Welcome to torchcrop

Introduction

torchcrop is a fully differentiable reimplementation of the LINTUL-5 crop growth model (Wolf, 2012). Every step of the simulation — from sowing to harvest — produces valid torch.autograd gradients, so mechanistic crop processes can be combined seamlessly with learnable components (neural residuals, learned stress responses, parameter networks) and calibrated end-to-end with standard torch.optim optimizers.

Features

• Differentiable Lintul5 — daily forward-Euler simulation of phenology, radiation interception, photosynthesis, partitioning, leaf and root dynamics, water balance and NPK uptake, all as torch.nn.Modules.
• Batch-first — every state, parameter and driver carries a leading batch dimension [B, ...] so that many sites, years, or parameter sets can be simulated in parallel on GPU.
• Hybrid modeling hooks — drop-in NeuralResidual, LearnedStressFactor and ParameterNet modules that plug into the mechanistic pipeline.
• Smooth options — stage-based branching (DVS < 1, maturity, etc.) can be switched between hard torch.where and sigmoid blends for second-order smoothness.
• Gradient-checked primitives — differentiable AFGEN-style interpolation and soft FST helpers (LIMIT, INSW, NOTNUL) pass torch.autograd.gradcheck.

Installation

pip install torchcrop

Quickstart

import torch
import torchcrop
from torchcrop.utils.io import make_constant_weather

weather = make_constant_weather(batch_size=2, n_days=150)
model = torchcrop.Lintul5Model()
output = model(weather, start_doy=60)

print(output.yield_)        # [B] final storage-organ biomass (g m-2)
print(output.lai.shape)     # [B, T+1] LAI trajectory
print(output.dvs.shape)     # [B, T+1] development stage trajectory

Gradient-based parameter calibration

import torch.nn as nn
from torchcrop import Lintul5Model, CropParameters

crop = CropParameters().to(dtype=torch.float64)
crop.rue = nn.Parameter(torch.tensor(3.0, dtype=torch.float64))

model = Lintul5Model(crop_params=crop).double()
optimizer = torch.optim.Adam([crop.rue], lr=1e-2)

for _ in range(50):
    optimizer.zero_grad()
    out = model(weather.to(torch.float64), start_doy=60)
    loss = ((out.yield_ - observed_yield) ** 2).mean()
    loss.backward()
    optimizer.step()

Hybrid modeling

Inject a neural residual on top of the mechanistic photosynthesis output:

from torchcrop.nn import NeuralResidual

residual = NeuralResidual(input_dim=8, output_dim=1, hidden_dim=32, scale=0.1)
hybrid = torchcrop.Lintul5Model(
    residual_modules={"photosynthesis": residual},
)

All parameters — mechanistic and neural — are surfaced by hybrid.parameters() and can be optimized jointly.

Package layout

torchcrop/
├── model.py                   # Lintul5Model(nn.Module)
├── engine.py                  # SimulationEngine time-stepping loop
├── config.py                  # RunConfig
├── parameters/                # CropParameters / SoilParameters / SiteParameters
├── drivers/weather.py         # WeatherDriver [B, T, C]
├── states/model_state.py      # ModelState tensor container
├── processes/                 # Biophysical processes (astro, phenology,
│                              # irradiation, evapotranspiration, water_balance,
│                              # photosynthesis, partitioning, leaf_dynamics,
│                              # root_dynamics, nutrient_demand, stress)
├── functions/                 # Differentiable primitives (AFGEN, FST, smoothing)
├── nn/                        # NeuralResidual, LearnedStressFactor, ParameterNet
└── utils/                     # I/O, visualisation, validation helpers

Development

pytest                    # run the test suite
flake8 torchcrop tests    # lint
black torchcrop tests     # format
pre-commit run --all-files

References

• Wolf, J. (2012). User guide for LINTUL5. Wageningen UR. https://models.pps.wur.nl/lintul-5-crop-growth-simulation-model-potential-water-limited-n-limited-and-npk-limited-conditions
• WUR-AI. diffWOFOST — Differentiable WOFOST crop model. https://github.com/WUR-AI/diffWOFOST
• The SIMPLACE Java reference implementation of Lintul5 (read-only) lives under simplace/sim/components/models/lintul5/ in this repository.