The influence of plant silica biomineralizations (silicophytoliths) in the soil matrix construction, in Pampean plain soils affected by agricultural practices.

OSTERRIETH, MARGARITA; ALVAREZ, M FERNANDA; BORRELLI, NATALIA; FERNÁNDEZ HONAINE, MARIANA

Congreso; 4th International Congress Eurosoil; 2012

ln Argentine, the soiis of the pampean piain are one of the most fertile of the worid ano they nave been used for agricultura! activities formore than 150 years. These human activities have modifíed the physical, chemicai and biological properties of the soils. The aim of the study is to define and quantífy the presence of silicophytoliths in soils, and in the matrix of the aggregates in the typical Argiudolls affected by agricultura! practicas. The presence of silicophytoliths in the soils ranges between 3% (parental material) and more than 50% (superficial horizons). In the epipedons (A) the stock of phytolith is about 59-72x103 Kg/ha, and the stock of Si from phytolith is 25-30x103 Kg/ha; the contribution of amorphous silica is relevant. These valúes are higher in the cultivated plots due to buming activities and the presence of crop residues. The matrix of the aggregates of strong pedal, is made up in turn by microaggregates with a recuning elemental composition, mainly consisting of carbón and Silicon. A higher land use leads to lower carbón content and to an increment of amorphous silica, along with calcium, ¡ron, aluminum subordinaies. Ths weatheringof silicophytoliths is an ongoing process in these soils and contribute to the fbrmation of amorphous silica-rich matrix of the aggregates and thus to maintain stabílity. Despite the intensity of tillage in cultivated soils, the negativo effect woutd be mitigated by the high contribution of the same silicophytoliths.