Phosphogypsum is a byproduct phosphoric acid production and is used widely in agriculture. However, researches on phosphogypsum as sulfur source are limited. On the other hand, sulfur supply to crops decreasing recently. It’s a matter of concern for insufficient sulfur supply. In this study, the effects of phosphogypsum on sulfur supply to Onion are investigated.

 Field experiments were carried out at Experimental Farm of Yamaguchi University, Japan. Phosphogypsum (PG) was applied on Nov. 26th, 2008 at application rate of 0, 100g, 250g, 500g/m². Onion was cultivated for two years.

 Exchangeable Ca, water soluble Ca and available S increased with PG application. Both Ca and S decreased in second year but the effects of PG still remain in soil (0-15cm). Sulfur content of onion increased with PG application at rate of 250g and 500g/m² in first year. In second year, it increased in all PG treatments. Pyruvic acid, which is an indicator of pungent flavor, increased with PG up to 250g/m² application