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The fate of N released from the fixed NH4+ pool in response to different straw application doses

Xia, Zhuqing ; Ma, Qiang ; Yu, Wantai ; Wang, Yanan ; Zhu, Mengmeng ; Zhang, Xinhui ; Gao, Yun ; An, Siyu ; Li, Shuailin

Geoderma, 2023-02, Vol.430, p.116312, Article 116312 [Periódico revisado por pares]

Elsevier B.V

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  • Título:
    The fate of N released from the fixed NH4+ pool in response to different straw application doses
  • Autor: Xia, Zhuqing ; Ma, Qiang ; Yu, Wantai ; Wang, Yanan ; Zhu, Mengmeng ; Zhang, Xinhui ; Gao, Yun ; An, Siyu ; Li, Shuailin
  • Assuntos: 15N tracing technique ; Fixed ammonium ; Microbial immobilization ; Nitrification ; Straw addition
  • É parte de: Geoderma, 2023-02, Vol.430, p.116312, Article 116312
  • Descrição: [Display omitted] •A fixed NH4+ pool was labelled under chloroform-fumigated conditions.•The straw addition rate showed a threshold for promoting and inhibiting fixed NH4+ release.•Most of the released NH4+ entered the organic N pool, stabilizing N in the soil.•Microbial immobilization was the major driving force for fixed NH4+ release during incubation.•Nitrification affected fixed NH4+ release primarily during the late stage. Ammonium (NH4+) can be fixed by clay minerals and subsequently released, and this process plays a vital role in promoting soil nitrogen retention and supply in agriculture. However, the process of fixed NH4+ release and its driving forces remain unclear, especially under inputs of exogenous organic matter. In this study, the fixed NH4+ pool of an Udoll (based on the USDA Soil Taxonomy System) in Northeast China was labelled using a 15N tracer under chloroform-fumigated conditions, and then the labelled soil was mixed with unlabelled (unfumigated) soil at four levels of straw incorporation: S0 (without straw), S4 (4 t ha−1), S8 (8 t ha−1), and S12 (12 t ha−1). By monitoring the tracer, we found that 20 %–24 % of the labelled fixed NH4+ was released at the end of the incubation period (288 d), and the release of fixed NH4+ was significantly affected by the straw addition rate. Generally, S4 promoted the accumulated release and fixation amounts, but S8 and S12 showed inhibitory effects compared with the S0 treatment. Moreover, microbial immobilization played a predominant role in the release of fixed NH4+ during stage 1 (0.5–72 d), while both nitrification and immobilization played important roles in promoting fixed NH4+ release during stage 2 (72–288 d). In addition, more than 47 % of the labelled fixed NH4+ released was incorporated into the nonmicrobial organic nitrogen pool after microbial turnover, reducing N loss and prolonging the N supply, and this proportion increased under increasing rates of straw application. This study clarifies the fate of fixed NH4+ derived N under different rates of straw addition, which is critical for our understanding of soil N cycling and to optimize straw application in agricultural soils.
  • Editor: Elsevier B.V
  • Idioma: Inglês
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  • Realização: ABCD-USP USP   Logos de Redes Sociais: Freepik

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