Field-Aged Shade Nets Residues Disrupt Rhizosphere Microbiota and Nitrogen Metabolism in Tea ( Camellia sinensis )

Plastic residues in agricultural production pose escalating risks to soil health and food security, yet the impacts of shade nets (SNs) residues in soil have received little attention. Here, we compared the effects of pristine and field-aged polyethylene SNs through a year-long exposure experiment with tea plants (Camellia sinensis). Both pristine and aged SNs impaired soil and plant health, but the adverse effects of aged SNs were more pronounced. Pristine SNs decreased soil pH and increased chromium content, while aged SNs further depleted soil available nitrogen, promoted stronger rhizosphere microbial restructuring, and induced ferroptosis-like lipid peroxidation in roots, leading to deterioration of tea quality. Beneficial rhizosphere groups such as Proteobacteria and Rozellomycota declined, while denitrifiers bacteria and saprotrophic fungi were enriched, aggravating nitrogen loss. These shifts disrupted the soil-plant C-N balance, impairing tea plant nitrogen metabolism, which in turn suppressed glutamate and theanine biosynthesis, reallocating metabolism toward bitter ester-type catechins, and ultimately reduced tea flavor and quality. Our findings show that aged SNs act as emerging agricultural pollutants, disrupting nitrogen metabolism across soil-root-leaf scales. Recognizing aged SNs as part of global plastic pollution highlights their dual agronomic and environmental risks, underscoring the need for sustainable management and recycling in high-value agriculture.