Arango, Jacobo

Cadisch, Georg

Egenolf, Konrad

Karwat, Hannes

Moreta, Danilo

Rao, Idupulapati M.

Rasche, Frank

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Tropentag, September 17-19, 2014, Prague, Czech Republic“Bridging the gap between increasing knowledge anddecreasing resources”Impact of “Biological Nitrification Inhibition” on N RecoveryEfficiency, N Leaching and N2O Emissions Using the Example ofBrachiaria humidicolaKonrad Egenolf1, Hannes Karwat1, Frank Rasche1, Georg Cadisch1, Danilo Moreta2,Jacobo Arango2, Idupulapati Rao21University of Hohenheim, Institute of Plant Production and Agroecology in the Tropics and Subtropics,Germany2International Center For Tropical Agriculture (CIAT), ColombiaAbstractBiological Nitrification Inhibition (BNI) has been reported for several plant species.Amongst these the tropical forage grass Brachiaria humidicola has gained major attentiondue to its high BNI-activity. An increased N-recovery efficiency (reduced N-leaching) andreduced N2O-emissions are proposed for B. humidicola based pastures. Breeding programstargeting on BNI-activity currently lack indicators suitable for large scale field evaluation.A promising approach could be the link between the plant 15N-signature and its N-nutrition(ammonium versus nitrate). As both pools usually possess different isotopic signatures, thenutritional contribution of each N-pool should be reflected in the plant, thus indicating themagnitude of nitrification inhibition (BNI-activity). Objectives of the present study are theevaluation of selected B. humidicola-hybrids regarding their BNI-activity; the assessmentof BNI’s impact on N recovery efficiency, N-leaching and N2O-emissions; and a correlationanalysis on the relation between the plant’s BNI-activity and its 15N-signature.The study was designed as a two phased greenhouse trial. In a first phase the plant 15N-signatures were analysed and assessed in relation to the 15N background signal of soil andfertiliser. In a second phase the fertilisation regime was switched to 15N-labeled ammoniumsulfate. This enabled tracing of N-fluxes, estimation of the hybrid’s BNI-activity (via thenitrification rates) and determination of overall N recovery efficiency. N-leaching and N2O-emissions were assessed in relation to the estimated BNI-activity.Plants were cultivated in PVC-tubes (Ø12cm * 100cm) on a ferralitic substrate. Nitrifica-tion rates and nitrate dislocation were derived on the basis of soil nitrate levels determinedby regular sampling of soil solution through suction tubes installed at different depths wi-thin the soil column. Anion exchange resin bags were installed at the bottom of the columnto quantify cumulative N-leaching. N2O-emissions were quantified after irrigation inducingreducing conditions.Keywords: Brachiaria, denitrification, N use efficiency, N2O emissions, nitrification, nitrificationinhibitionContact Address: Konrad Egenolf, University of Hohenheim, Institute of Plant Production and Agroecology in theTropics and Subtropics, Neuhauser Straße 23, 70599 Plieningen, Germany, e-mail: konrad.egenolf@uni-hohenheim.de

Impact of "Biological Nitrification Inhibition"on N recovery efficiency, N leaching and N2O emissions using the example of brachiaria humidicola

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Impact of "Biological Nitrification Inhibition"on N recovery efficiency, N leaching and N2O emissions using the example of brachiaria humidicola

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