Mulching decreased the abundance of microbial functional genes in phosphorus cycling under maize

Authors: ZHANG, NANNAN - Northwest University; Sainju, Upendra; ZHAO, FAZHU - Northwest University; GHIMIRE, RAJAN - New Mexico State University; REN, CHENGJIE - Northwest University; LAIANG, YINYAN - Northwest University; YANG, CAIDI - Northwest University; WANG, JUN - Northwest A&f University

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/1/2023
Publication Date: 2/7/2023
Citation: Zhang, N., Sainju, U.M., Zhao, F., Ghimire, R., Ren, C., Laiang, Y., Yang, C., Wang, J. 2023. Mulching decreased the abundance of microbial functional genes in phosphorus cycling under maize. Applied Soil Ecology. 187. Article 104833. https://doi.org/10.1016/j.apsoil.2023.104833.
DOI: https://doi.org/10.1016/j.apsoil.2023.104833

Interpretive Summary: Mulching is practiced to conserve soil water and sustain crop yields in dryland cropping systems, but mulching also may affect microbial functional genes related to phosphorus cycling that affect crop yields. Scientists at ARS, Sidney, MT, Northwest University, Xian, China, and New Mexico State University used metagonomic sequencing to identify functional genes responsible for phosphorus cycling and determine how ten years of mulching practices affect these genes. They identified 39 functional genes related to phosphorus cycling and reported that film and straw mulching reduced genes involved in phosphorus mineralization and availability and film mulching reduced genes involved in phosphorus uptake and transport compared to no mulching. Mulching affected the abundance of functional genes for phosphorus cycling by altering the carbon/phosphorus ratio and available phosphorus. Although mulching may enhance crop yield, this research shows that available soil phosphorus levels should be monitored when utilizing long-term film mulching. This will allow farmers to take preventative measures so that yield-limiting phosphorus deficiency resulting from reduced microbial gene function may be avoided.

Technical Abstract: Microorganisms play an important role in soil phosphorus (P) cycling and P availability in agroecosystems. However, how soil microbial functional genes regulate the response of soil P cycling to management practices is largely unknown. In this study, we used metagenomic sequencing to analyze functional genes related to P-cycling under maize with straw mulching (SM) and film mulching (FM) compared to no mulching (CK) for ten years. Thirty-nine microbial functional genes involved in P cycling were identified, including mineralization, availability, uptake, transport, and -immobilization. Compared to CK, SM and FM decreased the abundance of functional genes related to P-mineralization and availability by 8.8% and 13.9% (P < 0.05), respectively, and FM reduced the abundance of functional genes responsible for P-uptake and transport by 13.2% (P < 0.05). Soil available phosphorus (AP) was positively correlated to the abundance of all genes involved in microbial P cycling. Random forest analysis suggested that 13 of the 39 functional genes related to P cycling could be considered determinants of AP. In particular, gcd gene was the key gene responsible for P-mineralization and solubilization, and pstS gene for P-uptake and transport. The 13 key functional genes were associated with Proteobacteria, Actinobacteria, Acidobacteria, Planctomycetes, and Cyanobacteria and were lower in SM and FM than CK. The Mantel test analysis showed that soil C:P ratio was the most crucial factor affecting the abundance of microbial functional genes responsible for P cycling. The results showed that functional genes can be manipulated by using management techniques to enhance P mineralization and availability to maize.