Growth, nodulation, production, and physiology of leguminous plants in integrated production systems

Abstract Choosing the species suitable for cultivation in intercropped systems is a critical limiting factor for grain and forage production. This study aimed to evaluate the growth, nodulation, production, and physiology of cowpea (Vigna unguiculata) and guandu bean (Cajanus cajan) intercropped with buffel grass (Cenchrus ciliaris) and Eucalyptus urograndis (Eucalyptus grandis × Eucalyptus urophylla) in an integrated production system. Two experiments were conducted simultaneously, arranged in a 2 × 4 factorial scheme. The first factor consisted of the use of two integrated production systems. The second factor consisted of four distances (2, 4, 6, and 8 m) from the eucalyptus planting rows. In the first experiment, crop–forest systems (CFIS: eucalyptus trees and cowpea) and crop–livestock–forest systems (CLFIS: eucalyptus trees, cowpea, and buffel grass) were evaluated. In the second, livestock–forest systems LFIS1 (eucalyptus trees and guandu bean) and LFIS2 (eucalyptus trees, guandu bean, and buffel grass) were evaluated. In cowpea, nodulation was not influenced by production systems and distances, whereas in guandu bean, there was a reduction in the nodules’ number and dry mass with the distance from the trees. Higher growth, biomass production, and photosynthetic activity of cowpea and guandu bean were observed with the increasing distance from the eucalyptus planting rows. However, cowpea increased the 100‐seed weight at 2 and 4 m distances from the eucalyptus rows, improving the grains’ quality close to the trees. The simultaneous cultivation with buffel grass did not affect the leguminous plant yield, promoting greater diversification and increasing the total biomass production of the intercropping

Tolerance of Bradyrhizobium strains to glyphosate formulations

Application of glyphosate to soybean plants, resistant to this herbicide, may be harmful to Bradyrhizobium, the symbiotic bacterium. This study compared the effect of two glyphosate commercial formulations, ZappQi® and Roundup Transorb® with the standard N-(phosphonomethyl) glycine on the growth of four Bradyrhizobium strains under laboratory conditions. Commercial formulations were applied at a concentration of 43.2 μg L−1 of a.e. and the strains were inoculated in yeast extract mannitol (YEM) broth used with or without a mixture of aromatics amino acids (phenylalanine, tyrosine, tryptophan). Herbicide effect on the growth of the Bradyrhizobium strains was assessed by optical density reading in a spectrophotometer. Roundup Transorb® had the biggest effects, probably, because of the presence of ethylamine as a surfactant. Pure glyphosate had minimal effects on Bradyrhizobium strains when aromatics amino acids have been added to YEM broth. Glyphosate application as Roundup Transorb® in the initial stage of soybean development may affect the nodulation process by Bradyrhizobium

Características fisiológicas da soja e espécies de plantas daninhas

Objetivou-se com este trabalho avaliar as características relacionadas à capacidade fotossintética e à eficiência do uso da água de plantas de soja e das espécies daninhas Brachiaria decumbens (capim-marmelada) e Bidens pilosa (picão-preto). B. decumbens quando comparada com as demais espécies apresentou elevada eficiência nas características fisiológicas, como maior concentração de CO2 sub-estomática, temperatura da folha e eficiência do uso da água, e menor condutância estomática e taxa transpiratoria, além de apresentar também maior área e massa seca foliar. Não foram observadas diferenças entre espécies para as características taxa transpiratória, CO2 consumido, pressão de vapor, massa seca total, taxa de crescimento, área foliar específica, razão de área foliar e razão de peso foliar. Conclui-se que a B. decumbens apresenta maior eficiência tanto nas características fotossintéticas, como nas referentes ao uso da água. B. pilosa apresentou características fisiológicas semelhantes à cultura da soja

Physiologic characteristics of corn and Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster in intercropping cultivation

