Long-term effects of plastic mulching on soil structure, organic carbon and yield of rainfed maize

Plastic film mulching measures are considered effective for conserving water and increasing crop yields. However, the effect of their long-term use on sustaining crop production remain unclear, especially under dryland conditions. A field experiment was conducted for nine years (2013–2021) in the Loess Plateau region of China to evaluate the effects of normal flat sowing with land fully covered by plastic film mulch (P), ridge–furrow planting with 50% coverage with mulch (R), normal flat sowing with land fully covered by biodegradable film mulch (B), and normal flat sowing without mulching (CK). Mulching treatments (P, R, and B) decreased the bulk density of the surface 0.6 m (P < 0.05), and increased the soil porosity (4.1–7.6%). In addition, there was an increase in meso-and macroaggregates contents, as evidenced by wet sieving (54.3–104.9%) and dry sieving (1.1–10.4%) methods. The carbon contents varied with soil depth. Major portion carbon was observed to be retained in the microaggregates under CK (69.5%) while it moved to mesoaggregates (47.8–56.7%) with plastic mulching. Higher soil water contentment were maintained in soils under plastic mulches. Overall improvements in surface 1.0 m soil, where most of the roots reside, were 47, 26 and, 20 mm under P, R, and B, respectively, and 28, 17, and 4 mm in 1.0–2.0 m soil. As a consequence of the maintaining superior better hydro-physical regimes, the grain yield, averaged over 9-years, improved by 4784 (P), 2746 (R), and 2413 kg ha−1 (B) over control. The rainwater was also extracted efficiently by maize. The resultant water use efficiency was 3.2, 2.8, 2.7, and 2.1 kg m3 under P, R, B and CK, respectively. Based on these observations, flat planting plastic film mulching with full surface cover seems a viable option to improve maize productivity under rainfed conditions of the Loess Plateau region.