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

Sci Rep. 2015 Oct 26;5:15727. doi: 10.1038/srep15727.

Abstract

Globally only ≈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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / metabolism
  • Ammonium Compounds / chemistry
  • Ammonium Compounds / metabolism
  • Crops, Agricultural
  • Kinetics
  • Nitrogen / analysis
  • Nitrogen / metabolism*
  • Nitrogen Isotopes / analysis
  • Plant Roots / metabolism
  • Saccharum / growth & development
  • Saccharum / metabolism*
  • Soil / chemistry*

Substances

  • Amino Acids
  • Ammonium Compounds
  • Nitrogen Isotopes
  • Soil
  • Nitrogen