Nitrous Oxide-Novel Mitigation Methodologies: Objective 2 - Biochar effects on urinary-N N2O emissions
Authors: Dr T J Clough, Dr J L Ray, Associate Professor R R Sherlock, Professor L M Condron, Dr M O'Callaghan, Ms L E Buckthought
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Executive summary
- To determine the effects of biochar (derived from Pinus radiata), with and without urine amendment, on N2O emissions from urine, an experiment was performed over 29 days that included six treatments as follows:
- Control (soil + water).
- Soil + urine.
- Soil + urine + biochar (10 t ha-1)
- Soil + urine + biochar (20 t ha-1)
- Soil + urine + biochar (30 t ha-1)
- Soil + biochar + water (20 t ha-1)
- As the biochar rate was increased by 10, 20 or 30 t ha-1 the cumulative urinary N2O emissions were reduced by 15, 52 and 74% respectively. The percentage reduction in N2O emissions were positively related to biochar rate (y = 2.44x, r2 =0.97).
- No differences in NH3-N emissions were observed between treatments.
- Soil gravimetric moisture content decreased with increasing rates of biochar addition and this may have been a factor influencing the N2O production mechanisms.
- Biochar incorporation altered soil inorganic-N dynamics by lowering soil NH4 +-N concentrations. These lower concentrations occurred with increasing rates of biochar. This was presumably due to biochar enhancing the cation exchange capacity.
- Biochar, in the absence of urine-N produced a liming effect, raising the soil pH by approximately 0.5 pH units when biochar was applied at the equivalent rate of 20 t ha-1.
- Future work is urgently required to assess the effect(s) of biochar amendment on N2O emissions when applied to pasture soils under field conditions, effects on plant N uptake, and N leaching.
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