Abstract
Cover cropping (CC) is the most promising in-field practice to improve soil health and mitigate N losses from fertilizer use. Although the soil microbiota play essential roles in soil health, their response to CC has not been well characterized by bioindicators of high taxonomic resolution within typical agricultural systems. Our objective was to fill this knowledge gap with genus-level indicators for corn [Zea mays L.] monocultures with three N fertilizer rates (N0, N202, N269; kg N ha−1), after introducing a CC mixture of cereal rye [Secale cereale L.] and hairy vetch [Vicia villosa Roth.], using winter fallows (BF) as controls. A 3 × 2 split-plot arrangement of N rates and CC treatments was studied in a randomized complete block design with three replicates over two years. Bacterial and archaeal 16S rRNA and fungal ITS regions were sequenced with Illumina MiSeq system. Overall, our high-resolution bioindicators were able to represent specific functional or ecological shifts within the microbial community. The abundances of indicators representing acidophiles, nitrifiers, and denitrifiers increased with N fertilization, while those of heterotrophic nitrifiers, nitrite oxidizers, and complete denitrifiers increased with N0. Introducing CC decreased soil nitrate levels by up to 50% across N rates, and CC biomass increased by 73% with N fertilization. CC promoted indicators of diverse functions and niches, including N-fixers, nitrite reducers, and mycorrhizae, while only two N-cycling genera were associated with BF. Thus, CC can enhance the soil biodiversity of simplified cropping systems and reduce nitrate leaching, but might increase the risk of nitrous oxide emission without proper nutrient management. This primary information is the first of its kind in this system and provided valuable insights into the limits and potential of CC as a strategy to improve soil health.
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Claims 8
Claim · model-written summary
High-resolution bioindicators represented functional or ecological microbial shifts.
- Outcome
- specific functional or ecological shifts within the microbial communitye0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“our high-resolution bioindicators were able to represent specific functional or ecological shifts within the microbial community”
t0“corn [Zea mays L.]”
Claim · model-written summary
Indicators of acidophiles, nitrifiers, and denitrifiers increased with nitrogen fertilization.
- Treatment
- N fertilizatione0
- Outcome
- abundances of indicators representing acidophiles, nitrifiers, and denitrifierse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The abundances of indicators representing acidophiles, nitrifiers, and denitrifiers increased with N fertilization”
t0“corn [Zea mays L.]”
Claim · model-written summary
Indicators of heterotrophic nitrifiers, nitrite oxidizers, and complete denitrifiers increased at N0.
- Treatment
- N0e0
- Outcome
- heterotrophic nitrifiers, nitrite oxidizers, and complete denitrifierse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“those of heterotrophic nitrifiers, nitrite oxidizers, and complete denitrifiers increased with N0”
t0“corn [Zea mays L.]”
Claim · model-written summary
Cover cropping decreased soil nitrate by up to 50% across nitrogen rates.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Introducing CC decreased soil nitrate levels by up to 50% across N rates”
t0“corn [Zea mays L.]”
Claim · model-written summary
Nitrogen fertilization increased cover-crop biomass by 73%.
- Taxon
- cereal rye [Secale cereale L.]
Secale cerealet0 - Treatment
- N fertilizatione0
- Outcome
- CC biomasse0
- Direction
- increasede0
- Value
- 73%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CC biomass increased by 73% with N fertilization”
t0“cereal rye [Secale cereale L.]”
Claim · model-written summary
Cover cropping promoted indicators including N-fixers, nitrite reducers, and mycorrhizae.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CC promoted indicators of diverse functions and niches, including N-fixers, nitrite reducers, and mycorrhizae”
t0“corn [Zea mays L.]”
Claim · model-written summary
Only two nitrogen-cycling genera were associated with winter fallows.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“only two N-cycling genera were associated with BF”
t0“corn [Zea mays L.]”
Claim · model-written summary
Authors conclude cover cropping can enhance biodiversity and reduce nitrate leaching but may raise nitrous oxide risk.
- Outcome
- CC can enhance the soil biodiversity of simplified cropping systems and reduce nitrate leachinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CC can enhance the soil biodiversity of simplified cropping systems and reduce nitrate leaching, but might increase the risk of nitrous oxide emission without proper nutrient management”
t0“corn [Zea mays L.]”
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