Arango, Jacobo

Cadisch, Georg

Moreta, Danilo

Nuñes, Jonathan

Rao, Idupulapati M.

Sparke, Marc-Andre

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Tropentag, September 18-21, 2016, Vienna, Austria“Solidarity in a competing world —fair use of resources”Nitrate Reductase Activity as Potential Indicator for BiologicalNitrification Inhibition in Brachiaria humidicolaMarc-André Sparke1, Hannes Karwat1, Jacobo Arango2, Jonathan Núñez2, DaniloMoreta2, Idupulapati Rao2, Georg Cadisch11University of Hohenheim, Inst. of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), Ger-many2International Center for Tropical Agriculture (CIAT), ColombiaAbstract“Biological Nitrification Inhibition” (BNI) is a naturally occurring process by which soilnitrogen (N) is conserved in the less mobile form of ammonium (NH+4 ) resulting in a re-duction of nitrate (NO3) leaching losses and N2O emissions. The pasture grass Brachiariahumidicola (Bh) is currently the most prominent species showing potential to naturallyinhibit nitrification. This research aimed to identify in situ plant physiological indicatorsfor BNI activity and to evaluate Bh accessions for their BNI potential with a rapid andreliable methodological approach under field conditions, proposing a direct linkage betweennitrification deriving NO3 in soil and nitrate reductase activity (NRA) in plants. In vivoNRA in leaf was determined after N fertilisation and synchronised with soil sampling totest the relationship between soil nitrification rates and NRA. Soil N-NO3 was determinedin situ to facilitate correlation analysis. The genotypes tested included two B. humidicolaCIAT germplasm accessions (CIAT 16888 and CIAT 26146) as controls and four B. hu-midicola hybrids that were preselected based on greenhouse evaluation of BNI activity insoil. Beforehand enzyme substrate (NO3) inducibility was clearly verified and plant leavesturned out to be the main tissue of NO3 reduction (roots vs. leaves). The high BNI Bhaccession (CIAT 16888) showed the lowest NRA, whereas the low BNI accession (CIAT26146) showed highest NRA among all the tested materials. Previously, Bh-08–679 andBh-08–675 were identified as high BNI and low BNI hybrids, respectively. The NRA assayconfirmed these previous observations. Two Bh hybrids (Bh-08–700 and Bh-08–1149) sho-wed an intermediate level of BNI potential. Methodological comparison (soil nitrificationrates vs. in vivo NRA) resulted in discrepancies concerning ranking of BNI capacity. NRAin plant tissue correlated well with soil N-NO3 concentration (R2=0.81, p < 0.05). Thissignificant positive correlation between NRA vs. N-NO3 concentration in the soil indicatesthat plant tissue NRA can be a potential indicator of BNI in soil. Further research is nee-ded to estimate to what extent the high BNI Bh hybrids can contribute to N conservationin soil to benefit resource-poor smallholders in the tropics where synthetic nitrificationinhibitors are expensive and less effective.Keywords: Forages, nitrogen cycle, tropical grasslandsContact Address: Marc-André Sparke, University of Hohenheim, Inst. of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), 70593 Stuttgart, Germany, e-mail: marc.sparke@sparke-wohnbau.de

Nitrate Reductase Activity as Potential Indicator for Biological Nitrification Inhibition in Brachiaria humidicola

https://cgspace.cgiar.org/bitstream/10568/78727/3/Sparke_KixshJbi.pdf

Nitrate Reductase Activity as Potential Indicator for Biological Nitrification Inhibition in Brachiaria humidicola

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