Nitrate movement on surface and subsurface horizons of Udox and Udult soils with variable charges

Abstract

The objective of this work was to evaluate nitrate movement on soil columns considering mainly, total amount recovered, fit among experimental and model‑predicted transposition curves, and model‑obtained retardation factors. Samples of A and B horizons of Udox and Udult soils were used. A leaching experiment was carried out considering the miscible displacement theory, using 100 mL of a 10-mmol L^-1 KNO₃ solution as pulse. The amounts of nitrate leached and recovered in the columns for Udox and Udult soils in horizons A and B varied from 0.405 to 1.432 mmol L^-1. There was significant (p<0.05) correlation between experimental and model-predicted curves for columns Udult-A, Udult-B and Udox-B. The mathematical model used is suitable for predicting nitrate lixiviation in B-horizon columns in Udox and Udult soils. The retardation factor was greater than 1.0 in the soil columns with good fit among experimental and predicted data, which indicates that the nitrate movement is delayed in comparison to the advance of the soil wetting front.