Effects of macro-plastics on soil hydrothermal environment, cotton yield, and fiber quality under mulched drip irrigation in the arid region of Northwest China

Residual plastic pollution in terrestrial soils has emerged as a globally significant environmental challenge on a global scale, particularly in agricultural systems. Within extensive areas of plastic film-covered agriculture, the presence of residual macro-plastic debris (> 0.5 cm) has resulted in immeasurable losses to soil quality and crop production. To date, there is a lack of research investigating the potential impact of plastic mulching film residues on soil properties, crop yield, and the quality of cotton fiber. In this study, a field experiment was conducted for the first time to assess the effects of different amounts of residual plastic film (RPF) on soil hydrothermal characteristics, cotton growth, and fiber quality in drip-irrigated cotton fields. The experiment encompassed six amounts: RPF0 (0 kg ha−1), RPF5 (146.18 kg ha−1), RPF10 (228.03 kg ha−1), RPF15 (309.88 kg ha−1), RPF20 (391.73 kg ha−1), and RPF25 (473.58 kg ha−1). The trial spanned the period from 2020 to 2021. The elevation in the amount of RPF had a positive impact on irrigation water storage in the soil and resulted in decreased water consumption by cotton plants. Concurrently, it led to an increase in the average soil temperature and the accumulated active temperature in the 0–25 cm soil layer. However, there was a notable rise in the interannual levels of nitrate nitrogen in the soil with the augmentation of RPF. In addition, the abundance of macro-plastic debris in the soil correspondingly suppressed cotton fiber quality. To ascertain the effect of plastic film residue on soil properties, cotton economic benefits, and fiber quality, a structural equation model was developed. It is imperative to promptly adopt environmentally friendly agricultural mulch materials in order to minimize the input of macro-plastic debris and enhance the recycling of native soil plastic film residues.