Field experiments were conducted to obtain information on the effect of rainfall and irrigation on Ca mobility from application of powdered and granular gypsum to peanuts. After receiving 11.27 cm of water, only 15 kg/ha (23%) and 28 kg/ha (21%) of the applied Ca was recovered from the 0–2.54 cm soil depth at the 280 and 560 kg/ha rates of powdered gypsum, respectively. With the same amount of water, recovery of Ca from 560 kg/ha rate of granular gypsum was 30 kg/ha (19%); however, the data indicate that undissolved granules remained after extracting soil treated with this material. Increasing amounts of water applied to the plots decreased the amount of Ca recovered from plots treated with powdered gypsum through four successive samplings; whereas, there was an increase in the amount of Ca recovered from plots treated with granular gypsum. A similar response pattern was obtained when Ca recovery in the primary pegging zone (0–5.08 cm depth) was measured even though total quantities recovered increased with the increase in soil depth.

The 280 kg/ha application of powdered gypsum did not significantly increase available Ca in the 0–15.24 cm soil depth at harvest, but there was a slight increase from the 560 kg/ha rate. The 560 kg/ha rate of granular material significantly increased available Ca at harvest.