Períodos de dessecação de urochloa ruziziensis e seu reflexo na produtividade da soja RR

Two field trials were carried out to evaluate the effects of burn-down timing of Urochloa ruziziensis on transgenic soybean establishment and yield under the no-tillage system. One experiment was conducted in Colina, SP - Brazil, in 2007/2008 season, and the other in Jaboticabal, SP - Brazil, 2009/2010 season. In 2007/2008, the experiment was carried out in a 7-year-old grass pasture of U. ruziziensis, with four burn-down timings of vegetation cover being tested 30, 20, 10, and 0 days in advance to soybean sowing. In 2009/2010, the experiment was conducted in an old grass pasture of U. ruziziensis cropped with maize the summer before. After maize harvesting, a natural re-infestation of U. ruziziensis occurred, corresponding to more than 80% of the vegetation cover. In this experiment, treatments corresponded to six burn-down timings of vegetation cover 25, 20, 16, 7, and 0 days in advance to soybean sowing. In all experiments, 1.44 kg a.e. ha-1 of herbicide glyphosate was applied, and the soybean cultivar M-SOY 7908 RR was used. The experiments were arranged in a randomized block design, with four replicates. The evaluations were carried out by measuring crop stand 20 days after sowing and pre-harvest, plant height, first pod insertion height, number of pods per plant, grain yield, and estimated yield. Data were submitted to ANOVA and the Tukey test at 5% of probability. Burn-down of U. ruziziensis performed at the same day of crop sowing reduced plant height, number of pods per plant, and crop grain yield. Burn-down timing of U. ruziziensis using glyphosate was recommended to be between 10 and 20 days in advance to crop sowing. In conclusion, soybean yield was affected by burn-down timing of U. ruziziensis

Influência do resíduo de colheita de cana-de-açúcar sem queima sobre a eficiência dos herbicidas imazapic e imazapic + pendimethalin Sugar-cane harvest residue influence on the efficacy of the herbicides imazapic and imazapic + pendimethalin

Os resíduos deixados sobre o solo por ocasião da colheita mecanizada da cana-de-açúcar podem constituir-se em uma barreira física para a ação dos herbicidas no controle de plantas daninhas, quando aplicados em pré-emergência destas plantas sobre a palha da cana. Em virtude disso, o presente trabalho teve por objetivos analisar e quantificar a interferência dessa camada de palha sobre o solo na ação dos herbicidas imazapic e imazapic + pendimethalin no controle de plantas daninhas em áreas onde a cana-de-açúcar foi colhida mecanicamente sem a queima da palhada previamente à colheita. Foram realizados dois ensaios simultâneos: um com a retirada da palha dois dias após a aplicação dos herbicidas e o outro com a manutenção desta, ambos conduzidos em casa de vegetação. O imazapic isolado foi aplicado nas dosagens de 0, 122,5 e 147 g i.a.ha-1 e em mistura com pendimethalin na dosagem de 75 + 1500 g i.a.ha-1, com simulação de chuvas nas intensidades de 30, 60 e 90 mm. Após análise dos resultados de biomassa seca, altura e número de folhas das plantas de Sorghum bicolor e Cyperus rotundus, além de nota visual e biomassa seca de Panicum maximum, Brachiaria plantaginea, Digitaria horizontalis, Amaranthus viridis, Ipomoea grandifolia e Brachiaria decumbens, constatou-se eficiência proporcional dos herbicidas à dosagem utilizada, independentemente da presença da palha, à exceção de Ipomoea grandifolia e Brachiaria decumbens, além de haver menor controle nos tratamentos submetidos à chuva de 90 mm. Esses resultados indicam boas perspectivas quanto à aplicação destes herbicidas em áreas de colheita mecanizada de cana-de-açúcar sem queima, para controle de plantas daninhas em condições de pré-emergência.The residues left on the soil surface after sugarcane automated harvest, without previous slash-and-burn, constitute a physical barrier against the action of herbicides applied at pre-emergence conditions of the weeds. Thus, this research aimed to analyze and quantify the interference of this crop residue layer left on the soil surface in the action of the herbicides imazapic and imazapic + pendimethalin to control weeds. Two simultaneous assays were performed: one by removing the crop residue two days after herbicide application and the other by maintaining it, both conducted under greenhouse conditions. The imazapic was applied at the rates of 0, 122.5 and 147 g a.i. ha-1 and the mixture with pendimethalin at the a rate of 75 + 1500 g a.i. ha-1, with simulation of 30, 60 and 90 mm rainfall intensity. Analysis of dry biomass, height and leaf number results of the Sorghum bicolor and Cyperus rotundus plants, as well as visual rating and dry biomass of Panicum maximum, Brachiaria plantaginea, Digitaria horizontalis, Amaranthus viridis, Ipomoea grandifolia and Brachiaria decumbens, indicated that weed control efficacy was proportional to herbicide rate, regardless of the presence of crop residue, except for Ipomoea grandifolia and Brachiaria decumbens. There was less control in the treatments submitted to 90 mm rainfall. These results indicate good perspectives in spraying these herbicides in sugarcane automated harvest areas without previous slash-and-burn for weed pre emergence control

Interferência das plantas daninhas no feijoeiro carioca Weed interference in carioca beans (Phaseolus vulgaris)

Este trabalho foi realizado com o objetivo de determinar os períodos de interferência das plantas daninhas na cultura do feijoeiro (Phaseolus vulgaris) plantado em janeiro. A semeadura do cv. Carioca foi feita no sistema convencional e os tratamentos constaram de dois grupos: no primeiro, a cultura do feijão permaneceu livre da interferência das plantas daninhas desde a emergência até 10, 20, 30, 40, 50, 60 e 70 dias (todo o ciclo da cultura); no segundo, a cultura permaneceu sob interferência desde a semeadura até os mesmos períodos descritos anteriormente, totalizando assim 14 tratamentos. O delineamento experimental utilizado foi o de blocos casualizados com quatro repetições. A comunidade infestante foi composta por 13 espécies, com Alternanthera tenella, Blaenvillea rhomboidea e Cenchrus echinatus se destacandodas demais, representando 63,4% do total de indivíduos. O período anterior à interferência (PAI) ocorreu até os 17 dias após emergência da cultura, e o período total de prevenção à interferência (PTPI) ocorreu até 25 dias após a emergência da cultura. A interferência das plantas daninhas durante todo o ciclo de vida do feijoeiro reduziu-lhe a produtividade em 67%.<br>This work aimed to determine the periods of weed interference in 'Carioca' bean (Phaseolus vulgaris) during the dry season. The assay was conducted at the Experimental Farm of the Universidade do Estado de Sao Paulo-UNESP - Jaboticabal. The bean plants were sown under the conventional system. The experimental treatments consisted of two groups: in the first, the bean crop remained free of weed interference from emergence up to 10, 20, 30, 40, 50, 60, 70 days (the entire crop cycle). In the second, the bean crop remained under interference from the time of sowing up to the same periods previously described, totalizing fourteen experimental treatments. The experiments were arranged in a randomized block design with four replications. The weed community comprised thirteen species - with Alternanthera tenella, Blaenvillea rhomboidea and Cenchrus echinatus being the most prominent, accounting for 63.4% of the total. The period prior to weed interference (PPI) occurred up to 17 days after crop emergenceand the total period of interference prevention (TPIP) occurred up to 25 days after crop emergence. Weed interference throughout the crop cycle reduced 67% of its productivity