Gilberto Fernandes Corrêa

Alterações físicas introduzidas por diferentes níveis de compactação em latossolo vermelho-escuro textura média

This research was conducted with the objective of studying physical alterations due to different levels of compaction in a coarse silty Dark Red Latosol (Oxisol). Compaction was obtained through a hydraulic press and bulk densities were checked in a gamma ray apparatus. Using soil mechanical equations, it was observed that the application of a strength over the soil reduced the total porosity and the aeration space, while increased in the same proportion the solid and water volumetric content.

Macronutrientes no sistema solo-Pinus caribaea Morelet em palntios apresentando amarelecimento das acículas e morte de plantas

This study was carried out to diagnose senescence and pine trees death (Pinus caribaea Morelet), observed after yellowing and progressive necrosis of the needles in the Brazilian Cerrado in western Minas Gerais. The varieties caribaea and hondurensis, planted between 1977-82 were compared. In the three sites studied samples from twenty trees were collected; ten with yellowing of the needles and ten without symptoms. From each tree, phloem and xylem tissue from root segments and needles were collected and the contents of N, P, K, Ca, Mg and S were analyzed. The considered sites is formed by a Yellow Latosol (Typic Acrustox) with high clay content and the presence of positive charges (acric soil). Soil sampling was performed at the following depths: 0-5, 5-10, 10-20, 20-40, 40-60, 60-80, 80-100, 100-150, 150-200, 200-250 and 250-300 cm. Soil analysis was carried out to evaluate the contents of organic matter, concentration of Ca, Mg, P and K as well as pH in water and in KCl. The mean concentration of N, P, K and S did not differ significantly in the green and yellow needles but Ca and Mg contents were significantly lower in the yellow needles. Visual symptoms and laboratory tests revealed complex deficiency symptoms involving Ca and Mg.

Influence of silicon on grain discoloration and upland rice grown on four savanna soils of Brazil

Abstract In silicon (Si)‐deficient soils, calcium silicate fertilization can reducerice diseases and increase yields. Experiments were conducted in the greenhouse to investigate the effects of Si on rice yield and grain discoloration in four different savanna soils from Brazil, Typic Acrustox‐isohyperthermic (LEa), Typic Acrustox‐isohyperthermic (LVa), Rhodic Acrustox‐isohyperthermic (LRd), and Ustoxic Quartzipsammentic‐isohyperthermic (AQa). Five Si rates (0,120,240, 480, and 960 kg ha‐1) were applied to each soil. Silicon applications increased total grain weights and dramatically reduced grain discoloration independent of soil type. In addition, Si concentration increased in the leaves.

Atributos físicos e químicos de um latossolo, sob diferentes sistemas de cultivo

Diferentes sistemas de manejo impactam em intensidades diferentes os atributos fisicos e quimicos do solo. Com o proposito de avaliar alteracoes em propriedades fisicas e quimicas de um Latossolo Vermelho distrofico, conduziu-se um experimento na Fazenda Gloria/UFU, desde o ano 2000. O latossolo foi disposto num esquema de delineamento em blocos casualizados e conduzido durante sete anos para avaliar algumas alteracoes em atributos fisicos e quimicos do solo, nas profundidades de 0-5; 5-15 e 15-30 cm. Os sistemas de manejo avaliados foram o convencional e os considerados conservacionistas. Os parâmetros analisados foram: densidade do solo, porosidade total, macro e microporosidade, estabilidade de agregados, carbono orgânico total (COT), fosforo (P), calcio (Ca2+), magnesio (Mg2+), potassio (K+), nitrogenio (N) e aluminio (Al3+). Foram verificadas diferencas estatisticas entre os sistemas de manejo conservacionistas e o convencional. Os resultados indicam aumento da densidade do solo com a profundidade, associada a reducao da porosidade total e da relacao macro/microporos, bem como uma menor estabilidade de agregados no sistema convencional, em relacao aos sistemas conservacionistas. Para os atributos quimicos do solo, diferencas estatisticas entre os tratamentos conservacionistas e convencional foram observadas apenas nos primeiros 5 cm do solo, para os elementos P, Ca e K. A correcao do Al e mais eficiente no sistema convencional, devido a incorporacao do calcario ao solo, independente da aplicacao de gesso agricola.

Influence of Phosphorus and Carbon on Soil Microbial Activity in a Savannah Agroecosystem of Brazil

The microbial activity of soil plays an important role in the regulation of the transformation of carbon (C) and phosphorus (P). However, the activity of soil microbes is strongly related to the type of land-use system. The present work aimed to compare the microbial activity and metabolic responses of three different land-use systems to P (0 to 600 mg kg−1 of dry soil) and C additions in an Oxisol of the Brazilian savannah. The land-use systems studied were savannah vegetation (SV), 32-year-old pine plantation (PP), and 11-year-old no-tillage system (NT). The following analyses were carried out: amount of C carbon dioxide (CO2) evolved, total organic carbon (TOC), total glucose (TG), microbial biomass carbon (MBC), and metabolic yields (Y) from P and C additions to the soil. The different land-use systems affected the respiratory activity of microbiota, indicating an increase in SV and a decrease in PP when compared to the SV system under incubation for 17 days. The addition of P resulted in an increase of respiratory activity. The responses were adjusted by the Michaelis–Menten equation for all three land-use systems. The greatest TOC and lowest MBC were observed in NT and PP, respectively, when compared to SV. However, a lower content of TG was observed in NT in comparison to SV. Under bioassay conditions, the results confirm the greater microbial demand for P in PP and SV than in NT. The NT system showed greater metabolic yields when glucose was applied to the soil, suggesting that the response of microbiota in this system depends on easily available forms of C, as shown by the sugar content. The results showed expressive metabolic differences among the systems, suggesting that different soil uses change the dynamic of the responses of soil microorganisms.

