Felipe Carlos Alvarez Villanueva

Aproveitamento de nitrogênio pelo milho, em razão da adubação verde, nitrogenada e fosfatada

The objectives of this work were to evaluate corn (Zea mays) nitrogen (N) utilization from the green manure crops sunnhemp (Crotalaria juncea) and millet (Pennisetum glaucum L.) and from urea, and to calculate the contribution of soil N to the mineral nutrition of corn, as affected by nitrogen and phosphorus mineral fertilizers. The experiment was conducted in a greenhouse, in pots with 5 kg of soil (Rhodic Hapludox). The experimental design was completely randomized, with 32treatments and four replicates, in a 4x4x2 factorial array. The treatments were combinations of four N rates as urea: 0, 0.75, 1.50 and 2.25g N per pot (labeled or not with 15N); four P rates as triple superphosphate: 0, 0.175, 0.350 and 0.700g P per pot; and sunnhemp and millet labeled or not with 15N. Green manure dry matter provided 1 g N per pot. Corn plants were evaluated for dry mass yield, accumulated N, and N utilization from green manures, urea, and the soil. The mineral fertilizer supplied the largest amount of N to the corn plants, followed by N from soil and from green manures. The N utilization from sunnhemp by corn plants was greater than the N utilization from millet. The phosphorus application increased the assimilation of N from urea and from green manures.

Improving phosphorus availability from patos phosphate rock for Eucalyptus: a study with 32P radiotracer

Como geralmente os solos usados para plantacoes de eucalipto no Brasil sao de baixa fertilidade, a adubacao fosforica e indispensavel, incrementando o custo da plantacao. Especies mais eficientes no uso de fosforo (P) de fontes pouco soluveis poderiam ser uma opcao interessante. Porem, pouco se conhece ainda sobre o comportamento de eucalipto em relacao a capacidade de usar fosforo de fontes com diferente solubilidade em agua. O uso de P por eucalipto (E. urophylla, E. grandis, and E. urophylla ´ E. grandis), foi estudado em experimento de casa de vegetacao usando solo da Regiao de Cerrado, Latossolo Vermelho Amarelo hypodistrofico, e o metodo isotopico com 32P. As fontes de P usadas foram superfosfato triplo (SFT), rocha fosforica (RF) e a mistura de superfosfato triplo com rocha fosforica (SFT+RF). A eficacia das fontes de P em termos do aumento do rendimento de materia seca seguiu a ordem SFT = (SFT + RF) > RF e de P absorvido a ordem (SFT + RF) > SFT > RF por ambas as especies e o hibrido de eucalipto. O incremento na absorcao de P de RF, influenciada pela mistura com SFT foi de 217,3% em E. urophylla, 235,7% em E. grandis e 28,7% em E. urophylla ´ E. grandis, indicando o efeito benefico do SFT sobre a efetividade da RF. O hibrido E. urophylla ´ E. grandis foi o genotipo mais eficiente no uso de P do solo e E. grandis o mais exigente em P do fertilizante.

Aplicação de fósforo para imobilização química do cádmio em solo contaminado

The objective of the study was to evaluate the effect of phosphorus on the Cd availability to plants of a contaminated soil using 109Cd isotope and chemical extractants. The experiment was set in a randomized block design and the soil was labeled with 222 KBq of 109Cd per pot and received 5 rates of P as triple superphosphate, growing lettuce plants as test crop. The use of phosphorus reduced pH of soil which altered the Cd availability in DTPA and Mehlich extractants. The lettuce Cd content decreased but its accumulation and L value increased in all treatments compared to the control, demonstrating the inefficiency of phosphorus in reducing the Cd availability.

Chemical migration during soil water retention curve evaluation

Wetting and drying (W-D) cycles can induce important elemental migrations in soils. The main purpose of this work was to study the possible existence of soil chemical elemental migrations in samples submitted to repeated W-D cycles during evaluations of soil water retention curve (SWRC). The experimental measurements were carried out by Atomic Absorption Spectrometry (AAS) for Ca(2+), Mg(2+) and K(+) on samples of three different Brazilian tropical soils (Geric Ferralsol, Eutric Nitosol and Rhodic Ferralsol). Results demonstrate an increase in the electrical conductivity of the water extracted from the samples and significant losses of Ca(2+), Mg(2+) and K(+) during the applications of up to nine W-D cycles. It was also observed differences in SWRC for all soils when samples submitted to the application of several W-D cycles were compared with samples not submitted to it. These differences occurred at the region of both structural and textural pores. A possible explanation for these results could be the soil chemical migration during the sequences of W-D cycles, which can affect the soil structure development.

Fitodisponibilidad de Cd en suelo de diferente pH tratado con lodo albañal estimada por método isotópico y extracción química

The Cd phytoavailability in sewage sludge-amended soils of different pHs using the 109Cd L-value isotopic method and Cd extracted by DTPA has been determined. Maize plants (Zea mais L.) were grown under greenhouse conditions in a xanthic ferralsol at different pHs amended with five sewage sludge (SS) rates, and labeled with 74 kBq kg-1 of 109Cd. The SS rates altered the properties of the soil chemicals and these influenced the isotopic parameter (L-value) and percent of Cd uptake by plants from soil (%Cdpdfs) and SS (%CdpdfSS). L-values and Cd extracted by DTPA correlate significantly with SS rates and Cd uptake by plants and are efficient for predicting the Cd phytoavailability in the sewage sludge-amended soil.

Mudanças químicas e fitodisponibilidade de zinco estimada por método isotópico, em solo tratado com lodo de esgoto

Zn availability in Red Latossol (Rhodic Ferralsol) of different pH amended with different rates of sewage sludge was studied by the isotopic 65Zn L value method. Soil chemical properties were found to be altered by SS addition. Zn concentration and Zn derived from SS (ZnpfSS) in plant, and Zn phytoavailability (L value), were increased with increasing SS rates. The linear correlation coefficient of plant Zn with SS rates and with L value was significant at 1% probability. The L value proved an efficient method for predicting Zn phytoavailability in sewage sludge-amended soil with different pH under the soil conditions studied.

Solo contaminado com cádmio: extratibilidade do metal e cinética química de degradação da matéria orgânica de torta de filtro

The chemical kinetics of sugarcane filter cake (FC) organic matter degradation at rates (0, 40, 80, and 120 t ha-1) in non-contaminated and different degrees of cadmium-contaminated Oxisol (0.19, 28, 56, 112 and 200 mg Cd kg-1) and DTPA-extractable Cd was studied. FC degradation was determined by quantifying CO2 emitted from soil samples during 72 days of incubation. DTPA-extractable Cd was performed after the incubation period. FC degradation was described by a two-stage equation of chemical kinetics. FC degradation rates were between 15 and 33%. Total CO2 emitted from FC declined with increasing degree in Cd-contamination and the DTPA-extractable Cd declined with FC rates.