Análise de sensibilidade no processamento de dados de perfil instantâneo em classes texturais de solos

Abstract

Knowledge about the number of matric potential readings and moisture from soil in time, when performing the instant profile experiment, is important to produce results that represent the soil water dynamics in the best possible way. The present paper proposes the hypothesis that there is a sensitivity standard, for each textural class, in the analysis of soil water attributes, which allows to define data collection routine in experiments of instantaneous profile. The objective of this study was to perform sensitivity analysis of hydric atributes of soil in five soil texture classes from instantaneous profile experiments, in five soil texture classes, to establish a field data acquisition protocol when defining the hydraulic conductivity in satured soil and the coefficient  of the equation K() = K0 e(-0). The experiment was carried out in the molds to determine the hydraulic conductivity by the instantaneous hydraulic profile method. For the evaluation of the parameters sensitivity were applied 11 treatments with five replicates. The treatments were: control (original set of data) and changes in the original set of data, taking a complete reading of the data set (1st reading, 2nd reading, 3rd reading, 6th reading, 9th reading, 15th reading and last reading), taking final readings (last three readings) and considering the total potential gradient as unitary. In the sensitivity analysis, the values of the parameters obtained with the altered data [ln(K) and ] were compared with those values obtained with the original set of data [ln(K0) and 0] by the quotients /0 and ln(K)/ln(K0), respectively. Statistical analysis for both parameters was performed in a completely randomized design. For the comparison of the gamma () and ln (K) averages, the Dunnett test was applied at 5% significance, considering the integral data set as the reference. Parallelism and intercept analysis were also performed in the evaluation of the lines generated by each treatment in the relations:  versus time and ln(K) versus . We conclude that in the function K() = K0 e(-0) and  is as sensitive as ln [K()] to the exclusion of the first reading. However, ln(K) is more sensitive when considering the gradient of total unit potential in the clayey textured classes. For sandy-loam, sandy loam-clay and sandy loam textures in the moisture range between 0.159-0,187, 0.226-0,237 and 0.261-0.266 m³.m-³, respectively, and to loamy clay and clay In the range of 0.227-0.247 and 0.297-0.303, respectively, the individual withdrawal of a reading from the original dataset did little to interfere in the relationships of the parameters that define the hydraulic conductivity of the soil. The first reading is of greater importance for the definition of water redistribution and hydraulic conductivity, the more sandy the soil.