BackgroundKnowledge on quantity and location of grass within a ranch is of critical importance in management of rangelands for optimum productivity. Grass is harvested for winter-feed as well as grazed directly by livestock throughout the growing season. Therefore it is in the best interest of a rancher to monitor the grass growth, move cattle accordingly to prevent over-grazing, and track weed infestations.

It is also important to distinguish cured grass from new growth. The cured grass can be easily distinguished from the growing grass using remote sensed imagery because of its lower reflectance in the NIR. The rancher requested imagery for early summer to identify cured grass. Due to cloud cover problems, imagery at the appropriate time was not available. Since 2001 was very dry in Montana, the grass cured earlier than usual. As a consequence, grass was already entirely cured when the rancher received his imagery in mid-summer.

 Use of DataThough the data could not be used to identify cured grass from new growth, the image could be used for another purpose. After viewing the image, the rancher detected healthy vegetation at a time when he expected the vegetation had senesced. The healthy vegetation was weeds.

On the southern part of the pasture (left image) two areas appear with spots of intense red when it would have been cyan if only cured grass was present. A field check revealed that the non-dry vegetation was invasive weed species, primarily buckbush, wild rose and various other weeds. Using ArcView the rancher drew polygons, highlighting the two weed infested zones. He was then able to estimate the approximate acreage and percentage of the non-productive portion of his pasture.

 Economic and Environmental BenefitsConcerned by the extent of the damage and armed with exact locations of the invasive weeds, the rancher decided to implement a weed control program over these areas, starting in spring 2002. The rancher's comment was: "I have to admit I wouldn't have been convinced to start a weed control program without having the images to show me just how infested those particular pastures are." The rancher is even considering buying his own ultra light aircraft and sprayer to meet not only his own weed control needs, but also that of the other ranchers in the region.