Leandro Pereira Pacheco

Ciclagem de nutrientes por plantas de cobertura e produtividade de soja e arroz em plantio direto

The objective of this work was to evaluate nutrient cycling by cover crops and its influence on the performance of the rotation between upland rice and soybean. The crops were sown under no-tillage, in a Rhodic Haplustox, in the Cerrado region of the state of Goias, Brazil. The cover crops were sown mechanically, also under no-tillage, after the harvest of soybean (3/25/2008) and rice (4/7/2009). A randomized complete block design was used, split-plotted in time, with four replicates. The treatments consisted of the following cover crop species, besides fallow: Urochloa ruziziensis, U. brizantha, Pennisetum glaucum and U. ruziziensis + Cajanus cajan. The evaluation of the remaining nutrient in straw was performed at 0, 15, 30, 60, 90, and 120 days from the desiccation date of the cover crops. Urochloa ruziziensis and U. brizantha were the most efficient in the accumulation and release of nutrients, especially potassium. Urochloa ruziziensis is the most suited species for use as a cover crop previous to upland rice cultivation under no-tillage. However, none of the cover crop species significantly affect soybean grain yield.

Incompatibilidade física de misturas entre herbicidas e inseticidas

The objective ofthis study was to evaluate the physical interaction between simulated tank mixtures of different classes of pesticides. The experiment was conducted at the Chemistry Laboratory of the University of Mato Grosso, Brazil, from June to August 2010. The treatments consisted of mixtures of six herbicides (glyphosate SC, glyphosate WG, lactofen CE, fomesafen SC, haloxifop-R CE, and fluazifop-p-butyl EW) with six types of insecticide (methomyl CS, clorpirifos CE, teflubenzuron SC, triflumuron SC, cipermetrin CE, and tiametoxam + lambda-cialotrin SC) in the absence and presence oftwo pH reducers (pyroligneous acid and boric acid) with four replications. A scale from 1 to 5 was used to evaluate the degree of mismatch, where 1 is immediate separation of the mixture (which is recommended not to apply), and 5 is homogeneity of the mixtures. The major physical incompatibilities in the herbicide and insecticide mixtures were observed in the presence of glyphosate WG and lactofen SC. Pyroligneous acid and boric acid showed to be good alternatives as pH reducers in the preparation of sprays using the herbicide and insecticide mixtures. Tank mixtures of glyphosate formulation SC, clorpirifos CE, and lactofen CE + clorpirifos CE must be avoided.

Cover crops on the development of beggar's-tick

Studies to identify potential cover crops species for the no-till system and minimal amounts of biomass required to reduce the emergence and development of weeds in cereal crop areas may represent an important tool in the integrated weed management. Thus, this study aimed at evaluating the inhibition of the emergence and growth of Bidens pilosa plants, using different cover crops biomass levels on the soil surface. The experiment was carried out in a greenhouse located in Bom Jesus, Piaui State, Brazil, from December 2011 to March 2012, in a randomized experimental blocks design with four replications, in a (5x6)+1 factorial scheme, consisting of six cover crop species and five biomass levels on the soil surface, plus a control with no soil cover. The species evaluated were Pennisetum glaucum (ADR 7010 and ADR 300 cultivars), Crotalaria ochroleuca , Urochloa ruziziensis (syn. Brachiaria ruziziensis ), Crambe abyssinica and Fagopyrum tataricum , at five biomass levels corresponding to 4.0 t ha -1 , 8.0 t ha -1 , 12.0 t ha -1 , 16.0 t ha -1 and 20.0 t ha -1 . Urochloa ruziziensis and Fagopyrum tataricum were considered the best ones for controlling B. pilosa , with 4.0 t ha -1 of their biomass being sufficient to reduce the total number of emerged plants, germination speed index, shoot dry biomass, leaf area, root dry biomass and root volume of B. pilosa .

Elevada densidade de semeadura aumenta a produtividade da soja? Respostas da radiação fotossinteticamente ativa

Estudos recentes tem abordado o uso da pratica da elevada densidade de semeadura na cultura da soja. Entretanto, os resultados praticos dessa tecnica sao divergentes. Assim, pesquisas nesse campo sao importantes para elucidar os efeitos diretos dessa pratica de manejo, como, por exemplo, a interferencia no uso da radiacao fotossinteticamente ativa (RFA). Portanto, objetivou-se com este estudo avaliar a dinâmica da RFA em diferentes densidades de cultivo na cultura da soja. Para tanto, conduziu-se um experimento a campo com delineamento em blocos casualizados com os tratamentos distribuidos em arranjo fatorial 3 × 5: tres cultivares de soja RR® (P98Y12, TMG 132 e M-Soy 9056) e cinco densidades de semeadura (20, 30, 40, 50 e 60 plantas∙m–2) com quatro repeticoes. Foram avaliados massa seca da parte aerea, radiacao fotossinteticamente ativa no dossel inferior (RFA-I) e superior (RFA-S), intercepcao da RFA, taxa de crescimento da cultura (TCC), taxa de crescimento relativo (TCR), taxa de assimilacao liquida (TAL), eficiencia de uso da radiacao (EUR), coeficiente de extincao luminosa (k), indice de colheita de graos (ICG), peso de 1.000 graos e produtividade. Independentemente do cultivar, as densidades de 20 e 30 plantas∙m–2 proporcionaram os maiores valores de TAL, TCR, k, ICG e produtividade. Apenas o uso dos parâmetros EUR, TCC e RFA interceptada nao fornece informacoes solidas para predizer a eficiencia do cultivo adensado na cultura da soja. As densidades de cultivo tradicionalmente utilizadas se sobrepoem as demais quanto a qualidade da RFA no dossel e produtividade da soja.

