Effects of gypsum,sulfur, terraclor and terraclor super-x for potato scab control

An investigation was made to determine possible effects of gypsum and sulfur for control of common scab of potato Streptomyces scabies (Thaxt.) Waksman and Henrici] in a highly buffered calcareous soil. This investigation included a comparison of the effectiveness of gypsum and sulfur with Terraclor and Terraclor Super-X. Both gypsum and sulfur reduced potato scab and measurements indicate that change of soil pH was slight (0.1–0.4 pH reduction). Band applications of sulfur in the sulfate (gypsum) or elemental form were effective at 600 lbs/A (672.5 Kg/ha) but not at lower rates. The weight of tubers thrown out of grade with scab was reduced by 53% with the effective sulfur rate. Treatment effects of gypsum (600 lb S/A-672.5 Kg/ha) were not significantly different from sulfur dust (600 lb/A-672.5 Kg/ha), Terraclor or Terraclor Super-X (both at 25.0 lb PCNB/A-28.0 Kg/ha). Tissue analyses of tuber peelings showed a significant reduction in calcium from treatments involving sulfur and gypsum, indicating that calcium levels in tuber peelings were positively correlated with scab susceptibility.