Impact of Organic Soil Amendments on Fungal Population and Germination of Maize Seeds in Lead-Contaminated Soil

Abstract

Proliferation of industrial and other anthropogenic activities has led to an increase in heavy metal contamination of agricultural soil, elevating the risk of heavy metal (especially, lead) toxicity to all life forms. It is therefore imperative to develop effective bioremediation techniques for soil remediation. Cow dung and compost (Tithonia rotundifolia and poultry droppings) were added at 30 t/ha to lead contaminated soil. Abundance of heavy metal associated fungi in the contaminated soil was determined through pour plate isolation method using Potato Dextrose Agar. The effect of lead contamination and soil amendments was also determined on maize seed germination in the laboratory using Petri dishes in three replications. Heterotrophic fungal count in lead-contaminated soil decreased as Pb concentration increases. The abundance of soil associated fungi declined with an increase in lead concentration. It ranged from 3.2 × 103 to 0.00 CFU/mL in soils containing 0.36 g/kg lead and 63.01 g/kg lead, respectively both amended with cow dung. A. fumigatus, A. flavus, A. nudulans, A. tamarii, A. uvarum and A. terreus were the fungi species isolated from contaminated soil samples. A. fumigatus and A. flavus were the most prominent. A. fumigatus was able to survive at 100% concentration of lead amended with compost, 75% lead concentration amended with cow dung, 25% lead concentration amended with cow dung, and 100% lead concentration without amendment. Percentage germination of maize seeds also decreased with higher concentrations of lead in contaminated soil. High percentage germination (81.81 and 80.00) was observed in the control soil, and on 0.36 g/kg lead-contaminated soil, amended with cow dung, respectively. Organic fertilizers could be adopted to develop an efficient, cost-effective, and readily accessible bioremediation strategy for soil remediation, especially for the production of maize.