Transferênce de metais pesados, flúor e radionuclídeos para solos agrícolas na bacia do rio Corumbataí (SP)

The use of phosphate fertilizers and amendments in sugar cane crops may increase the concentration of some elements in soils, from where they would become available for plants (principally in acid soils) and transferred to me human food chain. This paper reports the transference of heavy metals (Cd, Cr, Cu, Ni, Pb and Zn), fluorine and radionuclides ( 238U, 234U, 226Ra, 232Th and 40K) from phosphate fertilizers and amendments to agricultural soils at Corumbatal River basin (SP). The products utilized and colleted in sugar cane crops at Corumbatai River basin are: phosphate fertilizers NPK 5:25:25 (two samples), limestones (three samples), phosphogypsum (two samples) and KCl (two samples). The heavy metals were determined by atomic absorption spectrometry (AAS), fluorine by potentiometry and radionuclides by alpha and gamma spectrometry. Heavy metals (17.8, 31.2, 75.2, 69.5, 138.8, 114.9 and 342.9 g/ha of Cd, Cr, Cu, Ni, Pb, Zn and F, respectively) and radionuclides (0.47, 0.16, 0.17 and 6.33 Bq/kg of soil to 238U, 226Ra, 232Th and 40K, respectively) incorporated in phosphate fertilizers and amendments are annually added in the sugar cane crops, but if utilized in accordance with the recommended rates, they do not raise the concentration levels in soils up to hazards values.

Tolerance of physic nut plants to aluminum activity in nutrient solution

Plants have different levels of tolerance to phytotoxic effects of aluminum and the exploitation of this characteristic is of significant importance to the use of acid soils. This research aimed to evaluate the effect of aluminum activity in nutrient solution on growth of physic nut young plant. After seven days of adaptation, plants were submitted to Al concentrations of 0; 200; 400; 600; 800 and 1,000 μmol L-1, corresponding to Al3+ activity solution, of: 14.5, 21.4; 46.6; 75.6; 108.3 e 144.8 μmol L-1, respectively. The increased activity of Al3+ decreased linearly the number of leaves, plant height, leaf area, shoot dry matter and root length of physic nut plant. Physic nut young plants are sensitive to high aluminum activity in solution. The root length, number of leaves, shoot dry matter and total dry matter were variables more affected by Al activity in solution, and can be used to discriminate the tolerance levels to aluminum in physic nut plants. The accumulation of aluminum increased in a activity-dependent manner; however, its translocation from root to shoot was low.

Influência do manganês no crescimento e na composição mineral de mudas de caramboleira

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação da tolerância ao alumínio em Urochloa spp

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Corretivos de acidez e fontes de fósforo na disponibilidade de P no solo, nutrição e produção do amendoim e do capim marandu

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dinâmica do carbono em pequenas bacias de drenagem sob uso de agricultura familiar na Amazônia Oriental

O presente estudo teve como objetivo avaliar a dinâmica do carbono em uma região da Amazônia Oriental, cujo uso da terra predominante é a agricultura familiar; a unidade espacial adotada neste estudo foram três pequenas bacias de drenagem. A dinâmica do carbono foi avaliada a partir de medidas hidrológicas e biogeoquímicas em águas dos igarapés Cumaru, Pachibá e São João entre junho de 2006 a maio de 2007. O ambiente aquático e a hidrogeoquímica fluvial foram caracterizados a partir de medidas in situ da condutividade elétrica, temperatura, pH e concentração de oxigênio dissolvido. Amostras de água foram coletadas e analisadas para determinação do carbono orgânico dissolvido (COD) e pressão parcial do dióxido de carbono (pCO 2 ). A partir dos valores de pCO 2 , foram calculadas as concentrações de carbono inorgânico dissolvido (CID). Já os fluxos de C02 foram medidos in situ e também calculados a partir do pC0 2 . Utilizando-se medidas de vazão instantânea a cada campanha mensal de campo, calcularam-se fluxos anuais de COD. A caracterização dos solos e do uso da terra nas porções estudadas das bacias, assim como os índices pluviométricos e fluviométricos, foram considerados na interpretação dos resultados. Podem-se enumerar como principais resultados o seguinte: 1) As características físico-químicas das águas fluviais das bacias estudadas retrataram seus solos ácidos, a vegetação ripária, e processos hidrológicos biogeoquímicos no ambiente aquático e terrestre, e com certa variabilidade sazonal; 2)0 pH e o oxigênio dissolvido se correlacionaram positivamente com o carbono dissolvido na coluna d'água; 3) O transporte de COD por unidade de área foi elevado quando comparado com outras bacias amazônicas, e mais intenso em períodos chuvosos; 4) O transporte de COD e a evasão de C0 2 pareceram responder positivamente à presença de vegetação secundária e floresta densa, e negativamente às atividades agropecuárias; e 5) As taxas de evasão de C0 2 foram elevadas comparando-as a outros rios amazônicos, e corroboram a hipótese de que pequenas bacias são importante fontes de C0 2 para atmosfera na região.

