Maria Isidória Silva Gonzaga

Rhizosphere characteristics of two arsenic hyperaccumulating Pteris ferns

Better understanding of the processes controlling arsenic bioavailability in the rhizosphere is important to enhance plant arsenic accumulation by hyperaccumulators. This greenhouse experiment was conducted to evaluate the chemical characteristics of the rhizosphere of two arsenic hyperaccumulators Pterisvittata and Pterisbiaurita. They were grown for 8 weeks in rhizopots containing arsenic-contaminated soils (153 and 266 mg kg(-1) arsenic). Bulk and rhizosphere soil samples were analyzed for water-soluble As (WS-As) and P (WS-P), pH, and dissolved organic carbon (DOC). Comparing the two plants, P.vittata was more tolerant to arsenic and more efficient in arsenic accumulation than P.biaurita, with the highest frond arsenic being 3222 and 2397 mg kg(-1). Arsenic-induced root exudates reduced soil pH (by 0.74-0.92 units) and increased DOC concentrations (2-3 times) in the rhizosphere, resulting in higher WS-P (2.6-3.8 times higher) compared to the bulk soil. Where there was no difference in WS-As between the rhizosphere and bulk soil in soil-153 for both plants, WS-As in the rhizosphere was 20-40% higher than those in bulk soil in soil-266, indicating that the rate of As-solubilization was more rapid than that of plant uptake. The ability to solubilize arsenic via root exudation in the rhizosphere and the ability to accumulate more P under arsenic stress may have contributed to the efficiency of hyperaccumulator plants in arsenic accumulation.

Management of soil organic matter and carbon storage in tropical fruit crops

Com este trabalho objetivou investigar as mudancas na dinâmica e no estoque de carbono em solos agricolas. Amostras de solo foram coletadas de 0-10 cm e 10-30 cm, em duas areas agricolas (cultivo de banana (Musa spp) e cultivo de citros (Citrus sinensis). Um solo em floresta nativa foi utilizado como referencia e para determinacao do Indice de Manejo de Carbono (IMC). A materia orgânica do solo (MOS) foi fracionada fisicamente em particulada (MOP, > 53 µm) e complexada (MOC, < 53 µm). O carbono orgânico total (COT) foi analisado para caracterizar a MOS. Comparando com o solo em mata nativa o cultivo da banana aumentou o teor de carbono orgânico do solo (TOC) em aproximadamente 14% enquanto o cultivo de citros reduziu o teor de TOC em cerca de 38%. O cultivo de fruteiras reduziu a fracao particulada em mais de 50% mostrando uma velocidade de decomposicao maior dos residuos orgânicos. Os valores do Indice de Manejo de Carbono foram menores que 1 em todos os tratamentos; entretanto, foram observados os melhores resultados para o pomar de citros (116,5). No geral, a mudanca no uso da terra de mata nativa para culturas de frutas reduziu o teor de materia orgânica do solo, especialmente sua fracao labil, e a qualidade do solo.

Uso de rejeito da dessalinização na solução nutritiva da alface, cultivada em fibra de coco

A escassez de agua de boa qualidade na regiao semiarida leva ao uso de agua salobra para a irrigacao. Este trabalho teve como objetivo avaliar o efeito do uso de rejeito da dessalinizacao na solucao nutritiva, sobre a producao da alface (Lactuca sativa L.), cultivada em sistema hidroponico com o substrato fibra de coco. O ensaio foi desenvolvido em um ambiente protegido do Departamento de Ciencias Ambientais, da Universidade Federal Rural do Semi-Arido, em Mossoro-RN, instalado em delineamento experimental de blocos ao acaso, em esquema fatorial com cinco x dois tratamentos e tres repeticoes, testando-se cinco niveis de salinidade da solucao nutritiva, obtidos com ou sem a necessidade de diluicao da agua de rejeito da dessalinizacao (CE 1,1; 2,4; 3,6; 4,7 e 5,7 dS m-1) e dois cultivares de alface (Veronica e alface roxa, cv. Quatro Estacoes). As plantas cresceram bem em todos os niveis de salinidade, mostrando que as aguas residuarias do processo de dessalinizacao podem ser usadas como fonte potencial de agua para a producao hidroponica de alface, embora as perdas de producao tenham aumentado com a salinidade, (6 a 8% por unidade de condutividade eletrica) , chegando a 28-35% para a solucao totalmente preparada com agua de rejeito. O cv. Quatro Estacoes mostrou maior tolerância a salinidade do que Veronica.

