Abstract
<p>In this work we have analyzed soil samples from Oxisols collected from two traditional communities, one formed by Guarany Indians at South of Brazil and other by African descendants on North of Rio de Janeiro State, Brazil. The content and fractional composition of humus was investigated and the isolated humic acids (HAs) were characterized by elemental composition, <sup>13</sup>C solid-state nuclear magnetic resonance, and high-performance size exclusion chromatography. The bioactivity of HAs was evaluated considering the effects on root growth of maize seedlings. Chemical properties from adjacent soils under native forest were used as control samples. The local field sites matching the traditional cropping requirements, were characterized by higher soil chemical fertility and soil organic matter hydrophobicity, as compared to the land plots considered as inadequate by rural peasants. The HAs from cropped soils revealed significant differences in respect to content, hydrophobicity, biostimulation and molecular dimension. Although all humic extracts promoted, both, root growth and the stimulation of lateral root emergence over control, the HAs from preferential local sites, revealed a larger bioactivity response on root stimulation even at lower concentration. The assessment of soil quality issued by local farmers, showed a valuable fitting with bio-chemical fertility indicators and SOM hydrophobicity.<strong></strong></p>
Highlights
1.1 Introduce the ProblemThe soil organic matter (SOM) is a key driving factor for the long term sustainability of agro-ecosystems
Multicropping system used by the Quilombolas community is characterized by cassava, pumpkin, maize, beans, pineapple, okra, cultivated in the same site adopting a local complex system for timing and spacing of plant type separation
SOM has been increasingly considered among the major indicators of soil quality, as much as one of the basic components of biosphere sustainability and stability (Slepetiene & Slepetys, 2005)
Summary
The soil organic matter (SOM) is a key driving factor for the long term sustainability of agro-ecosystems. The existing gap between scientific approaches on SOM studies, with, either, the operative cropping experiences and the practical farmers appraisal of specific soil managements, is worthwhile to be investigated With this respect, a useful standpoint may be represented by productive “marginal” areas of small, long term founded communities, in which original local techniques have been developed within a limited or weak combination with agro-technologies. In this work we collaborated with to two traditional communities, one formed by Guarany Indians at South of Brazil and other by African descendents at North of Rio de Janeiro State, with the aim to observe a possible relationship between the local viable selection of best fields for subsistence crop production, with the molecular characteristics of HAs, the soil chemical fertility and plant root stimulation
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