Calcium and magnesium content and soil acidity parameters in rice felds of Santa catarina State

The objective of this research was to evaluate Ca and Mg availability, base saturation (V%) and soil acidity parameters of rice fields in Santa Catarina (SC) to subsidize liming recommendations. The database was built with variables obtained from 2.464 soil samples analyzed during four agricultural crops cycles (2012-2015) in seven regions: Alto, Médio and Baixo Vale do Itajaí, Litoral Norte, Araranguá, Criciúma and Tubarão. The soil attributes were grouped in classes for interpretation according to limits established by current recommendation manuals. The soils of rice fields of SC are predominantly acidic. More than 50% of the soil samples from Criciúma, Médio and Baixo Vale do Itajaí regions, and 30-40% of those from Litoral Norte and Araranguá regions, indicated low levels of Ca. The diagnosis indicated the necessity of soil acidity correction for the most soil analyzes, if the farmers’ option is to sow the irrigated rice under dry soil conditions. For the pre-germinated system, most of the fields in the Tubarão, Araranguá, Alto Vale and Litoral Norte regions would require less than 200 kg ha-1 of effective dolomitic limestone to supply Ca and Mg.