José Carlos Polidoro

Nitrogen Source Effect on Gluconacetobacter diazotrophicus Colonization of Sugarcane (Saccharum Spp.)

Biological nitrogen fixation (BNF) in sugarcane is considered one of the principal reasons for the success of the Brazilian Ethanol Program (PRO-ALCOOL) for motor car fuel. The BNF influences positively the energy balance of sugarcane crops for alcohol production. Gluconacetobacter diazotrophicus is a nitrogen-fixing bacterium associated with sugarcane, and is particularly abundant and active in the early stages after germination. The objective of this work was to evaluate the effect of the addition of increasing amounts of two sources of mineral nitrogen (ammonium sulphate and calcium nitrate) on the population of G. diazotrophicus and also to evaluate its effect on nitrogenase (acetylene reduction) activity and accumulation of N by two sugarcane hybrids, SP 701143 and SP 792312. The results showed that both varieties differed in the form of nitrogen they prefer to uptake from the soil. The variety SP 701143 preferred ammonium sulphate, whilst the variety SP 792312 preferred N from calcium nitrate. In both varieties, the addition of increased doses of ammonium and nitrate inhibited the population of G. diazotrophicus but in the variety SP 701143 the inhibition was more pronounced in the presence of calcium nitrate. The acetylene reduction activity was inhibited in both varieties, especially in variety SP 792312 in the presence of either of the two nitrogen sources.

Frações lábeis da matéria orgânica em sistema de cultivo com palha de braquiária e sorgo

Resumo - O papel fundamental da materia orgânica nas caracteristicas fisicas, quimicas e biologicas do solo, justifica o crescente interesse pela identificacao de sistemas de uso e de manejo que contribuam para o aumento do estoque de carbono em solos tropicais. O objetivo desse trabalho foi avaliar o estoque de carbono (EstC) na fracao particulada (>53 µm) da materia orgânica do solo e na fracao associada aos minerais (<53 µm). Amostras de um Latossolo Vermelho Distrofico foram coletadas em cinco profundidades no municipio de Montividiu - GO, nos seguintes sistemas agricolas: a) cultivo de braquiaria ( Brachiaria ruziziensi) na entressafra de soja (Glycine max) (SB), b) cultivo de sorgo (Sorghum bicolor L. Moench) na entressafra da soja (SS) e como area de referencia, Cerrado. Foram analisados os teores de carbono orgânico total (COT) e o fracionamento granulometrico da materia orgânica do solo. A partir dos valores encontrados foram quantificados os estoques de carbono em cada uma das fracoes. Foram verificadas diferencas significativas para os teores de COT em todas as profundidades avaliadas. Os maiores valores de EstC foram encontrados em SB, em todas as profundidades de amostragem. A fracao particulada da materia orgânica (MOP) mostrou-se um parâmetro eficaz em demonstrar diferencas de manejo entre os sistemas, apresentando maiores teores no sistema SB devido ao maior aporte de biomassa nesse sistema, ja para a fracao ligada aos minerais os maiores teores foram verificados na area de referencia, seguida pelo sistema SS. Palavras-chave - Capim braquiaria. Sorgo. Palha-utilizacao na agricultura.

Yield, Quality Components, and Nitrogen Levels of Silage Corn Fertilized with Urea and Zeolite

The zeolite and urea mixture may be use to improve nitrogen (N)–use efficiency of silage corn. The objective of this study was to evaluate dry-matter yield and nutritional levels of N of silage corn fertilized with urea and zeolite mixture. The experimental design was a 2 × 4 × 4 factorial randomized block design with three replications. Treatments included two types of stilbite zeolite (natural and concentrated), four levels of nitrogen (0, 50, 100, and 200 kg ha−1), and four ratios of zeolite (25%, 50%, and 100% of N level). Treatments were applied 60 days after planting with the topdressing fertilization. The use of concentrated (650 g kg−1 of stilbite) or natural (470 g kg−1 of stilbite) zeolite with urea increased silage corn dry-matter production and leaf N concentrations.

Frações húmicas da matéria orgânica do solo cultivado com soja sobre palhada de braquiária e sorgo

The soil organic matter (SOM) is the waste product of the biota, mainly of vegetables, partially decomposed and synthesized in various stages of complexity and structural diversity. The dynamics of organic matter influences the main chemical, physi - cal and biological processes of soils, and often determines soil fertility. The objective of this study was to quantify the fulvic acid, humic acid and humin content and evaluate the stock of these fractions in an Oxisol cultivated with soybean on straw of grass and sorghum in a savanna, Montividiu county (GO). Soil samples were taken at three depths in an area with grass growing between soybean crops (SB) and the other with the cultivation of sorghum between soybean crops (SS). The chemi- cal composition of total organic carbon (TOC) and chemical fractionation of soil organic matter were evaluated. From these values, the carbon stocks in each fraction were quantified. There were significant differences for the TOC levels between all systems evaluated and in all soil depths. Regarding the chemical fractions of organic matter, there was a predominance of the humin fraction (C-HU) as compared to the the humic (C-FAH) and fulvic (C-FAF) acid fractions in the two samples evalu- ated.

Rapid and sensitive determination of nitrate in plant tissue using flow injection analysis.

