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Build a hectare-year (land-occupation) crop land extension.

Source: R/crop_land_extension.R
build_hayr_land_extension.Rd

Per-crop land occupation in hectare-years (the LCA m2*year convention): the land-time each crop's production ties up, \(occupation_i = harvested_i \times L_i/12 + fallow_i\).

The first term is active growing occupation — harvested area times mean cycle length \(L_i\) (months, from MIRCA2000). Because it uses harvested area, a field double-cropped twice contributes both cycles, and a long-cycle perennial contributes close to a full year. The second term is the rotational fallow attributed to the crop, which occupies land the whole year while it rests.

This is "active" occupation: land is charged only while a crop is growing on it or resting in its rotation, so the national total falls below physical cropland area (which also counts off-season idle). It is distinct from, and complementary to, the physical-area extensions (build_cropgrids_land_extension()): those measure the field area each crop holds; this measures how much land-time each crop's activity occupies. Short single-cropped crops and intensively double-cropped staples occupy less land-time per hectare than long-cycle and perennial crops.

Usage

build_hayr_land_extension(
  harvested = NULL,
  fallow = NULL,
  season = NULL,
  base = c("cropgrids_fallow", "cropgrids")
)

Arguments

harvested

Tibble of harvested area with columns year, area_code, item_cbs_code, harvested_ha. If NULL, built from get_primary_production() (and reused to build the fallow term).

fallow

Tibble of attributed rotational fallow with columns year, area_code, item_cbs_code, fallow_ha. If NULL: for base = "cropgrids_fallow" it is the difference between the fallow-inclusive and cropped CROPGRIDS physical extensions; for base = "cropgrids" it is zero (growing occupation only).

season

Tibble of mean crop cycle length with columns item_cbs_code, season_months (strictly positive, unique keys). If NULL, the packaged MIRCA2000 season table is used. Crops with no season are given the median cycle length.

base

"cropgrids_fallow" (default, include rotational fallow) or "cropgrids" (growing occupation only). Recorded in method_land as <base>_hayr.

Value

A tibble with columns year, area_code, item_cbs_code, impact_u (land occupation in hectare-years), and method_land.

Examples

harvested <- tibble::tribble(
  ~year, ~area_code, ~item_cbs_code, ~harvested_ha,
  2000L, 1L, 2807L, 200, # rice, double-cropped (two harvests per field)
  2000L, 1L, 2511L, 100 # wheat, single-cropped
)
season <- tibble::tribble(
  ~item_cbs_code, ~season_months,
  2807L, 5,
  2511L, 8
)
fallow <- tibble::tribble(
  ~year, ~area_code, ~item_cbs_code, ~fallow_ha,
  2000L, 1L, 2511L, 20
)
build_hayr_land_extension(harvested, fallow, season)
#> # A tibble: 2 × 5
#>    year area_code item_cbs_code impact_u method_land          
#>   <int>     <int>         <int>    <dbl> <chr>                
#> 1  2000         1          2807     83.3 cropgrids_fallow_hayr
#> 2  2000         1          2511     86.7 cropgrids_fallow_hayr