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Estimate nitrate leaching, topsoil denitrification and indirect N2O.

Source: R/n_balance_losses.R
calculate_n_leaching.Rd

Two methods for partitioning a nitrogen surplus into leached nitrate and topsoil-denitrified nitrogen. "meisinger_drainage" (the default, n_fun.r:932-988) is the full Spain_Hist cascade: 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 a much simpler global fallback using the flat FracLEACH = 0.24 constant already documented in build_crop_soil_n2o_extension().

Usage

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

Arguments

x

A tibble with n_surplus_t, fert_type, climate, irrig_cat, land_use, cn_input (may be NA), tillage (checked only for synthetic rows) and som_share.

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) or "ipcc_fracleach".

example

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

Value

x with no3_n_t, denitrification_n_t, 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 (verified n_fun.r:983). 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 (n_fun.r:939,942): 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.

Examples

calculate_n_leaching(example = TRUE)
#> # A tibble: 1 × 5
#>   n_surplus_t no3_n_t denitrification_n_t n2o_indirect_no3_n_t method_leaching
#>         <dbl>   <dbl>               <dbl>                <dbl> <chr>          
#> 1         100      24                  76                0.264 ipcc_fracleach