The development of gangrene of potato (Solanum tuberosum L., cv. Sakurafubuki) caused by Phoma exigua was suppressed with spent flue gas desulfurization absorbent residue (SGDAR) applied to sandy soil (Volcanogenous Regosols) in Hayakita-cho, Hokkaido, Japan. SGDAR consists of gypsum (CaSO_4) and coal ash which contain a large amount of Ca and B, respectively. A field experiment in the above-mentioned area in 1998 showed that application of Ca with gypsum (1.6 Mg Ca ha^<-1>) suppressed the development of gangrene. However, application of B (1.6 kg B ha^<-1>) with both coal ash and fritted trace element fertilizer (FTE) suppress it. Application of SGDAR and gypsum increased the concentration of exchangeable Ca did not in the soil and the concentration of Ca in tuber of potato. These results suggest that Ca eluted from gypsum in SGDAR increased the resistance of the tuber to the infection with the pathogen, P. exigua, in the sandy soil which contains little Ca nutrients. SGDAR and gypsum promoted the growth of the tuber and increased the tuber yield, and coal ash and FTE increased the number of tubers.
