P.V. Silva

Mapas de infestação de plantas daninhas em diferentes Sistemas de colheita da cana-de-açúcar

The objective of this work was to identify the differences between the seedbank of a sugarcane field harvested mechanically and a that of a burned sugarcane field, using precision agriculture techniques. The soil sampling for seedbank determination were performed using a 2 ha regular sampling grid. The weed infestation maps were obtained by the kriging interpolation technique. The green sugarcane field presented lower weed infestation potential compared to the burnt sugarcane field, specially the monocotyledonous species. However, some dicotyledonous species can be selected, such as the Ipomoea. It was concluded that precision agriculture can be useful tool for determination of weed infestation maps and that sugarcane straw can be used as a suppression factor for various species.

Potencial de lixiviação de herbicidas no solo submetidos a diferentes simulações de precipitação

The objective of this work was to evaluate the influence of rainfall on leaching of herbicides recommended for sugarcane crop in Dystrophic Red Latosol. The experiment consisted in spraying trifloxysulfuron-sodium + ametryn (1463 + 37 g ha-1), imazapic (84 g ha-1), imazapyr (200 g ha-1), 1diuron + hexazinone (1170 + 330 g ha-1) and 2diuron + hexazinone (1330 + 160 g ha-1) on top of PVC columns filled with soil. After spraying, simulated rainfall of 20, 40 and 80 mm was applied on top of the columns. Cucumis sativus (cucumber) was used in bioassays to detect herbicide leaching, with evaluations accomplished 14 and 21 days after application of the treatments. After a 20 mm rainfall simulation, it was verified that the trifloxysulfuron-sodim + ametrin mixtures caused decreasing symptoms of toxicity in the 0 to 20 cm plantules, while the other herbicides had an effect up to 10 cm. The 40 mm rainfall made the mixtures1,2 diuron + hexazinone cause severe symptoms in the cucumber plants at 15 cm depth and decreasing symptoms at depths of 20 cm (formulation 2) and 25 cm (formulation 1). The herbicides trifloxysulfurom sodium + ametryn and imazapyr were detected up to 20 cm of depth. The herbicide imazapic caused toxicity up to 15 cm of depth. At 80 mm rainfall, 1diuron + hexazinone caused toxicity up to 30 cm and 2diuron + hexazinone, imazapyr, trifloxysulfuron sodium + ametryn and imazapic presented toxicity up to 25 cm of depth. It was concluded that all the herbicides evaluated tend to be leached under the influence of rainfall or artificial irrigations.

Eficiência de herbicidas pré-emergentes após períodos de seca

This work aimed to study the effectiveness of pre-emerging herbicides after drought periods in two soil types. Two simultaneous experiments were carried out under greenhouse conditions: in the first, the herbicides (trifloxysulfuron-sodium + ametryn - 351 + 99 g ha-1) + (diuron + hexazinone - 1097 + 27,77 g ha-1), trifloxysulfuron-sodium + ametryn - 1463 + 37 g ha-1, diuron + hexazinone - 1170 + 330 g ha-1, imazapyr 200 g ha-1 and imazapic - 122,5 g ha-1 were applied in vases containing samples of Dystroferric Red Latosol (clay texture); in the second, the doses were adjusted in function of the organic matter and clay level of the soil and applied in vases with samples of Distrophic Red Latosol (medium texture). In each experiment, the species Cucumis sativus and Sorghum bicolor were used as bioindicators and 6 drought periods after herbicide applications (0, 10, 20, 40, 60 and 90 days), with four replicates. Intoxication symptoms were observed on the 7, 14 and 21 days after the bio indicators were sown. The herbicides presented greater stability, i.e. greater toxic effects on the bioindicators along the time on soil with higher clay level and organic matter; isoxaflutole and the mixtures (trifloxysulfuron-sodium + ametryn) + (diuron + hexazinone), and diuron + hexazinone showed greater residual effect in both soils affecting the bioindicators100%.

