Nitrogen immobilisation and enhancing denitrification. Louis Schipper, University of Waikato Paul Mudge, Landcare Research

Transcription

1 Nitrogen immobilisation and enhancing denitrification Louis Schipper, University of Waikato Paul Mudge, Landcare Research

2 Imports Grain Animal feed Fertilisers Synthetic Organic N Inputs Biological N fixation Pasture Other BNF Atmospheric deposition Biomass burning Fossil fuel combustion Redeposition of ammonia N Outputs Erosion/sediment loss Direct gaseous emissions Indirect gaseous emissions N 2 O, N 2, NO x Ammonia volatilisation N 2 O, N 2 Leaching Loss to oceans Attenuated loss Products Cultivation ΔSOM Net N immobilisation SOM-N Vadose zone Surface water Groundwater Adapted from IPCC (2006)

3 Net nitrogen immobilisation Net N immobilisation is an important sink of N N saturation of soils is occurring Soils with remaining storage (%) kg/ha/y 50 kg/ha/y 100 kg/ha/y Assuming a minimum C:N ratio of 10 Schipper, L.A.; Percival, H.J.; Sparling G.P. (2004) An approach for estimating maximum nitrogen storage in soils. Soil Use and Management 20: Years

4 Knowing the rate of net nitrogen immobilisation is important A typical Overseer run for Dairy allocates about 70kg/ha/y into organic matter pool What is a reasonable rate?

5 Flat land (0-0.3m) over about 27 years Representativeness? Sites (no.) Mean rate of N gain/loss kg N ha -1 y -1 95% CI for mean rate of N gain/loss kg N ha -1 y -1 All (122) Allophanic (29) Gley (25) RBPP (68) RBPP = Recent, Brown, Pumice, Pallic Derived from data in: Schipper, L.A.; Parfitt, R.L.; Fraser, S.; Littler R.A.; Baisden, W.T.; Ross, C. (2014) Soil order and grazing management effects on changes in soil C and N in New Zealand pastures. Agriculture Ecosystems and Environment. 184:

6 Hill country storage Need to know representativeness Interval Plot of 30Nratekg/ha/yr 23 Hill Sites 95% CI for the Mean Nratekg/ha/yr Project: N_ACCUM.MPJ; Worksheet: NewHillNoTussock.MTW; 14/02/2014; Ray Littler Derived from data in: Schipper, L.A.; Parfitt, R.L.; Fraser, S.; Littler R.A.; Baisden, W.T.; Ross, C. (2014) Soil order and grazing management effects on changes in soil C and N in New Zealand pastures. Agriculture Ecosystems and Environment. 184:

7 But there can be considerable short-term dynamics Parfitt et al. (2014) re-sampled 139 flat pastoral sites ( m) Accumulation rates of between 60 to 90 kg ha -1 yr -1 Some of the sites accumulated >200 kg N ha -1 y -1 Parfitt RL, Stevenson BA, Ross C, Fraser S Changes in ph, bicarbonate-extractable- P, carbon and nitrogen in soils under pasture over 7 to 27 years. New Zealand Journal of Agricultural Research 57(3):

8 Plans NZ focussed review of nitrogen immobilisation Forest to pasture Long term pasture Controls on net nitrogen immobilisation What are plans with Landcare Research Field scale measurement Effect of irrigation

9 Denitrifying bioreactors Will Robertson, Canada Wood chip bioreactor on a tile line draining 50 acres. Mark David The original Farm dairy effluent Iowa soybean growers tile drains Photo Stewart Cameron

10 Temperature effects C, n=57 >17 C, n=50 A meta-analysis of denitrifying bioreactors: Implications for nitrate abatement <7 C, n=12 Inflow nitrate concentration effects >35 mg N L -1, n= mg N L -1, n=30 Nicole Sacha 1, Kelly Addy 1, Arthur Gold 1, Laura Christianson 2, Mark David 3, and Louis Schipper 4 1 University of Rhode Island 2 The Conservation Fund, Freshwater Institute 3 Univesity of Illinois at Urbana-Champaign 4 Univeristy of Waikato <10 mg N L-1, n=29

11 Expansion

12 Planned and needed Special issue of Journal of Environmental Quality Laura Christianson and Louis Schipper Intent: Field-scale examples of denitrifying bioreactors in place and functioning Overview and meta-analysis Key questions Decline in performance with time? Where can they be placed/managed? Cost benefit?

13 Schipper, L.A.; Gold, A.J.; Davidson E.A. (2010) Managing denitrification in human dominated landscapes. Editorial for Ecological Engineering. 36 (11),

14 500 m New Rye Planned N 2 O work Rye Diverse Leading Partners in Science

15 Planned N 2 O work Supported by University of Waikato Paddock scale continuous N 2 O measurements Postdoc interviews next week 2 year project Looking for collaboration