EFFECTS OF GYPSUM ENHANCED COMPOSTS ON YIELDS AND MINERAL COMPOSITIONS OF BROCCOLI AND TALL FESCUE

Gypsum (CaSO4 center dot 2H2O) addition during composting of manure or biosolids can reduce ammonia nitrogen losses and represents a new method for controlling odors. Additional work is needed, however, to test the ability of the gypsum-containing composts to support plant growth and affect uptake of nutrients and heavy metals. A field study using broccoli (Brassica oleracea L. var. italica) and a growth chamber study using tall fescue (Festuca arundinacea) were conducted by application of composts at 10 Mg ha-1 for broccoli and 10 and 25 Mg ha-1 for tall fescue. Compared to composts without gypsum, at 10 Mg ha-1, gypsum composts significantly increased or had a strong trend to increase yields of broccoli and tall fescue. Gypsum composts affected concentrations of nutrient elements but did not increase concentrations of environmental concern elements in broccoli flowers and tall fescue tissue. Thus gypsum composts can be safely applied to soils to enhance crop growth.