Apolino José Nogueira da Silva

Matéria orgânica e propriedades físicas de um Argissolo Amarelo Coeso sob sistemas de manejo com cana-de-açúcar

The continuous cultivation of the sugar cane for long-term under different management systems in soils of Coastal Tablelands can cause alterations in the organic matter and in the physical properties of the soil. The effects of different management systems with sugar cane on the properties of a Cohesive Yellow Argisol, in the Triunfo Sugar Cane Mill, in the State of Alagoas, Brazil, were studied. The management systems consisted of an irrigated area, an area not irrigated, an area with vinasse application and an area under native forest in original condition. Samples were collected from each area at 0-0.2, 0.2-0.4 and 0.4-0.8 m depths to determine the modification in the consistence limits, compaction parameters, stability of aggregates and physical fractions of the organic matter of the soil. The results indicated that the cultivation of sugar cane under not irrigated and irrigated systems promoted a more expressive reduction in the plasticity limit, optimum moisture for compaction and aggregate mean weight diameter, in relation to soil under native forest, due to reduction in the contents of total organic carbon and of particulate organic matter. The management system with vinasse application promoted smaller degradation in physical and chemical properties of the soil in relation to soil under native forest.

Compactação e compressibilidade do solo sob sistemas de manejo e níveis de umidade

Soil water content and management systems can promote changes in compressibility parameters. The objective of this research was to study the effects that water content and sugarcane management systems have on the compaction degree and compressibility parameters of a cohesive Yellow Argisol. Four sites were selected in the surroundings of the sugar mill Triunfo, in the state of Alagoas, Brazil; one site with irrigation and a second without irrigation, a third with vinasse application and a fourth under native forest, taken as representative of the original soil condition. Samples from each site were collected at 0-0.2, 0.2-0.4 and 0.4-0.8 m depths and at 0-0.2 and 0.2-0.4 m, to determine alterations in the soil compaction and compressibility parameters, respectively. Management systems with and without irrigation increased the degree of soil compaction and resistance of aggregates to rupture as compared to those of the soil under native forest, resulting in an increase in the soil load support capacity. The increases in the soil water content reduced precompaction pressure and enhanced the compression index, resulting in a lower soil load support capacity.

Alterações físicas e químicas de um Argissolo amarelo sob diferentes sistemas de uso e manejo

Alterations in the chemical conditions of the soil due to different soil management systems with sugarcane can cause modifications in clay dispersion and in the state of aggregation of the soil. The effects of different soil management systems with sugarcane on the physical and chemical properties of a cohesive Yellow Argisol were studied, being selected four different use and management systems, constituted of a site with irrigated cultivation, a site with not irrigated cultivation, a site with vinasse application and a site under native forest as original condition. Samples of each site were collected at 0-0,2, 0,2-0,4 and 0,4-0,8 m depths to determine the alterations in the chemical and physical properties of soil. The management systems with sugarcane affected the chemical properties of the soil, resulting in reduction of cation exchange capacity and increase of the electrical conductivity, pH in water and critical flocculation concentration. These chemical alterations resulted in larger clay dispersion in the soil cultivated with sugarcane, reducing the stability of the aggregates in water.

Modificações na matriz de um Argissolo Amarelo Coeso sob diferentes sistemas de manejo com cana-de-açúcar

The management systems with sugarcane in soils of Coastal Tablelands can cause important alterations in the soil matrix. The effects of different management systems with sugar cane in the organization of the matrix of a Cohesive Yellow Argisol, in the Triunfo Sugar Cane Mill in State of Alagoas, as compared to a virgin soil were studied. The management systems consisted of irrigated area, not irrigated, with vinasse application and an area under native forest as original condition. Samples were collected from each site at 0-0.2, 0.2-0.4 and 0.4-0.8 m depths to determine the alterations in the soil structure, in pore system and in the arrangement of particles of the soils cultivated with sugarcane, in relation to the soil under native forest. The cultivated soils presented an association of natural porosity with planar pores resultant of the cultivation and a more compact arrangement of particles in the soil matrix. In the aggregates of the cultivated soils a massive aspect and orientation of clay particle was verified in relation to the aggregates of the soil under native forest.

