Heavy Metal Uptake During the Growth of Durum Wheat from Application of Sewage Sludge and Commercial Fertilizer

Repetitive application of commercial fertilizer continually introduces toxic heavy metals to the soil. Such metallic toxins are subsequently taken up by food crops. Sewage sludge, usually disposed of in landfills, contains high nutrient and organic contents and is now being recycled and applied to agricultural land worldwide in increasing amounts. Metals in sewage sludge are generally organically bound and generally less available for plant uptake than the more mobile metal salt impurities found in commercial fertilizers. However, it is predicted that a slow mineralization of organic matter in sludge releases metals into more soluble forms over time. ¹ This research is a preliminary project which gives indication as to metal accumulation in durum wheat roots and the difference between metal salt accumulation and the risk of a 20-year-old sludge with organically bound metals. Future studies will determine metal accumulation in different regions of the durum wheat plant. This information is especially important to phytoremediation issues, giving an indication as to which part of the wheat plant provides maximum uptake of a specific metal and as such, could be used to remove metal from the soils.

Initially, this project focused on screening of U.S. durum wheat lines, common commercial fertilizers, and sludge for 15 potentially threatening elements using inductively coupled plasma mass spectrometry (ICP-MS). Metal uptake studies in a high Cd durum wheat were carried out in greenhouse grown plants using applications of a 20-year-old sewage sludge from the Goshen, Indiana Waste Water Treatment Plant and a commonly used 13-13-13 commercial phosphate fertilizer. Results of this first-phase of research include: (1) an assessment of the effect of sludge application on Cd uptake in durum wheat roots; (2) a comparison of accumulation of Cd uptake in durum wheat using commercial fertilizers; (3) an evaluation of differing metal uptake following use of single or multiple application strategy; and (4) an identification of the metals in addition to Cd that may serve as a threat to the export of U.S. durum wheat.