02973naa a2200265 a 450000100080000000500110000800800410001910000180006024501430007826000090022152022110023065300180244165300300245965300170248965300160250665300100252265300210253270000130255370000150256670000230258170000140260470000170261870000170263577300550265211274772018-07-08       2018    bl uuuu     u00u1 u    #d1 aSANTOS, L. H.  aCarbon of humic substances in soil aggregates cultivated with onion under no-till and conventional tillage systems.h[electronic resource]  c2018  aCarbon (C) contents of humic substances (HS) in soil aggregates are a sensitive indicator of changes in the edaphic quality caused by soil management systems and/or cover plant species. The aim of this study was to assess total contents of C and HS of organic matter in soil aggregates cultivated with onion under a no-till vegetable production system (NTVS) and conventional tillage (CT) compared to a secondary forest area. Treatments consisted of single and mixed cover crops and onion under NTVS: spontaneous vegetation, 100% black oat; 100% rye; 100% oilseed radish; consortium of oilseed radish (14%) + rye (86%); consortium of oilseed radish (14%) + black oat (86%). An area cultivated with onion under CT (± 37 years) and a forest area (secondary forest; ± 30 years) were also evaluated. Five years after implementation of NTVS, undisturbed soil specimens were collected from the 0.0-0.05, 0.05-0.10 and 0.10-0.20 m layers and aggregates were obtained (8.00 mm &gt Ø ≥ 2.0 mm). In these aggregates, total organic carbon (TOC) and C of HS were determined, subdividided into a fulvic acid fraction (C-FAF), humic acid fraction (C-HAF) and humin (C-HUM). With the C values of the HS the following ratios were calculated: C-HAF/C-FAF and (C-HAF+C-FAF)/C-HUM. The highest content of TOC, C-FAF, C-HAF and C-HUM were found in the forest. In NTVS, the contents of TOC (at the 0.0-0.05 m depth) and C-HUM (0.0-0.05 and 0.05-0.10 m) were higher than those found under CT. The highest C-FAF contents were found under CT. NTVS compared to CT favors the humification process (higher C-HUM content and lower ratios of C-HAF+C-FAF/CHUM (at the 0.0-0.05 and 0.05-0.10 m depths) and the protection of organic matter (higher TOC contents at the 0.0-0.05 m depth)). A linear relationship was observed between C-HUM and N of HS. Among the cover plant species, rye alone and rye combined with oilseed radish had the best results regarding humification of organic matter with predominance of C-HUM and C-HAF. This pattern was also observed in the control for C-HUM, due to the abundance of plant families and species, indicating that plant biodiversification is an effective way to improve the quality of soil.  aAlliun cepa L  aconsortium of cover crops  afulvic acids  ahumic acids  ahumin  amacro-aggregates1 aLOSS, A.1 aCANTON, L.1 aSANTOS JÚNIOR, E.1 aKURTZ, C.1 aBRUNETTO, G.1 aCOMIN, J. J.  tIDESIA, Arica, Chilegv. 36, n. 1, p. 15-25, 2018.