FLOODING, EFFECTS ON SOIL STRUCTURE

TABOADA MIGUEL A.; FERNÁNDEZ, PATRICIA L.; VARELA, MARÍA FLORENCIA

Encyclopedia of Agrophysics

Springer

Año: 2010;

Soil structural behavior of flooded soils received considerable less attention, as compared with agricultural, dryland soils. A key factor determining soil structural behavior is the quality of flooding water, which depends on soil profile characteristics. Soils without a tough Bt horizon have no limitations for free down- and upward water movements throughout the profile. In them, water table rises can reach their top horizons and deposit soluble salts in them. In soils with a tough, impervious Bt horizon, water table rises are controlled by this horizon and cannot reach the topsoil. Flooding water in them is typically of rain origin and does not cause severe consequences on soil properties and vegetation. Flooding soils are subjected to seasonal flooding and subsequent dry periods. They undergo drastic structural changes due to alternate wetting and drying (W/D), which exert strong influences on: (1) soil structural stability, (2) soil mechanical properties, and (3) trapped air volumes. Soil structural behavior of flooding soils cannot be easilyexplained, following the criteria established for agricultural, unsaturated soils. Despite they often sustain grassland vegetation, whose roots are permanent stabilizing agents, the stabilization of topsoil structure seems to be mainly abiotic, based on the drastic W/D cycles. Grassland soils of the flooding Pampa of Argentina can be considered a good study case, which shows positiveeffect of flooding with rainwater in topsoil structure. In this region, structural damages occur in dry summer when livestock hooves crush surface aggregates. The build-up of trapped air pressures is an important fact in flooded soils. It results in soil swelling by air inflation. The influence of this process on soil structural recovery during flooding needs further investigation.