@article{fdi:010048398,
  title = {{S}hrinkage of microaggregates in {B}razilian latosols during drying : significance of the clay content, mineralogy and hydric stress history},
  author = {{R}eatto, {A}. and {B}ruand, {A}. and {S}ilva, {E}. {M}. and {G}uegan, {R}. and {C}ousin, {I}. and {B}rossard, {M}ichel and {M}artins, {E}. {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{P}>{L}atosols ({O}xisols, {F}erralsols) are characterized by a poor soil horizon differentiation, with a strong microgranular structure formed by microaggregates 50 to 300 mu m in size. {T}his microgranular structure is generally considered to be very stable and the shrinkage properties of microaggregates as poor or absent. {T}he objective of our study was to analyse the shrinkage properties of microaggregates in diagnostic {B}w horizons collected in {L}atosols with various particle size distributions and mineralogical compositions depending on their location in a regional toposequence across the {B}razilian central plateau. {W}e measured the water retention properties at -300 and -1500 k{P}a with a centrifugation method. {T}he morphology and size of elementary particles were examined by transmission electron microscopy; specific surface area ({SSA}) was determined by nitrogen adsorption. {W}e also determined the pore size distribution of microaggregates by the combined use of mercury intrusion and the nitrogen desorption isotherm. {O}ur results show that microaggregates of the {L}atosols studied were not rigid and shrank during drying. {T}he pore volume of the -300 and -1500 k{P}a-treated samples, that of the dried microaggregates and the {SSA} were closely related to the clay content. {T}he mineralogy of particles < 2 mu m played a secondary role in the properties studied. {O}ur results show that microaggregate shrinkage at -300 k{P}a and -1500 k{P}a varied with the location of the {L}atosols in the landscape. {T}hus, microaggregates of {L}atosols located on the upper highland surface of {L}ate {T}ertiary shrank less than those of the lowland surface of {L}ate {Q}uaternary, and this difference was attributed to their different hydric stress histories. {P}roprietes de retrait des microagregats de {L}atosols bresiliens: importance de la teneur en argile, de la composition mineralogique et de l'histoire hydrique. {R}esume {L}es {L}atosols ({O}xisols, {F}erralsols) sont caracterises par une faible differenciation de leurs horizons et une structure microgranulaire representee par des microagregats de 50 300 mu m de diametre. {C}es microagregats sont generalement consideres comme etant tres stables et leurs proprietes de retrait comme etant tres limitees, voire absentes. {L}'objectif de cette etude est d'analyser les proprietes de retrait des microagregats dans l'horizon diagnostic {B}w de {L}atosols de composition granulometrique et mineralogique variable en fonction de leur position le long d'une toposequence regionale selectionnee pour l'etude dans le {P}lateau {C}entral bresilien. {N}ous avons mesure les quantites d'eau retenues -300 et -1500 k{P}a en utilisant la methode par centrifugation. {L}a morphologie et la taille des particules elementaires ont ete etudiees en microscopie electronique transmission et l'aide de mesure de surface {BET}. {N}ous avons aussi determine la distribution de taille des pores dans les agregats deshydrates en combinant les donnees de la porosimetrie au mercure et celles issues de l'isotherme de desorption d'azote. {N}os resultats montrent que les microagregats des {L}atosols etudies ne sont pas rigides et diminuent de volume lors de la dessiccation. {L}e volume poral des microagregats -300 et -1500 k{P}a ainsi que leur volume poral apres deshydratation sont etroitement lies la teneur en argile. {E}n revanche, la composition mineralogique de la fraction < 2 mu m ne jouerait au plus qu'un role secondaire dans les variations du volume poral. {N}os resultats ont montre que les proprietes de retrait des microagregats varient en fonction de la position des {L}atosols dans le paysage. {A}insi, les microagregats des {L}atosols situes sur les hauts plateaux de la fin du {T}ertiaire diminuent moins de volume lors de la dessiccation que les agregats situes sur les surfaces du {Q}uaternaire recent et situees en contrebas dans le paysage. {U}ne telle difference de comportement serait liee l'histoire hydrique des {L}atosols, ceux situes sur les surfaces les plus anciennes ayant vraisemblablement subi des contraintes hydriques plus elevees que ceux situes sur les surfaces les plus recentes.},
  keywords = {},
  booktitle = {},
  journal = {{E}uropean {J}ournal of {S}oil {S}cience},
  volume = {60},
  numero = {6},
  pages = {1106--1116},
  ISSN = {1351-0754},
  year = {2009},
  DOI = {10.1111/j.1365-2389.2009.01189.x},
  URL = {https://www.documentation.ird.fr/hor/fdi:010048398},
}