Mobilidade e persistência de herbicidas aplicados em pré-emergência em diferentes solos

The objective of this work was to verify the mobility and persistence of herbicides applied in pre-emergence on different soils and amounts of sugarcane straw. The herbicides ametryn + clomazone (1,500 + 1,000 g i.a. ha-1), isoxaflutole (187,5 g.i.a. ha-1) and diuron + hexazinone (1,170 + 330 g i.a. ha-1) were applied in soil with clayey and medium texture under the following conditions:on 10 and 15 t ha-1 of sugarcane straw followed by rain simulation ; on the ground and covered with 10 t ha-1 of sugarcane straw; on the ground without straw; and control without herbicide. At 10, 20, 40 and 60 days after herbicide application (DAA), species bioindicators such as sorghum and cucumber were sown. Percentage of phytotoxicity was observed at 21 days after emergence. The mixture ametryn + clomazone applied directly on the soil affected the bioindicator up to 40 DAA; however, after this period, the residual effect was smaller. The sugarcane straw affected the performance of this product negatively. The herbicide isoxaflutole applied directly in the soil presented residual effect up to 60 DAA, with 82.5 and 77.5% of bioindicator control, in soils with clayey and medium texture, respectively, and the presence of 10 and 15 t ha-1 of straw did not alter efficiency up to 20 DAA. The herbicide diuron + hexazinone applied on the soil without straw presented residual effect up to 60 DAA, mainly in soil with clayey texture. With 15 t ha-1 of straw, significant reduction was observed in the effectiveness of this mixture.

Lixiviação de clomazone + ametryn, diuron + hexazinone e isoxaflutole em dois tipos de solo

Objetivou-se neste trabalho avaliar a lixiviacao de herbicidas pre-emergentes recomendados para cana-de-acucar em solos com textura argilosa e media. Os ensaios consistiram na aplicacao de ametryn + clomazone (1.500 + 1.000 g ha-1), isoxaflutole (187,5 g ha-1) e diuron + hexazinone (1.170 + 330 g ha-1) no topo das colunas de solo montadas em tubos de PVC. Foram simuladas precipitacoes pluviais de 10, 20, 40 e 80 mm decorridas 24 h da aplicacao dos herbicidas. Os tubos foram desmontados para a semeadura de Sorghum bicolor e de Cucumis sativus, tres dias apos a simulacao. O herbicida ametryn + clomazone em solo com textura argilosa foi detectado aos 20 e 35 cm de profundidade, nas aplicacoes de 10 e 80 mm de agua, respectivamente. Em solo com textura media, observou-se maior efeito deste herbicida em todas as precipitacoes, em relacao ao argiloso. Com a aplicacao de 40 e 80 mm de agua, o herbicida foi detectado ate 35 cm de profundidade em solo com textura argilosa. O herbicida isoxaflutole aplicado em solo argiloso causou albinismo na parte aerea das plantas ate 15 e 25 cm de profundidade no solo com chuvas de 10 e 80 mm, respectivamente. Em solo com textura media, as maiores simulacoes de chuva possibilitaram detectar este herbicida ate 30 cm. Com a simulacao de 80 mm de chuva, o herbicida diuron + hexazinone foi encontrado aos 30 cm de profundidade em ambos os solos, provocando efeitos toxicos sobre as plantas bioindicadoras de 25 e 60% em solos argiloso e medio, respectivamente. Concluiu-se que todos os herbicidas avaliados tem tendencia a serem lixiviados por influencia das precipitacoes pluviais ou de irrigacoes artificiais, com efeitos mais pronunciados em solos com textura media e com menor teor de materia orgânica.

Eficácia de herbicidas em diferentes quantidades de palha de cana-de-açúcar no controle de Ipomoea grandifolia

This work had as objective studies the effect of different amounts of sugarcane straw picked without burns about effectiveness of some herbicides in the I. grandifolia control. The experiment was conduced in field in the Centro de Ciencias Agrarias/UFSCar, in Araras, SP. The treatments consisted of herbicides herbicidas ametryn + trifloxysulfuron-sodium (1463 + 37 g ha-1), imazapic (84 g ha-1), imazapyr (200 g ha-1), 1diuron + hexazinone (1170 + 330 g ha-1) and 2diuron + hexazinone (1330 + 160 g ha-1) applied in pre emergence of Ipomoea grandifolia and on five growing amounts of sugarcane straw ( 0, 5, 10, 15 e 20 t ha-1). The effectiveness of control of weeds was evaluated to the 7, 14, 21 and 28 days after application of treatments (DAT).The straw reduced the population of I. grandifolia even in the treatments without herbicide use. The measure that increased the amount of straw there was reduction in the effectiveness of the herbicides and with 15 t ha-1 of straw the control was considered unsatisfactory for all of the treatments. With 20 t ha-1 the control was null for all the treatments, however, was observed that in this case, the own straw was efficient in the suppression of these weed, since the number of emerged plants was smaller, even in the treatment without herbicides.

