Evaluation of straw and plastic film mulching on wheat production: A meta-analysis in Loess Plateau of China

Field mulching is an important technique of wheat (Triticum aestivum L.) cultivation in the Loess Plateau (LP) of China, which alleviates the local agricultural water-shortage. At present, there are few bidirectional effect analyses on plastic film mulching (PM) and straw mulching (SM) in LP area. This study uses control variable method to estimate mulches response magnitude (yield, WUE and ET) for ecological factors. We collected a total of 118 peer-reviewed publications after 2000. The results showed that PM significantly increased wheat yield in most vulnerable eco-regions, but SM was more suitable in areas both with higher sunshine (> 2500 h) and air temperature (> 8 °C), or frost-free period > 200 days. Generally, the average yield increase of PM was 4.04% higher than SM. While annual precipitation exceeded 600 mm and air temperature exceeded 13 °C, film treatment had higher WUE, which reached 37.65 and 36.89 kg ha−1 mm−1 respectively. We also found that certain soil physicochemical properties such as soil water content, bulk density, sand content, pH, organic carbon, available nitrogen, available phosphorus would significantly affect wheat yield under mulching. When soil water content < 16% or > 24%, and soil temperature > 16 °C, PM had the relative dominance that corresponding effect sizes were 0.499, 0.667 and 1.176 respectively. By comparing the output input ratio (OIR), PM needed 6.77% cost higher than SM in premise of same yield. On the whole, the suitable cultivation regions of PM were wider than SM, so former was most important mulching technology in current LP. While SM had obvious advantages in “return on investment”, and more conducive to protecting soil ecosystem health or promoting agriculture sustainable development, hence it would lead local mulching technology innovation in the future.