Residual Dry Matter

Residual Dry Matter (RDM) is herbaceous plant material left standing or on the ground at the beginning of a new growing season. It indicates the combined effects of the previous season’s forage production, breakdown over summer, and its consumption by grazing animals of all types. If properly managed it can provide soil protection, fire prevention, and perennial grass restoration.

Estimating residual dry matter enables ranchers more flexibility to use livestock as a tool to protect soil and limit wildfire. It helps identify how much grass is being utilized by current grazing practices and allowing for adjustments in those practices. Applications of having RDM maps informs decisions such as:

•Water Development placement.

•Decreasing Stocking Rate in Low RDM Years.

•Increasing Stocking Rate in High RDM Years.

• Identifying Target Areas of High RDM for Fire Breaks.

RDM Field Collection

Once an RDM model is built for an area, we have automated the process so that accurate RDM estimates can be cheaply created with the click of a button once additional imagery becomes available (every 16 days). This allows for managers to access rapid change detection information so treatments can be assessed in a timely manor. The 2018 map on the left above was created from on-the-ground training points gathered in 2018. The 2015 map on the right above was created by applying the 2018 model to 2015 imagery that was radiometrically and image to image normalized to the 2018 image. The results were compared to independent on-the-ground measurements. The predicted were plotted against the measured and the accuracy was reported as an R^2 value of 0.72. From a management standpoint grazing resulted in better RDM management in 2018. This is indicated by less low RDM (red color) and less high RDM (blue color) in the 2018 map.

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