Decadal Nitrogen Fertilization Decreases Mineral‐Associated and Subsoil Carbon: A 32‐Year Study
Decadal Nitrogen Fertilization Decreases Mineral‐Associated and Subsoil Carbon: A 32‐Year Study
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DOI：
10.1002/ldr.2667
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发表时间：
2017-05
影响因子：
4.7
通讯作者：
M. Shahbaz;Y. Kuzyakov;Shafique Maqsood;Matthias Wendland;F. Heitkamp
中科院分区：
文献类型：
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作者：
M. Shahbaz;Y. Kuzyakov;Shafique Maqsood;Matthias Wendland;F. Heitkamp
作物残茬和肥料是土壤有机质形成的重要碳源。由于植物生产力的提高，施氮增加了作物残茬回报，但这往往只导致土壤有机质的少量增加。在我们的研究中，我们在德国普赫进行了长达32年的田间试验，展示了氮肥和有机碳添加如何影响SOM及其组分。5种有机添加，即不添加（对照）、粪肥、浆料、秸秆和秸秆+浆料，配以3种氮肥施用量（不施、中施和高施），可获得1·17-4·86 Mg C -投入ha‐1 y‐1。施氮增加了表层土壤（0 ~ 25 cm） SOM含量，这主要是由于自由光照部分（f‐LF）中的C含量增加所致。施用氮肥后，25 ~ 60 cm土层土壤有机质减少，这可能是由于根系在表层施氮后向Ap层迁移所致。尽管投入很高，秸秆对f - LF的贡献很小，但在不添加秸秆的情况下，施氮可以阻止矿物相关SOM部分（ρ >.1·6 g cm - 3）的C损失。地上（秸秆）和地下（根）残留物对SOM组分的影响相反。根C在轻组分中保留时间较长，是施氮后土壤有机质增加的原因。秸秆分解迅速（从f - LF），并为矿物相关的SOM馏分提供燃料。综上所述，土壤有机质的含量和组成不仅取决于有机质残留量（可通过添加和施氮来控制），还与有机质质量有关。为了维持土壤有机质水平、碳固存和土壤肥力，应考虑这样做。版权所有©2016 John Wiley & Sons， Ltd。
Crop residues and manure are important sources of carbon (C) for soil organic matter (SOM) formation. Crop residue return increases by nitrogen (N) fertilization because of higher plant productivity, but this often results only in minor increases of SOM. In our study, we show how N fertilization and organic C additions affected SOM and its fractions within a 32‐year‐long field‐experiment at Puch, Germany. Five organic additions, no‐addition (control), manure, slurry, straw and straw + slurry, were combined with three mineral N fertilization rates (no, medium and high fertilization), which resulted in 1·17–4·86 Mg C‐input ha‐1 y‐1. Topsoil (0–25 cm) SOM content increased with N fertilization, mainly because of the C in free light fraction (f‐LF). In contrast, subsoil (25–60 cm) SOM decreased with N fertilization, probably because of roots' relocation in Ap horizon with N fertilization at the surface. Despite high inputs, straw contributed little to f‐LF but prevented C losses from the mineral‐associated SOM fraction (ρ > 1·6 g cm‐3) with N fertilization, which was observed without straw addition. Above (straw) and belowground (roots) residues had opposite effects on SOM fractions. Root C retained longer in the light‐fractions and was responsible for SOM increase with N fertilization. Straw decomposed rapidly (from f‐LF) and fueled the mineral‐associated SOM fraction. We conclude that SOM content and composition depended not only on residue quantity, which can be managed by the additions and N fertilization, but also on the quality of organics. This should be considered for maintaining the SOM level, C sequestration, and soil fertility. Copyright © 2016 John Wiley & Sons, Ltd.