Cover Crops on Temporal and Spatial Variations in Soil Microbial Communities by Phospholipid Fatty Acid Profiling

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-to 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-fold larger, respectively). 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. Spatial distribution patterns of total microbial biomass, bacteria biomass and fungi biomass differed with time. 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.