Field-saturated hydraulic conductivity measured by two techniques and at different sampling positions relative to maize-crop rows and interrows

Abstract

Field-saturated hydraulic conductivity (Ks) reflects porous system ability to transfer water in the soil-plant system. The study aimed to measure Ks through two distinct techniques. One of them was carried out in the laboratory by applying the constant-head cylinder method (CHC) in undisturbed samples, herein referred to as a standard technique. The other consisted of a simplified falling-head technique to measure Ks in situ (SFH), as proposed by Bagarello et al. (2004). We also verified the correlations of the obtained Ks values with other soil physical properties. SFH method is simpler, faster and does not require sophisticated equipment, which can be executed directly in the field. The experiment was conducted in the city of Floresta (PR), Brazil, at Cocamar Technology Diffusion Unit. It consisted of four treatments: maize-crop interrow without recent machine traffic (MI), maize-crop interrow traveled by a harvester (MIT), maize-crop row (MR) and its relative position to brachiaria crop row sown in consortium, and in maize-crop interrow (BR). In each treatment, 10 sampling points were defined (repetitions), where Ks was determined by SFH and an undisturbed sample was taken to measure Ks in the laboratory. Ks values measured by methodological approaches were compared through the following statistical indices, with their respective results: Willmott's concordance index (0.944), maximum error (1.269) and mean absolute error (0.291), square root of normalized mean error (0.45), determination coefficient (0.88), residual mass coefficient (0.07), efficiency coefficient (0.72), performance index (0.80), and Pearson's correlation (0.85). A high agreement was found between the studied techniques, with measured values close to each other. Notably, we must give emphasis on SFH since it had a variation coefficient 1.4 times lower than the standard technique.