Impacts on the growth of Sweet Corn (Zea Mays) exposed to plastic weed fabric and soil amendment with and without earthworms

Abstract

Agricultural practices, such as farm field application of sewer sludge or use of plastic weed fabrics may impact yield of crop plants. Numerous studies have documented the presence of microplastics in wastewater treatment plant effluent and sludge and have noted negative impacts on terrestrial and aquatic organisms. Plastic mulch and weed fabrics are increasingly more common in small-scale farming and over time will degrade into finer microplastic particulate. Both plastic sources have the potential to leach residues into soils and adjacent waterbodies, with potential impacts on both plants and wildlife. Earthworm bioturbation has the potential to redistribute microplastics even deeper into the soils as they consume and lay castings. We established a greenhouse experiment to examine the effects of farming-associated plastics on Sweet Corn (Zea mays) in the presence of Red Worms (Eisenia foetida). We sowed 4 corn seeds per pot across 5 treatments (control, macroplastic, microplastic, amendment 1mm, amendment 355um) with 6 replicates per treatment and lined and covered the pots with screening. Once plants were established (13 days), two Red Worms were introduced to three pots across all treatments. Plant height was measured weekly and upon harvest, stem diameter, leaf abundance, and weights were obtained. Preliminary results suggest that the amendment hastened the date of first germination (6 days post-planting). All plants germinated in 1mm amendment and macroplastic, whereas minimum (88%) germination was observed in 355um amendment and microplastic treatments. There was a statistical difference in the height of Sweet Corn after a week with the tallest plants deriving from the 1mm amendment treatment (p = 0.037, F = 2.643, df = 119). This study serves to help elucidate the complex interactions of microplastic and soil-dwelling organisms on yield of crop plants. Our results will inform farmers and land managers about avoiding techniques that will potentially increase plastics inputs into ecosystems.