Ground cover rice production systems are more adaptable in cold regions with high content of soil organic matter

• Water-saving rice production GCRPS increase grain yield and nitrogen use efficiency.
• Lower N fertilizer and high SOM alleviate conflict of rice growth at various stages.
• GCRPS is highly suitable for rice production in cold regions with high SOM content.

Water-saving ground cover rice production systems (GCRPS) can increase grain yield in mountainous regions with seasonal water shortages and cold, stress-inducing temperatures. For GCRPS the soil surface is covered with a plastic film which can effectively alleviate low-temperature stress in the early growth stage due to thermal insulation. Since topdressing is not possible in GCRPS, farmers usually apply all fertilizer as basal dressing before transplanting; this can lead to excessive growth during the vegetative period and low crop growth during the reproductive stage. However, we hypothesized that the technique might be well suited for marginal rice growing regions in the Northeast of China. These areas are characterized by a short vegetation period and soils rich in organic matter, delivering the required amounts of nitrogen (N) over the course of the season due to N mineralization. Here we report on a two year experiment, conducted in the Northeast of China, that compared grain yields between GCRPS and conventional paddy rice production (paddy) at three N fertilizer rates (0, 90 and 135 kg N ha−1). Furthermore, crop growth rate, apparent nitrogen recovery rate and nitrogen physiological use efficiency were calculated. Compared to paddy, GCRPS significantly increased grain yield by 31%, 14% and 10% at N fertilizer rate of 0, 90 and 135 kg N ha−1, respectively. Grain yield at 135 kg N ha−1 was significantly higher than 90 kg N ha−1 in paddy, but no difference was found between N fertilizer rates in GCRPS. However, grain yield at 90 kg N ha−1 in GCRPS was still higher than that at 135 kg N ha−1 in paddy. The considerably higher number of filled grains in GCRPS indicates that crop growth rate during the reproductive stage was improved, likely due to the positive effect of higher mineralization of organic N on crops with a low rate of N fertilization. Our study demonstrates that GCRPS is a very promising and highly suitable technique for rice production in cold regions in the North of China that possess high content of soil organic matter. Moreover, it shows that N fertilization can be minimized due to the autochthonous N supply from soil rich in organic matter. In regards to the decomposition of SOM in GCRPS over time, mutual feedback mechanisms located both above and below ground revealed that the potential loss of SOM stocks can be compensated by a greater input of root biomass in GCRPS.