Increased N efficiency in pastoral systems: the urine-n cascade. Tim Clough

Transcription

1 Increased N efficiency in pastoral systems: the urine-n cascade Tim Clough

2 BIOLOGY SOIL PHYSICS CHEMISTRY

3 BIOLOGY SOIL PHYSICS TIME CHEMISTRY

4 SOIL PHYSICS BIOLOGY Soil factors Plant factors Climate Management TIME CHEMISTRY

5 UREA dominant urinary-n compound Soil concentration Concentration a function of animal N intake - plant N concentration & intake Time

6 UREA Duration a function of urease activity Soil concentration Concentration a function of animal N intake - plant N concentration Time

7 UREA Duration a function of urease enzyme activity Urease inhibition e.g. nbpt Soil concentration Concentration a function of animal N intake - plant N concentration Reduce plant N concentration N partitioning through diet? Time

8 UREA transformed to AMMONIUM (NH 4+ ) Ammonia (NH 3 ) loss Removed via NH 3 loss, plant uptake, nitrification Soil concentration Enhance plant N uptake Root archictecture? Plant activity? Nitrification inhibition? Gibberellic acid? ~ 2 weeks Time

9 UREA transformed to AMMONIUM (NH 4+ ) Ammonia (NH 3 ) loss: average of 10% of N deposited typically over 2-5 days urease Urea + H 2 O NH CO 3 2- Soil concentration CO H 2 O HCO OH - NH OH - NH 3 + H 2 O Soil ph 8-9 ~ 2 weeks Time

10 Ammonia volatilisation NH 3(g) atmosphere Urea fertiliser I NH 3(g) soil II III NH 3(aq) NH 4 + (aq) (NH 2 ) 2 CO V Organic N IV NH 4 + (exchange sites) SOSC 340, May 2014

11 Main factors affecting NH 3 volatilisation from soil - summary 1. soil ph and temperature 2. position of ammoniacal-n in soil 3. windspeed 4. urine-n rate 5. soil moisture SOSC 340, May 2014

12 AMMONIUM nitrified to NITRITE (NO 2- ) NO 2 - peak at ~ 7 days Soil concentration Gateway for most gaseous N losses. Time

13 Fig. 4 Transformations of mineral nitrogen in soil (for explanations see text). N Wrage, G.L Velthof, M.L van Beusichem, O Oenema Role of nitrifier denitrification in the production of nitrous oxide Soil Biology and Biochemistry, Volume 33, Issues 12 13, 2001,

14 Nutrient Cycling in Agroecosystems 52: , Kluwer Academic Publishers. Printed in the Netherlands. 131 Measurement of nitrous oxide and di-nitrogen emissions from agricultural soils R.J. Stevens1;2 & R.J. Laughlin2 Figure 1. Nitrogen transformation processes affecting nitrous oxide and di-nitrogen production in soil (1 = nitrification; 2 = denitrification; 3 = dissimilatory reduction of nitrate to ammonium; 4 = chemo-denitrification; 5 = nitrogen fixation)

15 NH 4 + (mg N kg -1 ) (mg N kg -1 ) NO 2 - (mg N kg -1 ) NO 3 - (mg N kg -1 ) + NO 3 - NO (a) NH 4 + (b) NO 2 - (c) NO 3 - Soil L Soil W 600 (d) NO NO Time (d) Venterea et al Nature Science Reports in revision

16 3.5 (a) Log 10 (c-no 2 - ) = 1.01Log 10 (c-slnh 3 ) (b) Log 10 (c-an 2 O) = 0.59Log 10 (c-no 2 - ) r 2 = 0.873, P < r 2 = 0.824, P < Log 10 (c-no 2 - ) Predicted Log 10 (c-no 2 - ) 2.5 Series Series 2 Log 10 (c-an 2 O) Log 10 (c-slnh 3 ) Log 10 (c-no - 2 ) 3.5 (c) - Log 10 (c-no 2 ) = Log10 (c-slnh + 4 ) (c-H + ) 3.0 R 2 = 0.926, P < Series 3 Predicted Log 10 (c-an 2 O) (d) 1.4 Log10 (c-an 2 O) = Log 10 (c-slnh + 4 ) (c-H + ) 1.2 R 2 = 0.893, P < Figure 6. Regression results. Singlefactor regression models of (a) cumulative nitrite (c-no 2- ) versus cumulative solution-phase ammonia (cslnh 3 ) and (b) cumulative actual N 2 O production (c-an 2 O) versus c-no 2 - with regression lines, and multiple regression models describing (c) c-no 2 - and (d) c-an 2 O as functions of cumulative solution-phase ammonium (c-slnh 4+ ) and cumulative acidity (c- H + ) with 1:1 lines, for all microcosm data (Series 1-3). Venterea et al Nature Science Reports in revision Observed Log 10 (c-no 2 - ) Observed Log 10 (c-an 2 O)

