Early‐Season Applications of Sulfur Fertilizers Increase Potato Yield and Reduce Tuber Defects

Abstract

Sulfur recommendations are based on avoiding deficiency. Since S may have additional effects, the objective was to determine whether S fertilizers increase yield and reduce tuber defects. Potato (Solanum tuberosum L.) cultivar Atlantic was treated with wettable sulfur (WS), ammonium sulfate (AS), and ammonium thiosulfate (TS) at 0, 28, 56, 84, and 112 kg S ha−1 applied at planting [in‐furrow (IF)], 11 d later [pre‐emergence (PE)], 11 d after emergence [postemergence (PT)], and at tuber initiation (TI). Separate trials were conducted for each fertilizer and application. Ammonium nitrate and urea were added to AS and TS to equalize N. Yield of U.S. “A” potato was increased 11 to 34% by fertilizers at S rates greater than 56 kg ha−1 at IF, PT, and by AS and WS at TI. These fertilizers applied IF and at TI reduced the incidence of common scab (Streptomyces scabies) on tubers. When applied PT, AS and TS reduced common scab; WS did not. The incidence of black scurf (Rhizoctonia solani) on tubers was reduced when AS and TS were applied PT but not when applied IF and at TI. Pre‐emergence application had no effect. Other tuber characteristics, e.g., specific gravity and vascular discoloration, were unaffected. Plant growth was inhibited by TS applied after emergence but recovered. Yield was increased by S at 56 kg ha−1 applied IF, PT, and at TI except for TS applied at TI. Common scab and black scurf were reduced depending on application timing and fertilizer.