01945naa a2200181 a 450000100080000000500110000800800410001910000180006024500890007826000090016752014300017665300080160665300240161470000190163870000170165770000170167477300720169110288782018-06-20       2003    bl ---       0--  u    #d1 aTOMASELLA, J.  aComparision of two techniques to develop pedotransfer functions for water retention.  c2003  aTwo pedotransfer function (PTF) approaches can be used for ob- tainiug the analytical expression of the whole retention curve: (i) soil basic data is used to estimate soil water retention at specific water potentials; and then an analytical expression of the retentlon curve is fitted to the estimated soil moisture values; and (li) soil basic data Is used for estimating the parameters of an analytical expression of water retention curves. The objective of tbis study was to compare the performance of both techniques using data representing the maio Brazilian soils. First, we derived PTFs for the parameters of vau Genuchten equation and for water contents at -6, -10, -33, -100, and -1500 kPa for the same deveiopment data sei. Second, we com- pared the performance of both techniques for the same validation data sei. The approach, based on the estimation of water contents at speclfic water potentiais, provlded better results: for the validation data set, tbis technique showed an average root mean squared error of 0.036 m3 m-3, compared with an averaged error of 0.098 m3 m-3 of the technique based on the direct estlmation of vau Genuchten parameters. A possible explanation for this result mlght be related to the fact that soil moisture Is controlled by different independent variabies at different ranges of soil water potentiai, and those diITer- ences are not directiy reiated to the vau Genuchten parameters.  aPTF  aRetenção de água1 aPACHEPSKY, YA.1 aCRESTANA, S.1 aRAWLS, W. J.  tSoil science society of America Journalgv. 67. p. 1085-1092, 2003.