Volume 33, Number 4, 2009

The input of organic matter to the soil by legumes in alley cropping systems may be an alternative for a sustainable soil use in the humid tropics. The objective of this study was to compare the input of oxidizable organic matter in a combination of residues from different legumes in alley cropping systems on an Ultisol. Two legume species were evaluated: leucena (Leucaena leucocephala) and pigeon pea (Cajanus cajan), which have high-quality residues, and Philippine pigeonwings (Clitoria fairchildiana) and acacia […]

The determination of As by hydride generation atomic absorption spectroscopy (HG-AAS) is a simple, sensitive, precise and low-cost method. However, this technique requires the pre-reduction of the existing As(V) species, which is obtained by the use of reducing agents such as KI. In extracts containing oxidizing agents, the pre-reduction of As is impaired, as it occurs in extracts obtained by the BCR (French acronym for Community Bureau of Reference) method for the sequential extraction of As in sediments. The objective […]

This study was carried out to characterize the possible changes in the chemical nature of humic acids extracted from an Oxisol (0-10 cm) by Fourier transform infrared spectroscopy (FTIR), in the experimental area of Embrapa Meio Ambiente, in Jaguariúna (SP), Brazil. The data were obtained after six corn cultivations, and application of variable doses of sewage sludge (dry basis) from Barueri (BSS), in the treatments: BSS0 – control without sewage sludge application; NPK – mineral fertilization as required by corn; application […]

Common bean (Phaseolus vulgaris L.) and cowpea (Vigna unguiculata (L.) Walp.) are among the main sources of plant protein for a large part of the world population, mainly that of low income, and nitrogen is the main constituent of these proteins. The objectives of this study were to evaluate, through the 15N-dilution technique and using rice and non-nodulating soybean as control plants, the relative contributions of nitrogen sources (symbiotically fixed N, soil native N and fertilizer N) on the growth […]

It is well-known that Amazon tropical forest soils contain high microbial biodiversity. However, anthropogenic actions of slash and burn, mainly for pasture establishment, induce profound changes in the well-balanced biogeochemical cycles. After a few years the grass yield usually declines, the pasture is abandoned and is transformed into a secondary vegetation called “capoeira” or fallow. The aim of this study was to examine how the clearing of Amazon rainforest for pasture affects: (1) the diversity of the Bacteria domain evaluated […]

Biological N2 fixation is a major factor contributing to the increased competitiveness of Brazilian soybeans on the international market. However, the contribution of this process may be limited by adverse conditions to symbiotic bacteria, such as fungicide seed treatments. This study aimed to evaluate the effects of the fungicides carbendazim + thiram and carboxin + thiram on soybean nodulation, plant growth and grain yield. Two field experiments were carried out in the Cerrado region of the State of Roraima, in […]

Currently research verified that glyphosate or ammonium glufosinate herbicides use for cover crop desiccation in conservationist systems may reduce N amount in straw. The aim of this study was to evaluate nitrogen mineralization in millet straw after glyphosate or ammonium glufosinate application and the N uptake by corn plants. A complete randomized design was used with six treatments and five replications, in a 3 x 2 factorial scheme: cover crop management (without herbicide application, glyphosate or ammonium glufosinate desiccation) and soil type […]

Si made available by Ca silicate can increase polyphenol formation, which could increase the persistence of crop residues on the soil surface. The present study evaluated the effect of silicate and lime on decomposition of different crop residues and the nutrient release for the development of common bean plants. An experimental design in randomized blocks, arranged as a 3 x 5 factorial combination, was used with four replications. Treatments consisted of three cover plant species: millet (Pennisetum americanum), brachiaria (Brachiaria brizantha), and […]

Sewage sludges contain high levels of organic N. If these residues are applied in excess to soils, there is the risk of polluting the groundwater with nitrate, a product of N mineralization. For this reason, one of the criteria underlying the determination of the maximum N application rate to soils is the crop available N. This paper presents the results of a 224 day laboratory leaching study on organic N mineralization of anaerobically-digested sewage sludges from two treatment plants, namely Franca […]

Humic substances can influence plant metabolism direct or indirectly, thus modifying its growth. The objective of this study was to evaluate the effect of humic-like substances (HS) on kinetics of K uptake, nutrient concentration and growth of common bean (Phaseolus vulgaris, L.). The experiment was performed on a laboratory bench with controlled light conditions. Plants were grown in pots with complete nutrient solution enriched with five levels (0; 2.5; 5; 10 and 20 mg L-1 of C) of alkaline soluble humic-like substances […]