Revisiting Field Capacity (FC): variation of definition of FC and its estimation from pedotransfer functions

Revista Brasileira de Ciência do Solo

Theophilo Benedicto Ottoni Filho²  Marta Vasconcelos Ottoni¹  Muriel Batista De Oliveira¹  José Ronaldo De Macedo¹  Klaus Reichardt¹ 

[1] ,Universidade Federal do Rio de Janeiro Department of Water Resources and Environment Rio de Janeiro RJ ,Brazil

关键词: internal drainage;    aeration capacity;    soil water retention;    drenagem interna;    capacidade de aeração;    retenção de água no solo;   

DOI  :  10.1590/S0100-06832014000600010

来源: SciELO

【 摘 要 】

Taking into account the nature of the hydrological processes involved in in situ measurement of Field Capacity (FC), this study proposes a variation of the definition of FC aiming not only at minimizing the inadequacies of its determination, but also at maintaining its original, practical meaning. Analysis of FC data for 22 Brazilian soils and additional FC data from the literature, all measured according to the proposed definition, which is based on a 48-h drainage time after infiltration by shallow ponding, indicates a weak dependency on the amount of infiltrated water, antecedent moisture level, soil morphology, and the level of the groundwater table, but a strong dependency on basic soil properties. The dependence on basic soil properties allowed determination of FC of the 22 soil profiles by pedotransfer functions (PTFs) using the input variables usually adopted in prediction of soil water retention. Among the input variables, soil moisture content θ (6 kPa) had the greatest impact. Indeed, a linear PTF based only on it resulted in an FC with a root mean squared residue less than 0.04 m³ m-3 for most soils individually. Such a PTF proved to be a better FC predictor than the traditional method of using moisture content at an arbitrary suction. Our FC data were compatible with an equivalent and broader USA database found in the literature, mainly for medium-texture soil samples. One reason for differences between FCs of the two data sets of fine-textured soils is due to their different drainage times. Thus, a standardized procedure for in situ determination of FC is recommended.

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