Effects of long-term Grain-soybean rotation on characteristics of soil dissolved organic matter in Northeast China

Aims Crop rotation has been proved that it can influence the content of soil dissolved matter, while variations in its quality have been largely overlooked. Thus, further study is needed to system assessment the impacts of rotation on soil DOM. Methods A 10-year field experiment conducted in Northeast China included five treatments: continuous soybean cropping (SC), wheat-soybean rotation (WS), soybean-wheat rotation (SW), maize-soybean rotation (MS), soybean-maize rotation (SM). The source, composition and characteristics of DOM were analyzed by three-dimensional fluorescence spectrum and parallel factor analysis. The soil microbial community were analyzed by high-throughput sequencing technology. Results The results indicated that soil DOM mainly consists of tyrosine-like substances and primarily originates from microbial endogenous inputs in soybean planting systems. The bioactivity and humification level of soil DOM were greater in grain-soybean rotation systems, while the molecular weight and the degree of aromaticity were reduced in comparison to the soybean monoculture system. The content of soil SOC, TN, TP and microbial community driving the variations of soil DOM characteristics. Furthermore, cluster analysis suggested that the difference in current season crop may indirectly drive the differentiation of rotation systems. Conclusions The present study showed that the grain-soybean rotation did not significantly alter the content of soil DOM, it influenced the characteristics of DOM by changing the content of soil SOC, TN, TP and microbial community.