Phytotoxic Effects of Polyethylene Microplastic on the Growth and Yield of Groundnut (Arachis hypogaea L.) and Soybean (Glycine max L.)

Abstract

Microplastic contamination of agricultural soils is an emerging environmental concern due to plastic accumulation in terrestrial ecosystems and its potential effects on crop growth, soil quality, food security, and human health. This study investigated the phytotoxic effects of polyethylene (PE) microplastic on germination, growth, and reproductive development of groundnut (Arachis hypogaea L.) and soybean (Glycine max L.). Treatments consisted of 0 mL (control), 6, 9, 12, and 15 mL PE microplastic. PE contamination altered soil physicochemical properties, although effects on electrical conductivity (p = 0.477) and water-holding capacity (p = 0.329) were not significant. PE significantly affected soybean germination (p = 0.004), but not groundnut germination (p = 0.534). Groundnut germination was delayed, with 9, 12, and 15 mL treatments recording 13.33%, 13.33%, and 20% germination, respectively, by Day 8, while soybean recorded no germination at 6, 12, and 15 mL and 13.33% at 9 mL. PE concentration significantly affected groundnut plant height, number of leaves, and leaf area, but not branches. In soybean, significant effects were observed for plant height, branches, leaves, and leaf area. Groundnut height declined from 32±9.8 cm in the control to 24±7.6 cm at 6 mL PE. Flowering was significantly affected in groundnut (p = 0.023), but not soybean (p = 0.189). Chlorophyll content also varied between treatments and crops. Overall, PE phytotoxicity was crop- and concentration-dependent, highlighting potential risks to agricultural productivity and food safety. Improved plastic waste management, reduced use of non-degradable plastics, soil monitoring, and sustainable agricultural practices are recommended.