Aplicação de calcário e gesso em sucessão de culturas em plantio direto irrigado: avaliações técnica e econômica

Pós-graduação em Agronomia - FEIS

Interação silício e alumínio em plantas de arroz de terras altas e mamona

Pós-graduação em Agronomia (Agricultura) - FCA

Calagem superficial e aplicação de gesso em sistema plantio direto de longa duração: efeitos no solo e na sucessão milho/crambe/feijão-caupi

Pós-graduação em Agronomia (Agricultura) - FCA

Influência do manganês no crescimento e na composição mineral de mudas de caramboleira

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Emissão de gases de efeito estufa e estoque de carbono no solo em função do manejo e correção de acidez

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aluminum toxicity in a tropical montane forest ecosystem in southern Ecuador

Aluminum phytotoxicity frequently occurs in acid soils (pH < 5.5) and was therefore discussed to affect ecosystem functioning of tropical montane forests. The susceptibility to Al toxicity depends on the sensitivity of the plant species and the Al speciation in soil solution, which can vary highly depending e.g., on pH, ionic strength, and dissolved organic matter. An acidification of the ecosystem and periodic base metal deposition from Saharan dust may control plant available Al concentrations in the soil solutions of tropical montane rainforests in south Ecuador. The overall objective of my study was to assess a potential Al phytotoxicity in the tropical montane forests in south Ecuador. For this purpose, I exposed three native Al non-accumulating tree species (Cedrela odorata L., Heliocarpus americanus L., and Tabebuia chrysantha (Jacq.) G. Nicholson) to increased Al concentrations (0 – 2400 μM Al) in a hydroponic experiment, I established dose-response curves to estimate the sensitivity of the tree species to increased Al concentrations, and I investigated the mechanisms behind the observed effects induced by elevated Al concentrations. Furthermore, the response of Al concentrations and the speciation in soil solution to Ca amendment in the study area were determined. In a final step, I assessed all major Al fluxes, drivers of Al concentrations in ecosystem solutions, and indicators of Al toxicity in the tropical montane rainforest in Ecuador in order to test for indications of Al toxicity. In the hydroponic experiment, a 10 % reduction in aboveground biomass production occurred at 126 to 376 μM Al (EC10 values), probably attributable to decreased Mg concentrations in leaves and reduced potosynthesis. At 300 μM Al, increased root biomass production of T. chrysantha was observed. Phosphorus concentrations in roots of C. odorata and T. chrysantha were significantly highest in the treatment with 300 μM Al and correlated significantly with root biomass, being a likely reason for stimulated root biomass production. The degree of organic complexation of Al in the organic layer leachate, which is central to plant nutrition because of the high root density, and soil solution from the study area was very high (mean > 99 %). The resulting low free Al concentrations are not likely to affect plant growth, although the concentrations of potentially toxic Al3+ increased with soil depth due to higher total Al and lower dissolved organic matter concentrations in soil solutions. The Ca additions caused an increase of Al in the organic layer leachate, probably because Al3+ was exchanged against the added Ca2+ ions while pH remained constant. The free ion molar ratios of Ca2+:Al3+ (mean ratio ca. 400) were far above the threshold (≤ 1) for Al toxicity, because of a much higher degree of organo-complexation of Al than Ca. High Al fluxes in litterfall (8.8 – 14.2 kg ha−1 yr−1) indicate a high Al circulation through the ecosystem. The Al concentrations in the organic layer leachate were driven by the acidification of the ecosystem and increased significantly between 1999 and 2008. However, the Ca:Al molar ratios in organic layer leachate and all aboveground ecosystem solutions were above the threshold for Al toxicity. Except for two Al accumulating and one non-accumulating tree species, the Ca:Al molar ratios in tree leaves from the study area were above the Al toxicity threshold of 12.5. I conclude that toxic effects in the hydroponic experiment occurred at Al concentrations far above those in native organic layer leachate, shoot biomass production was likely inhibited by reduced Mg uptake, impairing photosynthesis, and the stimulation of root growth at low Al concentrations can be possibly attributed to improved P uptake. Dissolved organic matter in soil solutions detoxifies Al in acidic tropical forest soils and a wide distribution of Al accumulating tree species and high Al fluxes in the ecosystem do not necessarily imply a general Al phytotoxicity.

