Differential responses of soil microbial N-cycling functional genes to 35-yr applications of chemical fertilizer and organic manure in wheat field soil on loess plateau.

Authors: LIANG, YINYANG - Northwest University; YANG, CAIDI - Northwest University; Sainju, Upendra; ZHANG, NANNAN - Northwest University; ZHAO, FAZHU - Northwest University; WANG, JUM - Northwest University

Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2023
Publication Date: 5/31/2023
Citation: Liang, Y., Yang, C., Sainju, U.M., Zhang, N., Zhao, F., Wang, J. 2023. Differential responses of soil microbial N-cycling functional genes to 35-yr applications of chemical fertilizer and organic manure in wheat field soil on loess plateau.. Science of the Total Environment. 13(6). Article 1516. https://doi.org/10.3390/agronomy13061516.
DOI: https://doi.org/10.3390/agronomy13061516

Interpretive Summary: Nitrogen cycling is associated with microbial functional genes, but little information is available about specific genes linked to nitrogen transformation processes due to fertilization in agroecosystems. Researchers in ARS, Sidney, MT in collaboration with Northwest University, Xian, China studied genes linked to nitrogen cycling in a 35-year old experiment receiving with or without manure and inorganic nitrogen fertilizer using metagenome sequencing. They found that the application of organic manure with or without inorganic nitrogen fertilizer increased the genes associated with nitrogen storage and mineralization, but inorganic nitrogen fertilization increase the gene associated with nitrogen availability. The study showed that genes linked to nitrogen cycling due to manure application can be manipulated for enhancing the long-term sustainability of the farming system which may help to reduce N fertilization rates and environmental degradation.

Technical Abstract: Fertilization changes nitrogen (N) cycling processes and associated microbial community in agricultural ecosystems. However, the long-term responses of N cycling potential and microbial functional genes to different fertilization sources remain unclear. Soil samples were collected to a depth of 15 cm under winter wheat applied annually with N fertilizer (NF), organic manure (OM), N fertilizer plus organic manure (NM) and a control without fertilization (CK) for 35-yr and analyzed for microbial functional genes involved in soil N cycling using metagenome sequencing in the Loess Plateau of China. Soil N fractions were greater with OM and NM than NF and CK. Compared to CK, OM and NM increased the abundances of genes associated with nitrification, denitrification, and dissimilatory nitrate reduction, assimilatory nitrate reduction, but decreased the abundance of gene related to organic N metabolism. The NF increased the abundances of genes associated with nitrification. Both OM and NM also enhanced the relative abundance of Proteobacteria that favors the growth of N cycling genes, but reduced Firmicutes and Cyanobacteria that inhibit the growth of genes. Soil organic C, total N, and potential C mineralization were the dominant factors affecting the abundances of N cycling genes. Long-term application of OM and NM can enhance N cycling by promoting genes due to increased microbial activity and soil organic matter compared to NF and CK.