S.O. Procópio

Sensibilidade de cultivares de cana-de-açúcar à mistura trifloxysulfuron-sodium + ametryn

The objective of this study was to evaluate the sensitivity of 11 cultivars (SP801842, SP79-1011, SP81-3250, SP80-1816, RB855113, RB835486, RB845210, RB867515, RB928064, RB72454 and RB855536) and four clones (RB947643, RB855002, RB957712 and RB957689) of sugarcane to the pre-formulated mixture of the herbicides trifloxysulfuron-sodium (18.5 g kg-1) + ametryn (731.5 g kg-1), termed Krismat®. Cultivars and clones were cultivated in vases under non-protected environment. In both assays, the herbicide mixture was applied at 60 days after sprouting. In assay 1, the herbicide mixture was applied at a single rate of 2.00 kg ha-1 on all the cultivars and clones, while in assay 2 it was applied at rates of 1.00; 2.00; and 6.00 kg ha-1 on cultivars RB855113 and RB867515. After herbicide application and harvest at 45 days after treatment (DAT), weekly evaluations of phytotoxicity (%),and dry matter were conducted as well. The variables plant height, leaf number, leaf area and dry matter of the aerial part and stalk were evaluated only in the second assay. RB855113 cultivar showed the highest sensitivity to the herbicide mixture; the genotypes SP80-1842, SP80-1816, SP79-1011 and RB957689 showed medium sensitivity and the clones presented good tolerance. For the RB855113 cultivar, the highest toxicity index was observed from 20 to 27 DAT. Reduction of plant height, leaf number, foliar area and dry matter of the aerial part and stalk was observed during this period due to the increase of the product doses. Cultivar RB867515 was tolerant at the lowest herbicide doses. However, it was found to be sensitive, at the highest tested dose.

Efeitos de dessecantes no controle de plantas daninhas na cultura da soja

The objectives of this work were to evaluate the efficiency of glyphosate and preformulated mixture paraquat + diuron as well as the effect of the interval between herbicide applications and soybean sowing on the control and re-growth impairment of the following weeds: Digitaria insularis, Synedrellopsis grisebach and Leptochloa filiformis. The experiment was carried out in a soybean area under no-till system and was arranged in a randomized block design, with 9 treatments and four replications. The following treatments were evaluated: glyphosate applied on sowing day; one day before sowing day; two days before sowing day; five days before sowing day; paraquat + diuron 20 days before sowing day and on sowing day; glyphosate 10 days before sowing day and paraquat + diuron on sowing day; glyphosate 15 days before sowing day and paraquat + diuron on sowing day; glyphosate 20 days before sowing day and paraquat + diuron on sowing day; and control (presence of weeds). Acceptable control and re-growth impairing of D. insularis and L. filiformis were obtained when glyphosate was applied five days before soybean sowing or when sequential applications of glyphosate and paraquat + diuron were applied. Sequential applications of paraquat + diuron were not efficient in controlling or impairing re-growth of the weeds D. insularis and L. filiformis. S. grisebachii showed to be tolerant to glyphosate.

Utilização de chlorimuron-ethyl e imazethapyr na cultura da soja Roundup Ready®

The objective of this work was to evaluate the efficacy and selectivity of the herbicides chlorimuron-ethyl and imazethapyr associated to glyphosate in controlling weeds on Roundup Ready (RR®) soybean crop. The experiment was carried out at the COMIGO Technological Center in Rio Verde-GO, during the 2005/2006-crop season. The variety used was Monsoy 7878 which had 18 seeds mechanically distributed per meter. The rows were spaced by 0.50 m. The experiment was arranged in a completely randomized block design with four replications for each treatment. Glyphosate doses (480, 960 and 1.440 g ha-1), applied alone, did not cause plant toxicity nor reduced height and biomass accumulation of RR® soybean plants. However, the addition of the herbicides imazethapyr and chlorimuron-ethyl to glyphosate caused plant toxicity in the soybean RR® plants, though at an acceptable degree. The symptoms caused by imazethapyr were more severe than those caused by chlorimuron-ethyl. The association of imazethapyr and glyphosate led to reduced height and biomass. The application of glyphosate alone at doses 480, 960 and 1.440 g ha-1, did not exert sufficient control over Euphorbia heterophylla, Commelina benghalensis, Chamaesyce hirta, Leucas martinicensis and Ipomoea grandifolia. Despite increasing control of most of the weeds, chlorimuron-ethyl and imazethapyr addition did not promote increased yield when applied on the RR® soybean crop.

