Timothy Huggins MSLE, The University of Melbourne Is it commercially viable to use dicyandiamide on a dairy farm in south-western Victoria? Co-authors: Kevin Kelly (DPIV), Helen Suter (UoM), Richard Eckard (UoM & DPIV)

Decreased nitrous oxide emissions Increased pasture dry matter grown Aims and objectives Decreased nitrous oxide emissions Increased pasture dry matter grown Economically feasible Barriers to adoption

N2O = 4% of Australia’s GHG emissions Nitrous oxide N2O = 4% of Australia’s GHG emissions Predominantly produced by agriculture – 86% Major sources are N fertiliser management, animal waste management, and soil cultivation Also need to include indirect production (N03- leaching, run-off and NH4+ volatilisation) Dairy 6.5 t CO2e/cow 10.2 t CO2e/ha Adapted from Eckard 2008 and Christie 2009

Animal urine accounts for 2/3 of the N2O from animal production The power of urine Animal urine accounts for 2/3 of the N2O from animal production Urine patch = approx. 1000 kg N/ha equivalent Urine patches cover 10-30% of farm in 12 months Eg. If urine covers 20% of farm at 1000 kg N/ha = 200 kg N/ha on top of 106 kg N applied. Can be huge excess of N in soil available for N2O production – distribution issue

DCD, nitrous oxide, and the N cycle NO3- can be lost through leaching or as nitrous oxide Indirect losses also reduced DCD lifespan depends on soil T, moisture, pH, O.M. Nitrosomonas goes back to work after 2-3 months 10 kg a.i. Applied twice per year NH2OH

Increasing pasture dry matter – milk pays What is possible? Likely response 0-35% increase from 2 applications (de Klein and Eckard, 2008) Eco-N (Ravensdown) advertised as 20% increase across the farm = 1.46 t DM/ha. If we take it only in urine patches = 560 kg DM in our case (7.6% across paddock) 560 kg DM = 48 kg MS (0.08 kg MS/kg DMI) 48 kg MS = $216/ha @ $4.95/kg MS Nett return = $216 - $165 = $50/ha BUT... we know that there could be issues with: Utilisation (not 100%, probably 60-70% but what about substitution?) Extra costs associated with turning that pasture into milk (look at marginal response per litre)

Spring (2009) and Autumn (2010) applications Our trial 6 commercial dairy farms in South-west Vic (range in soil, temperature and rainfall) Spring (2009) and Autumn (2010) applications Control vs Urine either at start or 1 month later – all repeated with and without DCD (6 treatments in total) Autumn 2010 schedule: T1. Nil urine applied. T2. Nil urine applied + DCD applied April. T3. Urine applied May. T4. DCD applied April, Urine applied May. T5. Urine applied April. T6. Urine + DCD applied April. 4 replicates of each treatment in RCBD, excised from grazing Soil testing, nitrous oxide measurements, pasture DM harvesting

Increasing pasture dry matter – our results What did we find? 0-15% increase in pasture DM in urine patches 3 farms in each season with significant increases (but not the same 3) and mostly in response to the urine at the start Farms with significant results all had different soil types, rainfall patterns and N fertiliser usage (background N would be different) Only in the second season was there an increase from DCD on control = idea of what happens between urine patches. This farm applied 266 kg N during the season – potential DCD impact on the fertiliser Across the whole paddock result = 2.5-3.75% increase in pasture DM (180-270 kg DM/ha) Nett return of $70-$100 per hectare without considering additional costs and assuming 100% utilisation

2 treatments – DCD or nothing with 35 reps of each Current grazing trial 70 plots of 10 x 10 m 2 treatments – DCD or nothing with 35 reps of each Graze, then apply DCD in May and August (3 months apart) followed by a 100 kg application of urea Measure pasture available before and after grazing with Ellinbank Plate Meter Soil testing

Summary and conclusions None of the potential benefits are big enough at this stage – need to show improvement in production/profitability Factors that would increase viability Future research showing larger increases in pasture DM Increased fertiliser price Reduced DCD price Need ETS rather than a C price

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