Abstract

The estimation of soil water status in cropped areas continues to be challenging for soil and climate scientists. This study contributes to this issue estimating soil water storage by the water balance of Thornthwaite and Mather, Rijtema and Aboukhaled, and Dourado and de Jong van Lier, combined with crop potential evapotranspiration estimated by Penman-Monteith, to compare them with soil water storage values calculated from polymer tensiometer data of a soybean crop field experiment. The experiment was conducted in Piracicaba, SP, with tensiometers installed at 0.05, 0.15 and 0.3 m depths. Results show that the tensiometers presented good performance to measure soil water pressure head in the whole range of the available water capacity for the crop. The tensiometer presents the advantage of allowing measurements of soil water storage in layers, in contraposition to climatologic water balance calculations which assume one single layer. Rijtema and Aboukhaled presented the best correlation with the water storage estimated from tensiometer data.

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