Optimizing Planting Density for p,p′-DDE Phytoextraction by Cucurbita pepo

Abstract

A field experiment was conducted to determine the optimum planting density of Cucurbita pepo subspecies pepo (zucchini) for the phytoremediation of weathered p,p′-dichlorodiphenyldichloroethylene (p,p′ -DDE). In previous greenhouse investigations, preliminary data indicated significant increases in remedial potential at higher planting densities. Three zucchini cultivars were grown in DDE-contaminated soil at cultivation densities of 1, 4, 8, or 16 plants per square meter (0.25 m depth)or approximately 270 kg of soil. At all densities, zucchini accumulated large amounts of the weathered contaminant, with root and stem bioconcentration factors, the dry weight ratio of DDE content in tissue to that in the soil, ranging from 8.5-14 and 6.8–10, respectively. The total plant biomass of the three cultivars, as well as the mass of individual tissue compartments, increased significantly as planting density rose from 1 to 4 plants/m2. However, further increasing cultivation density to 8 or 16 plants did not result...