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Crop requirement estimation

Source: R/calc_crop_N_demand.R
calc_crop_N_demand.Rd

Estimates the crop's nitrogen requirement based on unit crop absorption and expected yield, with a biological N-fixation correction for legumes.

Usage

calc_crop_N_demand(
  expected_yield_tons_ha = 10,
  crop = "Shredded corn class 700",
  apply_n_fixation = TRUE
)

Arguments

expected_yield_tons_ha

Expected crop yield in tons per hectare (t/ha).

crop

The name of the crop for which to calculate the requirement. Must be a valid value in the crop column of the uptake_table (English canonical names after NFert 0.12.0).

apply_n_fixation

Logical. If TRUE (default) the gross demand is multiplied by (1 - n_fixation_pct / 100) using NFert::crops.table. Set to FALSE to recover the pre-0.12.1 behaviour (no fixation correction).

Value

A list with N_requirement (kg/ha), units ("kg/ha") and n_fixation_pct (0-100, the fraction applied).

Details

The calculation is:


A_gross = unit crop absorption (kg N / t yield) * yield (t / ha)
A       = A_gross * (1 - n_fixation_pct / 100)

where n_fixation_pct is taken from NFert::crops.table$n_fixation_pct (0 for non-legumes, 85-100 for soybean, pea, faba bean, alfalfa, lupin, clover, etc.). Non-legume crops have n_fixation_pct = 0, so the correction is a no-op.

Note

The uptake_table should provide the unit crop absorption for the specified crop. The default table (NFert::uptake_table) may not be suitable for all regions or specific crop varieties.