O manejo das plantas daninhas em sistemas orgânicos de produção agrícola representa um grande desafio aos produtores. Para o enfretamento deste desafio torna-se necessário a exploração de práticas de manejo sustentáveis e o desenvolvimento de novas tecnologias. Ressalta-se que existe alternativas tecnológicas ou biológicas que podem ser utilizadas no manejo das plantas daninhas em sistemas orgânicos, e serem empregadas em grandes áreas. Estratégias culturais, biológicos, mecânicos e físicos de manejo podem ser eficientes no controle das plantas daninhas, bem como reduzir o uso de controle químico na agricultura convencional. Desta forma, esta revisão de literatura teve como objetivo o de apresentar métodos alternativos de controle de plantas daninhas e o potencial uso em áreas orgânicas de produção agrícola. Os métodos de controle das plantas daninhas em áreas orgânicas devem abordar sempre estratégias integradas e de forma sustentável.

Allelopathy contributes to the sustainable management of weeds in growing areas, due to its ability to inhibit the development of weed species. This study aimed to evaluate the allelopathic effect of Pachyrhizus erosus extract on Euphorbia heterophylla and Bidens pilosa germination. The experiment was carried out in a completely randomized design, in a 2 x 2 x 4 factorial scheme, with four replications. The first factor corresponded to the plant portion (shoot and tuberous root), the second to the extract preparation method (water at room temperature and boiling) and the third to the extract concentrations (0 %, 25 %, 50 % and 100 %). Phytochemical analyses were performed to identify the presence of secondary metabolites. The variables germination percentage, germination rate index and dry biomass decreased with increasing aqueous extract concentrations for both E. heterophylla and B. pilosa. When applied a P. erosus crude shoot extract (boiling), decreases of 18 % and 92 % were observed in the E. heterophylla and B. pilosa germination, respectively, with a decrease of 91 % in the dry biomass of E. heterophylla seedlings. The tuberous root extract (boiling), on the other hand, reduced the germination percentages for E. heterophylla and B. pilosa in 18 % and 80 %, respectively. The phytochemical evaluation indicated the presence of flavonoids, coumarins and saponins in the shoot and tuberous root extracts, while tannins were only observed in the shoot extract. Thus, it can be concluded that P. erosus extracts display an allelopathic effect on the weed species evaluated.

Os resíduos gerados no sistema de produção agrícola causam impactos imensuráveis ao meio ambiente. O cultivo e o processamento de culturas como cana-de-açúcar, laranja, açaí e mandioca, geram resíduos como o bagaço da cana-de-açúcar e da laranja, o caroço do açaí e a manipueira da mandioca, os quais podem alterar todo o ecossistema se não submetidos ao tratamento adequado de resíduos. Além de criar potenciais problemas ambientais, representam perdas de matéria-prima e energia, mas também podem proporcionar ganhos em outras atividades se corretamente tratados e/ou descartados. A gestão dos resíduos potencializa o processo de tratamento e a disposição final dos resíduos agrícolas de forma a reduzir os impactos ambientais causados por seus descartes inadequados. Desta forma, este trabalho teve como objetivo realizar uma pesquisa bibliográfica a respeito de resíduos provenientes de atividades agrícolas, bem como mostrar alternativas já existentes, de tratamento e aproveitamento destes resíduos, como forma de reduzir o impacto ambiental destes ao meio ambiente.

Selecting glyphosate-resistant Digitaria insularis may cause changes in the biological cycle of the species. Therefore, the objective of this study was to evaluate the biological cycle of susceptible and glyphosate-resistant D. insularis biotypes in two growth periods (summer/autumn and autumn/winter). Seeds were collected in the municipality of Alagoa Grande (07o02’59" S 35o37’01,5" W), and were considered susceptible (S1), in Cascavel (24o55’27" S 53o27’54.6 ”W) considered as resistant 1 (R1), Entre Rios do Oeste (24o40’44" S 54o17’05" W) considered as resistant 2 (R2) and Marechal Cândido Rondon (24o42’30" S 54o21’10" W) considered as resistant 3 (R3). Evaluations were carried out in the summer/autumn and autumn/winter periods. The collection periods of plants were: 14; 21; 28; 35; 42; 49; 56; 63; 70; 77; 84; 91; 98; 105; 112 and 119 days after emergence (DAE). The selection of glyphosate-resistant D. insularis biotypes in agricultural areas affected the biology of the species, in relation to the original population of the susceptible biotype. In the summer/autumn period (mean temperature 24.6 oC), the S biotype started the emission of tillers and flowering at 14 and 21 DAE on an average, respectively, before the resistant biotypes. However, in the autumn/winter period (mean temperature 19.0 oC) only the R1 biotype was able to develop and complete the biological cycle. The evaluated biotypes presented differences during the development, mainly between the phenological stages, so that the susceptible biotype was the most precocious and with a high reproductive potential. The physiological evaluations showed no differences among the S, R1, R2 and R3 biotypes, as verified in the TCR.