Efeito do silicato de cálcio e da autoclavagem na supressividade e na conducividade de dois solos à Rhizoctonia solani

The effect of calcium silicate slag and soil sterilization on the natural suppressiveness of a Typic Acrustox (clay Dark Red Latosol ¾ LEa) and the natural conduciveness of an Oxic Haplustoll (TRe) to Rhizoctonia solani were studied under greenhouse conditions. The experimental design was a three-replicate completely randomized one, with 2 x 3 x 2 factorial combination of the following treatments: two soil kinds (LEa and TRe, collected at 0-20 cm layer); three treatments with and without soil sterilization, calcium silicate slag and nontreated control; and uninfested and infested with R. solani. Each soil material was infested previously with 800 mg of the inoculum per kg soil. Application of silicate was done mixing 0,63 g of this product with 1 kg each soil material and incubated for 30 days. The application ofsilicate increased the exchangeable Ca2+ and bases amount in both soils. The decrease in the aluminum saturation level from 70 to 19% and the increase in base saturation from 9 to 21% altered significantly the natural suppressiveness of LEa to R. solani. Application of silicate to the TRe had no effect on its conduciveness, for its natural eutrophic character, which is benefic to R. solani development. Sterilization by autoclavation did not influence disease development on bean by R. solani. This suggests that possibly other abiotic factors were responsible for either suppressiveness or conduciveness of these soils.

Soil microbial response to glucose and phosphorus addition under agricultural systems in the Brazilian Cerrado

Conventional tillage (CT) and no-tillage (NT) management systems alter soil nutrient availability and consequently modify soil microbial response to nutrient additions such as carbon (C) and phosphorus (P). The objective of this study is to evaluate microbial response to the addition of C (glucose) and P (Na2HPO4.7H2O) under CT and NT in the brazilian Cerrado. In response to glucose addition, the NT system yielded higher microbial respiration rates and glucose consumption than the CT system. The best microbial response to C addition was after 0 - 12 h incubation in NT and 0 - 24 h in CT. The addition of P produced higher demand under CT than NT. After incubation, biochemical indicators such as microbial respiration, glucose consumption, dehydrogenase activity and metabolic yield confirmed the higher glucose demands under NT and higher phosphorus demands under CT. These results demonstrate that C and P addition alter significantly the microbial response, suggesting that soil microorganisms present nutrient differential demands between CT and NT management systems.

Fatores envolvidos na supressividade a Rhizoctonia solani em alguns solos tropicais brasileiros

The experiment was conducted under greenhouse conditions at the Federal University of Uberlândia, State of Minas Gerais, Brazil, from March to August 1995. The purpose of this study was to determine if suppression of seven soil classes could inhibit infection of soybeans by R. solani, and how suppression might relate to the physical, chemical and biological characteristics of these soils. After infesting soils with R. solani, grown on autoclaved sorghum grains, disease intensity increased in soybean seedlings grown in all soils infested. This intensity was always greater in the 0-20 cm layer, which was associated with a higher organic matter content. However, one exception was found for the organic soil (SOe), which presented a similar disease intensity of the fungus in two layers from 0-20 and 20-40 cm due to high organic matter content in both layers. The suppressive effect on R. solani was observed with the Typic Plinthaquox (PTd) and Typic Acrustox (Dark-Red Latosol - LEa) soils, probably due to the clay texture, high aluminum saturation and vegetation (cerrado phase), even in the absence of Trichoderma spp. The organic soil, Acric Rhodustox (LRd) and Udic Argiustoll (TRe) was more conducive to soybean infection by R. solani, possibly due to its eutrophic character and the content of its organic matter originating from plant cover type (vegetation phase). The Typic Haplustox soil (LEam) and Typic Acrustox (Red-Yellow Latosol - LVa) materials had an intermediate reaction. The disease intensity was negatively correlated with aluminum saturation level and clay content of the soil and positively correlated with the base saturation and pH. Mineralogical characteristics of the examined soils do not appear to influence the suppressiveness of R. solani or soil conduciveness directly or to any appreciable extent, possibly because soil mineralogy only differs in its iron oxides forms.

Investigação de possíveis obstruções sílico-aluminosas em tecidos condutores em Pinus caribaea var. Hondurensis relacionadas à senescência e morte de plantas

This work was carried out based on the hypothesis that polymers associated with silicone (Si) would be obstructing tracheid, therefore contributing to a nutritional collapse of Pinus caribaea forest bulks, in the Triângulo Mineiro and Alto Paranaiba (MG) plains. Previous studies showed a narrow relationship between these physiologic patterns with nutritional deficiencies. However, it is known that seeds used in the establishment of these bulks presented great genetic variability well expressed in diversity of plant behavior, inasmuch as part of them remains healthy and the others start a changeable intensity senescence, which ends up in the death of the plant. In this study, it was sampled segments of root and apical shoots of apparently normal (green needles) plants at different senescence stages (yellow needles) and dead plants. Those samples, after being dried until critical point, were observed by scanning electron microscope coupled to an X-ray microprobe. It was noted the presence of Si and Al in xylem and phloem tissues in the aerial section as well as in the roots, and the greatest contents were found in xylem of the plants. However, it was not observed any obstruction or any presence of Si-Al bodies in the conducting tissues of the analyzed parts. But, it was observed that the presence of Si associated to Al occurred according to a 2.6 order Al/Si ratio. Data also revealed that Si variation amplitude is 1.5 times greater than the Al variation amplitude. It concluded that Si variation amplitude is greater than the one of Al, which establishes a variation relationship (Si-Al).