Impacts of straw addition on ryegrass (Lolium perenne L.) heavy metal absorption and microbial community structure

Soil contaminated with heavy metals not only affects human health and safety but also poses a potential threat to the ecological balance of soil microbes. Ryegrass effectively extracts heavy metals from soil. Straw can increase the biomass of ryegrass, but the effects of straw addition on heavy metal absorption and changes in soil microbial community structure remain unclear. Our objective was to determine whether straw addition was beneficial to heavy metal accumulation in ryegrass and how straw addition changed the soil microbial community structure.

In our study, straw was added to soil contaminated with cadmium, copper, and zinc. We planted ryegrass in the greenhouse and measured the heavy metal content in the roots and shoots of ryegrass at 50 days.

Straw addition increased available heavy metal conversion, soil microbial biomass, and ryegrass yield, increasing heavy metal absorption by ryegrass. An opposite trend was observed between the available heavy metals and soil microbial biomass during the ryegrass growth period. The bacterial community structure was primarily affected by the available heavy metal concentrations and the soil physicochemical properties. Bacteria with heavy metal resistance and straw decomposition ability dominated the soil after straw addition.

This study showed that straw addition can not only increase the heavy metal absorption of ryegrass but also act as a substrate to change the bacterial community structure. The results of this study provided directions for increasing the ability of plants to extract heavy metals and changing the soil microbial community structure using straw.