Submitted to: Society for Range Management Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 11/1/2002
Publication Date: 2/1/2003
Citation: HEITSCHMIDT, R.K., HAFERKAMP, M.R., KLEMENT, K.D. GRAZING AND DROUGHT: EFFECTS ON QUANTITY OF FORAGE PRODUCED. SOCIETY FOR RANGE MANAGEMENT MEETING ABSTRACTS. 2003. ABSTRACT #107. Interpretive Summary:
Technical Abstract: Drought is a common feature of rangeland environments. A basic question facing rangeland managers is how to manage grazing animals during drought. The objectives of this research were to examine the impacts of grazing during and after spring drought on herbage growth dynamics and forage production. Experiment was conducted on the USDA-ARS, LARRL in Miles City, Montana from 1998 through 2001. A simulated drought was imposed from early April to late June for two years (i.e., 1998-99). Sheep were used to graze the plots in early May, June, and July of 1998, 1999, and 2000. Three grazing treatments and two drought treatments were imposed. Grazing treatments were: 1) graze both the years of and the years after drought; 2) graze during the years of drought, rest the year after; and 3) rest both the years of and the years after drought. These same treatments were repeated on non-drought plots. Herbage growth dynamics and forage production were estimated, in both studies, by frequent harvesting of standing crop. The year of the imposed drought (i.e., 1998) precipitation was below normal. Thus, the imposed drought of 1998 only reduced total forage production about 20% as compared to 1999 when the second year of spring drought reduced production about 40%. The principal species group responsible for the 1998 decline was cool-season perennial grasses whereas the 1999 decline was from both cool- and warm-season perennial grass production. However, the effects of the 1998 and 1999 droughts were not apparent in either 2000 or 2001 when averaged across grazing treatments. Grazing treatments did clearly impact forage production estimates during drought. In 1998, total forage production was greater with than without grazing largely because of increased cool-season perennial grass production. The effects of grazing on total forage production were less clear in 1999 with production in the ungrazed treatment (i.e., 1683 lbs/ac) intermediate to the two grazed treatments (i.e., 1,423 and 1,844 lbs/ac). However, grazing enhanced warm-season grass production (i.e., 352 vs. 140 lbs/ac) and depressed cool-season perennial grass production (595 vs. 958 lbs/ac). This trend was carried over to 2000 but had completely disappeared by 2001. Both time and amount of precipitation have major implications to forage dynamics. Understanding the interactions of grazing and precipitation are critical to proper management of Northern Great Plains rangelands.