods of darkness after diquat application (0, 1, 2, 3, 4, 5, and 6 h), in addition to the control treatment without any application. Growth inhibition and mass evaluations of the sourgrass plants were performed in both experiments, whereas photosynthetic activity and H2O2 accumulation in the leaves were evaluated in the greenhouse experiment. The results showed an increase in the sourgrass growth inhibition with an increase in the period of darkness after application. There was a need for a minimum of 6 h of darkness after diquat application to fully inhibit growth (100%) of the sourgrass, whereas plants that remained in the sun since application exhibited less than 50% inhibition. The increase in the period of darkness after diquat application resulted in a reduction in photosynthetic activity and, consequently, lower accumulation of H2O2. Thus, the maintenance of sourgrass in the dark for at least 6 h enables total control of the growth of the plants, preventing regrowth.

Herbicide efficacy in the fall management of Richardia brasiliensis, Commelina benghalensis, Conyza sumatrensis AND Digitaria insularis

Other herbicides, alone or in combination with glyphosate, may be effective in controlling Richardia brasiliensis, Commelina benghalensis, Conyza sumatrensis e Digitaria insularis. Therefore, the aim of this study was to evaluate the efficacy of herbicides, alone or in combination, in the control of these weeds in the off-season. Three composite experiments were conducted by applying herbicides, alone or in combinations. Experiments 1 and 2 were conducted in Palotina, State of Paraná (PR), Brazil. Experiment 3 in Iporã, PR, Brazil. The three during fall 2017 in fallow areas after soybean harvest. The experiment was a randomized complete block design with 4 replications and weed control at 7, 14, 21, 28, 35, and 42 days after application (DAA). The control of R. brasiliensis and C. benghalensis was evaluated in the three experiments, the control of C. sumatrensis, in experiments 1 and 2, while the control of D. insularis was evaluated only in experiment 3. Data were subjected to analysis of variance and F-test (p < 0.05). The treatment means values of experiments 1 and 2 were compared by Tukey's test (p < 0.05), and the treatment mean values of experiment 3 were grouped by the Scott and Knott test (p < 0.05). Some herbicide combinations were effective in controlling R. brasiliensis, C. benghalensis, in a single or sequential application. Herbicide combinations were effective in controlling C. sumatrensis with sequential application. Herbicide combinations in a single application did not provide satisfactory final control (≥ 80%) for D. insularis.

Produção de forragem e potencial de utilização do capim faixa-branca submetido a frequências de desfolhação / Production of forage potential of utilization of digit grass subjected to high defoliation frequencies

O objetivo deste trabalho foi avaliar a produção de forragem e o potencial de utilização do capim faixa-branca submetido a frequências de desfolhação. Os tratamentos foram constituídos de quatro frequências de desfolhação: muito alta (25cm), alta (35cm), média (45cm) e baixa (55cm), avaliados em duas épocas do ano (maior e menor insolação), entre 2015 e 2016. Utilizou-se o delineamento em blocos ao acaso, com quatro repetições e medidas repetidas no tempo. A produção diária de folhas foi menor na frequência muito alta em relação às outras frequências. A redução das frequências de desfolhação aumentou a produção diária de colmo, senescência diária de folhas, produção total diária e acúmulo líquido diário de forragem e diminuiu o potencial de utilização da forragem. No período de maior insolação, a produção diária de colmos, o acúmulo líquido diário de forragem e o potencial de utilização de forragem foram maiores e a senescência diária de folhas foi menor. A frequência de desfolhação muito alta não proporcionou um bom desenvolvimento da planta, enquanto a frequência baixa apresentou elevada produção de colmos. As frequências de desfolhação alta e média são mais indicadas para a desfolhação do capim faixa-branca, promovendo uma melhor proporção de folhas em relação a colmos.(AU)

The objective of this study was to evaluate the production of forage and the potential of utilization of digit grass subjected to four defoliation frequencies: very high (25cm), high (35cm), medium (45cm), and low (55cm), evaluated at two times of the year (higher and lower insolation), from January 2015 to January 2016. A randomized-block design with four replicates was adopted and measures repeated over time. The daily production of leaves was lower at the very high frequency in relation to the other frequencies. The reduction in defoliation frequency increased the daily production of stems, the daily leaf senescence, the total daily forage production, and the daily forage accumulation, and decreased the potential of forage utilization. At the time of higher insolation, the daily production of stems, the daily forage accumulation, the potential of utilization of forage were higher, and the daily leaf senescence was lower. The very high frequency of defoliation did not provide a good development of the plan, while the lower frequency displayed a high production of stems. The high and medium frequencies of defoliation are more indicated to the defoliation of digit grass, enabling a better proportion of leaves in relation to stems.(AU)

Alternatives for chemical management of sourgrass / Controle químico de capim-amargoso

Intensive use of Glyphosate has been selected multiple resistant sourgrass biotypes in the areas of intensive agriculture in Brazil. Thus, it is important that viable management alternatives are evaluated for this invasion, which currently is regarded as the main problem of Brazilian agriculture. The study aimed to evaluate strategies for chemical management of sourgrass. Three trials divided according to the weed development stages were performed: Post- Initial (up to tillering), Post-Delayed (one to four tillers) and Adult-Plant (adult stage characterized by the beginning of the reproductive phase). The sourgrass seeds were collected from biotypes with evidence of Glyphosate tolerance in the municipality of Rio Brilhante ­ MS. In each trial were evaluated thirteen treatments and one witness, where the treatments were herbicide mixtures applications with subsequent sequential applications at different dates (7, 10 and 14 days after the first application) and the herbicides application without mixtures. Sourgrass plants are tolerant to Glyphosate and Clethodim herbicides. Formulated mixtures of Paraquat + Diuron and Haloxifop are the most suitable for controlling sourgrass plants derived from seeds, regardless of the control period. Treatments that have the Haloxyfop herbicide in the first application provided better control when compared to the other treatments with mixtures and sequential applications at all stages of applications.

