Ag Data Commons
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Grass-Cast Database - Data on aboveground net primary productivity (ANPP), climate data, NDVI, and cattle weight gain for Western U.S. rangelands

posted on 2024-02-15, 22:25 authored by Chris DorichChris Dorich, Justin Derner, Greg Torell, Jerry Volesky, Jameson Brennan, David Archer, John Blair, Alan Knapp, Jesse Nippert, David Hartnett, Mitchel McClaran, Greg Maurer, Douglas Moore, Pat Clark, William Parton, Dannele Peck, Lauren Kramer, William Kolby Smith, Emile Elias, Brian Fuchs, Walter H. Schacht, John Hendrickson, Keith Harmoney, Scott Collins, Lauren Baur, Lauren Porensky, Lance Vermeire, Kevin Wilcox

Grass-Cast: Experimental Grassland Productivity Forecast for the Great Plains

Grass-Cast uses almost 40 years of historical data on weather and vegetation growth in order to project grassland productivity in the Western U.S. More details on the projection model and method can be found at

Every spring, ranchers in the drought‐prone U.S. Great Plains face the same difficult challenge—trying to estimate how much forage will be available for livestock to graze during the upcoming summer grazing season. To reduce this uncertainty in predicting forage availability, we developed an innovative new grassland productivity forecast system, named Grass‐Cast, to provide science‐informed estimates of growing season aboveground net primary production (ANPP). Grass‐Cast uses over 30 yr of historical data including weather and the satellite‐derived normalized vegetation difference index (NDVI)—combined with ecosystem modeling and seasonal precipitation forecasts—to predict if rangelands in individual counties are likely to produce below‐normal, near‐normal, or above‐normal amounts of grass biomass (lbs/ac). Grass‐Cast also provides a view of rangeland productivity in the broader region, to assist in larger‐scale decision‐making—such as where forage resources for grazing might be more plentiful if a rancher’s own region is at risk of drought. Grass‐Cast is updated approximately every two weeks from April through July. Each Grass‐Cast forecast provides three scenarios of ANPP for the upcoming growing season based on different precipitation outlooks. Near real‐time 8‐d NDVI can be used to supplement Grass‐Cast in predicting cumulative growing season NDVI and ANPP starting in mid‐April for the Southern Great Plains and mid‐May to early June for the Central and Northern Great Plains. Here, we present the scientific basis and methods for Grass‐Cast along with the county‐level production forecasts from 2017 and 2018 for ten states in the U.S. Great Plains. The correlation between early growing season forecasts and the end‐of‐growing season ANPP estimate is >50% by late May or early June. In a retrospective evaluation, we compared Grass‐Cast end‐of‐growing season ANPP results to an independent dataset and found that the two agreed 69% of the time over a 20‐yr period. Although some predictive tools exist for forecasting upcoming growing season conditions, none predict actual productivity for the entire Great Plains. The Grass‐Cast system could be adapted to predict grassland ANPP outside of the Great Plains or to predict perennial biofuel grass production.

This new experimental grassland forecast is the result of a collaboration between Colorado State University, U.S. Department of Agriculture (USDA), National Drought Mitigation Center, and the University of Arizona. Funding for this project was provided by the USDA Natural Resources Conservation Service (NRCS), USDA Agricultural Research Service (ARS), and the National Drought Mitigation Center.

Watch for updates on the Grass-Cast website or on Twitter (@PeckAgEc). Project Contact: Dannele Peck, Director of the USDA Northern Plains Climate Hub, at or 970-744-9043.

Resources in this dataset:

  • Resource Title: Cattle weight gain.

    File Name: Cattle_weight_gains.xlsx

    Resource Description: Cattle weight gain data for Grass-Cast Database.

  • Resource Title: NDVI.

    File Name: NDVI.xlsx

    Resource Description: Annual NDVI growing season values for Grass-Cast sites. See readme for more information and NDVI_raw for the raw values.

  • Resource Title: NDVI_raw .

    File Name: NDVI_raw.xlsx

    Resource Description: Raw bimonthly NDVI values for Grass-Cast sites.

  • Resource Title: ANPP.

    File Name: ANPP.xlsx

    Resource Description: Dataset for annual aboveground net primary productivity (ANPP). Excel sheet is broken into two tabs, 1) 'readme' describing the data, 2) 'ANPP' with the actual data.

  • Resource Title: Grass-Cast_sitelist .

    File Name: Grass-Cast_sitelist.xlsx

    Resource Description: This provides a list of sites-studies that are currently incorporated into the Database as well as meta-data and contact info associated with the data sets. Includes a 'readme' tab and 'sitelist' tab.

