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Estimate ammonia-N volatilisation with the MANNER process-based model.

Source: R/manner_model.R
calculate_manner_nh3.Rd

Ports the MANNER (Nicholson et al. 2013) process-based ammonia volatilisation model. Dispatches on fertiliser to one of two independent paths: a synthetic-fertiliser path ("Urea", "AN", "CAN", "AS") driven by soil pH, application rate, rainfall and temperature, and an organic-manure path ("cattle_slurry", "pig_slurry", "FYM", "poultry_manure", "urban") driven by rainfall, temperature, wind speed, application technique, system (arable/grassland) and incorporation delay.

Usage

calculate_manner_nh3(
  n_applied_t = NULL,
  fertiliser = NULL,
  drivers = list(),
  example = FALSE,
  temp_method = c("misselbrook_2004", "source_port")
)

Arguments

n_applied_t

Numeric, nitrogen applied (t).

fertiliser

One of "Urea", "AN", "CAN", "AS" (synthetic path) or "cattle_slurry", "pig_slurry", "FYM", "poultry_manure", "urban" (organic path).

drivers

A named list of driver values. Synthetic path: soil_ph (numeric soil pH), rate_kg_ha (numeric N application rate, kg N/ha), rainfall_mm (numeric period precipitation, mm), irrigated (logical), temp_c (numeric application-period temperature, deg C), temp_c_annual_mean (numeric annual mean temperature, deg C; not used for Urea). Organic path: rainfall_mm, irrigated, windspeed_ms (numeric wind speed, m/s), technique (one of the six manner_params technique keys), system ("Arable" or "Grassland"), temp_c, incorporation_delay_h (numeric hours between surface application and soil incorporation, or Inf/NA for no incorporation), species (optional; one of the eight manure_inorganic_n species, used only to look up inorganic_n_fraction; when omitted it falls back to the manure type's default species, and it is ignored entirely for "urban").

example

If TRUE, return a small fixture instead of computing from drivers. Defaults to FALSE.

temp_method

Synthetic path only: which temperature-equation form AN and AS use, "misselbrook_2004" (default) or "source_port". See Details.

Value

A tibble with n_applied_t, ef (realised emission factor), nh3_n_t and method_manner. The synthetic path also returns method_manner_temp, the temp_method used.

Details

The organic path's inorganic_n_fraction lookup (manure_inorganic_n) maps manure_type to its ammoniacal manure_stream ("Liquid" for "cattle_slurry"/"pig_slurry", "Solid" for "FYM"/"poultry_manure") and reads that stream's fraction for the actual species driver supplied by the caller. This matches the source implementation, which maps every species' solid stream to the FYM MANNER class yet looks the inorganic-N fraction up per real species. When species is omitted it falls back to the manure type's default species (Cattle for "cattle_slurry"/"FYM", Pigs for "pig_slurry", Poultry for "poultry_manure"). "urban" bypasses this lookup entirely: it fixes inorganic_n_fraction = 0.5 regardless of species, matching the source implementation. For the AG availability and incorporation factors, "urban" maps to the FYM manure class, as the source coefficient table does, including the 0.4 Org_ef correction.

The synthetic path's temperature factor (Misselbrook et al. 2004, doi:10.1079/SUM2004280) is an exponential scaled on UK monthly temperatures. It is capped at 1, as the UK ammonia inventory that runs this model caps it (Misselbrook et al. 2015, Inventory of Ammonia Emissions from UK Agriculture 2014). Without the cap, warm application months returned emission factors above 1. With it, ef never exceeds the fertiliser's max_nh3 in manner_params.

Two forms of that factor exist. Urea always takes the absolute form, exp(0.1386 (temp_c - 8.4)) / 3; CAN always takes the anomaly form, exp(0.2197225 (temp_c - temp_c_annual_mean)) / 3. AN and AS depend on temp_method:

  • "misselbrook_2004" (default): AN takes the anomaly form on every soil, and AS takes the anomaly form on non-calcareous soils and the absolute form on calcareous soils (soil_ph > 7). This is the assignment of Misselbrook et al. (2004, p. 367): eq. 3 (anomaly) "for AN and other N to all soils and AS/DAP to non-calcareous soils", eq. 4 (absolute) "for urea and UAN to all soils and AS/DAP to calcareous soils". The UK inventory agrees for AS, which it treats on calcareous soils "as for urea" (Misselbrook et al. 2015, notes to Table A11).

  • "source_port": the forms of the regional implementation this model was ported from. AN takes the absolute form, and AS takes the anomaly form on every soil.

Examples

calculate_manner_nh3(example = TRUE)
#> # A tibble: 1 × 4
#>   n_applied_t     ef nh3_n_t method_manner        
#>         <dbl>  <dbl>   <dbl> <chr>                
#> 1          10 0.0333   0.333 manner_synthetic_Urea