Disponibilidade no solo, estado nutricional e recomendação de enxofre para o arroz irrigado = Soil availability, nutritional status and sulfur recommendation for flooded rice

The Depressão Central region in the State of Rio Grande do Sul, Brazil, is characterized
by large areas of sandy soil that were intensively cultivated with flooded rice in the last decades.
Currently, the high rice yields, along with the low organic matter content of these soils and the
fertilization practices are favorable conditions for the appearance of sulfur (S) deficiency.
With the purpose of determining sulfur distribution in the soil profile and recommending levels
of this element for flooded rice based on the calibration curve and crop response to sulfur
fertilizer, a study was carried out at 12 sites in the Depressão Central region during the 2004/
2005 and 2005/2006 growing seasons. Sulfur availability in the soil profile did not correlate
with organic matter and clay content. Sulfur content in plant tissue increased with soil sulfur
availability and with soil-applied sulfur rates, but did not reach the sufficiency range determined
by the interpretation system used in Brazil. The critical content determined in the soils of the
Depressão Central in the State of Rio Grande do Sul is higher than the one currently used in
Southern Brazil. The sulfur rates for the maximum technical efficiency (36 kg ha-1) and
economic efficiency (26 kg ha-1) for flooded rice on soils with sulfur availability below the
critical level resulted in similar grain yields.