Corn (Zea mays L.) is one of the most important crops in China. It was estimated that 31% of corn grains was produced in the northeast region (Dong et al., 2017). This also led to the production of large amounts of corn straws. According to statistics, the production of corn straw in the northeast China reached 98 million tons in 2015. As a common agricultural practice, most corn stalks produced are burned in field. However, the burning of crop residues would emit harmful substances, including particulate matter (PM), volatile organic compounds, greenhouse gases or other toxics, to atmosphere, which is contributing to air pollution and threatening human health. (Subramanian, 2014; Chen et al., 2017; Liu et al., 2019). In an effort to reduce air pollution and protect human health, Chinese government has officially banned the direct straw burning, which was implemented in April 2014 (Hong et al., 2016). Therefore, it is an urgent need to develop environment-friend and low-costly techniques for the straw utilizations (Qu et al., 2012).
Five common utilizations for crop residues included the uses as energy, fertilizer, feed, industrial raw material, and base material (Li et al., 2018). Among such utilizations, many technologies have been developed for corn straws, such as direct-combustion for power generation (Wang et al., 2018), briquette fuel processing (Zhang et al., 2019), production of biochar (Wang et al., 2019), syngas (Hu et al., 2019), butanol and pulp (Xia et al., 2019), biomass films (Li et al., 2019), rigid polyurethane composite foams (Jiang et al., 2020), special animal feeds, etc. However, straw return into soil still remains as the most common utilization in China. Estimated 32% of the total straws produced were returned to soil annually (Bi et al., 2008), and this number is increasing recently.
Returning straws to soil has been considered as a sustainable, low-cost practice that enhances carbon sequestration, increases soil organic matter and improves soil health. The degradation of straws in soil is usually involved in microbial activity, which requires certain temperature, moisture and other environmental conditions. However, in Northeast China, the practice of straw return to soil has become a challenge due to the cold and dry winter, which limits microbial activity in soil and straw degradation processes. It is therefore critical to develop effective practices to overcome the constraints on straw decomposition caused by the cold and dry climate in Northeast China to promote straw incorporation strategies.
Plastic film cover on soil surface was confirmed as an effective practice in Northeast China that reduced soil water evaporation and increased soil water content and temperature during earlier spring, consequently yielding significantly higher corn grain and water use efficiency. Jin et al. (2018) used an in situ 13C-tracing technique and confirmed that plastic film cover enhanced the decomposition of corn straw in soil. The ridge-furrow with polyethylene film cover and straw incorporation in loess soils showed improved soil organic carbon stocks, water storage, grain yields, and higher water use efficiency in compared to the ridge-furrow with film cover only. The ridge–furrow plastic film cover combined with straw ditch burying was reported to improve soil hydrothermal conditions, accelerated straw decomposition, and enhanced crop growth and yields in the loess, relatively dry region of northwestern China (Li et al., 2020).
Despite various benefits of plastic film cover with straw incorporation during growing season, the effects of fall film cover with straw incorporation on straw decomposition, soil properties, corn yield and water use efficiency were little elucidated and still largely unknown. We hypothesized that fall straw incorporation combined with film cover would improve soil water availability and temperature, consequently promoting straw degradation, improving soil health, and increasing corn water use efficiency and grain yield under the semi-arid climate of Northeast China. The objectives of this field study were to investigate the impacts of fall straw incorporation with film cover on soil properties and straw degradation and quantify corn growth, yield and water use efficiency in Northeast China.