Years of whole-field plastic mulching improving soil and crop yield on winter wheat/rape rotation field

Abstract: Whole plastic film mulching is commonly used for crops on the Loess Plateau, which can significantly improve rainfall use efficiency and crop productivity. However, no systematic analysis of the productivity increment and soil microbial environmental effects of this technique has been undertaken previously. A field experiment was conducted from 2012 to 2016 to study the effects of whole plastic film mulching on soil microbial biomass carbon, soil microbial biomass nitrogen, soil enzyme activities, soil moisture and temperature. The 3 treatments applied were: whole plastic film mulching with soil covering and bunch seeding (M1), whole plastic film mulching and bunch seeding (M2), and soil uncovered and bunch seeding (M0). The soil water content and soil temperature were recorded, and the soil microbial biomass carbon, soil microbial biomass nitrogen, and soil enzyme activities were calculated. The M1 and M2 treatments averagely increased the soil moisture content by 3.83%-15.85% and 2.53%-15.53%, soil temperature by 0.9-1.7 and 0.8-2.7 ℃ respectively compared with M0 before winter wheat jointing stage and rape flowering stage. As compared with M0, both M1 and M2 treatments averagely increased soil microbial biomass carbon content by 25.64% and 23.55% from winter wheat re-greening to jointing stage, and by 24.70% and 24.63% from rape re-greening stage to flowering stage, significantly. As compared with M0, both M1 and M2 treatments averagely increased soil microbial biomass nitrogen content by 20.42% and 12.65% from winter wheat re-greening stage to jointing stage, and by 18.41% and 15.35% from rape re-greening stage to bud stage, significantly. As compared with M0, the urease enzyme activities of M1 and M2 were significantly higher at each growth stage of winter wheat and rape (except winter wheat booting, maturing stage in 2013), and the sucrase enzyme activity of M1 was significantly higher at each growth stage of winter wheat and rape, whereas alkaline phosphatase enzyme activity of M1 was lower (except winter wheat maturing stage in 2013). The increased extent of soil thermal-moisture status and soil microbial activities was higher in 2015 and 2016. There is a positive correlation between soil microbial biomass carbon, microbial biomass nitrogen, urease enzyme, sucrase enzyme and soil moisture and soil temperature. Based on the regulatory effect of soil thermal-moisture status and microbial activities, compared with M0, the winter wheat yield of M1 and M2 increased by 30.44% and 22.25%, and the rape yield of M1 and M2 increased by 21.36% and 14.02%, respectively. The increased extent of yield and water use efficiency was higher in a dry year than that in a wet year. Consequently, whole plastic film mulching ameliorated soil thermal-moisture status in dry spring, and increased soil microbial biomass carbon content, microbial biomass nitrogen content, urease enzyme activity, sucrase enzyme activity, and crop yield.