Fijación biológica de nitrógeno por cuatro fabáceas en suelos ácidos de Tabasco, México

La fijación biológica de nitrógeno (FBN) es un proceso que ocurre en la naturaleza y representa la fuente de N más barata para los suelos ácidos del trópico húmedo. El objetivo de este trabajo fue cuantificar la cantidad de N fijado por cuatro especies de fabáceas a través de técnicas isotópicas con 15N, en un suelo de sabana en México. Los tratamientos se establecieron bajo un diseño de bloques completos al azar, con cuatro repeticiones. Las variables evaluadas fueron; biomasa fresca (BF), materia seca (MS), número de nódulos (NN), masa seca de nódulos (MSN), Nitrógeno total (Nt) y Nitrógeno fijado biológicamente (Nf). Los resultados muestran que Mucuna deerengiana L. presentó mayor producción de BF y MS (17,50 y 5,47 Mg ha-1) así como MSN (58,79 mg planta-1) y también mayor contenido de Nt y Nf (526,94 y 522,11 kg ha-1) respectivamente, en comparación con Cajanus cajan L., Phaseolus lunatus L. y Sesbania emerus L., especies que mostraron valores bajos en dichas variables. Se concluye que Mucuna deerengiana L. tolera bien los factores desfavorables que predominan en los suelos ácidos y por ello expresa una eficiencia superior a 500 kg ha-1 de Nf; se considera adecuada para aumentar el nivel de nitrógeno en los suelos de sabana sin aplicar fertilizantes químicos.

Comparación del poder de neutralización de enmiendas calcáreo-magnésicas en suelos de la Pampa llana santafesina

El objetivo de este trabajo fue comparar el poder de neutralización de enmiendas calcáreo- magnésicas y evaluar su efecto sobre el complejo de intercambio catiónico en suelos de la pampa llana santafesina. Para ello, se aplicaron tres enmiendas (caliza, dolomita y enmienda mezcla) a dos dosis (neutralización del 100% y 150% del hidrógeno de intercambio). Se evaluó: pH actual, pH potencial, hidrógeno, calcio y magnesio intercambiable luego de 60 días de incubación. El pH actual no mostró diferencias entre dosis, mientras que el incremento de pH de las enmiendas fue caliza > dolomita > mezcla. El pH potencial fue más sensible al tipo de enmienda y dosis. Todos los tratamientos redujeron el nivel de insaturación, aunque ninguno neutralizó la totalidad del hidrógeno intercambiable. En relación con el calcio intercambiable, todos los tratamientos produjeron aumentos y la mayor saturación cálcica se obtuvo con la aplicación de caliza o enmienda mezcla con la dosis necesaria para neutralizar 1,5 veces el hidrógeno intercambiable. En cuanto al magnesio, las enmiendas dolomita y mezcla aumentaron significativamente el contenido independientemente de la dosis. La información aquí presentada es de utilidad para la prescripción de enmiendas calcáreo- magnésica en los suelos de la Pampa llana santafesina.

