Eighteen months after application, FGD gypsum resulted in higher total and extractable sulfur levels in the soil, but this may not have made a noticeable difference in plant growth because none of the soils in this study were sulfur-deficient. Elevated levels of extractable phosphorous and zinc, and total zinc and nickel remained in the soil due to the application of biosolids, but the levels of these metals in the soil were not high enough to pose a potential risk to ecological life.

A one-time addition of biosolids and FGD gypsum will not improve the soil quality of marginal lands over an 18-month time period. The initial soils were so deficient in nutrients that the plant available fraction of nutrients was likely used by the Miscanthus plants, leaving low nutrient build-up in the soil. Any improvements in soil physical properties and soil nutrient content will take a longer time period to become evident, so further study of this system is necessary. It is likely that reapplication of these nutrients will help to further improve soil properties and nutrient contents.

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