Fábio Ribeiro Pires

Ciclagem de nutrientes por plantas de cobertura na entressafra em um solo de cerrado

The objective of this work was to evaluate the accumulation and the liberation of nutrients (N, P, K, Ca, Mg and S) of cultural residues by three species of cover crops, in off-season. Tested cover crops were amaranthus (Amaranthus cruentus L.), pearl millet (Pennisetum glaucum L.) and finger millet (Eleusine coracana (L.) Gaertn.). The experiment was carried out in a Typic Haplorthox clay texture soil. A randomized block desing in a split-plot array in time, with four replications, was used. At the flowering of the species, the production of dry matter and the accumulation of nutrients were evaluated. Proportional samples of dry matter of each cover crop species were placed in litter bags, which were distributed on the field plots surface, collected and weighed every 30 days, until 240 days after installation of the bags. The largest amounts of accumulated nutrients in the dry matter of the cover crops were observed with the pearl millet and the finger millet. The potassium was the nutrient accumulated in larger amount, reaching 416.9 kg ha -1 , in pearl millet. The largest rates of nutrient liberation were observed in the cultural residues of the amaranthus.

Desempenho de plantas de cobertura em sobressemeadura na cultura da soja

Oxa0objetivo deste trabalho foi avaliar a capacidade de estabelecimento de plantas de cobertura em sobressemeadura na cultura soja. A soja foi semeada em diferentes epocas para que, no estadio R7 (maturacao fisiologica), ocorressem diferentes condicoes climaticas para implantacao das plantas de cobertura. Oxa0experimento foi realizado em Rio Verde, GO, na safra de verao 2005/2006, em Latossolo Vermelho distroferrico. Foram avaliadas seis plantas de cobertura: Brachiaria brizantha, B.xa0ruziziensis, B.xa0decumbens, Eleusine coracana, Pennisetum glaucum e o hibrido Cober Crop [Sorghum bicolor (L.)xa0Moench x Sorghum sudanense Piper Stapf], e uma testemunha mantida em pousio. A soja foi semeada em quatro epocas: 27/10/2005, 10/11/2005, 24/11/2005 e 14/12/2005. Axa0sobressemeadura das plantas de cobertura foi realizada manualmente, a lanco, quando a soja atingiu o estadioxa0R7. Com excecao da segunda epoca de semeadura da soja, que apresentou a menor media de estande em todas as plantas de cobertura, em razao da maior matocompeticao, todas as demais possibilitaram crescimento inicial satisfatorio das plantas de cobertura sobressemeadas em R7, com base na emergencia, altura de plantas, cobertura do solo e producao de palhada. B.xa0ruziziensis, B.xa0brizantha, B.xa0decumbens e o hibrido Cober Crop apresentam maior potencial para a producao de palhada durante a entressafra no Cerrado, com uso da sobressemeadura.

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.

Soybean crop oversowing used as a technique to suppress weed emergence

The objective of this experiment was to evaluate the efficiency of soybean oversowing, using cover crops, in reducing weed emergence and its reflections on the productivity of the soybean cultivated in the following season. The experiment was arranged in a randomized block design, in split-plot, with four replications. The soybean was sown four times: 1) 10/27/2005, 2) 11/10/2005, 3) 11/24/2005 and 4) 12/14/2005, under a no-tillage system, corresponding to four times of soybean oversowing, occurring respectively, on 01/30/2006; b) 02/13/2006; c) 02/22/2006; and d) 03/14/2006. Six cover crops were evaluated [Brachiaria brizantha, B. ruziziensis, B.xa0decumbes, Eleusine coracana, Pennisetum glaucum and cover crop - sorghum hybrid (Sorghum bicolor cv. Bicolor) with Sudan- grass (Sorghum bicolor cv. Sudanense)] and untreated (spontaneous vegetation) in four oversowing times. Oversowing was performed manually when the soybean reached the R7 stadium (beginning of defoliation during physiological maturation), in each of the four sowing times of the 2005/06 soybean crop. The first cover crop desiccation was carried out on 10/23/2006. After 20xa0days, the second desiccation was applied, followed by soybean sowing, cultivar MSOYxa06101, early cycle, 0.45 m spaced, aimed at a population of 500.000xa0plantsxa0 ha-1 . Soybean oversowing, especially when using brachiaria, showed to be an important tool for the integrated management of weed plants, since it provides a larger biomass contribution and soil cover and sustainability to no-till systems in the cerrado.

Biomassa, decomposição e cobertura do solo ocasionada por resíduos culturais de três espécies vegetais na região centro-oeste do Brasil

