Abstract
Improvement of sulfur nutrition of orchardgrass (Dactylis glomerata L.) by phosphogypsum was evaluated. Phosphogypsum is a by-product of phosphoric acid production and 1.9 million Mg is produced annually in Japan. Recently the utilization of phosphogypsum in the agricultural field is under consideration. The experiments were conducted in two aged pastures (3 and 13 years after establishment). 1. The dry matter yields were increased 11 and 4% in 3 years old field and 12 and 9% in 13 years old field with 120 and 600kg ha^<-1> phosphogypsum applications, respectively. 2. Sulfur contents of orchardgrass of no treatment plots in 3 and 13 years old fields were 0.09 and 0.06%, respectively, which were lower than the critical value of sulfur content (0.1%) defined by the Japanese feeding standard for beef cattle. With 600kg ha^<-1> phosphogypsum application, sulfur content of orchardgrass was increased to 0.13% and 0.1% in 3 and 13 years old fields, respectively. 3. Available sulfur content of soil was significantly increased from 34.3mg kg^<-1> to 100.1mg kg^<-1> with 600kg ha^<-1> phosphogypsum application in 13 years old field. From these results, it was concluded that phosphogypsum is useful as sulfur supply material to crops.
