Residual film hinders maize root-soil water coordination and root-shoot growth thereby reducing yield and water-nitrogen use efficiencies

Context

Plastic film mulching enhances crop productivity in arid China, but residual film impairs maize root development and soil structure, reducing yield and water-nitrogen use efficiencies. However, the specific mechanisms by which residual film affected maize root-soil water coordination and root-shoot growth, as well as their impacts on crop yield and water-nitrogen use efficiencies, are still not fully understood.

Methods and objective

A field experiment was conducted from 2017 to 2018. Five levels of residual film amount were set to simulate the accumulation of residual film over different years: 0 kg ha⁻¹ (M0) for 0 year, 90 kg ha⁻¹ (M90) for 10 years, 180 kg ha⁻¹ (M180) for 25 years, 360 kg ha⁻¹ (M360) for 55 years, and 720 kg ha⁻¹ (M720) for 120 years, to examine how residual film impacts soil water movement, root development, root-shoot ratio, dynamic changes of leaf area and aboveground biomass, grain yield, and water-nitrogen use efficiencies, and to further explore relationships among these variables.

Results

The results showed that residual film increased the soil moisture difference in the vertical profile and affected root distribution and length. Specifically, relative to the no film residual treatment, higher residual film levels (180 kg ha⁻¹-720 kg ha⁻¹) significantly reduced total root length by 6.32 %-24.31 % and increased shallow root distribution in the 0–30 cm layer by 6.31 %-20.72 %, demonstrating a clear negative impact on root system architecture. The coupling coordination degree of soil moisture and root system in the 0–30 cm soil layer was enhanced due to the increased residual film. However, residual film had a significant negative impact on leaf area index and leaf area duration. When the residual film amount exceeded 180 kg ha⁻¹, pre-anthesis dry matter translocation and post-anthesis dry matter accumulation were reduced. At the tasseling stage, the root-shoot ratio increased. Compared to the treatment without residual film, grain yield, water use efficiency, and nitrogen partial factor productivity were significantly reduced by 20.26 %-50.54 %, 16.85 %-36.19 %, and 17.06 %-42.42 %, respectively. The structural equation model demonstrated a good fit to the data (CFI = 0.967, GFI = 0.931), and revealed that residual film exerted a direct negative effect on root-soil water coordination, which in turn reduced yield indirectly by limiting biomass production. Furthermore, root-soil water coordination had a strong direct negative effect on both water use efficiency and nitrogen partial factor productivity. The path analysis quantified the negative influence of residual film, with coefficients of −0.241 for yield, and −0.767 for both WUE and NPFP.

Conclusions

Excessive residual plastic film (>180 kg ha⁻¹) hindered root-soil water coordination and root-shoot growth, resulting in reduced maize yield and lower water-nitrogen use efficiencies.

Significance

This study provides a theoretical basis for addressing residual film pollution and supports sustainable agricultural development.