Leaf blade quantitative anatomy of sugarcane cultivars and clones

The objective of this study was to make a quantitative assess of the anatomic characteristics of leaf blade of the sugarcane cultivars RB855113, SP80-1842, SP80-1816, RB867515 and clone RB957689 presenting different sensitivity to the mixture of sodium trifloxysulfuron + ametryn herbicides. Compared to the other cultivars assessed, RB855113 cultivar, considered more sensitive to the herbicide mixture, presented relevant differences such as greater proportion of bulliform cells, greater tissue proportion in the transverse section of the leaf blade, greater stomata and trichome density on both surfaces, thinner epidermis on the adaxial surface and length of stomata on both surfaces. The external paraclinal wall of the bulliform cells was thinner than in the common epidermis cells in all the genotypes on the adaxial and abaxial surfaces. Multivariate analysis of the data on the variables considered most relevant to explain the herbicide penetration singled out the sensitive RB855113 from the other materials. Such characteristics can explain the greater penetration, and consequently, greater sensitivity of this cultivar to the sodium trifloxysulfuron + ametryn mixture.

Fitorremediação de solo contaminado com picloram por capim-pé-de-galinha-gigante (Eleusine coracana)

The long-term residual effect of the herbicide picloram poses risks of leaching and phytotoxicity to successive crops. Phytoremediation can abbreviate the long carryover effect. This research was carried out from September 2006 to February 2007, under green house conditions, in Rio Verde, Goias, Brazil, to study the influence of Eleusine coracana population density on phytoremediation of soil contaminated with picloram. The treatments consisted of the combination of four Eleusine coracana population densities (0, 7, 14 and 21 plants per pot, corresponding to 0, 172, 344 and 516 plants m-2, respectively) and three picloram rates (0, 80 and 160 g ha-1 - applied directly to the pots, simulating soil contamination levels). After growing the phytoremediation species on substrate during 100 days, soybean was sown as a bioindicator species in the same pot. E. coracana was able to remediate soils contaminanted with picloram. At densities above 172 plants m-2, there was no further reduction of the carryover effect to soybean sown in succession.

Fitorremediação de solo contaminado com trifloxysulfuron-sodium por mucuna-preta (Stizolobium aterrimum)

O emprego de especies vegetais que apresentem capacidade fitorremediadora pode ser uma das alternativas para reduzir a persistencia de agroquimicos no ambiente. O objetivo deste trabalho foi avaliar a fitorremediacao do herbicida trifloxysulfuron-sodium em campo, pela especie Stizolobium aterrimum (mucuna-preta), em diferentes densidades populacionais. O delineamento experimental utilizado foi o de blocos casualizados em esquema fatorial 4 x 2, com quatro repeticoes. Os tratamentos foram compostos por quatro densidades de plantio de mucuna-preta (0, 10, 25, e 40 plantas m-2), associadas a duas doses do trifloxysulfuron-sodium (0,00 e 15,00 g ha-1), aplicadas cinco dias apos o preparo do solo para semeadura da mucuna-preta. As plantas fitorremediadoras foram mantidas na area por 65 dias. Apos esse periodo, a area experimental foi novamente sulcada e fertilizada de acordo com a analise do solo, considerando as necessidades da cultura do feijao (Phaseolus vulgaris). Aos 45 dias apos a semeadura do feijao, avaliou-se a altura e a biomassa seca da parte aerea das plantas. Ao final do ciclo da cultura, determinou-se, ainda, o rendimento de graos, o numero de vagens por planta e o peso de 100 sementes. O cultivo previo de mucuna-preta nas densidades populacionais de 10, 25 ou 40 plantas m-2 proporcionou rendimento de graos de feijao nas parcelas tratadas com trifloxysulfuron-sodium no solo semelhante ao obtido na area nao-tratada. A densidade populacional minima desse adubo verde que proporcionou maior rendimento de graos a cultura do feijao foi de 25 plantas por metro quadrado.

Atividade residual de herbicidas pré-emergentes aplicados na cultura da soja sobre o milheto cultivado em sucessão