17 Normalized gene copy number (a) amoa-b (b) amoa-a (c) nxra Soil L Soil W Figure. 5. Gene copy abundances in Series 3 microcosm experiment. (a) amoa-b, (a) amoa-a, and (c) nxra following addition of Ur at 1000 mg N kg -1 soil with soils at 85% of FC. Asterisks indicate significant differences between soils at P < Normalized gene abundances are expressed relative to the number of copies of prokaryotic (bacteria+archaea) 16S rrna genes in each sample (45). Venterea et al Nature Science Reports in revision Time (d)

18 Ammonium (NH 4+ ) nitrified to nitrite (NO 2- ) cont d. So we need to retain the NH 4 + and prevent NO 2 - formation Soil concentration Nitrification inhibition - add chemicals manually or biologically e.g. BNI - (targeting who?) Or enhance plant N uptake Root archictecture? Plant activity? Gibberellic acid? Time

19 Nitrite nitrified to nitrate (NO 3- ) Soil concentration Removed via plant uptake, leaching, denitrification, immobilisation. Time

20 Fig. 4 Transformations of mineral nitrogen in soil (for explanations see text). N Wrage, G.L Velthof, M.L van Beusichem, O Oenema Role of nitrifier denitrification in the production of nitrous oxide Soil Biology and Biochemistry, Volume 33, Issues 12 13, 2001,

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22 N 2 O-N (mg m -2 h -1 ) a Balaine et al. showed Bulk density Balaine et al. SSSAJ 2013, 77: WFPS (%)

23 Experimental set up for measuring relative soil gas diffusivity. Rolston and Moldrup Methods of Soil analysis Part 4. pp

24 100 N 2 O-N (mg m -2 h -1 ) Bulk density Wet Balaine et al. SSSAJ 2013, 77: Dp/Do Dry

25 Cumulative N 2 O-N (% of applied N) D p /D o 1.1 (-10 kpa) 1.2 (-10 kpa) 1.3 (-10 kpa) 1.4 (-10 kpa) 1.1 (-6.0 kpa) 1.2 (-6.0 kpa) 1.3 (-6.0 kpa) 1.4 (-6.0 kpa) 1.5 (-6.0 kpa) 1.1 (-0.2 kpa) 1.2 (-0.2 kpa) 1.3 (-0.2 kpa) 1.4 (-0.2 kpa) 1.5 (-0.2 kpa)

26 Cumulative N 2 -N (% of applied N) D p /D o 1.1 (-10 kpa) 1.2 (-10 kpa) 1.3 (-10 kpa) 1.4 (-10 kpa) 1.1 (-6.0 kpa) 1.2 (-6.0 kpa) 1.3 (-6.0 kpa) 1.4 (-6.0 kpa) 1.5 (-6.0 kpa) 1.1 (-0.2 kpa) 1.2 (-0.2 kpa) 1.3 (-0.2 kpa) 1.4 (-0.2 kpa) 1.5 (-0.2 kpa)

27 Cumulative N 2 -N : N 2 O-N ratio a 1.1 (-10 kpa) 1.2 (-10 kpa) 1.3 (-10 kpa) 1.4 (-10 kpa) 1.1 (-6.0 kpa) 1.2 (-6.0 kpa) 1.3 (-6.0 kpa) 1.4 (-6.0 kpa) 1.5 (-6.0 kpa) 1.1 (-0.2 kpa) 1.2 (-0.2 kpa) 1.3 (-0.2 kpa) 1.4 (-0.2 kpa) 1.5 (-0.2 kpa) Dp/Do

28 Relate microbial process to Dp/Do? use isotopomers? How much does critical Dp/Do vary with soil O 2 demand? Cumulative N 2 O-N (% of applied N) ? O 2 supply/consumption Nitrifierdenitrification? 1.1 (-10 kpa) 1.2 (-10 kpa) 1.3 (-10 kpa) 1.4 (-10 kpa) 1.1 (-6.0 kpa) 1.2 (-6.0 kpa) 1.3 (-6.0 kpa) 1.4 (-6.0 kpa) 1.5 (-6.0 kpa) 1.1 (-0.2 kpa) 1.2 (-0.2 kpa) 1.3 (-0.2 kpa) 1.4 (-0.2 kpa) 1.5 (-0.2 kpa) Denitrification D p /D o Nitrification

29 Fig. 1 Development of mean maximum N2O concentration and observed diffusion flux (a), time- and depth-specific contour plot of the N2O concentration over time for treatment TC (b), time- and depth-specific contour plot of the redox potential over time... Hansen et al Flooding-induced N2O emission bursts controlled by ph and nitrate in agricultural soils Soil Biology and Biochemistry, Volume 69, 2014, 17-24

30 What don t we know with respect to increasing N use efficiency? Dissolved organic-n leaching Horotiu soil, autumn urine event leads to DON concentrations ~ 30% of NO 3 - Immobilisation of urinary-n? Priming? Urine patch and fertiliser N interaction: Effects of fertiliser rate and season of urine application on nitrate leaching and pasture N uptake. Buckthought et al. Agriculture Ecosystems & Environment 203, 2015, Pages

31 Summary - Interventions: Chemical: Inhibitors and growth promoters (nbpt, nitrification inhibitors, GA). Biological: Plant: N content, rooting structure, activity. Physical: Soil oxygen status, ph Do we know which microbes to target with interventions?