Estimate nitrate leaching, topsoil denitrification and indirect N2O.

Two methods for partitioning a nitrogen surplus into leached nitrate and topsoil-denitrified nitrogen. "meisinger_drainage" (the default) is the full cascade of the source implementation: bins annual drainage and soil organic matter share, looks up a topsoil denitrification share from meisinger_denitrification, applies subsoil NO3 reduction (subsoil_no3_reduction) and a carbon-to-nitrogen leaching attenuation, then re-derives denitrification_n_t as the residual of n_surplus_t minus the computed no3_n_t (the raw denitrification share is only an intermediate; see Details). "ipcc_fracleach" is the IPCC 2019 Tier 1 leached fraction, keyed on moisture_regime and water_regime, with every factor read from ipcc_2019_soil_n_ef: FracLEACH-(H) is 0.24 on wet rows and on dry irrigated rows and 0 on dry rainfed rows (IPCC 2019 Refinement Vol 4 Ch 11 Section 11.2.2.2 p. 11.25: 0.24 "for wet climates or in dry climate regions where irrigation (other than drip irrigation) is used"), and EF5 is 0.011 (Table 11.3 (Updated) p. 11.26). All irrigation is treated as non-drip, since no layer says which is drip: an upper-bound assumption for dry irrigated land. On wet and dry irrigated rows the rest of the surplus is booked as denitrification_n_t, as in the Meisinger cascade. On dry rainfed rows, where FracLEACH is 0, it is booked as retained_profile_n_t, nitrogen left in the soil profile, and denitrification_n_t is 0: FracLEACH says that surplus does not leach, not that it denitrifies, and no method here estimates its fate. Each row is stamped "ipcc_fracleach_wet", "ipcc_fracleach_dry_irrigated" or "ipcc_fracleach_dry_rainfed_retained". Eq. 11.10 and Table 11.3 define FracLEACH-(H) per kg of N added (F_SN + F_ON + F_PRP + F_CR + F_SOM), so it multiplies n_input_for_n2o_t, the same input set that prices direct N2O in build_nitrogen_balance(), not the surplus. "fracleach_surplus" applies the same fractions to n_surplus_t instead, the form before whep#1535: a surplus-based deviation from the IPCC definition, kept selectable for comparison, stamped "fracleach_surplus_wet" and so on. Under every method no3_n_t + denitrification_n_t + retained_profile_n_t equals n_surplus_t.

Usage

calculate_n_leaching(
  x,
  drainage_mm = NULL,
  method = c("meisinger_drainage", "ipcc_fracleach", "fracleach_surplus"),
  example = FALSE
)

Source

IPCC (2019) 2019 Refinement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Vol 4, Ch 11, Section 11.2.2.2, p. 11.25 (FracLEACH-(H)) and Table 11.3 (Updated), p. 11.26 (EF5).

Arguments

x

A tibble with n_surplus_t. method = "meisinger_drainage" requires fert_type, climate, irrig_cat, land_use, cn_input (may be NA), tillage (checked only for synthetic rows) and som_share; method = "ipcc_fracleach" requires moisture_regime ("wet" or "dry"), on dry rows water_regime ("rainfed" or "irrigated"), and n_input_for_n2o_t, the N added in IPCC Eq. 11.10; "fracleach_surplus" requires the first two.

drainage_mm

A numeric vector aligned to x's rows giving annual drainage (mm), or a single string naming a column of x to use instead. Kept as a separate argument (rather than a static x column) because in the full pipeline it flows in from Module A's gridded water balance.

method

"meisinger_drainage" (default), "ipcc_fracleach" or "fracleach_surplus".

example

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

Value

x with no3_n_t, denitrification_n_t, retained_profile_n_t (0 under "meisinger_drainage", which books every non-leached tonne as denitrified), n2o_indirect_no3_n_t and method_leaching appended.

Details

For method = "meisinger_drainage", denitrification_n_t is computed twice: first as n_surplus_t * denit_share (the raw Meisinger share) to derive no3_n_t, then overwritten as n_surplus_t - no3_n_t, as in the source implementation. The RETURNED denitrification_n_t is this second, residual value, not the raw share product; this is a deliberate two-step sequence in the source, not a redundant computation to simplify away. Drainage and soil organic matter bins are matched with the source's strictly-open s_min < s < s_max filter: a value exactly on a shared bin edge, or outside the covered range, matches no bin and aborts via the unmatched-row check (the source drops it), rather than being pulled into an adjacent or ceiling bin.

Manure/organic rows (fert_cat == "Manure", i.e. every fert_type other than "Synthetic") always join the Meisinger table's tillage == "Not_specified" row regardless of x$tillage. Synthetic rows join on x$tillage, but only "Tillage" exists in the source's synthetic block: a synthetic row with tillage == "No_tillage" aborts.

For method = "ipcc_fracleach", a missing or invalid moisture_regime aborts as in calculate_soil_n2o(), and a dry row without a water_regime aborts (whep_missing_water_regime for an absent column, whep_water_regime_value for a missing or unknown value, naming the count): dry irrigated and dry rainfed land leach 0.24 and 0 of their surplus, so a dry row of unknown regime has no defensible fraction. Wet rows need no water_regime. "fracleach_surplus" checks the same.

Under "ipcc_fracleach" leaching is capped at n_surplus_t, so it never exceeds the nitrogen left after crop uptake. IPCC Tier 1 has no such cap; rows where it binds carry the suffix "_capped_surplus" on their stamp (e.g. "ipcc_fracleach_wet_capped_surplus"). A missing n_input_for_n2o_t column, or a missing value in it, aborts (whep_missing_n_added, whep_n_added_na): read as zero it would leach nothing while the partition still closed.

Examples

calculate_n_leaching(example = TRUE)
#> # A tibble: 1 × 8
#>   n_surplus_t moisture_regime n_input_for_n2o_t no3_n_t denitrification_n_t
#>         <dbl> <chr>                       <dbl>   <dbl>               <dbl>
#> 1          60 wet                           100      24                  36
#> # ℹ 3 more variables: retained_profile_n_t <dbl>, n2o_indirect_no3_n_t <dbl>,
#> #   method_leaching <chr>