Lime and phosphogypsum application and sulfate retention in subtropical soils under no-till system

Abstract

This study reports long- and medium-term effects of the application of up to 12 Mg ha-1 of phosphogypsum (PG) as soil conditioner and source of Ca and S, in two field trials, conducted under no-till systems. One field trial was located in Ponta Grossa, state of Paraná (PR), Brazil, on a loamy Oxisol, which received lime and PG applications in 1993. Another area of study was located in Guarapuava (PR), on a clayey Oxisol,which received PG in 2005. After thirteen years of surface-applied lime on the loamy Oxisol, we observed soil acidity reduction up to 80 cm depth, while PG effects Ca2++ and S-SO42-contents were more pronounced at deeper soil layers. Sulfate distribution in soil profiles was mostly correlated with Fed and Fed-Feo. However, there was no long-term effect of lime and PG additions on no-till maize (Zea mays) and wheat (Triticum aestivum) yields. An appreciable movement of SO42--S to the subsoil was observed in soil samples from the clayey Oxisol after surface-applied PG. This was observed even in the medium term (3.5 years) and despite the higher adsorption capacity of sulfate. In this case, PG addition had positive benefits on maize and triticale (X Triticosecale) yields due to the supply of Ca2++ and SO4-2-S to the plants.