The objective of this work was to evaluate the effect of weed competition on the accumulation of nitrogen and phosphorus in the leaves and on the dry weight of the roots of cassava (Manihot esculenta) in the conventional and no-tillage systems, in two crop cycles. The experiments were carried out in a randomized complete block design, with split-split plots and four replicates. The plots consisted of conventional tillage or no-tillage; the split plots, of the competition or not with weeds; and the split-split plots, of the evaluation periods (0, 25, 50, 75, 100, 125, 150, 175, 200, and 225 days after planting/pruning). In the first cycle, weed competition reduced the accumulation of nitrogen in 82.6 and 81.3% and of phosphorus in 65.7 and 85.3% under conventional tillage and no-tillage, respectively. In the second cycle, the reductions in the accumulation of nitrogen were of 41.1 and 52.4% and of phosphorus of 44.1 and 52.6%, in conventional tillage and no-tillage, respectively. The root dry weight of cassava grown with weed competition showed reductions of 15.8 and 11.2% under conventional tillage and no-tillage, respectively, only in the second cycle. Weed competition reduces the accumulation of nitrogen and phosphorus in the leaves of cassava in the conventional and no-tillage systems in both crop cycles, but reduces the dry matter of cassava roots only in the second cycle.

Companies have sought to improve, more and more, the quality control of the seeds produced, improving tests that evaluate the vigor of the seeds with greater speed and precision. The objective of the present work was to study the effects of imbibition time on the results of the electrical conductivity test to evaluate the vigor of millet seeds and to correlate with the other tests carried out. Six seeds lots of the ADR300 cultivar with different vigor levels were used. Germination, first germination count, accelerated ageing, emergence and emergence speed of seedlings in sand and electrical conductivity with variations in water volume were performed (50 And 75 cm 3 ), during the imbibition time of 2, 4, 6 and 8 hours, at 25 ºC. The time of 2 hours of the seed imbibition in 75 cm 3 in water proved to be efficient to evaluate the vigor of millet seeds in all lots tested.

Plantas de cobertura podem causar a supressão de plantas daninhas devido aos efeitos físicos e alelopáticos produzidos pela palhada. O objetivo deste trabalho foi o de avaliar o manejo da palhada de mucuna-preta (superficial ou incorporada) no controle de plantas daninhas na cultura da alface-crespa. O delineamento experimental foi o de blocos ao acaso, dispostos em parcelas subdividas, com quatro repetições. As parcelas compreenderam os dois sistemas de manejo de palhada da mucuna-preta (superficial ou incorporada) e as subparcelas foram constituídas pela prática da capina manual (com ou sem capina). Os resultados reportaram que não houve redução na massa seca de plantas daninhas com o uso da palhada superficial ou incorporada. No entanto, o manejo com a palhada proporcionou aumento de 27% na área foliar e de 20% na massa seca na cultura da alface-crespa, além de ganhos de 32% na produtividade, quando utilizada de maneira incorporada ao solo e associada à prática da capina. Desta forma, concluiu-se que apesar do pouco efeito na supressão das plantas daninhas, o uso de palhada de mucuna-preta pode proporcionar maior produtividade para a cultura da alface-crespa, especialmente quando incorporada ao solo.

A new cycle of growth begins after pruning of cassava, and weed control is necessary. Thus, this study aimed to evaluate the selectivity and efficiency of sequential application of herbicides alone and in mixture with and without of foliar fertilizer after pruning of cassava. Two experiments were carried out in a randomized block design with four replications. The treatments of Experiment 1 consisted of control without weeding; control with weeding; mesotrione; mesotrione/mesotrione; mesotrione + foliar fertilizer/mesotrione + foliar fertilizer; mesotrione/mesotrione + foliar fertilizer; mesotrione + clethodim; mesotrione + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer; mesotrione + clethodim/mesotrione + clethodim; mesotrione + clethodim/chlorimuron; mesotrione + clethodim/chlorimuron + foliar fertilizer; mesotrione + clethodim + foliar fertilizer/chlorimuron + clethodim + foliar fertilizer; mesotrione + clethodim/chlorimuron + clethodim]. Treatments of Experiment 2 consisted of control without weeding; control with weeding; chlorimuron; chlorimuron + foliar fertilizer/chlorimuron + foliar fertilizer; chlorimuron/chlorimuron; chlorimuron + clethodim; chlorimuron + clethodim + foliar fertilizer/chlorimuron + clethodim + foliar fertilizer; chlorimuron + clethodim/chlorimuron + clethodim; chlorimuron + clethodim/mesotrione + foliar fertilizer; chlorimuron + clethodim/mesotrione; chlorimuron + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer; chlorimuron + clethodim/mesotrione + clethodim. The doses of mesotrione, clethodim, and chlorimuron used in both experiments were 240, 120, and 20 g ha-1, respectively, while 2.5 L of the commercial product Amino Plus® was used as foliar fertilizer. The first application was carried out at 50 days after pruning and the second application at 22 days after the first application. In Experiment 1, the application of mesotrione, mesotrione/mesotrione, and mesotrione + clethodim/mesotrione + clethodim showed selectivity to cassava and were efficient in weed control. In Experiment 2, chlorimuron + clethodim/mesotrione, chlorimuron + clethodim + foliar fertilizer/mesotrione + clethodim + foliar fertilizer, and chlorimuron + clethodim/mesotrione + clethodim were efficient in weed control, but no treatment was selective. The addition of foliar fertilizer to the spray solution did not contribute to increase selectivity.