Desempenho agronômico do sorgo em função de doses e épocas de aplicação do herbicida 2,4-D

Sorghum is part of the current plan of agricultural system management for the cer rado. However, few field studies have been carried out on this cultures behavior and selectivity towards herbicide 2,4 D. The objective of this study was to evaluate the effects of 2,4-D on plant growth, dry matter production and green biomass and grain yield in sorghum. The experiment was conducted between January and May 2008 in Nova Xavantina-MT in dystrophic Oxisol. Sorghum (cv. Buster) was sown in a cultivated area under no-tillage, with 0.50 m spacing between rows, and ten seeds distributed per meter. Treatments were arranged in a 4 x 4, involving four levels of 2,4-D (0, 335, 670, and 1.005 g ha -1 ) and four application times (pre-sowing, three fully-expanded leaves, six leaves, and pre-flowering).A randomized block design was used, with four replica tions. Weed control in the culture was performed manually, using a hoe. Toxic effects caused to sorghum by 2,4-D were observed at 15 days after application (DAA), regardless of dose or time of application. The increasing levels of 2,4-D caused a linear reduction in plant height, biomass and green dry matter accumulation, both at 30 DAA as the point of rollover. The application of 2,4-D affected sorghum yield, especially at doses above 1.005 g ha -1 and late applications. In general, the use of 2,4-D in pre-sowing proved to be a good alternative for the management of weeds in sorghum crop.

PRODUÇÃO DE FITOMASSA E CICLAGEM DE NUTRIENTES POR PLANTAS DE COBERTURA NO CERRADO PIAUIENSE

Research on the performance of cover crops in crop systems of annual crops in the Brazilian state of Piauí contributes to increases in yield, greater efficiency of fertilizers and mitigation of environmental impacts. The aim of this study was to evaluate the performance of cover crops in terms of biomass production and the accumulation and release of nutrients during the crop season (November to April) in an oxisol in the Brazilian Cerrado in the state of Piauí that was submitted to different crop production systems including soybeans, maize and upland rice. The experiment was established during the 2010/11 and 2011/12 crop years in the rural area near the municipality of Bom Jesus, Piauí. The experimental design was a randomized block in a split-plot array. Different soil management systems (conventional and no-till) were evaluated in the main plots. Different crop production systems consisting of cover crops sown in the off-season (April to November), and annual crops sown during the crop season (November to April) were implemented in the subplots. The crop production systems that included Urochloa ruziziensis and Pennisetum glaucum overseeded on soybeans and Urochloa ruziziensis simultaneously intercropped with maize stood out in terms of biomass production and the accumulation and release of nutrients. Yields of maize and upland rice declined when sown under newly implemented no-till soil management.

Sistemas de produção no controle de plantas daninhas em culturas anuais no Cerrado Piauiense

O estudo foi conduzido para avaliar a contribuicao do uso de plantas de cobertura em sistema de plantio direto e convencional nas culturas de soja, milho e arroz no Cerrado piauiense. O experimento foi realizado nos anos agricolas 2010/2011 e 2011/12, de outubro 2010 a abril de 2012, na Serra do Quilombo, Fazenda Celeiro, municipio de Bom Jesus, PI. O delineamento utilizado foi o de blocos casualizados, em parcelas subdivididas, com os sistemas de manejo do solo: preparo convencional e plantio direto avaliados nas parcelas, e nas subparcelas, cinco sistemas de producao com culturas anuais (soja, milho e arroz) e plantas de cobertura. O sistema de plantio direto, por meio da producao de fitomassa oriunda da sobressemeadura de Urochloa ruziziensis e Pennisetum glaucum na soja, Urochloa ruziziensis semeada em consorcio simultâneo com o milho, resultou em reducoes significativas na emergencia e acumulo de fitomassa seca das plantas daninhas predominantes na area (Spermacoce latifolia, Chamesyce hirta, Amaranthus viridis, Digitaria sanguinalis e Cenchrus echinatus).

