Alessandra Monteiro Salviano Mendes

Bioavailability of cadmium and lead in a soil amended with phosphorus fertilizers

Fertilizantes fosfatados sao essenciais para obtencao de altas produtividades, entretanto, eles podem conter metais pesados que podem contaminar o solo e ameacar a saude humana e animal. Este trabalho objetivou a determinacao da concentracao de Cd e Pb em diferentes fertilizantes fosfatados, bem como a absorcao desses metais por plantas de mucuna preta cultivadas em casa-de-vegetacao em solo submetido a diferentes doses desses fertilizantes. Os tratamentos foram arranjados em esquema fatorial 4 x 5, dispostos em delineamento experimental inteiramente casualizado, com tres repeticoes, sendo os fatores quatro fontes de P (superfosfato triplo-ST, termofosfato de Yorin-TY, fosfato de Araxa-FA e fosfato de Gafsa-FG) e cinco doses de P2O5 (0, 92, 183, 275 e 366 kg ha-1). Os dados foram submetidos a analise de variância e equacoes de regressao foram ajustadas. A disponibilidade de Pb para mucuna preta nos solos nao foi alterada pela aplicacao de nenhum dos fertilizantes testados. No entanto, a absorcao de Cd pelas plantas foi significativamente aumentada pela aplicacao de qualquer um dos fertilizantes, sendo esta absorcao proporcional as doses aplicadas. O TY e o ST foram responsaveis pelas maiores concentracoes de Cd na parte aerea das plantas, enquanto as menores foram observadas com a aplicacao dos fosfatos naturais. Todas as fontes de fosforo disponibilizaram Cd para as plantas no primeiro cultivo. Entretanto, a absorcao de Cd so foi detectada no segundo cultivo para os fertilizantes ST e FG.

Crescimento de meloeiro e acúmulo de nutrientes na planta sob irrigação com águas salinas

This study was conducted in a greenhouse at the Environmental Sciences Department of the Federal Rural University for the Semi-Arid. Four soil types, traditionally used for cantaloupe production in the Mossoro Region, were used and irrigated with solutions corresponding to eight electrical conductivities (EC = 100; 250; 500; 750; 1,250; 1,750; 2,250 and 3,000 µS cm-1) and two sodium adsorption ratios [SAR = 4 and 12 (mmol L-1)1/2], combined as salinity treatments. The experiment was a factorial arrangement of 4 x 8 x 2 (four soils, eight EC and two SAR), with three replicates, and 192 experimental units, in a randomized block design. Plant characteristics (fresh and dry matter production and mineral composition) were evaluated. Fresh and dry cantaloupe production was reduced with increased water salinity in two successive crops, leading to plant death a few days after transplanting in the second cycle. Increased water salinity elevated Ca, Mg, Na, K and Cl accumulation in the plants. Saline water use increased salinity and sodicity of all studied soils, diminishing cantaloupe growth.

Decomposição e liberação de nutrientes de coquetéis vegetais para utilização no Semiárido brasileiro

The decomposition and release of nutrients from plant residues can play an important role in the maintenance of soil fertility in semi-arid regions. Thus this study aimed to evaluate the rate of decomposition of dry matter (DM) and the release of carbon (C) and nutrients from plant mixtures used as green manure in the Brazilian Semi-arid regions. The experiment was carried out in a greenhouse, from November 2007 to July 2008, using plant mixtures made up of leguminous species (L) (calopo, Crotalaria juncea, Crotalaria spectabilis, jackbean, pigeon pea, lab-lab) and non-leguminous species (NL) (sesame, sunflower, castor, millet and sorghum) combined to give the following treatments: T1 - 100% NL, T2 - 100% L, T3 - 75% L and 25% NL, T4 - 50% L and 50% NL, T5 - 25% L and 75% NL. The rates of decomposition and the release of nutrients were monitored through collection of the residue at 8; 15; 30; 60; 90; 120; 150; 180 and 210 days after the beginning of the experiment. A randomized-block design was used, with three replications. The mixtures showed similar decomposition rates of DM and nutrient release, except for Ca, Cu and Mn, where the mixtures composed predominantly of NL species showed a higher release rate./ From the average values of k for all of the mixtures, it was possible to establish the following order of release of macronutrients: K> N> Ca> Mg> P and micronutrients: Fe> Mn> Cu> Zn> B.

Acúmulo de metais pesados e alterações químicas em Cambissolo cultivado com meloeiro

Soil cultivation using agrochemicals may increase the concentration of availability of heavy metals to plant and cause contamination of the trophic chain as well. This work was carried out to evaluate the influence of length of time under cultivation with melon (Cucumis melo L.) on the heavy metals accumulation and chemical alterations in Ultisol. Melon plantations of one, two and three years were studied. A benchmark area under natural vegetation was used to compare the data obtained. The results showed that the lengthiest time under cultivation altered the chemical characteristics of the soil. An increase in pH and contents of N, P and K was observed for the two soil layers evaluated. On the other hand, Ca contents were decreased by cultivation. The larger the cultivation time the higher the concentration of N, Pb, Cu, and Mn in the soil surface layer, whereas the Fe and Zn concentrations were diminished in both analyzed soil layers, though available concentrations are still regarded as low in soil.

Response of Passiflora setacea to Mycorrhization and Phosphate Fertilization in a Semiarid Region of Brazil

The Caatinga is a unique biome that encompasses nearly 11% of Brazils territory and contains diverse vegetation composed of trees and bushes that have been scarcely studied from the economic perspective. In this context, Passiflora setacea may constitute a strategic alternative for agriculture because it produces fruit that has commercial potential and is tolerant to some diseases. Some species of Passiflora show more robust growth when associated with arbuscular mycorrhizal fungi (AMF) and are dependent on mycorrhization. In this study, the response of P. setacea to phosphate (P) fertilization and mycorrhization with Claroideoglomus etunicatum was evaluated. The experimental design included eight replicates of four randomized treatments: non-inoculated plants (NI), plants fertilized with phosphorus (P), mycorrhized plants (AMF), and plants that were both fertilized and mycorrhized (P+AMF). The plant height, leaf number, leaf area, fresh biomass (FB), and dry biomass (DB) of the shoots and roots, nutrient content, mycorrhizal colonization (MC), and the number of glomerospores (NG) in the rhizosphere were evaluated. The MC and the NG were reduced by phosphate fertilization. The development of the mycorrhized plants was significantly better than the NI and P treated plants for all of the variables tested. Inoculation with C. etunicatum promoted the growth of P. setacea seedlings even in the absence of phosphate fertilization, reducing production costs and strengthening the potential of P. setacea as a viable agricultural alternative for the semiarid region.

Physical attributes of ultisol of Brazil’s northeastern semiarid under organic farming of wine grapes

The purpose of this study was to evaluate the effects of organic farming of wine grapes under physical and chemical characteristics of Ultisol Brazils northeastern semiarid region. The samples of soil were collected from the row and interrow of the farming and from the fallow area, at the depths of 0.0-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.60 m. The samples were collected at six and twelve months after the culture implementation to evaluate the state of aggregation, bulk density and total soil porosity, flocculation index and organic matter contents, calcium, magnesium, and sodium. The results were submitted to statistical analysis. The adoption of organic farming contributed to the soil aggregation process. The bulk density and total soil porosity did not differ significantly between the evaluations, but were within the critical limits for sandy soils. The index flocculation did not have a great influence on the aggregates formation, being this process influenced by organic matter. The period of one year was considered short to obtain conclusive results in improving the soil quality by organic farming, since there are difficulties in tropical soils in promoting significant increases in organic matter content in short time.