Effects of polyethylene microplastics on the microbial community structure of maize rhizosphere soil

The use of agricultural polyethylene films results in polyethylene microplastic accumulation in the soil, causing microplastic pollution, which has attracted the attention of scholars worldwide. To study the effects of polyethylene microplastics on the microbial community structure of crop rhizosphere soil, corn was grown with different polyethylene powders (average molecular weights:2000, 5000, and ≥ 100 000) to simulate microplastic pollution in agricultural soil. There were five treatments in this experiment:planting maize without polyethylene (CK), planting maize with 2000 (T1), 5000 (T2), and ≥ 100 000 (T3) molecular weight polyethylene powder, and non-planting maize without polyethylene (CK0). Differences in mineral element metabolism in different parts of maize plant at the heading stage and variation in the rhizosphere soil microbial community structure were analyzed. The results showed that the mineral element content differed in different parts of maize. Iron and copper were mainly concentrated in the roots; calcium, manganese, and magnesium were most abundant in the leaves; and potassium was mainly concentrated in the stems. After adding the polyethylene microplastics of different molecular weights, the mineral elements in different parts of the plant increased compared with CK; the increase was greatest under the 2000 molecular weight polyethylene treatment. Microbial diversity analysis showed that the polyethylene microplastics had different effects on the microbial community composition in the maize rhizosphere. Except for Proteobacteria and Burkholderiaceae, the abundance of bacteria decreased under the 2000 molecular weight polyethylene treatment compared to CK. The abundance of bacteria and fungi increased under the ≥ 100 000 molecular weight polyethylene treatment compared to CK. In general, the mineral elements contents in different parts of the maize plant increased compared with CK after the addition of polyethylene. Two-thousand molecular weight polyethylene reduced the abundance of bacteria and fungi in the soil, whereas ≥ 100 000 molecular weight polyethylene increased the abundance of bacteria and fungi in the soil; the number of microorganisms related to the degradation of environmental pollutants in each treatment increased, which helped the soil cope with microplastics stress.