HIGHLIGHTS:

Elevated compaction and the micropores flattened retention curves.

Slight field capacity - permanent wilting point differencev.

Ground-based data (GF) demonstrate excellent accuracy for Andisols and for Oxisols at different depths.

ABSTRACT

Soil is a medium that stores and transfers air, water, nutrients and heat to microorganisms and plants. Its water storage capacity is studied by analysing water retention curves (WRCs), which establish the relationship between soil water content and the force with which water is retained. The objective of this work was to evaluate the capacity of functional geostatistics in predicting the spatial distribution of water retention curves in two types of soils. Experimental areas with two types of soil, Andisol and Oxisol, were selected, and a regular grid of 75 sites was established, from which water retention curves were obtained at two depths. The curves were subjected to geostatistical functional analysis (GF), and the applicability of this method was evaluated by obtaining the usable water table (LAA) and comparing the results with experimental data obtained using traditional methods. Based on cross-validation, it was verified that GF produced a better fit for the Andisol since the coefficient of determination between the LAA values for the measured data and predictions was high, with an R² of 99%; however, the proposed methodology was also reliable for the Oxisol, since an R² of 94% was obtained at the two depths studied.

Key words:
usable water; spatial variability; functional data; functional kriging