Nitrate uptake and carbon exudation – do plant roots stimulate or inhibit denitrification?

• Published in: Plant and soil Vol. 459; no. 1/2; pp. 217 - 233
• Main Authors: Rummel, Pauline Sophie, Well, Reinhard, Pfeiffer, Birgit, Dittert, Klaus, Floßmann, Sebastian, Pausch, Johanna
• Format: Journal Article
• Language: English
• Published: Cham Springer Science + Business Media 01.02.2021; Springer International Publishing; Springer; Springer Nature B.V
• Subjects: Availability; Biomedical and Life Sciences; Botanical research; carbon; Carbon dioxide; Corn; Denitrification; Dry matter; Ecology; Efflux; Emissions; Exudation; Fluxes; Labeling; Life Sciences; Nitrates; Nitrous oxide; Physiological aspects; Plant growth; Plant Physiology; Plant roots; Plant Sciences; Regular Article; REGULAR ARTICLES; Rhizosphere; root growth; Roots; Roots (Botany); Shoots; Silphium perfoliatum; Soil moisture; Soil Science & Conservation; Soil water; Translocation; Water uptake; Zea mays; Germany; Dinitrogen; Nitrogen mineralization; C labeling; Rhizodeposition; Carbon cycling; Nitrous oxide; N
• ISSN: 0032-079X; 1573-5036
• DOI: 10.1007/s11104-020-04750-7

Background and aims Plant growth affects soil moisture, mineral N and organic C availability in soil, all of which influence denitrification. With increasing plant growth, root exudation may stimulate denitrification, while N uptake restricts nitrate availability. Methods We conducted a double labeling pot experiment with either maize ( Zea mays L.) or cup plant ( Silphium perfoliatum L.) of the same age but differing in size of their shoot and root systems. The 15 N gas flux method was applied to directly quantify N 2 O and N 2 fluxes in situ. To link denitrification with available C in the rhizosphere, 13 CO 2 pulse labeling was used to trace C translocation from shoots to roots and its release by roots into the soil. Results Plant water and N uptake were the main factors controlling daily N 2 O + N 2 fluxes, cumulative N emissions, and N 2 O production pathways. Accordingly, pool-derived N 2 O + N 2 emissions were 30–40 times higher in the treatment with highest soil NO 3 − content and highest soil moisture. CO 2 efflux from soil was positively correlated with root dry matter, but we could not detect any relationship between root-derived C and N 2 O + N 2 emissions. Conclusions Root-derived C may stimulate denitrification under small plants, while N and water uptake become the controlling factors with increasing plant and root growth.