The soil-water retention curve (SWRC) is essential to understand the physical-hydric soil behavior. However, data for the construction of the SWRC are obtained in slow and expensive processes. This study hypothesized the possibility that SWRC could be constructed based on fewer tension data within a shorter time, without affecting the accuracy. The objective was to determine the tension data required for the construction of an accurate SWRC in less time. Undisturbed soil samples were collected from a Eutrophic Red Oxisol under long-term no-tillage. For the SWRC construction, soil water contents were evaluated at tensions of 0; 10; 20; 40; 60; 80; 100; 200; 300; 500; 700; 1,000; 3,000; 5,000, and 15,000 hPa. Combining the 15 tensions used, 450 SWRC were obtained and adjusted by the van Genuchten model. Variance analysis for the α, m, n and Ug res parameters generated for the model were considered for statistical procedures. Means were subjected to the Scott-Knott cluster analysis procedure (p = 0.05). The hypothesis that the SWRC can be constructed with fewer tension measurements within a shorter time, without reducing the accuracy, was confirmed. The 15,000 hPa tension must be included in the combination of tensions used to determine the SWRC, if the adjusted van Genuchten model is applied for data fitting. The Eutrophic Red Oxisol water retention curve determined with the combined data at tensions of 0; 60; 700; 15,000 hPa, 0; 80; 700; 15,000 hPa, 0; 100; 1,000; 15,000 hPa, 0; 20; 60; 100; 700; 15,000 hPa, 0; 80; 300; 700; 15,000 hPa and 0; 100; 300; 1,000; 15,000 hPa by the van Genuchten adjusted model estimated the soil water content at different tensions with the same accuracy, compared to the reference curve based on a set of 15 tension measurements.
van Genuchten model; soil physical properties; soil physics
