1 research outputs found
Molecular and Dual-Isotopic Profiling of the Microbial Controls on Nitrogen Leaching in Agricultural Soils under Managed Aquifer Recharge
Nitrate (NO3β) leaching is a serious
health and ecological concern in global agroecosystems, particularly
those under the application of agricultural-managed aquifer recharge
(Ag-MAR); however, there is an absence of information on microbial
controls affecting NO3β leaching outcomes.
We combine natural dual isotopes of NO3β (15N/14N and 18O/16O)
with metagenomics, quantitative polymerase chain reaction (PCR), and
a threshold indicator taxa analysis (TITAN) to investigate the activities,
taxon profiles, and environmental controls of soil microbiome associated
with NO3β leaching at different depths
from Californian vineyards under Ag-MAR application. The isotopic
signatures demonstrated a significant priming effect (P < 0.01) of Ag-MAR on denitrification activities in the topsoil
(0β10 cm), with a 12β25-fold increase of 15NβNO3β and 18OβNO3β after the first 24 h of flooding, followed
by a sharp decrease in the enrichment of both isotopes with βΌ80%
decline in denitrification activities thereafter. In contrast, deeper
soils (60β100 cm) showed minimal or no denitrification activities
over the course of Ag-MAR application, thus resulting in 10β20-fold
of residual NO3β being leached. Metagenomic
profiling and laboratory microcosm demonstrated that both nitrifying
and denitrifying groups, responsible for controlling NO3β leaching, decreased in abundance and potential
activity rates with soil depth. TITAN suggested that Nitrosocosmicus and Bradyrhizobium, as the major nitrifier and
denitrifier, had the highest and lowest tipping points with regard
to the NO3β changes (P < 0.05), respectively. Overall, our study provides new insight
into specific depth limitations of microbial controls on soil NO3β leaching in agroecosystems