Nitrifying Microbes in the Rhizosphere of Perennial Grasses are Modified by Biological Nitrification Inhibition

• Main Authors: Yi Zhou, Christopher J. Lambrides, Jishun Li, Qili Xu, Ruey Toh, Shenzhong Tian, Peizhi Yang, Hetong Yang, Maarten Ryder, Matthew D. Denton
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Microorganisms
• Subjects: microbial community; metagenomics; root exudation; turfgrass; forage
• Online Access: https://www.mdpi.com/2076-2607/8/11/1687

Soil nitrification (microbial oxidation of ammonium to nitrate) can lead to nitrogen leaching and environmental pollution. A number of plant species are able to suppress soil nitrifiers by exuding inhibitors from roots, a process called biological nitrification inhibition (BNI). However, the BNI activity of perennial grasses in the nutrient-poor soils of Australia and the effects of BNI activity on nitrifying microbes in the rhizosphere microbiome have not been well studied. Here we evaluated the BNI capacity of bermudagrass (<i>Cynodon dactylon</i> L.), St. Augustinegrass (<i>Stenotaphrum secundatum</i> (Walt.) Kuntze), saltwater couch (<i>Sporobolus virginicus</i>), seashore paspalum (<i>Paspalum vaginatum</i> Swartz.), and kikuyu grass (<i>Pennisetum clandestinum</i>) compared with the known positive control, koronivia grass (<i>Brachiaria humidicola</i>). The microbial communities were analysed by sequencing 16S rRNA genes. St. Augustinegrass and bermudagrass showed high BNI activity, about 80 to 90% of koronivia grass. All the three grasses with stronger BNI capacities suppressed the populations of <i>Nitrospira</i> in the rhizosphere, a bacteria genus with a nitrite-oxidizing function, but not all of the potential ammonia-oxidizing archaea. The rhizosphere of saltwater couch and seashore paspalum exerted a weak recruitment effect on the soil microbiome. Our results demonstrate that BNI activity of perennial grasses played a vital role in modulating nitrification-associated microbial populations.