Plastic film mulching has been widely used to increase maize yield in the semiarid area of China.  However, whether long-term plastic film mulching is conducive to agricultural sustainability in this region remains controversial.  A field experiment was initiated in 2013 with five different film mulching methods: (i) control method, flat planting without mulching (CK), (ii) flat planting with half film mulching (P), (iii) film mulching on ridges and planting in narrow furrows (S), (iv) full film mulching on double ridges (D), and (v) film mulching on ridges and planting in wide furrows (R).  The effects on soil organic carbon (SOC) content, storage, and fractions, and on the carbon management index (CMI) were evaluated after nine consecutive years of plastic film mulching.  The results showed that long-term plastic film mulching generally maintained the initial SOC level.  Compared with no mulching, plastic film mulching increased the average crop yield, biomass yield, and root biomass by 48.38, 35.06, and 37.32%, respectively, which led to the improvement of SOC sequestration.  Specifically, plastic film mulching significantly improved CMI, and increased the SOC content by 13.59%, SOC storage by 7.47% and easily oxidizable organic carbon (EOC) by 13.78% on average, but it reduced the other labile fractions.  SOC sequestration and CMI were improved by refining the plastic film mulching methods.  The S treatment had the best effect among the four mulching methods, so it can be used as a reasonable film mulching method for sustainable agricultural development in the semiarid area.

Ridge-furrow film mulching has been widely used as a water-saving and yield-increasing planting pattern in arid and semiarid regions.  Planting density is also a vital important influencing factor of crop yield, and the optimal planting density will change in different environments (such as ridge-furrow film mulching).  How the combination of film mulching and planting density affect the growth, physiology, yield, and water and radiation use efficiencies of winter oilseed rape is not clear yet. Therefore, a three-year (from 2017 to 2020) field experiment was conducted to explore the responses of leaf chlorophyll content (LCC), net photosynthetic rate (P_n), leaf area index (LAI), aboveground dry matter (ADM), root growth and distribution, yield, evapotranspiration (ET), water use efficiency (WUE) and radiation use efficiency (RUE) of winter oilseed rape to different film mulching patterns (F, ridge-furrow planting with plastic film mulching over the ridges; N, flat planting without mulching) and planting densities (LD, 100,000 plants ha^–1; MD, 150,000 plants ha^–1; HD, 200,000 plants ha^–1).  The results showed that F treatments obtained significant greater LCC, P_n, LAI and ADM, and a stronger root system than treatments without film mulching throughout the whole winter rapeseed growing seasons.  Winter oilseed rape in MD treatments had a better physiological (LCC and P_n) and growth (LAI, ADM, taproot and lateral root) conditions than LD and HD at late growth period after stem-elongation.  Grain yield in FMD was the greatest, and was 34.8–46.0%, 6.7–9.6%, 87.8–108.3%, 38.7–50.3%, and 50.2–61.8% significantly greater than that in FLD, FHD, NLD, NMD, and NHD, respectively.  Furthermore, FMD consumed equivalent ET with FLD and FHD, 12.2–18.4%, 14.5–20.3%, and 14.6–20.4% markedly lower ET than NLD, NMD, and NHD.  Finally, WUE and RUE in FMD were significantly improved by 88.5–94.0% and 29.0–41.8% in comparison to NHD (local conventional planting pattern and planting density for winter rapeseed).  In summary, FMD is a favorable cultivation management strategy for winter oilseed rape to save water, increase yield and improve resources utilization efficiencies in northwest China.