Managing nitrous oxide emissions in grains cropping systems on clay soils with contrasting soil carbon status and land management

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1 Managing nitrous oxide emissions in grains cropping systems on clay soils with contrasting soil carbon status and land management Mike Bell QAAFI Kingaroy,

2 Overview The contribution of nitrous oxide to greenhouse gas emissions from cropping The N cycle in cropping soils Factors generating emissions in the field the perfect storm Limiting N 2 O emissions - it s all about nitrogen use efficiency Legume N versus fertilizer N local NAMI experiences The role of nitrification inhibitors in the field at Kingaroy Future activity in NANORP

3 Australian Agriculture & Prescribed burning of savannas 17% Agricultural ``` Soils Manure management GHGs Enteric fermentation Agriculture 16% of Australia s GHGs 59% of all CH 4 86% of all N 2 O N 2 O from soils 3% of national GHGs 17% of agricultural GHGs

4 Why focus on N 2 O? It can represent a significant proportion of farm GHG emissions It is an indicator of N losses by denitrification (although not a quantitative one) Reducing denitrification losses and improving N use efficiency is an issue of profitability as well as environmental impact.

5 An example 350 ha cropping on black soil (300ha dryland, 50ha irrigated) N fertilizer used - 80 kg N/ha dryland, 120 kg N/ha irrigated Fuel use 3000L diesel/year Total emissions 130 t CO 2 equivalents/year Fuel CO2 Soils CO2 Fertilizers N2O More than 2/3 from N 2 O

6 What is the science behind this? Plants take up mineral N from the soil solution. The dominant form of mineral N in the soil is nitrate (NO 3- ). When soils waterlog, microbes remove oxygen from NO 3 -, reducing it to N 2 O and ultimately N 2. These gases have low solubility in water, so tend to escape to the atmosphere.

7 The key requirements A high concentration of NO 3 -N (after fertilizing, manure application, decomposing legume residues) Lots of organic matter (to sustain the microbial activity) Wet soil Not necessarily under water all you need are low O 2 micro-sites in clods etc. All 3 conditions must be met simultaneously!

8 Using these criteria, we can map regional N 2 O emission potential Low Medium High No data/uncertain Grace, unpub.

9 Some local data collected during recent NAMI projects Ley pastures/forages returned to cropping Event-based sampling around rainfall occurrence Relative measures only can t calculate a total loss

10 4/08/ /08/ /08/ /08/ /08/ /08/2010 6/09/2010 7/09/ /09/ /11/ /11/ /11/2010 2/12/2010 9/12/ /12/2010 Brigalow Grey Vertosol Burgundy bean - N Lablab - N Forage sorghum - N Forage sorghum - Y During the fallow, losses are low. There is a trend for higher losses in the legumes than forage sorghum (more N). Once sorghum was planted and fertilizer N (urea) applied, these losses dominated in the forage sorghum (more residue)

11 N2O flux (gn/ha/day) Same at Kingaroy surprisingly! Lucerne 15N Rhodes grass 15N Lucerne 75N Rhodes grass 75N S1 15 Dec S2 17 Dec S3 20 Dec S4 5 Jan S5 22 Feb Normally our red soils drain too well for denitrification to occur. N losses generally dominated by leaching The previous summer was an exception!

12 How big are these losses N 2 O? We have run trials at Kingaroy with QUT in the NORP program looking at N rates and nitrification inhibitors last winter and summer. Crops were wheat (after mungbean), followed by corn Automated chambers were used to monitor losses through the season Data courtesy of Massimiliano De Antoni Migliorati

13 N 2 O-N Flux [g ha -1 ] N 2 O-N Flux [g ha -1 ] Cumulative N 2 O generation in the 2 seasons N 2 O cumulative fluxes Winter L1 0 KgN/ha L2 20 KgN/ha L3 80 KgN/ha L4 80 DMPP KgN/ha L1 40 KgN/ha Summer L2 100 KgN/ha L3 180 KgN/ha L4 180 DMPP KgN/ha