Com a crescente adocao da semeadura direta na regiao Centro-Oeste do Brasil, faz-se necessario maior conhecimento sobre as plantas de cobertura para producao de palha. O presente estudo teve como objetivo avaliar a producao de biomassa verde e seca, a percentagem de cobertura do solo, bem como a dinâmica da decomposicao da palhada de tres especies de plantas de cobertura em safrinha: amaranto (Amaranthus cruentus L. BRS Alegria), milheto (Pennisetum glaucum L. var. ADR500) e capim-pe-de-galinha [Eleusine coracana (L.) Gaertn.]. O trabalho foi conduzido em um Latossolo Vermelho distroferrico textura argilosa. O delineamento experimental utilizado foi o de blocos casualizados, no esquema de parcelas subdivididas no tempo, com quatro repeticoes. Nas parcelas foram alocadas as especies, subdivididas em nove epocas de avaliacao (0, 30, 60, 90, 120, 150, 180, 210 e 240xa0dias) apos dessecacao quimica das especies em estudo. Amostras proporcionais da biomassa seca de cada especie foram acondicionadas em bolsas de decomposicao, que foram dispostas sobre o solo, sendo coletadas a cada 30xa0dias e pesadas ate 240xa0dias apos a instalacao, para avaliar a dinâmica de decomposicao, apos o manejo das plantas de cobertura. O milheto ADR500 e o capim-pe-de-galinha proporcionaram maior producao de biomassa verde e seca, maior cobertura do solo e menores taxas de decomposicao da palhada, nao diferindo entre si. O milheto ADR500 apresentou maior relacao C/N, seguido pelo capim-pe-de-galinha e amaranto. Ajustaram-se, para a percentagem de cobertura do solo e a decomposicao de palhadas com o tempo, os modelos sigmoidal e exponencial decrescente, respectivamente. O milheto ADR500 e o capim-pe-de-galinha apresentaram comportamentos semelhantes, nao diferindo na comparacao dos modelos de cobertura do solo e decomposicao de palhadas.

Sistema radicular de plantas de cobertura sob compactação do solo

With the objective of evaluate the root growth capacity in the compacted soil layer, four vegetal species of the cover crops (amaranth, pearl millet ADR500, finger millet and kenaf) were cultivated in columns of PVC with increasing levels of subsurface compaction (soil bulk densities: 1.18; 1.34; 1.51 and 1.60 Mg m-3). The experiment was carried out in a greenhouse conditions, using a Dusky Red Latosol. The subsurface compacted layer was restrictive to the roots growth of the studied species, causing the root concentrating to the surface. Pearl millet ADR500 and the amaranth were the species that had detached in the production of dry matter weight and developed itself in the compacted layers and below of them. Pearl of millet ADR500 presented the biggest root length density in all layers. Finger millet and the amaranth had similar behavior in relation to the shoot length root. Finger millet and kenaf had presented minor dry matter weight of root in relation to the other species. The kenaf presented minors values of dry matter, but it was not affected by the presence of compacted layers.

Fitorremediação de solos contaminados com tebuthiuron utilizando-se espécies cultivadas para adubação verde

O emprego da fitorremediacao na despoluicao de solos contaminados com compostos orgânicos, inclusive herbicidas, vem sendo pesquisado ultimamente. Como o tebuthiuron pode causar serio impacto ambiental, por ser muito utilizado, apresentar longo efeito residual no solo e possibilidade de contaminacao do lencol de agua subterrâneo, desenvolveu-se este trabalho com o objetivo de avaliar a capacidade de sete especies vegetais na despoluicao de solos contaminados com esse herbicida. As especies avaliadas neste experimento foram: Cajanus cajan, Canavalia ensiformes, Dolichos lablab, Pannisetum glaucum, Estizolobium deeringianum, Estizolobium aterrimum e Lupinus albus. Elas foram semeadas e cultivadas, por 60 dias, em vasos cujo solo recebeu quatro doses do tebuthiuron (0,0; 0,5; 1,0; e 1,5 kg ha-1). As testemunhas foram constituidas por vasos sem planta, aos quais foram aplicadas as mesmas doses de herbicidas. Aos 60 dias apos a semeadura, colheu-se a parte aerea de todas as plantas, sendo semeada, nos mesmos vasos, Avena strigosa, utilizada como planta indicadora, para realizacao do bioensaio. Depois de 60 dias da semeadura da especie bioindicadora, esta foi colhida, sendo avaliadas as seguintes caracteristicas: altura de plantas, sintomas de toxicidade e biomassa seca da parte aerea das plantas. Ate a dose de 0,5 kg ha-1 de tebuthiuron, a especie que melhor fitorremediou esse herbicida no solo foi L. albus. Quando o solo foi tratado com 1,0 kg ha-1 de tebuthiuron, C. ensiformes foi a especie que melhor fitorremediou o herbicida. Isso foi concluido com base na maior altura de plantas, biomassa seca da parte aerea e menor toxicidade de A.xa0strigosa, quando foi cultivada em sucessao a essas plantas remediadoras. Nenhuma das especies avaliadas cresceu em solo que recebeu a maior dose de tebuthiuron (1,5xa0kgxa0ha-1).

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.

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.

Liberação de nutrientes pela palhada de milheto em diferentes estádios fenológicos

This study was carried out in an experimental area of the Faculdade de Agronomia of the Universidade de Rio Verde, from October 2004 to May 2005, in a clayey dystroferric Red Latosol (Oxisol). The purpose of the experiment was to evaluate nutrient release from Pennisetum glaucum straw, cv. ADR300, in three different phenological stages (pre-booting, pre-flowering and early flowering). Pennisetum glaucum was used as cover crop in a no tillage system, in a randomized block design, and split plots in time, with four replications, totalizing 9 m2. To evaluate nutrient release, a decomposition bag system was used. After Pennisetum glaucum management, decomposition was evaluated during 150 days, at intervals of 30 days. Nutrient accumulation was highest at the early flowering stage. Nutrient release dynamics differed in all phenological stages, with exception of K, which was the nutrient of easiest release, regardless of the phenological stage.