02266naa a2200277 a 450000100080000000500110000800800410001910000180006024501450007826000090022352014420023265300160167465300180169065300170170865300160172565300180174165300190175970000130177870000200179170000140181170000170182570000140184270000170185670000170187377300980189011274782018-07-08       2018    bl uuuu     u00u1 u    #d1 aSANTOS, L. H.  aTotal nitrogen and humic substances in aggregates of soils with onion crops under no-tillage and conventional system.h[electronic resource]  c2018  aThe objective of this study was to evaluate the soil total nitrogen (TN), and N contents in humic substances (HS) of the organic matter in aggregates of soils cultivated with onion under no-till system for horticulture (NTSH) and conventional tillage system (CTS), comparing with an area of forest. The evaluated treatments were natural vegetation (control), 100% black oats, 100% rye, 100% oilseed radish, intercrop of oilseed (14%) + rye (86%), intercrop of oilseed (14%) + black oats (86%), area under CTS of onion for ±37 years, and area with secondary forest for ±30 years. Five years after the NTSH implementation, undisturbed soil samples from the layers 0-5 cm, 5-10 cm, and 10-20 cm were collected; these samples presented aggregate sizes between 2.0 mm and 8.00 mm. The TN, and N contents of the HS were subdivided into fulvic acids (N-FA), humic acids (N-HA), and humin (N-HU) fractions. The change from CTS to NTSH increases the TN and N-HU contents in the 0-5 cm soil layer. The intercrop of oats and oilseed radish, used as soil plant cover species in NTSH, presented a greater increase in N-HU (0-20 cm) than the other treatments. Black oats, and naturalvegetation presented a greater increased in N-HA, and N-FA contents, respectively, in the 10-20 cm layer, than the other treatments in NTSH and CTS. CTS with millet as soil plant cover presented a greater increase in N-FA (0-20 cm) contents than the NTSH treatments.  aaggregation  aAllium cepa L  acover plants  ahumic acids  asoil nitrogen  atillage system1 aLOSS, A.1 aLOURENZI, C. R.1 aSOUZA, M.1 aGONZATTO, R.1 aKURTZ, C.1 aBRUNETTO, G.1 aCOMIN, J. J.  tREVISTA COLOMBIANA DE CIENCIAS HORTÍCOLAS, Bogotá, Colombiagv. 12, n. 1, p. 166-174, 2018.