Ammonium bicarbonate‐DTPA extraction of elements from waste‐amended calcareous soil

Abstract

Use of soil testing for both nutrient and heavy metal interpretations could prove to be a readily available tool for management of calcareous soils amended with solid waste products. The ammonium bicarbonate‐DTPA (di‐ethylenetriaminepentaacetic acid) AB‐DTPA] extradant was used in this study, based on its successful use in other calcareous regions, and existence of interpretations for both nutrients and selected heavy metals. In southern Florida, addition of large volumes of composted waste products to shallow agricultural soils formed from crushed Oolitic limestone appears to be a viable disposal alternative to rapidly expanding lanfills or incineration. For two years, the effects of processed wastes (PW) on selected, AB‐DTPA‐extractable soil mineral element concentrations were determined for tomato (Lycospresicon esculentum Mill.) and squash (Cucurbita maxima Duch. Ex Lam.) grown with three different irrigation rates (3.78, 2.53, or 1.25 L/min). The PW composts were added at supplier‐recommended rates for soil addition, resulting in a range of loading rates varying with source, with which the AB‐DTPA extradant could be evaluated. The PW composts were: i) Agrisoil Compost (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) applied at 24 Mg/ha, and iv) no PW (control). There were no significant interactions between irrigation and PW treatment or effects of irrigation treatment on any of the soil‐extracted elements following either crop, with the exception of AB‐DTPA‐extractable copper (Cu) following squash in 1991. Treatment with Agrisoil resulted in the greatest increase 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, particularly manganese (Mn), lead (Pb), nickel (Ni), and Cu, were generally higher in the Agrisoil‐amended soil than in the other treatments. These observations could be traced to loading rates of individual elements. The lowest mineral element concentrations were in the non‐amended soil. The results of this study indicate that nutrients and selected heavy metals can be monitored successfully using the AB‐DTPA extractant. Accumulation of nutrients, including metals, in PW‐amended soil was minimal when supplied to the soil at manufacturers’ recommended rates, which were well below the U.S. Environmental Protection Agency's maximum loading rates.