Influência de tensões compressivas na pressão de precompactação e no índice de compressão do solo

The objectives of this study were to determine the compressibility parameters of an Acrisol through uniaxial compression tests, with three application times of compressive pressure (7.5 s, 1 and 2 min) and in two moisture contents (0.113 and 0.164 kg kg-1), and to verify the mechanical soil behavior after the removal of the loads. The Acrisol was collected in an experiment conducted in areas physically degraded and upgraded, in the Agricultural Experimental Station of the UFRGS. The physically degraded condition presented the highest values of precompaction pressure in relation to the upgraded condition, for both moisture contents. There was no significant difference among the values of precompaction pressure determined with the soil compression curve for the times of 7.5 s, 1 and 2 min compressive pressure application in both moisture contents as well in both physical conditions of the soil. The physically upgraded condition presented higher compression index compared to the degraded condition in both moisture contents. The relief promoted by the removal of the compressive pressures imposed on the soil promoted a small increment in the total porosity and reduction in the bulk density.

Especificidade hospedeira de variantes Bradyrhizobium spp em soja (cvs peking e clark), caupi e guandu

The expansion of the soybean crop has evidenced a high host specificity, indicating the requirement of new strains with capacity of nodulating soybean and competition capacity with the natural soil rhizobial population. The purpose of this study was to evaluate the host specificity of mutants isolated from Bradyrhizobium spp strains in relation to nodulation and relative N2 fixation effectiveness in soybean (cultivars Peking and Clark), cowpea and pigeon pea. The experiment was carried out under controlled conditions in a growth chamber, where B. japonicum and B. elkanii mutants and the respective original strains were tested for their nodulation ability on soybean, cowpea and pigeon pea. The crop was harvested 35 days after planting and the nodulation (number, dry nodule weight), shoot dry matter production and relative N2 fixation effectiveness were evaluated. The mutants and strains of Bradyrhizobium spp nodulate Glycine max (cultivars BR-16, Clark and Peking), Vigna unguiculata and Cajanus cajan, however the interaction rhizobia-leguminous demonstrated significant symbiotic effectiveness for Glycine max only.

Compressibilidade de um Argissolo Vermelho fisicamente degradado e recuperado

The reclaimation of physically degraded soils has been done using conservationist systems. However, improvement of soil structure makes then very susceptible to intense deformation when bearing compression through mechanization. The compressibility of a Acrisol, physically degraded and reclaimed, collected in the Agricultural Experimental Station of the Federal University of Rio Grande do Sul, in Eldorado do Sul, RS, in two moisture levels, was evaluated with uniaxial compression tests. The soil compression curve, porosity, soil density and resistance to penetration were determined. The physically reclaimed soil samples were more compressible, noteably at higher moisture levels. After applying stresses from 25 to 500 kPa, the reclaimed samples were very similar to the degraded ones. The low resistance to compression showed by the physically reclaimed soil makes evident the difficulty in making compatible the management of conservationist and upgrading structure systems with agricultural mechanization as practiced today. This also strengthens the necessity in finding alternatives to reduce stresses on soils or to make them able to offer higher resistance to compression.

Relative planting times on the production components in sesame/cowpea bean intercropping in organic system

Aiming at better land use, small farmers usually plant sesame and cowpea bean intercropped with other crops. The aim of this work was to analyze and quantify the influence of four relative planting times of the cowpea bean in intercropping with sesame from the standpoint of their production components, plant productivity and the index of land equivalent ratio (LER). The field experiment was conducted in a randomized blocks with four treatments and four replicates. The treatments were the sesame and the cowpea bean in intercropping with the cowpea bean planted at the same time, 7, 14 and 21days after than the sesame. A greater part of the production components of both the sesame as well the cowpea bean was affected by the intercropping and significant differences were noted among the treatments in a larger part of the parameters. As the planting of the cowpea bean became more distant from that of the sesame, the yield of the Pedaliaceae increased and the yield of the Fabaceae decreased. The results for LER findings on the other hand suggest that in the sesame/cowpea bean intercropping, when the Fabaceae is planted seven days after the sesame, there is better use of the land and a largest possibility to the producer earning a profit.