Brachiaria species influence nitrate transport in soil by modifying soil structure with their root system

M V Galdos, E Brown, C A Rosolem, L F Pires, P D Hallett, S J Mooney* (Corresponding Author)

*Corresponding author for this work

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Leaching of nitrate from fertilisers diminishes nitrogen use efficiency (the portion of nitrogen used by a plant) and is a major source of agricultural pollution. To improve nitrogen capture, grasses such as brachiaria are increasingly used, especially in South America and Africa, as a cover crop, either via intercropping or in rotation. However, the complex interactions between soil structure, nitrogen and the root systems of maize and different species of forage grasses remain poorly understood. This study explored how soil structure modification by the roots of maize (Zea maize), palisade grass (Brachiaria brizantha cv. Marandu) and ruzigrass (Brachiaria ruziziensis) affected nitrate leaching and retention, measured via chemical breakthrough curves. All plants were found to increase the rate of nitrate transport suggesting root systems increase the tendency for preferential flow. The greater density of fine roots produced by palisade grass, subtly decreased nitrate leaching potential through increased complexity of the soil pore network assessed with X-ray Computed Tomography. A dominance of larger roots in ruzigrass and maize increased nitrate loss through enhanced solute flow bypassing the soil matrix. These results suggest palisade grass could be a more efficient nitrate catch crop than ruzigrass (the most extensively used currently in countries such as Brazil) due to retardation in solute flow associated with the fine root system and the complex pore network.

Original languageEnglish
Article number5072
Number of pages11
JournalScientific Reports
Publication statusPublished - 19 Mar 2020

Bibliographical note

Many thanks to Dr Brian Atkinson at the Hounsfield facility for assistance with the CT scanning and analysis. We also thank Wolf Seeds for kindly providing Brachiaria brizantha cv. Marandu and Brachiaria ruziziensis seeds for the experiment. This work was undertaken as part of NUCLEUS: a virtual joint centre to deliver enhanced NUE via an integrated soil-plant systems approach for the United Kingdom and Brazil. This work was supported by FAPESP—São Paulo Research Foundation [Grant 2015/50305-8]; FAPEG—Goiás Research Foundation [Grant 2015-10267001479]; FAPEMA—Maranhão Research Foundation [Grant RCUK-02771/16]; and the Biotechnology and Biological Sciences Research Council [grant number BB/N013201/1]. LFP would like to acknowledge the financial support provided by the Brazilian National Council for Scientific and Technological Development (CNPq) and the Coordination for the Improvement of Higher Education Personnel (Capes) through the Grants 303726/2015-6 (Productivity in Research) and 88881.119578/2016-01 (Visiting Scholar).


  • environmental sciences
  • plant sciences


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