Can we reduce nitrous oxide emissions from crops? - Sally Officer
DEPARTMENT OFPRIMARY INDUSTRIES Can we reduce nitrous oxide emissions from crops? Sally J. Officer, Gavin Kearney, Frances Phillips, Roger Armstrong and Kevin Kelly. N2O Network
Atmospheric nitrous oxide is increasing in the same “hockey stick” pattern as carbon dioxide and methane.Atmospheric gasconcentrations overthe past 1000 years
84% of nitrous oxide emissions come from agriculture in Australia.75% of this nitrous oxide isgenerated by micro-organisms in agricultural soil,using N derived from:-•Nitrogen fertilizer•Soil disturbance•Animals
“66% of nitrogen fertiliser is used on cereals in Australia.” Additional slide to be used at your “90% of the discretion increase in N2O emissions from 1990 to 1999 was due to an increase in the rate of N fertiliser application” (Dalal as soil reaches saturation. DCD may now beVery large increase in emissions in July et al, 2003)ineffective, but we will not be sure until statistical modelling is completed.
Measuring N2O emissions from fertilised crops TGAAutomated chamber systemmeasuring nitrous oxide 16 times a day
Comparison of emissions from wheat cropping soilswith either N fertiliser or a legume rotation as the source of N
Rainfall during emissions monitoring 80 70 Annual rain 60 Rainfall (mm) 50 372 mm 402007 30 20 GSR rain 10 0 205 mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Decile 2 Drought years, good indicators of future conditions 80 Annual rain 70 60 322 mm Rainfall (mm) 502008 40 30 20 GSR rain 10 0 183 mm Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Decile 1
Daily average emissions and soil moisture 2007 12 50 Sowing Harvest 45 10 40 Soil moisture content (v/v%) 2007 Increased Flux in 2007 35Flux N2O (g N.ha-1.d-1) 8 300 250 30 200 6 64% 23% 25 g/ha 150 A marked increase in N2O flux from cultivated plots immediately after cultivation and 20 100 planting. Possible early effect of the DCD (need statistical analysis. 4 15 50 0 10 2 No N fertiliser 50 kg N/ha 50 kg N/ha 5 0 0 Apr-2007 Jun-2007 Aug-2007 Oct-2007 Dec-2007 Jan-2008 Wheat, No N fertiliser Wheat and N fertiliser Wheat and N fertiliser and irrigation Soil water
Daily average emissions and soil moisture 2008 Sowing Harvest Increased flux in 2008 160 140 120 100 84% g/ha 80 60 154% 40 20 0 No N fertiliser No N fertiliser 50 kg N/ha
Soil mechanisms O2Nitrification NH4+ CO2 cycle N 2O N2O (aerobic) NO3-
Soil mechanisms O2 Nitrification NH4+ CO2 cycle N 2O N2O (aerobic) NO3- NO- N2 N2Denitrification NO3- N2 cycle (anaerobic) NO2- N2O N 2O NO
O2 NH4+ CO2 N 2O N2O NO3- NO-The application of band of concentrated urea N2 N2 granules to NO3- N an aerobic (drained) soil 2causes large losses of nitrous oxideNO2- through N2O nitrification pathway the NO
1) A clear increase in nitrous oxide emissions associated with the use of urea2) No yield advantage from urea in two relatively dry years3) Legume rotations supplied sufficient N for semiarid wheat under low rainfall and also generated less nitrous oxide
Legumes can be difficult to establish and may not grow wellin drier years, while a year of more reliable non leguminousgrain crop has been lost.Nevertheless, encouraging farmers to increase their use oflegume rotations should reduce emissions from Australiangrain crops.