Improving Estimates of Nitrate Leaching for Quantifying New Zealand’s Indirect Nitrous Oxide Emissions

New Zealand’s indirect nitrous oxide (N2O) emissions have been estimated to contribute approximately 23% of the national nitrous oxide inventory. However, there is great uncertainty about this figure. Currently the intergovernmental panel for climate change (IPCC) calculation is used, where a proportion (FracLEACH) of nitrogen (N) applied to land as animal excreta or fertiliser is leached or runs off, and a further proportion is later emitted as N2O. New Zealand has been using a value of 0.15 (FracLEACH[NZ]) and this paper examined whether (FracLEACH[NZ]) is appropriate for New Zealand conditions. For a range of typical farming systems, we compared N leaching estimates calculated using the IPCC formula with estimates obtained using the OVERSEER® nutrient budget model calibrated for New Zealand conditions. The comparison suggested that FracLEACH[NZ] is too high for dairy and sheep and beef farming systems. In␣contrast, the FracLEACH values estimated for arable and intensive vegetable systems using the OVERSEER® model were much closer to 0.3 (the IPCC default value). However, in New Zealand, arable cropping and intensive vegetable farms occupy only a small proportion of land compared to pastoral farming. Based on this study, we suggest that a FracLEACH value of 0.07 is appropriate for New Zealand conditions; this more accurately reflects the proportion of N applied to pastoral land that may leach or runoff. Using this value in the IPCC calculation for the New Zealand inventory would approximately halve the national estimate of indirect N2O emissions due to leaching or runoff of N, reducing the national estimate of N2O emissions by 12%.

[1]  D. Chadwick,et al.  Nitrogen flows and losses in dairy farms in New Zealand and the UK: effects of grazing management , 2002 .

[2]  C. Nevison.  Review of the IPCC methodology for estimating nitrous oxide emissions associated with agricultural leaching and runoff , 2000 .

[3]  B. E. Ruz-Jerez,et al.  A comparison of nitrate leaching under clover-based pastures and nitrogen-fertilized grass grazed by sheep , 1995, The Journal of Agricultural Science.

[4]  Rehema M. White,et al.  Nitrate leaching from a drained, sheep-grazed pasture. I. Experimental results and environmental implications , 1996 .

[5]  C. Kroeze,et al.  Progress in source strength estimates of nitrous oxide , 2002 .

[6]  P. Williams,et al.  Comparison of initial wetting pattern, nutrient concentrations in soil solution and the fate of15N-labelled urine in sheep and cattle urine patch areas of pasture soil , 1994, Plant and Soil.

[7]  G. Francis,et al.  Effects of mixed cropping farming systems on changes in soil properties on the Canterbury Plains , 1990 .

[8]  P. Groffman,et al.  Nitrous oxide production in riparian zones and its importance to national emission inventories , 2000 .

[9]  Carl J. Rosen,et al.  Potato yield response and nitrate leaching as influenced by nitrogen management , 1998 .

[10]  S. Ledgard,et al.  Nitrogen losses from grazed dairy pasture, as affected by nitrogen fertiliser application , 1996 .

[11]  J. Penman,et al.  Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories CH 4 Emissions from Solid Waste Disposal 419 CH 4 EMISSIONS FROM SOLID WASTE DISPOSAL , 2022 .

[12]  G. Francis,et al.  Nitrogen mineralization, nitrate leaching and crop growth following cultivation of a temporary leguminous pasture in autumn and winter , 1992, Fertilizer research.

[13]  G. Francis,et al.  Winter nitrate leaching losses from three land uses in the Pukekohe area of New Zealand , 2003 .

[14]  C. Rahn,et al.  The use of measurements of soil mineral N in understanding the response of crops to fertilizer nitrogen in intensive cropping rotations , 1998, The Journal of Agricultural Science.

[15]  G. Hofman,et al.  N mineralization and nitrate leaching from vegetable crop residues under field conditions: a model evaluation , 1998 .

[16]  J. L. Gaunt,et al.  Soluble organic nitrogen in agricultural soils , 2000, Biology and Fertility of Soils.

[17]  D. Q. Kellogg,et al.  Mechanisms, rates and assessment of N2O in groundwater, riparian zones and rivers. , 2002 .

[18]  R. Monaghan,et al.  Nitrogen and phosphorus losses in overland flow from a cattle‐grazed pasture in Southland , 2003 .

[19]  D. J. Greenwood.  The 1988 shell lecture Plant Nutrition and Human Welfare: The World Scene† , 1989 .

[20]  Carolien Kroeze,et al.  Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories : Chapter 4. Agriculture , 1997 .

[21]  K. Goulding,et al.  Nitrate leaching from the Broadbalk Wheat Experiment, Rothamsted, UK, as influenced by fertilizer and manure inputs and the weather , 2000 .

[22]  D. Powlson,et al.  Influence of soil type, crop management and weather on the recovery of 15N-labelled fertilizer applied to winter wheat in spring , 1992, The Journal of Agricultural Science.

[23]  J. Webb,et al.  The effect of crop residue incorporation date on soil inorganic nitrogen, nitrate leaching and nitrogen mineralization , 2000, Biology and Fertility of Soils.

[24]  D. Powlson,et al.  Effects of season, soil type and cropping on recoveries, residues and losses of 15N-labelled fertilizer applied to arable crops in spring , 1997, The Journal of Agricultural Science.

[25]  J. Quinn,et al.  Water quality and sediment and nutrient export from New Zealand hill‐land catchments of contrasting land use , 2002 .

[26]  Carolien Kroeze,et al.  Closing the global atmospheric N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle. (OECD/IPCC/IEA Phase II Development of IPCC Guidelines for National Greenhouse Gas Inventories). , 1997 .

[27]  K. Goulding.  Nitrate leaching from arable and horticultural land , 2000 .

[28]  S. Ledgard,et al.  Nitrogen inputs and losses from clover/grass pastures grazed by dairy cows, as affected by nitrogen fertilizer application , 1999, The Journal of Agricultural Science.

[29]  K. L. Johns,et al.  OVERSEER ® nutrient budgets – moving towards on-farm resource accounting , 2022 .

[30]  C. Nevison,et al.  Closing the global N2O budget: nitrous oxide emissions through the agricultural nitrogen cycle , 1998, Nutrient Cycling in Agroecosystems.

[31]  N. Bolan,et al.  Leaching losses of major nutrients from a mole-drained soil under pasture , 1991 .

[32]  E. A. Garwood,et al.  Nitrate leaching from grazed grassland lysimeters: effects of fertilizer input, field drainage, age of sward and patterns of weather , 1993 .

[33]  G. Francis,et al.  Fate of urea applied to winter spinach in New Zealand , 2003, Nutrient Cycling in Agroecosystems.

[34]  D. Powlson,et al.  The nitrogen cycle in the Broadbalk Wheat Experiment: recovery and losses of 15N-labelled fertilizer applied in spring and inputs of nitrogen from the atmosphere , 1986, The Journal of Agricultural Science.

[35]  P. Ball,et al.  Impacts of management on leaching of nitrate from pastures , 1990 .

[36]  M. G. Lambert,et al.  Losses of nitrogen phosphorus, and sediment in runoff from hill country under different fertiliser and grazing management regimes , 1985 .