  • Resource Title: Grass-Cast_AgDataCommons_overview.

    File Name: Grass-Cast_AgDataCommons_download.html

    Resource Description: Html document that shows database overview information. This document provides a glimpse of the data tables available within the data resource as well as respective meta-data tables. The R script (R markdown, .Rmd format) that generates the html file, and can be used to upload the Grass-Cast associated Ag Data Commons data files can be downloaded at the 'Grass-Cast R script' zip folder. The Grass-Cast files still need to be locally downloaded before use, but we are looking to make a download automated.

  • Resource Title: Grass-Cast R script .

    File Name:

    Resource Description: R script (in Rmarkdown [Rmd] format) for uploading and looking at Grass-Cast data.


USDA-ARS: 58-3012-7-009



Data contact name

Dorich, Chris

Data contact email


Ag Data Commons

Intended use

See Every spring, ranchers in the drought‐prone U.S. Great Plains face the same difficult challenge—trying to estimate how much forage will be available for livestock to graze during the upcoming summer grazing season. This database combines historical data including grass ANPP production, cattle weight gain data, satellite‐derived normalized vegetation difference index (NDVI), and potentially weather and simulations and simulation models down the road. The database provides the data necessary for model Grass-Cast model calibration, but can also be used for various other projects looking at ANPP production across western rangelands. Please let us know what kind of projects you are working on.

Use limitations

Measuring ANPP (annual aboveground net primary productivity) on grasslands is a difficult task (e.g., estimating removal by grazing, measurement of standing dead with live biomass, time of measurement, etc) with variable methods used across data sets. We therefore encourage reaching out to data providers for clarity on methods and suggestions of use when possible. Disclaimers: As with any forecast, Grass-Cast’s accuracy depends on how far into the future we try to look, according to ARS economist Dannele Peck, Director of the USDA Northern Plains Climate Hub. Its accuracy improves with time as the growing season unfolds, so it should be consulted more than just once during the growing season. Grass-Cast is updated every two weeks to incorporate newly observed weather data and emerging trends in the forecast, such as the flash drought in the western Dakotas and eastern Montana in 2017. It should be noted that Grass-Cast cannot tell the difference between desirable forage species and undesirable species. So it is important for producers to know what proportion of a pasture is occupied by weeds, and how well those weeds respond to rain (or lack of rain) compared to the desirable species. Producers should monitor these different vegetation types to see if one is responding to the weather better than the other. Furthermore, Grass-Cast does not directly account for local management practices, such as grazing intensity in previous years. Producers should therefore adjust Grass-Cast’s grid-level productivity estimates accordingly. Producers should not rely on Grass-Cast as a sole source for making management decisions. Similarly, public land managers should not use Grass-Cast as a sole source of information for setting stocking rates, determining turnout dates, or other aspects of lease agreements, allotments or permits.

Temporal Extent Start Date


Temporal Extent End Date



  • irregular


  • Not specified

Geographic Coverage


Geographic location - description

Western U.S. Rangelands

ISO Topic Category

  • climatologyMeteorologyAtmosphere
  • environment
  • farming

Ag Data Commons Group

  • Long-Term Livestock Production

National Agricultural Library Thesaurus terms

databases; net primary productivity; meteorological data; normalized difference vegetation index; cattle; weight gain; grasslands; Great Plains region; data collection; models; spring; ranchers; forage; grazing; summer; uncertainty; prediction; growing season; ecosystems; rangelands; grasses; biomass; decision making; risk; drought; retrospective studies; biofuels; Colorado; USDA; Arizona; evapotranspiration; adaptive management

OMB Bureau Code

  • 005:18 - Agricultural Research Service
  • 005:53 - Natural Resources Conservation Service

OMB Program Code

  • 005:040 - National Research

Primary article PubAg Handle

Pending citation

  • No

Public Access Level

  • Public

Preferred dataset citation

Dorich, Christopher D.; Derner, Justin; Torell, Greg; Volesky, Jerry; Brennan, Jameson; Archer, David; Blair, John; Knapp, Alan; Nippert, Jesse; Hartnett, David; McClaran, Mitchel; Maurer, Greg; Moore, Douglas; Clark, Pat; Parton, William; Peck, Dannele; Kramer, Lauren; Smith, William Kolby; Elias, Emile; Fuchs, Brian; Schacht, Walter H.; Hendrickson, John; Harmoney, Keith; Collins, Scott; Baur, Lauren; Porensky, Lauren; Vermeire, Lance; Wilcox, Kevin (2021). Grass-Cast Database - Data on aboveground net primary productivity (ANPP), climate data, NDVI, and cattle weight gain for Western U.S. rangelands. Ag Data Commons.