BIOCARVÃO DE LODO DE ESGOTO E SEU EFEITO NO CRESCIMENTO E NAS CARACTERÍSTICAS MORFOLÓGICAS DE MUDAS DE EUCALIPTO ( Eucalyptus grandis W.Hill ex Maiden)

The use of sewage sludge (biosolids) biochar in the forest seedlings growing media can become an environmentally interesting strategy to improve seedlings quality. Therefore, the aim of this study was to evaluate different rates of application (0, 20, 40, 80 and 100 t ha -1 ) of biosolid biochars on the growth and morphological traits of eucalyptus ( Eucalyptus grandis ) seedlings. The treatments were arranged in a completely randomized design with four replications. Ten-week old eucalyptus seedlings were transferred to the pots and allowed to grow for eight weeks. Chlorophyll content, plant height and stem diameter were measured at 0 (time 1), 30 (time 2) and 60 (time 3) days after transplant. Shoot and root biomass were measured after plant harvest. Biochar was effective in improving the seedlings quality. Increasing rate of application of biochar did not significantly influence chlorophyll content. At 60 days after planting, plant height increased and stem diameter decreased when high doses of biochar were applied. The use of sewage sludge biochar improved the growth and the morphological traits of the eucalyptus seedlings, therefore its application can be recommended as soil amendment and soil conditioner. According to the Dickson Quality Index, the best eucalyptus seedlings were obtained with 20 and 40 t ha -1 of biochar.

PRODUÇÃO E APORTE DE CARBONO, NITROGÊNIO E FÓSFORO NA SERAPILHEIRA FOLIAR DO PARQUE NACIONAL SERRA DE ITABAIANA

Litter is a major route of return of nutrients in the system plant–soil -plant and its determination allows to analyze the restructuring of anthropogenic forest environments. Knowledge of litter production is a critical in determining the potential for regeneration of an area through the intake and nutrient cycling. This study aimed to quantify the litter production and the carbon contribution and leaf fraction nutrients in areas of occurrence of Quartzipsamments with vegetation at different stages of regeneration in National Park Serra de Itabaiana in Sergipe, state. In each of the areas of Areia Branca Aberta (ABA), Areia Branca Intermediaria (ABI) and Areia Branca Fechada (ABF), settled collectors where the litter was collected monthly from January to December 2011. In the litter subsamples amounts of carbon (C), nitrogen (N) and phosphorus (P) were determined. Along with the action of fire in the areas of Areias Brancas of Serra de Itabaiana Park, it became clear that it changes the state of dynamic equilibrium achieved by the ecosystem, so the nutritional soil conditions are modified. The accumulation of C, N and P showed no significant seasonal variation according to the production of litter in each area studied, and the ABF area provided the largest accumulations of these elements throughout the evaluation period.

MATÉRIA ORGÂNICA E ÍNDICE DE MANEJO DE CARBONO DE SOLO TRATADO COM RESÍDUO COMPOSTADO E EM COMPOSTAGEM LAMINAR

The use of organic residues and compost is a common practice to improve soil quality and content of organic matter. In this study, the labile and stable fractions of soil organic matter were evaluated after application of layers of fresh (non-composted) or composted organic residues in a 6-year-old citrus orchard. The experiment was set up as a randomized block design, with 6 treatments: control without NPK, control with NPK, non-composted organic residue (NCOR, with and without NPK), and composted organic residue (humus, with and without NPK), with three replicates. The treatments were applied under the plant canopy. Soil samples were collected from the 0-0.05, 0.05-0.10, and 0.10-0.15 m layers. There were increases of 10.3, 22.4, 16.3, and 37.1 % in the organic carbon contents of the surface soil for the treatments using NCOR without NPK, NCOR with NPK, humus with NPK, and humus without NPK, respectively. The organic carbon contents of the labile fraction varied from 1.0 to 12.8 g kg, representing between 8 and 62 % of the total carbon. The carbon concentrations in the stable fraction varied from 3.1 to 9.7 g kg , representing between 38 and 92 % of the total carbon, and this was the dominant fraction for most of the treatments.