Effects of Soil Plastic Contamination on the Early Growth of Pea Plant (Pisum sativum)

Nowadays, contamination by plastics is one of the most serious environmental issues. Although marine plastic pollution has attracted considerable attention for a long time, recent scientific papers suggest that terrestrial ecosystems have turned into significant sources of contamination with microplastics. The presence of plastics in soil is caused by agricultural activities. It includes the use of mulch films, irrigation equipment, greenhouse covers, compost, sewage sludge, packaging materials, and degraded plastic waste. Under environmental conditions, plastic waste is fragmented into microplastics – plastic particles with a size less than five millimeters. They affect soil physical characteristics, hydrological regime, nutrient supply, soil microbiota, and plant growth. Being crucial for crop development, soil is also an object of study regarding the impact of plastic pollution on crop development. The aim of this study is to examine the effects of plastic-contaminated soil on germination and early growth of pea plants (Pisum sativum). Pea plants were chosen because of fast germination and the rapid development of root and shoot systems. In addition, these plants are commonly used in biological experiments. There were four experimental treatments: Soil (control), Plastic 1, Plastic 2, and Plastic + Soil. The same amount of pea seeds was used in all treatments and grown under the same environmental conditions: the same irrigation schedule, light intensity, temperature, soil amount, and containers' sizes. Roots' lengths, shoots' lengths, germination success rate, and plants' biomass were examined to evaluate the effects of different plastic treatments on plant development. The results of the experiment revealed some significant differences between treatments. The shortest average root length was detected in Plastic 2 treatment, which means that Plastic 2 had a negative effect on root development. Some differences were found for shoot lengths and biomass. The Plastic + Soil treatment had the highest average plant biomass, which means that the effects of plastic on plant growth may be dependent on both properties of soil and plastic. Even though the sample size is relatively low, the results are consistent with the conclusions of previous studies concerning the issue. This study adds another piece of information to existing literature on terrestrial microplastic pollution and its effects on agricultural crops. Further investigation should be conducted with bigger sample sizes, different crop species, long experimental period, and various plastic concentrations.