AMMONIUM BICARBONATE-DTPA EXTRACTION OF ELEMENTS FROM WASTE-AMENDED CALCAREOUS SOIL

Use of soil testing for both nutrient and heavy metal interpretations could prove to be a readily available tool for management of calcareou s soils amended with solid waste products. The ammonium bicarbonate-DT PA (diethylenetriaminepentaacetic acid) [AB-DTPA] extractant was used in this study, based on its successful use in other calcareous regions , and existence of interpretations for both nutrients and selected hea vy metals. In southern Florida, addition of large volumes of composted waste products to shallow agricultural soils formed from crushed Ooli tic limestone appears to be a viable disposal alternative to rapidly e xpanding lanfills or incineration. For two years, the effects of proce ssed wastes (PW) on selected, AB-DTPA-extractable soil mineral element concentrations were determined for tomato (Lycospresicon esculentum M ill.) and squash (Cucurbita maxima Duch. Ex Lam.) grown with three dif ferent irrigation rates (3.78, 2.53, or 1.25 L/min). The PW composts w ere added at supplier-recommended rates for soil addition, resulting i n a range of loading rates varying with source, with which the AB-DTPA extractant could be evaluated. The PW composts were: i) Agrisoil Comp ost (processed municipal garbage and yard clippings) applied at 48 Mg/ ha, ii) Daorganite (processed sewage sludge) applied at 16 Mg/ha, and iii) Eweson Compost (processed municipal garbage and sewage sludge) ap plied at 24 Mg/ha, and iv) no PW (control). There were no significant interactions between irrigation and PW treatment or effects of irrigat ion treatment on any of the soil-extracted elements following either c rop, with the exception of AB-DTPA-extractable copper (Cu) following s quash in 1991. Treatment with Agrisoil resulted in the greatest increa se in mineral element accumulation in the soil followed by Daorganite and Eweson sources for both crops during each year. Although there was variability among crops and years, mineral element concentrations, pa rticularly manganese (Mn), lead (Pb), nickel (Ni), and Cu, were genera lly higher in the Agrisoil-amended soil than in the other treatments. These observations could be traced to loading rates of individual elem ents. The lowest mineral element concentrations were in the non-amende d soil. The results of this study indicate that nutrients and selected heavy metals can be monitored successfully using the AB-DTPA extracta nt. Accumulation of nutrients, including metals, in PW-amended soil wa s minimal when supplied to the soil at manufacturers' recommended rate s, which were well below the U.S. Environmental Protection Agency's ma ximum loading rates.