Nitrogen fluxes at the root-soil interface show a mismatch of nitrogen fertilizer supply and sugarcane root uptake capacity

Globally only approximate to 50% of applied nitrogen (N) fertilizer is captured by crops, and the remainder can cause pollution via runoff and gaseous emissions. Synchronizing soil N supply and crop demand will address this problem, however current soil analysis methods provide little insight into delivery and acquisition of N forms by roots. We used microdialysis, a novel technique for in situ quantification of soil nutrient fluxes, to measure N fluxes in sugarcane cropping soils receiving different fertilizer regimes, and compare these with N uptake capacities of sugarcane roots. We show that in fertilized sugarcane soils, fluxes of inorganic N exceed the uptake capacities of sugarcane roots by several orders of magnitude. Contrary, fluxes of organic N closely matched roots' uptake capacity. These results indicate root uptake capacity constrains plant acquisition of inorganic N. This mismatch between soil N supply and root N uptake capacity is a likely key driver for low N efficiency in the studied crop system. Our results also suggest that (i) the relative contribution of inorganic N for plant nutrition may be overestimated when relying on soil extracts as indicators for root-available N, and (ii) organic N may contribute more to crop N supply than is currently assumed.

Näsholm, TorgnySwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Umeå universitet,Umeå Plant Science Centre (UPSC),Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83 Umeå, Sweden,Institutionen för skogens ekologi och skötsel,Institutionen för skoglig genetik och växtfysiologi,Department of Forest Genetics and Plant Physiology(Swepub:slu)48242 (författare)
Robinson, NicoleSchool of Agriculture and Food Sciences, The University of Queensland, QLD, 4072, Australia (författare)
Guillou, StephaneSchool of Agriculture and Food Sciences, The University of Queensland, QLD, 4072, Australia (författare)
Vinall, KerrySchool of Agriculture and Food Sciences, The University of Queensland, QLD, 4072, Australia (författare)
Lakshmanan, PrakashSugar Research Australia, 50 Meiers Road, Indooroopilly, QLD 4068, Australia (författare)
Schmidt, SusanneSchool of Agriculture and Food Sciences, The University of Queensland, QLD, 4072, Australia (författare)
Inselsbacher, ErichSwedish University of Agricultural Sciences,Sveriges lantbruksuniversitet,Institutionen för skogens ekologi och skötsel,Department of Forest Ecology and Management,University of Vienna(Swepub:slu)47110 (författare)
Queensland, QLD, 4072, AustraliaUmeå Plant Science Centre (UPSC) (creator_code:org_t)
Sveriges lantbruksuniversitet

Av författaren/redakt...: Brackin, Richard; Näsholm, Torgny; Robinson, Nicole; Guillou, Stephan ...; Vinall, Kerry; Lakshmanan, Prak ...; visa fler...; Schmidt, Susanne; Inselsbacher, Er ...; visa färre...

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