Researchers from the Utah Agricultural Experiment Station say grazing practices in the Mountain West region may have to be modified in order to maintain the productivity of crested wheatgrass stands.
The researchers said results of a three-year study indicate that heavy grazing according to "range readiness" may be harming crested wheatgrass stands. Millions of acres of rangelands in the Intermountain West have been seeded for crested wheatgrass. The range provides forage for livestock and big game animals and helps to control erosion.According to the study, tiller (shoot) production was not reduced by grazing before mid-May. However, heavy grazing after mid-May, as allowed under many range readiness guidelines, led to a decline of tillers in crested wheatgrass stands.
Moderate grazing of crested wheatgrass after mid-May may not be detrimental if the stand is allowed to recover the following year, says range scientist James Richards.
"Crested wheatgrass stands can't be grazed heavily after mid-May year after year without a decline in tiller density."
The study by Richards and range scientist Bret Olson also examined the effects of intensive grazing systems such as short-duration grazing.
"Intensive grazing systems probably are not a feasible management alternative for livestock producers in the Intermountain region," Richards said.
"Forage or cattle production may increase slightly in the short-term, but at the expense of the long-term stability of the stand. The costs of implementing and managing an intensive system would probably not be offset by the slight increases in production, unless the systems could be used for longer periods of the year instead of seasonally. The spring growing season is just too short and variable."
In previous studies, UAES researchers found that crested wheat-grass is superior to native perennial grasses in its ability to produce tillers after spring grazing. This tillering ability means that the native grazing-sensitive wheatgrass should be grazed before crested wheatgrass, reversing the grazing sequence now used by many ranchers.
Richards said only moderate grazing of crested wheatgrass should be allowed or less intensive grazing following a year of heavy spring grazing. He said the latest findings contradict some popular theories about the growth of perennial grasses, theories that have guided range management for years.
"The traditional range readiness rule-of-thumb says that bluebunch wheatgrass is grazed after mid-May, which damages plants more than earlier grazing. We need to re-evaluate grazing recommendations, especially for native species," he said.
Richards and Olson report their recent research results in UAES' Bulletin 516, "Grazing Effects on Crested Wheatgrass Growth and Replacement in Central Utah." Copies are available from UAES Information, USU, Logan, UT 84322-4845 for $4 plus postage.