14 Cumulative N2O loss (kg N/ha/season) Grain yield (t/ha) Losses in wheat 7 Grain yields increased with N application Similar yields with 80N as urea or Entec coated urea N 2 O losses relatively low (<0.4 kg/ha) Losses increase with higher N inputs Entec reduced N2O emissions by 1/3 for the same N rate N 20N 80N 80N Entec (DMPP) 0N 20N 80N 80N Entec Queensland (DMPP) Government

15 Cumulative N2O loss (kg N/ha/season) Grain yield (t/ha) Losses in corn Large grain yield increases with N application Similar yields with 160N as urea or Entec coated urea N 2 O losses much higher, but still <1.5 kg/ha Losses increase with higher N inputs Entec reduced N2O emissions by 2/3 for the same N rate N 100N 160N 160N Entec N 100N 160N 160N Entec

16 Emission factor (kg N2O/t grain) Emission factors - summer v winter crops Winter cooler soils, lower N rates, less stubble (after mungbeans) Summer warmer, wetter for longer, large wheat stubble loads (5-7 t/ha) Wheat 0N Wheat 20N Wheat 80N Wheat 80N Entec Corn 40N Corn 100N Corn 160N Corn 160N Entec

17 N2O (g/n/ha -1 /day -1 ) So what - <1 kg N/ha as N 2 O! Data from Dalby, courtesy of Prof. Peter Grace (QUT) Remember not all denitrification occurs as N 2 O. In fact, far more is lost as N 2 /N 2 O = 70/1 How much more?? Lost 28% of applied N kg N/ha VWC (%) N2 (g/n/ha -1 /day -1 ) kg N/ha VWC % Rowlings & Grace, EGU, Days Working 80 together with the Rowlings & Grace, EGU, 2009 Days

18 Nitrate N (mg/kg) How much N can this represent? Denitrification losses in recent wet summers at Colonsay Profile NO3 measured before and after waterlogging Big denitrification losses Nov-10 Mar-11 Loss = 93 kg N/ha 0-30cm 30-60cm 60-90cm

19 Summary Nitrous oxide emissions are a significant component of whole farm GHG emissions in cropping areas These losses will occur sporadically, based on coincidence of stubble, wet soil and high NO 3 -N When they do occur, losses can be large Nitrification inhibitors show promise, but are not yet economic More information is being collected in the NANORP program to look at inhibitors, sources of N and the impact of improved soil C on denitrification, NUE and N 2 O emissions

20 Regional footprint N response trials Trials managed from 4 regional centres Emerald, Kingaroy/Toowoomba, Tamworth and Trangie Sites will be selected in consultation with grower groups and advisors. Variation in soil C, crop rotations, fallow length etc Preplant N and soil water Biomass production, fertilizer N recovery, crop yield and grain N removal

21 Activities (ii) Detailed N loss studies Two sorghum field trials in SQld each year (2012 sites shown). Similar designs to regional studies, but including 15N Trials will be conducted in a different district each year, but kept closer to Kingaroy/Toowoomba More detailed soil and plant sampling and15n recovery to determine fate of applied N/total losses N rate (kg N/ha) N N N

22 Activities (iii) - assessment of N 2 O emissions 2 core locations (Kingaroy and Kingsthorpe) where automatic chambers and N rate/product/source issues are followed, with 15 N ( ). The 2 roving annual trials with 15N focussing on soil test N fertilizer rate response in different districts. These sites will have manual chambers and event-based sampling for N 2 O.

23 Effect of N sources core sites only Fertilizer with or without nitrification inhibitors Ley pastures elevated C and/or N Grain legumes v cereal grains Organic wastes manures and biosolids

24 Outcome Growers and advisors in the northern region will have access to N response curves and nitrous oxide emissions data for sorghum, and in more southern production areas, canola. The data will describe the influence of soil organic matter, rotation and nitrogen management on fertilizer N requirement. Success will be assessed by the submission of scientific manuscripts and adoption of findings by the fertiliser industry in updated decision support systems.