O uso intensivo do herbicida glyphosate tem selecionado vários biótipos resistentes de capimamargoso nas áreas de agricultura intensiva no Brasil. Dessa forma, é importante que sejam estudadas alternativas viáveis de manejo para esta invasora, que hoje é considerada como um dos principais problemas da agricultura brasileira. O trabalho teve como objetivo a avaliação de estratégias para o manejo químico de capim-amargoso. Foram realizados três experimentos divididos em função dos estágios de desenvolvimento da planta daninha: Pós-inicial (até o perfilhamento), Pós-tardio (um a quatro perfilhos) e Planta Adulta de capim-amargoso (estágio adulto, caracterizado pelo inicio da fase reprodutiva). As sementes de Capim-amargoso foram coletadas de biótipos com indícios de tolerância ao herbicida Glyphosate no município de Rio Brilhante ­ MS. Em cada experimento foram avaliados treze tratamentos e uma testemunha, onde os tratamentos foram constituídos por aplicações de misturas de herbicidas com posteriores aplicações sequenciais com diferentes datas de aplicações da sequencial (7, 10 e 14 dias após a primeira aplicação) e pela aplicação de herbicidas sem misturas. As plantas de Capim-amargoso apresentam tolerância aos herbicidas Glyphosate e Clethodim. A mistura formulada dos herbicidas Paraquat + Diuron e o herbicida Haloxifop foram os melhores para o controle de plantas de capim-amargoso provenientes de sementes, independente da época de controle. Os tratamentos que possuem o herbicida Haloxifop na primeira aplicação proporcionaram melhores controles quando comparados aos demais tratamentos com misturas e aplicações sequenciais em todos os estágios de aplicações.

Germination and early growth of soybean, dry bean and turnip grown UNDER Digitaria horizontalis straw / Germinação e desenvolvimento inicial de soja, feijão e nabiça cultivados sob palhada de Digitaria horizontalis

The study aimed to evaluate the possible inhibitory effects of different concentrations of crabgrass (Digitaria horizontalis Willd.) dry mass incorporated to the soil over the germination and early growth of soybean (Glycine max (L.) Merril.), dry bean (Phaseolus vulgaris L.), and turnip (Raphanus raphanistrum L.). The experimental design adopted was completely random, with four replications where, each one was consisted of a 2.5 L capacity pot. Dry mass of crabgrass at equivalent amounts of 0, 2.5, 5.0 and 10 t ha-1 were incorporated into the soil. Crops seedling emergence was checked daily, and germination, speed germination index, mean germination time, relative frequency and synchronization index of germination were computed at the final of 10 days .The height and dry mass of plants were evaluated at 35 days after sowing. The incorporation to the soil of D. horizontalis dry mass caused significant reduction of the height and dry weight of soybean, dry bean and turnip, but were not observed consistent influence over the germination of these species.

Indicadores clínicos como respuesta a la suplementación parenteral en vacas Brahmam primíparas durante la pretemporada de monta / Clinical indicators as a response to parenteral supplementation in first calf brahman cows during the pre-season breeding

El objetivo del presente estudio fue evaluar indicadores clínicos, en respuesta a la suplementación parenteral pretemporada de monta en 32 vacas Brahman de primer parto, pertenecientes a la Estación Experimental La Cumaca, distribuidas al azar en dos grupos de tratamientos: 1) Grupo experimental (GE; n=16) con suplementación parenteral (SP) y 2) grupo control (GC; n=16) sin suplementación. La alimentación basal fue a pastoreo con Panicum maximun, Cynodom niemfluenses, Digitaria swazilandensis y Brachiaria decumbes; concentrado comercial (18 por ciento PC; 2 kg/vaca/día) y mezcla mineral ad-libitum. Se evaluaron los indicadores clínicos: glucosa (Glu), colesterol total (CT), fructosamina (Fru), proteínas totales (PT), albúmina (Alb) y hematocrito (Hto), a los 32, 25, 18 y 7 días pretemporada de monta (DPT). Los datos fueron analizados a través del análisis de la varianza de Mínimos Cuadrados y, se utilizó la prueba de Tukey para la comparación de medias mediante el programa SAS 6.0. No se observaron diferencias significativas en Glu, Fru y CT, no obstante, se obtuvo un efecto significativo (P<0,05) en la Alb a los 25 DPT, (31,43 vs 35,70 g/L) en las vacas del GC y GE, respectivamente, lo que refleja un balance más estable del metabolismo protéico en las vacas del GE, posiblemente por la ación de la suplementación parenteral.