Dados do Trabalho

Título

INTRODUCING THE CONCEPT OF EFFECTIVE SOIL HYDRAULIC PARAMETERS ON AGRO-HYDROLOGICAL MODELING

Resumo

Agro-hydrological models often differ in the representation of soil hydraulic properties, allowing or not the stratification of the soil profile into hydraulic layers. Such distinction may hinder a fair comparison of model performance, especially the prediction of water balance components and crop productivity. This study aimed to derive a single set of soil hydraulic parameters (SHP) for four layered soils of different classes (Nitisol, Acrisol, and Ferrasols). A three-step procedure was implemented using the SWAP model calibrated for conditions of southeast Brazil: i) simulation of internal drainage experiments for an initially wet soil profile with free drainage at the profile bottom (200 cm), without rainfall or evapotranspiration; ii) coupling of an optimization algorithm to minimize the differences between the water fluxes simulated in the drainage experiments using the SHP of the layered soil and the water fluxes simulated with a single layer of SHP representing the effective values for the entire soil profile; iii) comparison of some model outputs for a season of soybean in Piracicaba, SP, Brazil, using the original SHP and the effective SHP of each soil profile. The root mean squared difference of prediction (RMSD), and the coefficient of determination (R²) for soil water fluxes were ≤ 0.002 cm/d and ≥ 0.990, respectively. The effective SHP of the four soils were validated for predictions of transpiration (RMSD ≤ 0.11 mm/d, R² ≥ 0.99), evaporation (RMSD ≤ 0.38 mm/d, R² ≥ 0.94), and productivity of soybean (aerial dry matter: RMSD ≤ 0.098 t/ha, R² ≥ 0.999; grains: RMSD ≤ 0.073 t/ha, R² ≥ 0.999). Although promising, the concept of effective parameters may not apply to soils with very contrasting hydraulic layers, as this may lead to a particular hydraulic behavior not allowing to be represented by a single set of effective parameters.

Palavras-chave

Hydraulic properties; SWAP model; Water fluxes; Soybean.

Instituição financiadora

São Paulo Research Foundation (FAPESP, 2020/07294-3 and 2022/03770-0).