The effect of gypsum on the point of zero charge-PZC, calcium, magnesium, potassium and sulfate dynamics, and water retention were evaluated in a very clayey dystrophic gibbsitic Red Latosol. Six doses of gypsum (corresponding to 0, 3, 6, 9, 12 and 15 Mg ha-1) and two water supply conditions (with and without water deficit) were imposed to soybean crop. Soil was sampled at the depths of 0-0.2 m and 0.7-0.9 m, representing the A and Bw horizons, respectively. Soil samples were placed in PVC tubes (0.2 m in length and 0.1 m of diameter), simulating two layers: the upper layer had A horizon soil, which was amended with dolomitic limestone; and the bottom layer had Bw horizon soil, under the natural pH. Both layers had soil density of 1 kg dm-3. The PZC was changed by gypsum; as gypsum dose increased, calcium concentration increased in both soil layers. There was no difference in S value in the upper layer due to gypsum; however it increased in the subsurface layer as gypsum was applied. Lower Mg concentration was found in the upper layer, whereas increases in Mg were noticed in the bottom layer as gypsum doses increased. No changes in water retention and K concentration were found in response to gypsum and water supply regimes.
PZC; leaching; soil fertility; soil correction; water retention