Sorção e dessorção de diuron em Latossolo sob a aplicação de biochar

The objective of this study was to verify the kinetics of sorption and desorption of diuron in an Oxisol under application of biochar. The samples were collected in a field experiment conducted in randomized design blocks consisted of 2 base fertilization levels (0 and 400 kg∙ha−1 NPK 00-20-20 fertilizer formula) and 3 doses of biochar (0, 8 and 16 Mg∙ha−1). In the evaluation of sorption and desorption, Batch Equilibrium method was used. The kinetics of sorption and desorption of diuron, total organic carbon, fulvic acid, humic acid and humin, pH and partition coefficient to organic carbon were evaluated. The Freundlich isotherm was adjusted appropriately to describe diuron sorption kinetics in all the studied treatments. The application of biochar provided increment in the sorption (Kf) and reduction in the desorption of diuron in 64 and 44%, respectively. This effect is attributed to the biochar contribution to the total organic carbon and C-humin and of these to diuron through hydrophobic interactions and hydrogen bonds. The positive correlation between the partition coefficient to organic carbon and Kf confirms the importance of soil organic compartment in the sorption of diuron. There was no competition of NPK fertilizer for the same sorption site of diuron. The increase and reduction in sorption and desorption, respectively, show that the application of biochar is an important alternative for the remediation of soil leaching of diuron, especially in sandy soils.Bragantia, Campinas, v. 75, n. 4, p.487-496, 2016 AbstrAct: The objective of this study was to verify the kinetics of sorption and desorption of diuron in an Oxisol under application of biochar. The samples were collected in a field experiment conducted in randomized design blocks consisted of 2 base fertilization levels (0 and 400 kg∙ha−1 NPK 00-20-20 fertilizer formula) and 3 doses of biochar (0, 8 and 16 Mg∙ha−1). In the evaluation of sorption and desorption, Batch Equilibrium method was used. The kinetics of sorption and desorption of diuron, total organic carbon, fulvic acid, humic acid and humin, pH and partition coefficient to organic carbon were evaluated. The Freundlich isotherm was adjusted appropriately to describe diuron sorption kinetics in all the studied treatments. The application of biochar provided increment in the sorption (Kf) and soil And PlAnt nutrition Article

Efeito de fungicidas para o controle da Ramularia areola na cultura do algodoeiro

Among the diseases that cause leaf spots in the cotton crop, ramularia leaf spot has become important in tropical environments since the weather conditions are favorable to the pathogen development. The aim of this study was to evaluate the performance of fungicides difenoconazole, triphenyltin hydroxide, trifloxystrobin, prothioconazole and mancozeb, alone or in mixtures, in controlling ramularia leaf spot in the cotton crop. The experiment was carried out in the 2014/2015 crop season, at a farm located in Sapezal Municipality, Mato Grosso State. Experimental design was in randomized blocks with four replicates and split plot in time. Seven Lopes, L.O.; Lacerda, J.J.J.; Mielezrski, F.; Ratke, R.F.; Lira, D.N.S.; Pacheco, L.P. Effect of fungicides on Ramularia areola control in the cotton crop. Summa Phytopathologica, v.43, n.3, p.229-235, 2017. evaluations of ramularia spot severity levels were performed with seven treatments. Fungicides were applied eight times, at 15-day intervals. At the end of the experimental period, the yield and the control effectiveness of fungicides were evaluated in comparison with control. Fungicide applications reduced yield damage caused by the attack of the fungus Ramularia areola. Triphenyltin hydroxide alone or in combination with difenoconazole allowed greater control of ramularia spot severity than the combination of trifloxystrobin + prothioconazole with difenoconazole, or diphenoconazole

Produção de fitomassa em sistemas de produção de soja em sucessão a culturas e plantas de cobertura

The objective of this work was to evaluate the biomass (leaves and stems) production of annual and cover crops sown as second crop, and its effects on soybean yield in succession. The experiment was carried out in the 2014/2015 and 2015/2016 crop seasons. Soybean was sown in the crop season and in the second crop, in a randomized complete block design, in nine production systems (treatments) consisting of annual crops (corn, sunflower, and cowpea) and cover crops (Pennisetum glaucum, Crotalaria breviflora, C. spectabilis, Urochloa ruziziensis, Cajanus cajan, Stylosanthes sp., and U. brizantha), which were grown in monocropping or intercropping systems, besides fallow as a control. Monocropped P. glaucum and U. ruziziensis showed a faster establishment and growth of plants, higher-total biomass and soil cover rate in the 2014 crop season. In 2015, corn intercropped with U. ruziziensis and C. spectabilis, and sunflower with U. ruziziensis stood out for total biomass production during flowering and after harvesting of corn and sunflower grains. Biomass composition in the systems showed greater proportions of stems than of leaves, and C. spectabilis stood out after senescence. Sown as a second crop, C. spectabilis promotes yield increase of soybean grown in succession in the no-tillage system.