Soil solution composition affects microstructure of tropical saline alluvial soils in semi-arid environment

摘要

The remediation of soils stressed by salinity improves soil quality for food production. However, information on how remediation techniques affect microstructural stability/elasticity and resistance is lacking. Hence, the objective of this study was to characterize the microstructure of saline alluvial soils from a semi-arid environment, and to evaluate how the techniques of leaching soil and Na+ substitution by other cations affect the microstructure strength and elasticity evaluated by rheological techniques. Homogenized soil of sixteen horizons of four salinized soil profiles (an Abruptic Solonetz, a Eutric Gleysol, and two Hypereutric Planosols) were collected in Northeast of Brazil. Each horizon was analyzed separately in a completely randomized design, with three replications. The treatments corresponded to soils saturated with 1 x 10(-4) mol m(-3) of KCl (+K), CaCl2 (+Ca) or MgCl2 (+Mg), leaching of salts (LS) by successive leaching with alcohol 60%, and untreated soil (control). The soils were submitted to an amplitude sweep test with controlled strain in a compact modular rheometer. The obtained variables were strain and stress at the end of the linear viscoelastic interval (LVR) (gamma(LVR) and tau(LVR), respectively), strain (gamma(YP)) and stress (G'(YP)) at the yield point, shear stress (tau(max)), and integral Z (Iz). The rheological properties varied greatly between the horizons of the same soil profile. The LS increased. LVR compared to control, while the saturation with cations caused reduction in gamma(LVR), especially in soils of higher clay content. The saturation with saline solution increased gamma(YP) and Iz, with greater effect in + K treatment. Both leaching of salts and cation saturation increased soil shear strength at the end of the LVR and at the yield point. Leaching of salts caused destabilization of soil microstructure, which is an important finding that needs to be addressed by measures accompanying remediation of salinized soils to maintain soil physical quality.