Unsaturated hydraulic conductivity, K(h), can be determined rapidly and economically using numerical models in comparison to field measurements. For this is necessary to develop more accurate models. The objective of this paper was to verify if the model based upon S index (the slope of the soil-water retention curve at its inflection point) and soil-water tension at this inflection point (hi) is suitable to determine unsaturated hydraulic conductivity of soils of different textural classes. The study was done on 2166 samples covering 'Cerrado' soils of Mid-West, North and Northeast regions of Brazil, of which there was information about soil texture, saturated hydraulic conductivity, and soil-water retention in data base of Soil Laboratories of Embrapa Arroz e Feijão and Embrapa Cerrados. It was observed that unsaturated hydraulic conductivity at the inflection point of soil-water retention curve (Ki) can be determined from S index and hi, independently of soil texture. Determinations of K(h) based upon Ki showed a high correlation to measured values. The use of S index and hi to determine K(h) should be further tested to determine its predictive power.
soil-water retention curve; soil texture; soil-water tension
