Sampling soil water in sandy soils: Comparative analysis of some common methods

A field study was conducted to compare and evaluate chemical composition of soil water collected in sandy soils by three common methods: (i) ceramic suction cup sampling, (ii) drainage lysimetry, and (iii) gravimetric soil sampling. The ceramic cups were installed either by surrounding the cup with silica slurry or sand. The experiment was arranged as a nested factorial design where the three factors were: (i) sampling method, (ii) location, and (iii) time of sampling. Analysis of variance (ANOVA) was used for statistical analysis of data. The study shows that the method of installation (use of silica slurry vs. sand) of ceramic cups had a negligible effect on the mean values, but it appears that by using silica the uncertainty associated with the mean was reduced considerably. The average concentration of NO₃ and Cl were higher for soil sampling than those measured by ceramic cups. The mean values of NO₃, PO₄, and Cl were higher for ceramic cups than for lysimeter although differences proved statistically insignificant.