Abstract The determination of nitrate in waters and soil extracts by the reduction of nitrate to nitrite by metallic or liquid reductants followed by the colorimetric determination of NO2 ‐using the Griess‐Ilosvay reaction has been automated for use with air‐segmented auto‐analyzers or flow injection techniques. However, this technique is not applicable to plant extracts as organic species in the extracts inactivate the reduction columns. The objective of this study was to develop an automated procedure that would allow the determination of NO3 ‐in plant extracts without the necessity of prior manual treatment. A flow injection technique was developed that successively traps and releases NO3in an anion exchange column thereby removing pigments and other non‐ionic and cationic species that otherwise interfere with conversion of NO3 ‐ to NO2 ‐on a copperized cadmium column. This reduction step is subsequently followed by standard Griess‐Ilosvay colorimetric detection of this ion at a wavelength of 530 nm. The technique uses relatively simple and inexpensive equipment, principally a spectrophotometer equipped with a flow‐through cell and a pen recorder output, a 6‐channel peristaltic pump with accompanying tubing and a Perspex injector/commutator valve made in a laboratory workshop. The technique was found to avoid any significant interference of pigments or other organic compounds in the plant extracts, and the results compared favorably with those obtained using the manual transnitration technique. Analysis time was approximately 1.5 min per sample and could detect NO3’ concentration as low as 0.1 ug NO3’‐N ml/1 in plant extracts (10 ug NO3’‐N g‘1of plant material).

Evaluation of Techniques for Determination of Molybdenum in Sugarcane Leaves

Abstract In crops of the sugarcane, the concentrations of molybdenum (Mo) in the leaves are generally lower than 0.3 mg Mo kg−1. These low concentrations have resulted in limitations in the methods and instruments that can be used for these analyses. The objective of this study was to evaluate three different techniques to determine the concentration of Mo in sugarcane leaves sampled in the principal sugarcane‐producing areas in Brazil. Two spectrometric techniques were evaluated by using ICP‐EAS (Inductively Coupled Plasma‐Emission Automated System) and DCP‐MEAS (Direct Coupled Plasma–Multiple Emission Automated System) and a colorimetric technique of the reaction between potassium iodide and hydrogen peroxide (KI‐H2O2). The techniques ICP‐EAS and KI‐H2O2 produced results of satisfactory accuracy and precision, whereas the DCP‐MEAS consistently overestimated the Mo concentrations in cane leaves. The KI‐H2O2 technique showed sensitivity 5 times greater than the ICP‐EAS, with minimum detection limits of 0.1 and 0.5 mg Mo kg−1, respectively.

Eficiência agronômica e de recuperação de P de fertilizante fosfatado organomineral granulado produzido com cama de frango em solo arenoso e argiloso

The objective of this work was to evaluate the effect of inoculation with Azospirillum brasilense, associated with N rates and sources, in soil of the Cerrado (Brazilian savanna), on the grain yield of irrigated wheat (Triticum aestivum). The experiment was carried out under a no-tillage system in a Typic Haplustox. The experimental design was randomized complete blocks with four replicates, in a 2x5x2 factorial arrangement: two N sources (urea and urea with NBPT urease inhibitor); five N rates applied as topdressing (0, 50, 100, 150, and 200 kg ha-1); and with or without seed inoculation with A. brasilense. The increase in the N rates positively affected spike length, number of spikelets and of grains per spike, number of spikes per meter, N accumulation in the straw, leaf chlorophyll content, and grain yield of irrigated wheat, regardless of the use of NBPT urease inhibitor with conventional urea. Singly, inoculation with A. brasilense does not affect production components and grain yield, despite the increase in N content in wheat straw. The inoculation with A. brasilense, associated with the application of 140 kg ha-1 N, provides the highest grain yield of irrigated wheat cropped after corn in low-altitude Cerrado.

Additives incorporated into urea to reduce nitrogen losses after application to the soil

The objective of this work was to develop urea-based fertilizers with internal incorporation of urease inhibitors and other additives in the granule. The effects of the incorporation of NBPT, copper (Cu+2), boric acid (H3BO3), elemental sulphur (So), and a clay mineral from the zeolite group in powder urea – with ten different combinations of these additives – were evaluated as to N losses by volatilization and leaching. The losses in laboratory-developed formulations were compared with those of commercial fertilizers coated with the same additives (Super N, FH Nitro Mais, and FH Nitro Gold). The evaluations were made in greenhouse conditions, using a Ultisol accommodated in PVC columns. Nitrate and ammonium leaching was evaluated in the solution percolated through the soil columns. Ammonia volatilization was measured with a semi-open static chamber. The incorporation of urease inhibitors (NBPT, H3BO3, and Cu+2) into the urea granules was efficient to reduce N volatilization. Ammonia volatilization in the laboratory-developed ureas was lower than in commercial fertilizers coated with the same additives, while ammonium sulfate losses by leaching were similar. The addition of zeolite does not reduce N volatilization. Mineral N leaching in the soil profile is not affected by urease inhibitors.

Chemical changes in an Oxisol cultivated with maize ( Zea mays, L. ) after six years disposal of sewage sludge

Sewage sludge is composed of predominantly organic matter and can be used to improve soil characteristics, such as fertility. Therefore, its application in agriculture is an adequate alternative for its final disposal. However, there is a lack of information on its long-term effects on soil changes in tropical areas. Thus, the objectives of this study were to determine: (a) the effect of sewage sludge application on heavy metal build-up in soil and maize grains and (b) the effects of soil amendment with sewage sludge on the chemical properties of a Brazilian Oxisol. Besides the increasing levels of Zn, Cu, Ni, Cd, Pb and Cr, amending soil with sewage sludge also alters the distribution of these metals by increasing the mobile Phases, which correlated significantly with the increase in metal extraction with two single extractants, Mehlich 1 (HCl 0.05 mol L –1 + H2SO4 0.0125 mol L –1 ) and DTPA (Diethylenetriaminepentaacetic acid). Nevertheless, metal build-up in soil and plants was within the allowed limits. The data obtained does not indicate any expressive drawbacks in the use of sewage sludge as a soil amendment, as the heavy metal concentrations observed are unlikely to cause any environmental or health problems, even overestimated loadings.