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 […]

The acclimatization of pineapple plantlets propagated by plant tissue culture is slow. The intensification of root growth by the use of humic acids may be useful during this process. The aim of this study was to evaluate the greenhouse acclimatization of ‘Vitória’ pineapple propagated by plant tissue culture in response to different doses of humic acids isolated from vermicompost and filter cake. Leaf anatomy, photosynthetic pigment content, shoot and root growth, and leaf nutrients were evaluated. An increase in growth […]

Knowledge on variations in vertical, horizontal and temporal characteristics of the soil chemical properties under eucalyptus stumps left in the soil is of fundamental importance for the management of subsequent crops. The objective of this work was to evaluate the effect of eucalyptus stumps (ES) left after cutting on the spatial variability of chemical characteristics in a dystrophic Yellow Argisol in the eastern coastal plain region of Brazil. For this purpose, ES left for 31 and 54 months were selected […]

Fertility properties, total C (Ctot), and chemical soil organic matter fractions (fulvic acid fraction – FA, humic acid fraction – HA, humin fraction – H) of anthropogenic dark earths (Terra Preta de Índio) of the Amazon basin were compared with those of Ferralsols with no anthropogenic A horizon. Terra Preta soils had a higher fertility (pH: 5.1-5.4; Sum of bases, SB: 8.93-10.33 cmolc kg-1 , CEC: 17.2-17.5 cmolc kg-1 , V: 51-59 %, P: 116-291 mg kg-1) and Ctot (44.6-44.7 g kg-1) than adjacent Ferralsols (pH: 4.4; SB: 2.04 cmolc kg-1, […]

The determination of structural characteristics of humic substances (HS) is essential to understand the behavior of surface chemistry of highly weathered soils. Humic acids (HA) and fulvic acids (FA) isolated from the surface horizon of seven Oxisols of different locations of Brazil were characterized by analyses of elemental composition, total and carboxylic acidity, oxidation capacity and spectroscopic techniques. The oxidation degree of the humic substances was high, while acidity and molecular weight were relatively low, indicating a very reactive alkaline […]

Soil organic matter is the largest carbon reservoir in natural systems. In such systems the carbon quality and stability can be estimated based on the increase of humified fractions which, among other factors, is related to the balance between losses and accumulations involving oxidation and reduction reactions of the soil organic matter. The objective of this study was to evaluate the electrochemistry of humic acids isolated from soils cultivated continually with sugar-cane, with or without pre-harvest burning and annual vinasse […]

Electrochemistry and organic matter concentrations in the surface horizons of Oxisols are closely related. This study evaluated the electrochemical properties in the surface horizon of seven Brazilian Oxisols after the removal of humic substances by alkaline extraction. Based on their mineralogy the soils were grouped as kaolinitic or oxidic. Less than 3 % of the total organic matter were soluble humic substances extractable by NaOH 0.1 mol L-1, indicating their strong specific adsorption to the inorganic mineral sites. The removal […]

The humification degree and the chemical nature of organic residues are essential factors controlling their degradation and nutrient release. To characterize the organic matrix, samples of sewage sludge, poultry, pig, cattle and quail manure, besides commercial compost, organic substrate and humic material were analyzed for: pH, electric conductivity, cation exchange capacity (CEC), water retention capacity, concentration of total N and mineral N, organic matter, total organic carbon (TOC) and the TOC fractions: humic acid C-fraction; fulvic acid C-fraction, water soluble […]

In São Paulo State, the autumn – winter seasons rainfall distribution restriction as well as high temperatures constitute a serious limitation for soil surface covering and crop production. For this reason it is very important to study alternatives for the no tillage system establishment in that State, specially for biomass production and for adequate management for better mulching in amount enough to improve soil physical quality and organic matter content. This study was carried out at the Lageado Experimental Station […]

The agroforestry systems have been widely promoted as one sustainable agricultural system, mainly for developing areas, where the external use of resources are not feasible. The aim of this study was to evaluate the impact of one conventional and four agroforestry systems on the contents of total soil nitrogen, mineral nitrogen and different organic nitrogen fractions after five years of experimental cultivation on a Luvisol (Alfisol). The study area was in the semi-arid zone at the National Caprine Research Center […]