Competition between weeds and crops results in a lower availability of some resources to crop species, which causes deficiencies, such as water and nutritional deficiencies and low light quality or quantity. The aims of this study were to evaluate the effects of Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster, cv. Xaraes (brachiaria) emergence times comparing with corn (Zea mays L.), in addition to the fertilization and application of different nicosulfuron and atrazine herbicides levels, on the physiological characteristics of intercropped species. The physiological characteristics Brachiaria plants that were treated with herbicides were negatively affected. The emergence time of Brachiaria plants in comparison with corn altered the physiological characteristics of both. The Brachiaria plants that emerged before corn presented higher photosynthetic and transpiration rates and reduced the intensity of these characteristics in corn. Thus, the Brachiaria plants that emerged before the corn crop presented a higher physiological efficiency, and they were more competitive than the weeds that emerged during other seasons

Persistence of auxinic herbicides applied on pasture and toxicity for succeeding crops

ABSTRACT The aim of this work was to determine the persistence of auxinic herbicides applied on tropical pasture and toxicity for succeeding crops. The herbicides were applied in an area of dystrophic red‒yellow latosol with pasture infested of weeds. At 40, 80, and 280 days after application of herbicide, the soil samples were collected at depths of 0 to 20 cm. Soil with residues of 2,4-D, 2,4-D + picloram, triclopyr, and a soil without herbicide application were analyzed with six replicates. Seven crops were cultivated in these soils: cucumber (Cucumis sativus L.), velvet bean [Mucuna pruriens (L.) DC.], pigeon pea [Cajanus cajan (L.) Millsp.], alfalfa (Medicago sativa L.), lablab bean [Lablab purpureus (L.) Sweet], corn (Zea mays L.), and sorghum [Sorghum bicolor (L.) Moench]. The plants of cucumber, pigeon pea, and alfalfa were the most susceptible to the auxinic herbicide residues. However, the lablab bean was the only one among the dicot evaluated that showed tolerance to the 2,4-D + picloram residual when cultivated in soils at 280 days after application of herbicide. Corn and sorghum showed lower chlorophyll content in soils with 2,4-D + picloram residual up to 80 days after application of herbicide

Atrazine and nicosulfuron affect the reproductive fitness of the predator Podisus nigrispinus (Hemiptera: Pentatomidae)

Abstract Herbicides can impact non-target metabolic pathways in natural enemies and lead to the reduction of these populations in the field. Behavioral characteristics, morphology and histology of reproductive structures and reproduction of females of Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) were evaluated under the effect of the herbicides atrazine, nicosulfuron and the mixture of both. The number of mature oocytes per ovary was lower in females exposed to the herbicides atrazine, nicosulfuron and the mixture of both. Herbicides did not affect the longevity and mortality of P. nigrispinus, therefore, they are selective for this predator. On the other hand, herbicides can cause sublethal effects by affecting the reproduction of predators

TOXIDADE DE HERBICIDAS A GENÓTIPOS DE CANA-DE-AÇUCAR

Objetivou-se com esse trabalho avaliar a intoxicação de herbicidas a genótipos de cana-de-açúcar, mais cultivados no Brasil. Para isto foi montado experimento em ambiente protegido, em delineamento de blocos casualizados em quatro repetições no esquema fatorial 4 x 8. O fator A foi composto pelos genótipos de cana-de-açúcar (RB925345, RB867515, RB855146 e SP80-1816) e o B pelos; herbicidas aplicados em pós emergência da cultura,  tembotrione ;  MSMA; diuron + hexazinona; sulfentrazone; trifloxysulfuron-sodium; tebuthiuron; clomazone, mais uma testemunha ausente da aplicação de herbicidas. A avaliação de intoxicação da cana-de-açúcar pelos herbicidas em percentagens foi realizada aos 6, 13, 20, 27, 34 e 41 dias após aplicação dos herbicidas, na ultima avaliação efetuou-se a coleta das plantas para secagem em estufa para determinar a massa da matéria seca da parte aérea. A maioria dos herbicidas testados provocou elevados sintomas de intoxicação nos cultivares de cana-de-açúcar, com exceção do tembotrione e do tebuthiuron, onde a injúria foi baixa. De forma geral os genótipos avaliados apresentaram a massa seca total influenciada negativamente pelos herbicidas testados, com destaque para a mistura de diuron + hexazinona e trifloxysulfuron-sodium. Pode-se concluir que todos os genótipos avaliados apresentam algum grau de sensibilidade aos herbicidas testados, variando de acordo com as características do herbicida e do próprio cultivar