Abstract

The objective of the study is to investigate the interaction of lime and gypsum during incubation of soil samples in response to pH and also check the possibility of using more than one treatment for a single model by model identity method. The analysis of the potential hydrogen ion (pH) was performed in the Laboratory of Agricultural Chemistry, Federal Institute Goiano, Campus Rio Verde - GO, Brazil. The soil used is classified as Quartzarenic Neosol loam sandy and its corresponding soil taxonomy is Quartzipsamment. The experiment was  completely randomized  with four replications in a factorial 5 × 3 design, five doses of lime (CaCO₃) - DL (0, 1, 2, 3 and 4 t ha^-1) and three doses of gypsum (CaSO₄) - DG ( 0, 0.7 and 5 t ha^-1). The sources of CaCO₃ and CaSO₄, dolomitic lime and gypsum were used, respectively. Incubation was done in plastic containers with 20 ml of soil, and pH analysis was done every two days for 10 days. In general, it was frequently observed that reducing the pH of the reaction in the soil was attributed to higher DG applied together with CaCO₃. Due to the difference in all models tested by identity models, it is explained that the range of CaSO₄ doses and incubation periods promoted major change in the model either by interception, angulation or both. The reduction of pH in the soil is attributed to higher rates of gypsum used together with lime.

Key words: Active acidity, identity models, incubation period.