Impact of surface application of flue gas desulfurization gypsum on infiltration, phosphorus behavior and total sulfur in a previously manured coastal plain soil

Flue gas desulfurization (FGD) gypsum was surface-applied on a poorly drained cultivated Coastal Plain soil in Maryland containing excessive amounts of plant-available phosphorus (P). Using a constant head double-ring infiltrometer, a field experiment indicated a slight increase in final infiltration rate (FIR) at 10 and 15 Mg ha-1 application rates, however a laboratory rainfall simulation showed no significant effect of FGD gypsum on FIR. Water extractable phosphorus (WEP) decreased by 13-47% one year after application of FGD gypsum. Linear relationships were established between Mehlich 3 (M3) and ammonium oxalate extractions of P and aluminum (Al) (r2 = 0.83, 0.56, respectively), supporting previous research on the reliability of M3 in place of ammonium oxalate to predict P loss. One year after FGD gypsum application total S was 3-150% higher at 15 cm and 44-74% higher at 30 cm depths. No significant difference in total S was apparent at deeper depths.