Abstract
The aim of this work was to evaluate the humus composition from an Ultisol from Campos dos Goytacazes, RJ, Brazil. Soil samples of four depths (0-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m) and its chemical nature were analysed by elemental composition, E4/E6 ratios and Fourier transformed infrared spectroscopy. The bioactivity of these humified substances was evaluated through their action on maize root growth and H+-ATPase activity of roots microsomes. In topsoil, the content of high condensed alkaline soluble humic substances is greater than that found in the subsuperficial layers. The chemical nature of humic and fulvic acids also varied with the soil depth. The humic acids isolated from the soil samples exhibited higher bioactivity compared with the fulvic acids. Moreover, the results suggest that more condensed humic substances can promote highest stimulation of the microsomal H+-ATPases from maize roots. These data reinforce the concept that the activity of the H+ pumps can be used as a biochemical marker for evaluation of humic substances bioactivity.
Highlights
The content of organic matter in tropical soils represent only about 1% of the soil mass, the humus is one of the most important fractions of these soils
The acid-soluble fraction less condensed consisting in free fulvic acids (FFA) varied from 10 to 8% of the total organic carbon (Table 2)
The alkali-soluble fulvic acid (FA) content was higher compared with the fulvic acids fraction (FFA) fraction
Summary
The content of organic matter in tropical soils represent only about 1% of the soil mass, the humus is one of the most important fractions of these soils. The benefits of soil humus have been summarised by Skjemstad et al (1998) who stated that it is a source of slow-released nutrient, it has a high sortive and exchange capacity for trace or other metal ions, it improves the physical conditions of the soil, buffer the soil against the rapid changes in reactions and reduces toxicity of natural and synthetic toxic compounds. Façanha et al (2002) have found that humic acids isolated from vermicompost can induce the plasma membrane H+-ATPase activity and root development. L.P. Canellas and A.R. Façanha of maize. This effect was studied in detail by Canellas et al (2002), who described hormonal activity of these humic acids on lateral root development
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
