Stephen Bramwell
Washington State University Extension
Sarah Hamman
Ecostudies Institute
Melissa Habenicht
Ecostudies Institute
Sierra Smith
Washington State University Extension
Most rangelands west of the Cascades in the Pacific Northwest occur on sites that historically supported native prairie.
For prairie habitat protection on grazed land, conservation grazing practice (CGP) recommendations are needed that improve forage composition, soil quality, and productivity.
This study assessed soil quality parameters and forage species changes in grazed and ungrazed prairie, and in response to CGPs including native forb seeding and a spring grazing deferment.
Grazing treatments (CGP versus business as usual (BAU) grazing) and site management (grazed versus ungrazed) were evaluated for their effect on summer biomass, residual stubble height, and soil quality parameters including soil bulk density, soil nutrients, and soil temperature.
Significantly different residual heights were observed between sites (grazed and ungrazed) and grazing treatments (CGP = 5.72 in, BAU = 2.00 in).
Soil temperatures were highest at ungrazed sites and lowest in grazed sites (69.5 F in ungrazed, 67.4 F in grazed BAU, and and 65.1 F grazed CGP). Summer average daily high soil temperatures were lower and July biomass productivity higher in CGP as compared to BAU plots.
No differences in soil nutrient status were observed in response to management (CGP versus BAU), but overall soil fertility was higher at grazed versus ungrazed sites.
Mean soil bulk density in CGP and BAU were 1.14 g/cm3 and 1.15 g/cm3, respectively, and were not significantly different.
Lastly, the percent cover of more palatable and more productive grass species increased from 4.5% to 10.2% in CGP plots. These findings suggest the potential for CGPs applied by ranchers and conservation land managers to improve soil quality, forage productivity and composition, and overall resiliency of grazed western Washington prairies.