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Crop-Growth Forward Model (Logistic / Expolinear Biomass)

Source: R/ode_templates.R
crop_growth_forward_model.Rd

A ready-to-use ode_forward_model() specialisation for the canonical single-state crop biomass-accumulation curve. Above-ground biomass \(B\) follows a logistic growth law $$\frac{dB}{dt} = r\,B\left(1 - \frac{B}{B_{\max}}\right),$$ the standard sigmoid description of a crop's dry-matter accumulation over a season: an early near-exponential phase at relative growth rate \(r\), decelerating to a canopy- and resource-limited ceiling \(B_{\max}\) (Goudriaan & Monteith 1990). The calibration parameters are the relative growth rate r, the asymptotic biomass b_max, and the initial biomass b0.

Usage

crop_growth_forward_model(
  times,
  solver = c("rk4", "desolve"),
  n_steps = 10L,
  ...
)

Arguments

times

Numeric vector of strictly increasing observation times (for example thermal-time or days-after-sowing), length at least two. The first entry is the initial time; biomass is reported at every later entry.

solver

Character. "rk4" (default) or "desolve", as in ode_forward_model().

n_steps

Integer. Fixed RK4 sub-steps between observation times (default 10L).

...

Further policy arguments forwarded to pesto_forward_model() via ode_forward_model() (for example on_failure, parallel, fidelity).

Value

A pesto_forward_model() S7 object with param_names c("r", "b_max", "b0") and n_obs = length(times) - 1L.

Details

The forward map integrates the logistic ODE across times and returns the modelled biomass at every time after the first – exactly the shape a destructive-harvest or remote-sensing biomass series takes, so the returned object calibrates directly against an observed biomass-over-time vector through pesto_ies_callback(). The single-state logistic form is deliberately the simplest defensible crop-growth template; richer multi-organ partitioning models compose through the same ode_forward_model() entry point by supplying a vector-valued derivs.

References

Goudriaan, J. & Monteith, J. L. (1990). A mathematical function for crop growth based on light interception and leaf area expansion. Annals of Botany, 66(6), 695–701.

See also

ode_forward_model() for the generic builder; seir_forward_model() for the compartmental epidemic template; pesto_ies_callback() for calibration.

Examples

# Simulate a biomass series at a known parameter, then recover it.
times <- seq(0, 120, by = 15)
fm <- crop_growth_forward_model(times = times)
truth <- matrix(c(0.06, 1400, 20), nrow = 1L,
                dimnames = list(NULL, c("r", "b_max", "b0")))
biomass <- as.numeric(pesto_evaluate(fm, truth))
round(biomass)
#> [1]   48  113  248  485  793 1067 1243 1331