Contribution of elemental interactions in total essential nutrient and heavy metal content in cabbage under treated wastewater irrigation

Abstract

A greenhouse experiment was conducted in Agrinion, Greece, using a randomized block design, testing five levels of treated municipal wastewater (TMWW), i.e., 0%, 25%, 50%, 75%, and 100% of irrigation water, in four replications. The vegetable Brassica oleracea var. capitata (cabbage) was used as a test plant. The purpose of the experiment was to investigate the effect of different TMWW levels on the contribution of elemental interactions in total macroelement, microelement, and heavy metal content of different cabbage plant parts (roots, leaves, stems, and heads), with emphasis on the edible parts (heads). From the 362 statistically significant interactions, 70.72% were synergistic, 16.85% antagonistic, 8.01% synergistic–antagonistic, and 4.42% antagonistic–synergistic. The highest mean contribution of elemental interactions regarding total macroelements in cabbage heads was observed for potassium (K), calcium (Ca), and magnesium (Mg) with 1256.2, 1022.6, and 155.98 mg/100 g head dry matter (dm), respectively, whereas the lowest was found for heavy metals i.e., lead (Pb), nickel (Ni), chromium (Cr), and cobalt (Co) with 0.642, 0.143, 0.0112, and 0.0046 mg/100 g head dm, respectively. The toxic cadmium (Cd) did not contribute to heads in statistically significant levels.