Using Landsat and Sentinel Imagery to Monitor Alfalfa and Grass Pastures in Western Colorado

This is a Preprint and has not been peer reviewed. This is version 2 of this Preprint.


Download Preprint


Amandeep Vashisht , Stephen J Leisz


Crop phenology of alfalfa and grass pasture fields on the western slope of Colorado, USA, was tracked using an NDVI time series derived from Landsat 7 (ETM+), Landsat 8 (OLI) and Sentinel 2a MSI to obtain high temporal frequency information of crop growth stages. These perennial pastures, which occupy a majority of irrigated land in the region and typically have more than one growing/cutting cycle, are quite diverse in terms of agronomic conditions, and their growth stages do not match average reported, conventional values documented almost two decades ago. Divergence of crop growth from these conventional published values have been recognized for other crop types and regions in the past, and refinement of crop growth calendars to reflect actual regional patterns encouraged. Regional practitioners often turn to the conventional published values for guidance in crop and water management, however we document here that the conventional published values are not applicable for this study region. Besides the climatic differences due to latitudinal and elevation characteristics of the region, anthropogenic interventions like multiple cuttings or grazing in a growing season progressively compound the effect of divergence from the conventional published values in the growing season. Using the data available, we summarize regional crop growth stage lengths, which may be used as a reference in absence of real time remote sensing or other ground information. This study serves as an example of the application of a combination of freely available Landsat and Sentinel satellite data to monitor crop calendars in a region of interest, in order to enhance crop management. The results have an associated uncertainty due to limited temporal coverage of cloud-free satellite images, and will benefit from further improvements such as using increased sites, more years of data, and additional satellites (e.g., addition of Sentinel 2b) for increased temporal frequency.



Engineering, Physical Sciences and Mathematics


NDVI, Landsat, Sentinel, Crop calendar, Agricultureirrigated pastures, NDVI, increased temporal frequency, Crop growth calendar, Crop growth stage length


Published: 2021-02-10 18:43

Last Updated: 2021-02-12 02:27

Older Versions

CC BY Attribution 4.0 International

Additional Metadata

Conflict of interest statement:

Add a Comment

You must log in to post a comment.


There are no comments or no comments have been made public for this article.