Partitioning of 35S in ryegrass grown in sulfur-deficient soils

A pot study was conducted in a growth chamber using S-35 labelled gypsum to study the fate of applied S-35 fertilizer in a soil-plant system. The distribution among plant parts and soil fraction of applied S-35 was investigated with ryegrass grown in sulfur-deficient soils. Of the applied S-35, 19-35% was recovered in the shoot and 4-16% in root tissues. Within the soil, extractable S-35 accounted for 41-55% of applied S, microbial biomass S-35 accounted for 2-6%, and the remaining 4-14% was unrecoverable. In addition to the available soil S fraction, it was concluded that S in the unharvested plant residue could be an important supplementary S source for succeeding crops.