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Determining stocking rates by land mapping process

published: October 30th 2009

Land mapping of “ecosites” in pastures is helping producers determine stocking rates. This mapping process identifies potential forage production for all the individual ecosites to determine the number of acres needed to provide the nutritional requirement for a cow for a month.
    Did you know this process commonly is called acres per animal unit month (AUM) per pasture?
    The process seems complicated, but times are changing. The concept of individual ecosites within a pasture and relative productivity is very real, and according to Kris Ringwall, a beef specialist, it is time to listen up and get with the program.
    Those of us involved in beef cattle have more than likely fed beef cattle. We want to make sure we feed our cattle correctly. For those in charge of rations, the National Research Council (NRC) is referred to often.
    The NRC publication contains the nutrient requirements of beef cattle through the many stages of development. The publication also is a guide to how those requirements might be met. Most nutritional sources go to great lengths to provide the best estimate of the expected value of the cattle feed.
    For example, the NRC estimates the crude protein value of wheat straw at 3.6 percent and oat straw at 4.4 percent. Neither would meet the 7.7 percent daily protein requirement of a 1,300-pound mature cow during the last third of pregnancy. Astute cattle producers know a complete straw diet never will meet the nutritional needs of cows.
    On the other hand, crested wheatgrass hay that is cut during full bloom has an estimated 9.8 percent crude protein value and would meet the nutritional requirements of the same 1,300-pound cow. In fact, crested wheat hay generally would meet the protein nutritional requirement for mature cows, except for the high-milking cows. In that case, more protein is needed.
    One could go on regarding the nutritional needs of cattle. I prefer to return to the initial point that we can all keep learning.
    Learn we shall. Just like the world of nutrition, modern technology has documented the many acres of land we ranch. Through the U.S. Depart-ment of Agriculture’s Natural Resources Conser-vation Service (NRSC), considerable information is available on many parcels of land across the country.
    A quick click on the web at http://websoilsurvey. nrcs.usda.gov/app/ shows that "Web Soil Survey” provides soil data and information produced by the National Cooperative Soil Survey. It is operated by the USDA’s NRCS and provides access to the largest natural resource information system in the world.
    The website says, “NRCS has soil maps and data available online for more than 95 percent of the nation's counties and anticipates having 100 percent in the near future. The site is updated and maintained online as the single authoritative source of soil survey information."
    What a great asset for those who make their living off the land. However, what is more important, by learning new techniques and processes, the land we farm and ranch becomes more like the straw and crested wheatgrass hay we talked about previously.
    There are great differences on the productivity of the various ecosites within a farm or ranch. As the Dickinson Research Extension Center jumped on the learning curve, we discovered that native range pasture varies from 4.62 acres per AUM to 2.42 acres.
    Keep in mind that one AUM assumes 30 pounds of dry-matter intake being consumed daily by a 1,000-pound cow for 30.5 days. However, just as cows cannot survive on an all-straw diet, they will not survive, nor will the land, on overstocked pasture.
SLS