-1 ), diclosulam (0,035 kg ha-1), sulfentrazone (0,600 kg ha-1) e flumioxazin (0,050 kg ha-1) e uma testemunha, aplicados logo apos a semeadura do cultivar de soja Msoy-6101. Nas subparcelas, realizou-se a semeadura do milheto, cultivar ADR-7010, em quatro periodos, correspondendo a 0, 40, 80 e 120 dias apos a aplicacao dos herbicidas (DAA). Durante a conducao do ensaio, foram determinados os niveis de intoxicacao, estande, altura e massa seca da parte aerea das plantas de milheto. No final do ciclo foi avaliado o rendimento de graos da cultura. O hibrido de milheto ADR-7010 apresentou elevada sensibilidade com relacao a atividade residual dos herbicidas sulfentrazone, diclosulam e imazaquin quando cultivado logo apos a aplicacao destes. A bioatividade dos herbicidas imazaquin, diclosulam e flumioxazin nao foi suficiente para alterar o rendimento de graos do milheto cultivado em sucessao a soja (120 DAA), mostrando que esse intervalo de tempo e suficiente para dissipacao desses herbicidas. Dos herbicidas pre-emergentes avaliados, o sulfentrazone apresentou maior atividade residual, influenciado negativamente o rendimento da cultura durante o intervalo de tempo estudado. Palavras-chave: carryover, sulfentrazone, diclosulam, imazaquin, flumioxazin, Pennisetum glaucum. ABSTRACT - The objective of this study was to evaluate the persistence of herbicides applied in pre-emergence in soybean crop and the effects of these herbicides on pearl millet grown in succession. The herbicides imazaquin (0.160 kg ha-1), diclosulam (0.035 kg ha-1), sulfentrazone (0.600 kg ha-1), and fumioxazin (0.050 kg ha-1) were used immediately after sowing of soybean Msoy-6101, in plots of 80 m2, divided into sub-plots of 20 m2 (5 x 4 m). A randomized block design with four replications was used in a split-plot scheme 5 x 4. In the sub-plots, pearl millet hybrid ADR-7010 was sown in four periods after herbicide application, corresponding to 0, 40, 80 and 120 days after herbicide application (DAA). Pear millet injury, stand, height and dry biomass of the plant were evaluated at 7, 15, and 28 days after emergence; crop grain yield was evaluated at the end of the cycle. Pearl millet hybrid ADR-7010 showed high sensitivity to the residual activity of sulfentrazone, imazaquin, and diclosulam when grown immediately after herbicide application. The bioactivity of imazaquin, diclosulam, and flumioxazin was not sufficient to affect grain yield of millet grown after soybean (120 DAA), suggesting that this interval is sufficiently long for dissipation of these herbicides. Among the pre-emergent herbicides, sulfentrazone showed longer residual activity, negatively influencing the crops yield during the time interval studied.

Controle de Capim-Arroz (Echinochloa spp.) em função de métodos de manejo na cultura do arroz irrigado

RESUMO - Objetivou-se com este trabalho avaliar a eficacia do herbicida penoxsulam emfuncao do inicio da irrigacao permanente e da epoca de sua aplicacao e dose no controle decapim-arroz ( Echinochloa crusgalli e E. colona), bem como sua seletividade a cultura do arrozirrigado, cultivar Qualimax-1. O experimento foi conduzido a campo em delineamentoexperimental de blocos ao acaso com quatro repeticoes, no esquema fatorial 2 x 3 x 4,representando epocas de inicio da irrigacao por inundacao (21 e 30 dias apos a emergencia– DAE), epocas de aplicacao (pre-emergencia e pos-emergencia inicial e tardia) e doses doherbicida penoxsulam (0, 18, 36 e 72 g ha

Weed management in raw sugarcane

In the last years, the sugarcane harvesting process has undergone changes imposed by law, environmental awareness or social pressure, leading to the exclusion of the traditional slash and burn before harvesting and inclusion of crude sugarcane harvest. This process is denominated crude harvesting. The adoption of this new harvesting system promoted alterations in the entire sugarcane tillage system, including wider row spacing and the formation of a mulching layer due to the deposition of sugarcane residues on the soil surface. This new crop management system affects directly the weed dynamics in these areas and soil fertility as well. Weed shifting has been observed, producing weed species with higher germination and emergence capacity under a thicker straw layer, compared to those unable to germinate due to the physical or allellopathic action of the straw. In addition, pre-emergence herbicides are usually less efficient under this system due to their retention in the straw, not reaching the soil in sufficient concentrations to promote weed control. In this literature review, the major results involving weed management in crude sugarcane areas are described to provide information to researchers, extension workers, and farmers on how to improve sugarcane integrated weed management, mainly under this new harvesting process. The results show that reduction of herbicide dependence is feasible, leading to improved soil quality in these fields.

Potencial competitivo de cultivares de soja em relação às plantas daninhas

The use of cultural methods in conservationist agricultural system is important for weed management, since it decreases the amount of the chemical products applied. The use of more competitive cultivars seems to be one of the most important weed management methods, which valid for soybean as well as other crops. Two field experiments were carried out to evaluate the competitive potential of soybean varieties, among those officially recommended for southwestern Goias, against weeds in Rio Verde,GO aiming to propose the cultivation of better-quality varieties in areas with high weed pressure. Four short-season soybean varieties were evaluated in experiment 1: (Monsoy 6101, Monsoy 8001, Emgopa 316 and Coodetec 204) and four medium-season soybean varieties in experiment 2 (Conquista, Coodetec 211, Emgopa 315 and Vencedora). All the cultivars were evaluated under both weed management systems, i.e., manual weed control (absence of weeds) and no weed control (presence of weeds). At the 16th, 25th and 46th days after sowing (DAS), both plant height and plant dry matter were evaluated; at the 63rd DAS, the percentage of soil covered by the soybean cultivars was evaluated and at the end of the plant season, yield was evaluated. All the cultivars displayed yield reduction in the system with no weed control. However, Emgopa 316 and Coodetec 204 were found to be the most competitive among the short-season cultivars. Among the medium-season cultivars, Emgopa 315 showed the same tendency. Therefore, these two varieties are the most recommended to be cultivated in areas with high weed pressure.