Effect of Irrigation with Industrial Wastewater and Gypsum Amendments on Heavy Metal in Soil and Black Cumin (Nigella sativa L.) Seed

Abstract

ABSTRACT Irrigation with wastewater is possible in many arid and semi-arid countries that suffering from water shortage. Furthermore, addition of gypsum (CaSO4. 2H2O) to soil may be reduce effluent problems. This research targeted the consequences of gypsum and wastewater on soil properties, yield components, and element content in soils and Black cumin (Nigella sativa L.) seeds. Factorial and completely randomized designs were conducted at the research station of Avicenna herb garden. The results showed that gypsum (0, 3.48, 4.34, and 5.21 g kg–1) and treated wastewater (0, 25, 50, 75, 100%), significantly affected soil heavy metal content. The highest concentrations of heavy metals found in the soil were iron (Fe), and the lowest copper (Cu) but, their values were below the critical level. The highest concentration of heavy metal in black cumin was iron found in the roots and stems, and the lowest was copper in the same plant parts. Generally, gypsum at the rate of 5.21 gkg−1 and the irrigation with 75% concentration of effluent, increased significantly the plant yield components and heavy metals concentration in different black cumin organs. Still, the concentrations of all heavy metals studied were found within the standard limits.