Compost application modulates growth, physiology and metal uptake by Pisum sativum grown in two different pH soils irrigated with contaminated wastewater

Background and aimsGreen waste compost (GWC) could alleviate the toxicity of Cu/Zn-contaminated wastewater (WW) to plants, but its differential behaviour in neutral and acidic soils remains unelucidated. Therefore, this pot study evaluated the alleviative effect of GWC on the toxicity of Cu and/ or Zn contaminated wastewater to soil dehydrogenase activity (DHA), growth, physiology and metal accumulation by common pea in acidic and neutral soils.MethodsThe four WW treatments were: uncontaminated WW, Cu-contaminated WW, Zn-contaminated WW, and Cu+Zn-contaminated WW. Thus, there were 16 treatment combinations (4 wastewater- x 2 soils- x 2 compost levels), each having three replicates.ResultsContaminated WW had statistically similar negative effects on soil DHA, growth and chlorophyll contents of pea plants in both soils. Pea plants accumulated more Cu and Zn in acidic-pH soil than in neutral soil. The ameliorative effect of the GWC amendment was statistically similar in both soils. The GWC improved soil organic matter (30-49%), soil DHA (38-63%), and growth (6-37%) and chlorophyll contents (14%-2-fold) of pea plants as compared to No-Compost. Conversely, the GWC amendment notably and equally decreased Cu and Zn accumulation in pea shoots in both soils. The principal component analysis revealed that Cu concentration and content were negatively related to soil DHA, growth and chlorophyll contents of pea plants.ConclusionHence, it is concluded that Zn is less toxic than Cu, and compost can be used as soil conditioner in acidic as well as neutral soil to reduce the metal uptake and their concentration in pea shoots.