Monitoramento do banco de sementes de plantas daninhas em áreas com Cana-de-Açúcar colhida mecanicamente

O objetivo deste trabalho foi monitorar o banco de sementes de area cultivada com cana-de-acucar colhida mecanicamente por seis anos e um ano, utilizando-se tecnicas de agricultura de precisao. As amostragens de solo para determinacao do banco de sementes foram realizadas utilizando-se grade amostral regular de 1,6 ha. Os mapas de infestacao foram obtidos pela tecnica de interpolacao por krigagem. Observou-se que o talhao de cana colhida mecanicamente por seis anos apresentou menor potencial de infestacao de varias especies de plantas daninhas em relacao ao talhao onde esse manejo foi adotado recentemente. Plantas daninhas monocotiledoneas, como Cyperus rotundus e Brachiaria decumbens, foram reduzidas pela adocao da colheita mecanizada. Todavia, algumas dicotiledoneas foram selecionadas, como as dos generos Ipomoea e Euphorbia. Verificou-se que a palha de cana-de-acucar, em sistemas de cana-crua, pode ser utilizada como fator de supressao e selecao de varias especies.

INFLUENCE OF SUGARCANE STRAW AND SOWING DEPTH ON THE EMERGENCE OF WEED SPECIES

This study aimed to understand the influence of sowing depth and the amount of sugarcane straw on the emergence of weed species Luffa aegyptiaca Miller (Cucurbitaceae); Mucuna aterrima Piper & Tracy (Fabaceae - Leguminosae) and Ricinus communis (Euphorbiaceae). A completely randomized design with a 5 x 4 x 3 factorial layout with four replications was used, at five sowing depths (0, 2, 4, 8 and 10 cm), four different amounts of sugarcane straw (0, 5, 10 and 15 t ha-1) and three different evaluation periods (7, 14 and 21 days after sowing). After sowing, different amounts of sugarcane straw (0, 5, 10 and 15 t ha-1) were deposited on soil. Seedling emergence was analyzed at 7, 14 and 21 days after sowing, counting the number of seedlings that had emerged. At the end of the trial, weed height (cm), leaf area (cm2) and shoot dry mass (g) were measured. In relation to emergence ability, studied species presented different responses according to sowing depth and to the amount of sugarcane straw deposited on the soil. For the L.aegyptiacaand M.aterrima, no significant difference was observed in the interaction between depth and sugarcane straw, showing the adaptation of these species to no-burn sugarcane system. For R.communis, seeds placed at 0 cm of sugar cane straw depth were observed to favor the emergence of seedlings.

Initial growth of tree species under herbicide drift

PALAVRAS-CHAVE Fitotoxicidade Restauração Herbicidas ABSTRACT: The present study aimed to evaluate the effect of different doses of the herbicides picloram, glyphosate, glyphosate + 2.4-D, and 2.4-D on the survival and growth of the tree species Croton floribundus and Heliocarpus americanus and Myrsine coriacea. The experimental design was completely randomized with four replicates. The tree species were sprayed with 0; 2.5; 5; 10; 20; 40; 60; 75; 90 and 100% of the commercial dose of each herbicide. The percentage of phytotoxicity, chlorophyll content, height, stem diameter, leaf area and aerial dry biomass of the species were evaluated. For H. americanus, the herbicides glyphosate, 2.4-D and glyphosate + 2.4-D were phytotoxic. Among the evaluated herbicides, picloram was the most phytotoxic for all species. Glyphosate presented lower phytotoxicity at lower doses for M. coriacea compared with C. floribundus and H. americanus. A negative impact of 2.4-D was verified in all species, even at the lowest doses. The mixture glyphosate + 2.4-D also presented high phytotoxicity, with lower values for the species M. coriacea. The results showed that the application of these herbicides should be directed and protected, and even low dosages have deleterious effects on these species.