Organic amendments tighten nitrogen cycling in agricultural soils: a meta-analysis on gross nitrogen flux
IntroductionUnderstanding how nutrient inputs affect nitrogen (N) transformations and storage is vital for developing sustainable agroecosystems. Organic N inputs, such as crop residues (e.g., cover crop biomass and stover) and animal manures, can accelerate N cycling by increasing mineralization an...
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| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Frontiers Media S.A.
2025-02-01
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| Series: | Frontiers in Agronomy |
| Subjects: | |
| Online Access: | https://www.frontiersin.org/articles/10.3389/fagro.2025.1472749/full |
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| Summary: | IntroductionUnderstanding how nutrient inputs affect nitrogen (N) transformations and storage is vital for developing sustainable agroecosystems. Organic N inputs, such as crop residues (e.g., cover crop biomass and stover) and animal manures, can accelerate N cycling by increasing mineralization and immobilization rates to provide crops with more opportunities to intercept N as it moves through bioavailable pools. We aimed to understand how organic and synthetic soil amendments inhibit or promote N mineralization, immobilization, and nitrification rates.MethodsWe conducted a meta-analysis of peer-reviewed studies to assess N transformation rates in agroecosystems. Specifically, we targeted studies employing 15N pool dilution methods to quantify N mineralization, immobilization, and nitrification rates in response to organic and synthetic soil amendments.Results and discussionOur findings indicate that adding synthetic, manure, and crop derived residues as soil amendments increased mineralization by 60%, 135%, and 214%, respectively, relative to the unamended controls. While manure and residue produced similar mineralization rates, residue amendments induced significantly higher immobilization rates than synthetic and manure amendments – a sevenfold and fourfold increase, respectively. Furthermore, only residue N amendments enhanced the ammonium (NH4+) pool size, while synthetic and manure amendments resulted in no change in NH4+ pool size. These results suggest that residue amendments encourage tighter coupling of the carbon (C) and N cycles compared to manure or synthetic amendments by delivering C rich substrates (e.g., C:N ratio >20:1) to soil microbes. This tighter coupling with residue amendments leads to faster mineralization-immobilization processes and larger NH4+ pools than those observed with manure or synthetic amendments. As such, residue amendments encourage soil N recycling between inorganic and organic forms, which is crucial to supporting crop N needs throughout the growing season while minimizing N losses. |
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| ISSN: | 2673-3218 |