Cover crops on temporal and spatial variations in soil microbial communities by phospholipid fatty acid profiling

Authors: RANKOTH, LALITH - University Of Missouri; UDAWATTA, RANJITH - University Of Missouri; GANTZER, C - University Of Missouri; JOSE, SHIBU - University Of Missouri; Veum, Kristen; DEWANTO, H - University Of Missouri

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/4/2019
Publication Date: 5/23/2019
Citation: Rankoth, L.M., Udawatta, R.P., Gantzer, C.J., Jose, S., Veum, K.S., Dewanto, H.A. 2019. Cover crops on temporal and spatial variations in soil microbial communities by phospholipid fatty acid profiling. Agronomy Journal. 111(4):1693-1703. https://doi.org/10.2134/agronj2018.12.0789.
DOI: https://doi.org/10.2134/agronj2018.12.0789

Interpretive Summary: Cover crops are thought to play a major role in soil quality improvement, yet the effects of cover crops on the soil microbial community are not well understood. The objective of this study was to quantify the cover crop effects on total soil microbial biomass as well as specific groups of soil microorganisms under a corn-soybean rotation. The study was conducted at the Chariton County Cover Crop Soil Health Research and Demonstration Farm in Missouri, USA, where cover crops were first established in 2012. Soils were sampled in 2016, 2017, and 2018 and phospholipid fatty acid (PLFA) profiles were determined. From the PLFA profiles, microbial biomass and specific microbial groups (total fungi, total bacteria, rhizobia, gram (-), and actinomycetes), were found to be significantly greater under cover crops compared to no cover crops in two of the three years. Also, ratios of microbial groups suggested that the microbial community responded to differences in the soil environment due to cover crop management. Overall, this study demonstrated that cover crops can affect the soil microbial community, which has potential environmental, production, and soil quality implications. This study provides information to help producers and landowners understand the effects of conservation management practices on soil, and emphasizes the need for further study of the soil microbial community.

Technical Abstract: Although cover crops (CC) are believed to play a major role in soil quality improvement, the effects of CC on microbial populations and community structure is not well understood. The objective of this study was to quantify CC effects on soil microbial biomass and community structure under a corn (Zea mays L.)-soybean (Glycine max (L.) Merr.) rotation. The study was conducted at the Chariton County Cover Crop Soil Health Research and Demonstration Farm (CCSH) in Missouri, USA, where CC were first established in 2012. Soils were sampled in 2016, 2017, and 2018 from the 0-10 cm depth layer using a grid sampling design and phospholipid fatty acid (PLFA) profiles were determined. Microbial biomass and microbial community structure (total fungi, total bacteria, rhizobia, gram (-), and actinomycetes biomass), as estimated from the PLFA biomarkers, were significantly greater (p < 0.05) in the CC treatment compared to no cover crop (NCC) in 2016 and 2018 (2.4 and 1.7 times larger, respectively). In summer 2016, the gram (+):gram (-) ratio and the saturated:unsaturated fatty acid ratio were significantly higher in NCC compared to CC, suggesting that the microbial community was responding to differences in the environmental conditions due to management. Within the CC treatment, differences by soil type were also observed, finding that the silt loam soil supported greater total microbial biomass than the loam soil in 2018. Overall, this study demonstrated that the CC treatment affected the soil microbial community biomass and structure, which has potential environmental, production, and soil quality benefits.