Estudio de la ecología de Ulmus laevis Pallas en la Península Ibérica

Esta tesis doctoral pretende profundizar en el conocimiento de la ecología de Ulmus laevis Pallas, especie autóctona en peligro de extinción en la Península Ibérica, con el fin de proponer medidas adecuadas para su conservación. Se ha estudiado la distribución natural de la especie atendiendo a aspectos edáficos. Los resultados muestran que U. laevis presenta menor capacidad de acidificación de la rizosfera, menor actividad de la reductasa férrica y menor homeostasis que U. minor Mill. cuando crecen en sustratos con una disponibilidad de hierro limitada. Estas diferencias ayudan a comprender la distribución de ambas especies en la Península Ibérica: U. laevis se ve restringido a suelos ácidos o moderadamente ácidos, mientras que U. minor es capaz de habitar tanto suelos ácidos como básicos. Se han analizado las propiedades hidráulicas y anatómicas de U. laevis, constatando que sus características son favorables en ambientes con gran disponibilidad hídrica y que se trata del olmo ibérico más vulnerable a la cavitación por estrés hídrico, por lo que la aridificación del clima y la pérdida de los freáticos supone un riesgo para sus poblaciones. Para evaluar la capacidad de recuperación de la especie se han estudiado la diversidad y estructura genética espacial de las dos mayores poblaciones españolas. Los resultados evidencian que estas poblaciones mantienen niveles de diversidad equiparables o ligeramente superiores a los europeos, pese a haber sufrido un cuello de botella prolongado durante las glaciaciones y a las reducciones poblacionales recientes. En la actualidad la endogamia no representa un riesgo para estas poblaciones. También se ha analizado la producción, dispersión y predación de semillas en Valdelatas (Madrid). Los resultados han mostrado que el viento dispersa las sámaras a corta distancia (<30 m) y que los años no veceros las probabilidades de establecimiento de regenerado son bajas. Además, la producción de sámaras vanas puede tratarse de un carácter adaptativo que aumenta la eficiencia biológica de la especie, ya que favorece la supervivencia de las semillas embrionadas disminuyendo sus tasas de predación pre- y post-dispersión. La modificación del hábitat de esta especie como consecuencia de las actividades humanas afecta de manera negativa al establecimiento del regenerado. La conservación de esta especie a largo plazo requiere la recuperación de los niveles freáticos y de regímenes hidrológicos que permitan avenidas, ya que estas crean las condiciones adecuadas para el establecimiento de regenerado al eliminar la vegetación preexistente y depositar barro. ABSTRACT Ulmus laevis Pallas is an endangered species in the Iberian Peninsula. Therefore, in order to be able to propose adequate management guidelines for its conservation, this PhD Thesis intends to advance the knowledge on the species ecology in the region. Firstly, the species natural distribution was studied in relation to soil nature. Results show that U. minor Mill. had a higher root ferric reductase activity and proton extrusion capability than U. laevis, and maintained a better nutrient homeostasis when grown under iron limiting conditions. These differences in root Fe acquisition efficiencies proved helpful to understand the distribution of these species in the Iberian Peninsula, where U. laevis is restricted to acid or moderately acid soils, whereas U. minor can grow both in acid and basic soils. Secondly, we studied Ulmus laevis’ xylem anatomy and hydraulic traits. These proved favourable for growing under high water availability, but highly susceptible to drought-stress cavitation. Therefore, this species is vulnerable to the Iberian Peninsula’s aridification. Spatial genetic structure and diversity were evaluated in two of the biggest U. laevis populations in Spain in order to evaluate their recovery capabilities. These populations maintain similar or slightly higher diversity levels than European populations, despite having undergone an ancestral genetic bottleneck and having suffered recent population size reductions. No inbreeding problems have been detected in these populations. Seed production, dispersal and predation were assessed in Valdelatas’ elm grove (Madrid). Despite U. laevis samaras being winged nuts, wind dispersed them short distances from the mother tree (<30 m). The seed shadow models show that non-mast years provide very few chances for the stand to regenerate due to their low full seed flux. Empty samaras deceive pre- and post-dispersal predators increasing full seed survival probabilities. Therefore, empty fruit production might be an adaptive trait that increases plant fitness. Finally, human-induced changes in water-table levels and river regulation may affect U. laevis seed dispersal and regeneration establishment negatively. The long-term conservation and expansion of this species in the Iberian Peninsula requires the recovery of water-tables and of natural hydrological regimes, as flooding eliminates vegetation, creating open microhabitats and deposits mud, creating the ideal conditions for seedling establishment.