SOIL SULFUR AND NITROGEN AVAILABILITY IMPROVES ROOT BIOMASS GROWTH OF RYEGRASS (Lolium multiflorum L.)

Soil sulfur (5) deficiencies have been detected lately, affecting crop production and nitrogen (N) uptake. The objective of this study was to assess the effect of S application on crop N recovery efficiency. N and S mineralization, potentially available N, and urease activity were measured in Andisol and Mollisol soils. No differences were found (P <= 0.05) between the soils in terms of microbiological parameters, but soil mineralization kinetics showed a small increase in the Andisol soil. The Mollisol soil was used to carry out a pot assay with rye grass (Lolium multiflorum), including four treatments: S, N, the combined application of S and N at a rates of 30 kg S ha(-1) and 100 kg N ha(-1), and a control treatment. Crop biomass dry matter, N concentration, and N recovery efficiency were determined sixteen weeks after sowing. N recovery efficiency increased by 26% with S application, but it was not significantly different from the control treatment (P >= 0.05). The S content in the crop biomass was low, and a large residual soil S was observed at the end of crop growth. However, the combined application of N and S resulted in an increase (P <= 0.05) in the root growth of plants.