Métodos químicos para extração de boro no solo.

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Effect of glyphosate on nodule formation and its interrelation with nickel content in glyphosate-resistant soybeans.

Recent research has demonstrated that glyphosate can decrease biological nitrogen fixation in glyphosate-resistant (GR) soybeans, however this reduction has been attributed directly to the effect of glyphosate on the microorganisms or indirectly through its intermediates that are also toxic to these microorganisms. This work aims to demonstrate that glyphosate can influence the symbiotic N2 fixation by lowering nickel content available to the microorganisms. The experiment was conducted in the greenhouse at the State University of Maringá, PR, Brazil during the summer cropping season, 2008. The experimental design was a completely randomized blocks in a factorial scheme 4 x 3 x 2 where the first factor was: (T1 - single application of glyphosate (900 g a.e. ha-1) at the four-leaf stage; T2 - sequential application (450 + 450 g a.e. ha-1) at the four-leaf and five-leaf stage; T3 - without glyphosate; T4 - non-GR parental line]; the second factor, maturity group (early, medium and late;) and third factor soil type. Under glyphosate use, GR soybeans showed reduced photosynthetic parameters, nickel contents, and nodule, shoot and root dry biomass

Effect of glyphosate on nutrient contents in glyphosate-resistant soybeans.

Although GR soybean technology is spread all over the countries involved in soybean production, there is no particular fertilizing recommendation under glyphosate use and not much has been reported in the influence of glyphosate on GR soybean status. The objective of this work was to evaluate the mineral status of GR soybeans and their non-GR parental lines under glyphosate use. Considering different soil types and cultivar maturity groups, a significative decrease in macro and micronutrients leaf contents and in photosynthetic parameters (chlorophyll, photosynthetic rate, transpiration and stomatal conductance) was observed under glyphosate use (single or sequential application), both when compared to their respective non GR parental lines and GR soybeans not submitted to glyphosate use. Shoot and root dry biomass productions were affected by glyphosate presence for all cultivars evaluated in both soils, probably because of a sum of effects: decrease of photosynthetic parameters, nutrient uptake and content into the plants

Effect of increasing doses of glyphosate on water use efficiency and photosynthesis in glyphosate-resistant soybeans.

The increase cultivated area of GR soybeans across different regions of the world have raised questions not yet answered as related secondary effects of glyphosate on physiology of GR soybeans. In this work, we attempted to measure the effect of increasing glyphosate doses on water absorption and photosynthetic parameters of soybean, cv. BRS 242 GR. Plants were grown in completed nutrient solution (Hoagland & Arnon, 1950) in a greenhouse equipped with an evaporative cooling system (25?35 : 20?22C day/night) under natural daylight. The commercially formulated isopropylamine salts of glyphosate was sprayed on foliar doses of 450, 675, 900, 1350 and 1800 g. e.a ha-1 either in single application at four leaf stage (24 DAE) and in sequential application (24 and 36 DAE) (50%-50%) at four and five leaf stages, respectively. Using an infrared gas analyzer (IRGA), fluorometer (pulse-modulated) and chlorophylometer, before and after herbicide application net photosynthesis (A), transpiration rate (E), stomatal conductance (gs), sub-stomatal CO2 (Ci), carboxilation efficiency (A/Ci), fluorescence (Fs), maximal fluorescence (Fms); yield of quantum efficiency (Y=Fm-Fs/Fms) and chlorophyll contents were monitored. In addition, water absorption was measured daily and biomass yield and water use efficiency (WUE) were estimated by harvesting plants at R1 stage. All measures of photosynthetic parameters (A, E, gs, Ci) and Fs, Fms and Y were affected by increasing glyphosate doses. Chlorophyll contents were reduced right after glyphosate use, however with decreased in chlorophyll content and carboxilation efficiency, (A/Ci) the values suggest that glyphosate might have interfering, in some way, in the synthesis of chlorophyll and/or in carboxilative metabolism of photosynthesis (Calvin cycle), which contributed to dry biomass reductions. Total amount of water absorbed and biomass production by plants were also decreased as glyphosate doses increased, with a more intense effect of single application, as compared to sequential. WUE was also significantly reduced with increasing glyphosate doses. Under single and sequential application, soybean plants need 13 to 20% and 8 to 14% more water to produce the same amount of biomass, respectively

Produção, carbono e rentabilidade econômica de Pinus elliottii e Eucalyptus grandis em sistemas silvipastoris no Sul do Brasil.

O presente trabalho teve por objetivos estimar a produção de madeira, o estoque de carbono e a rentabilidade econômica, incluindo a venda de créditos de carbono de plantações de Eucalyptus grandis e Pinus elliottii em consórcio com pastagens. Foram utilizados dois experimentos com cada espécie, todos instalados em Alegrete, RS, em áreas de pastagem natural. Os experimentos possuíam três tratamentos, dois deles constituídos por sistemas silvipastoris implantados em fileiras triplas de árvores, com ambas as espécies no espaçamento de 3,0 m x 1,5 m, sendo o primeiro com um corredor de 14 m, entre as fileiras triplas, destinado ao pastejo dos animais, e o outro com um corredor de 34 m. O terceiro tratamento possuía o cultivo isolado das duas espécies florestais, com espaçamento de 3,0 m x 3,0 m. Foram simulados desbastes e corte final aos 21 anos de idade para todos os tratamentos. As árvores propiciaram retorno econômico em todos os sistemas testados, com rentabilidade a partir do desbaste aos 7 anos de idade. A venda de créditos de carbono torna o componente florestal ainda mais atrativo devido, principalmente, à receita auferida desde o início do projeto