The rhizosphere: a hotspot of N 2 O action Liz Baggs Li et al 2004 - PowerPoint PPT Presentation

The rhizosphere: a hotspot of N 2 O action Liz Baggs

Li et al 2004 Biol Fertil Soils

3 cores 1 core 15 N-KNO 3 - glucose Loick et al 2017. Geoderma

Nitrogen Oxygen Rhizosphere adapted N 2 O Bulk soil adapted N 2 O N 2 O N 2 O Unsaturated soil Giles et al 2012. Frontiers in Microbiology

N 2 O Nitrogen Oxygen N 2 O Rhizosphere adapted N 2 O Bulk soil adapted N 2 O N 2 O N 2 O Root in unsaturated soil Giles et al 2012. Frontiers in Microbiology

NO, N 2 O, N 2 C C transfer NO 3 - NO 2 - NO N 2 O N 2 NH 4 + NO 3 - NO 2 -

0.80 organic acids sugars amino acids 0.60 N2O : N2 mole ratio 0.10 0.08 75 µg C g -1 day -1 0.06 K 15 NO 3 0.04 20 g N m -2 0.02 0.00 Succinate Butyrate Acetate Malic acid Sucrose Glucose Arginine Cysteine Morley et al 2014. PLoS one

Organic acids: enhanced N 2 O reductase efficiency major constituent of labile root C exudation organic acid sugar amino acid 75 µg C g -1 day -1 K 15 NO 3 20 g N m -2 0 4 12 8 0 0 4 12 4 12 8 8 Days Days Days Morley et al 2014. PLoS one

1.4 1.2 1.0 Citric acid 0.8 0.6 0.4 0.2  l N 2 O-N L -1 0.0 0 1 2 3 4 5 6 7 Distance from C source (cm) 300 250 Glutamine 200 150 100 50 0 . 0 1 2 3 4 5 6 7 Distance from C source (cm) Giles et al 2017. Soil Biol Biochem

Water filled pore Sub-oxic microsite Oxic zone N 2 Denitrification a b Ammonia oxidation Nitrate N 2 O N uptake ammonification a b a b C flow

Plant- & soil-C driving N 2 O production 1600 13 C-depleted (-38.5‰) CO 2 1400 360 µmol mol -1 1200  g 15 N-N 2 O m -2 d -1 r = 0.51 K 15 NO 3 , 20 g N m -2 1000 800 r = 0.61 Low SOM 600 Plant C 400 SOM C 200 0 -20 0 20 40 60 80 100 Plant or SOM-derived C (mg CO 2 -C m -2 h -1 )  13 C-CO 2 to distinguish between plant- and SOM derived C

Plant-C driving N 2 O production 250 13 C-depleted (-38.5‰) CO 2 750 µmol mol -1 200  g 15 N-N 2 O m -2 d -1 K 15 NO 3 , 20 g N m -2 150 r = 0.70 High SOM 100 Plant C 50 0 100 120 140 160 180 200 220 240 260 Plant-derived C (mg CO 2 -C m -2 h -1 )

Maize genotype screening for C & N cycling

Thanks to… collaborators funders Lumbani Mwafulirwa Eric Paterson Maddy Giles Nick Morley Tim Daniell Nadine Loick Laura Cardenas Christian Thierfelder Jill Cairns