Cover Crop Nitrogen Calculator (CC-NCALC) API

Base URL:

https://api.covercrop-ncalc.org/

(also available at https://developapi.covercrop-ncalc.org/ for testing)

Endpoint

GET /surface

The endpoint returns nitrogen mineralization estimates based on weather, soil, and crop traits.

Parameter	Type	Units	Required	Description	Model
lat	number	degrees	✅	Latitude	both
lon	number	degrees	✅	Longitude	both
start	string	YYYY-MM-DD	✅	Start (planting) date	both
end	string	YYYY-MM-DD	❌	Termination date. Defaults to `start + 90 days`	both
n	number	%	✅	N concentration in cover crop	both
biomass	number	kg/ha	✅	Dry biomass at termination	both
lwc	number	g water/ g dry biomass	❌	Leaf water content (default: 4)	surface
carb	number	%	❌	Carbohydrate content (default: `24.7 + 10.5 * n`)	both
cell	number	%	❌	Holocellulose (default: `69 - 10.2 * n`)	both
lign	number	%	❌	Lignin (default: `100 - (carb + cell)`)	both
om	number	%	❌	Organic matter (from SSURGO if omitted)	both
bd	number	g/cm³	❌	Bulk density (from SSURGO if omitted)	both
in	number	ppm	❌	Inorganic N in soil (default: 10)	both
pmn	number	mg N/kg	❌	Potentially mineralizable N (default: 7)	both

Output Format

Default: JSON

To get CSV, add &output=csv to your request.

Notes

Any or all of the inputs may be arrays. This allows you to run multiple models together.
If multiple inputs are arrays, they must have the same length.
You can include custom parameters in your query (e.g., site=Field_A) — they will be echoed back in the output.
For future dates, soil data is based on 5-year daily averages.

Streaming Support

Use the query string stream=true to enable streaming output for large batch queries (only available on POST requests).

This can help overcome Cloudflare's ~20s timeout due to lack of output activity. However, it will not bypass Cloudflare’s total timeout limit of 100 seconds.

To avoid timeouts, you can:

Break your data into smaller batches
Add client-side retry logic for timeouts

Example GET Request

http://api.covercrop-ncalc.org/surface?start=2020-04-26&end=2020-10-22&lat=34.88689&lon=-83.41941&n=3&biomass=3000&lwc=10

Example POST Requests

Single Site


  {
    "start": "2023-10-01",
    "end": "2024-04-15",
    "lat": 35.9,
    "lon": -83.95,
    "summary": true,
    "stream": true,
    "n": [2.6],
    "biomass": [3000],
    "carb": [50],
    "cell": [45],
    "lign": [5],
    "site": ["TN_101"]
  }

Multiple Sites


  {
    "start": "2023-10-01",
    "end": "2024-04-15",
    "lat": 35.9,
    "lon": -83.95,
    "summary": true,
    "stream": true,
    "site": ["TN_101", "TN_102"],
    "n": [2.6, 3.1],
    "biomass": [3000, 1800],
    "carb": [50, 60],
    "cell": [45, 35.5],
    "lign": [5, 4.5]
  }