Analysis of phytolith inputs from natural plant communities and crops and soil silicon availability (Southeastern Pampean region, Argentina)

Silica phytoliths constitute an important source of Si to terrestrial environments. Different plant communities contribute varying amounts of phytoliths to soils due to differences in plant taxa. In Pampean region, Argentina, agriculture has largely replaced natural communities like grasslands and wetlands. This replacement affects the specific plant composition of the area, modifies the potential phytolith input from plants to soils, and as a consequence, the soil Si content. Since no study specifically measures the potential phytolith contribution from natural communities and crops in the region, we aimed to quantify and compare phytolith production in natural plant communities and typical crops from Pampean region and its relation to available soil Si content. Three natural communities and three crops were selected. Phytolith content in plant communities was estimated by the phytolith amount produced in plant tissues (calcination technique) and plant biomass, while soil Si was measured by UV–VIS spectrophotometry. Phytolith content differed between natural communities and crops. The communities with the highest phytolith content were those that contained high phytolith-producing species and / or high plant biomass (959.61 ± 95.64 and 665.27 ± 382.38 kg/ha, wheat and "juncal", respectively). There were no significant differences in Si content between natural and cropland soils, and phytolith production differences in plant communities were not reflected in the soils. Probably soil genesis, vegetation history and / or management can explain the lack of differences. Continuous monitoring of phytolith production, plant biomass and soil Si content could explain the Si cycle in this region.