Date Published: April 30, 2018
Author(s): Rui Jiang, Xiao Li, Wei Zhu, Kun Wang, Sheng Guo, Tom Misselbrook, Ryusuke Hatano.
•We evaluated the effect of a ridge mulched system (RM) on soil water and inorganic N.•RM increased soil water storage and decreased evapotranspiration during the pre-silking stage.•RM increased soil inorganic N in the topsoil under the ridge and reduced N leaching.•RM led to high inorganic N accumulation in soil after three years maize cultivation.
Plastic film mulching has developed rapidly following it’s introduction to China in 1978 and is now widely applied in crop production in arid and semiarid regions (Dong et al., 2009; Li et al., 2004). Several mulching systems have been used in recent years, including 1) fully mulched ridge and furrow system: two ridges and furrow fully mulched with plastic film (Zhou et al., 2009); 2) ridge mulched system: alternating ridge and furrow with plastic film mulched-ridge (Liu et al., 1989); 3) flat half mulched system: alternating mulched row and bare row in flat cultivation (Liu et al., 1989); and 4) flat fully mulched system: flat plot all mulched with plastic film (Liu et al., 1989). Of these, the ridge mulched system has been most widely adopted, leading significant increases in crop yield rain-fed agricultural areas of Chinese Loess Plateau, especially in areas with 400–600 mm annual precipitation (Jiang et al., 2016; Wang et al., 2015; Wang et al., 2016). The yield increases under plastic film mulching have been attributed to factors including: 1) reduction in soil evaporation and increase in crop transpiration; 2) increase in water harvesting; 3) increase in soil temperature; and 4) increase in activation of soil nutrients (Zhou et al., 2009; Zhao et al., 2002; Zhou, 1996). These factors change the soil environment, improving conditions for crop growth, resulting in higher water use efficiency and nutrient availability.
Implementing an RM mulched system compared with traditional (flat) cultivation significantly changed the soil water and inorganic N distribution over the 3-year study period. Compared with F, RM improved the soil water storage significantly during the pre-silking stage by decreasing the soil evaporation and increasing the plant transpiration, which improved the water use efficiency and contributed to enhanced grain yield. Higher SWS at sowing played an important role in maize production in rain-fed agriculture on the Loess Plateau, thus treatments such as plastic film mulching or straw residue left after harvest may be helpful in harvesting and storing rainfall in fallow season for subsequent use by the following crop. The soil inorganic N in RM accumulated in the top soil layer (0–10 cm) under the mulched ridge, probably because of reduced N leaching, increased soil mineralization, and lateral N movement from the furrow to the ridge. This was associated with a decrease in nitrate leaching to deeper soil layers. However, the nitrate leaching from the furrow was observed in the RM system at the higher N application rate. Inorganic N accumulation under the RM system increased by two to three times after three years of maize cultivation, which may be explained by enhanced soil mineralization. However, the mechanism for soil inorganic N accumulation under plastic film mulching systems is not clear, with potential interactions between a number of factors and soil processes, and further study is required. Overall, our result showed that RM-N180 could obtain high grain yield with low risk of nitrate leaching after one year of cultivation, but after three years of cultivation was associated with increased inorganic N accumulation in the soil profile. Thus, the recommended N application rate for traditional maize cultivation in this region may not be suitable under RM. Development of new recommendations for N fertilizer application rates under RM are needed to ensure the sustainability of rain-fed agriculture on the Chinese Loess Plateau.