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Functional N-cycle genes in soil and N2O emissions in tropical grass-maize intercropping systems

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Grassmann, Camila S. ; Mariano, Eduardo ; Diniz, Priscila P. ; Borges, Beatriz M. F. ; Borges, Clovis D. ; Tsai, Siu M. ; Rosolem, Ciro A.
Total Authors: 7
Document type: Journal article
Source: SOIL BIOLOGY & BIOCHEMISTRY; v. 169, p. 12-pg., 2022-06-01.

There is evidence that forage grasses such as Megathyrsus and Urochloa can suppress nitrification, with direct or indirect consequences on soil inorganic N dynamics and nitrous oxide (N2O) emissions. However, the influence of soil chemical properties on the dynamics of functional N-genes and losses of N in maize (Zea mays L.) inter cropped with forage grasses under N fertilization is poorly understood. In this study, soil samples and N2O emissions were analyzed from a field experiment in which maize (fertilized or not with ammonium-based fertilizer) was intercropped with Guinea grass (M. maximus cv. Tanzania), palisade grass (U. brizantha cv. Marandu), and ruzigrass (U. ruziziensis cv. Comum). Soil N-cycle microorganisms [16S rRNA of bacteria and archaea, nifH (gene encoding N2-fixing bacteria), ammonia-oxidizing bacteria (AOB) and archaea (AOA), nirS (encoding nitrite reductase), and nosZ (encoding nitrous oxide reductase)] were influenced by forage grass, N fertilization, and sampling time, but no evidence of biological nitrification inhibition was found. Palisade grass was associated with a higher abundance of nifH (7.0 x 105 gene copies g-1 soil, on average) in the absence of N compared with the other grasses (4.3 x 105 gene copies g-1 soil, on average). Nitrogen fertilization increased the abundance of AOB but not AOA. Furthermore, N2O flux was influenced by AOB, water-filled pore space, and N fertilization, whereas the cumulative N2O emission and fertilizer-induced emission factor (0.36%, on average) were not affected by the grasses. In conclusion, this study reveals the strong dominance of AOB under ammonium supply, potentially stimulating N2O emissions in maize-forage grass intercropping systems. (AU)

FAPESP's process: 15/50305-8 - A virtual joint centre to deliver enhanced nitrogen use efficiency via an integrated soil-plant systems approach for the UK & Brazil
Grantee:Ciro Antonio Rosolem
Support Opportunities: Research Projects - Thematic Grants
FAPESP's process: 16/25253-7 - Nitrogen dynamics in a cropping system with forages as cover crops and corn
Grantee:Camila da Silva Grassmann
Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
FAPESP's process: 17/02517-1 - Nitrogen dynamics in a production system using Brachiaria as a cover plant
Grantee:Eduardo Mariano
Support Opportunities: Scholarships in Brazil - Post-Doctoral