Performing Department
PANHANDLE RES & EXTENSION CNTR
Non Technical Summary
Sandhills and mixed-grass prairies in western Nebrask and the adjoining states experienced 5 years of prolonged drought during 2000-2005.Measurable declines in forage production potential and ecological condition have occurred on rangelands throughout this vast region. Proposed studies will quantify defoliation by soil-water interactions needed to deveolp grazing management decision-support tools designed to accomplish a wide range of animal production and natural resource management objectives.
Animal Health Component
(N/A)
Research Effort Categories
Basic
15%
Applied
75%
Developmental
10%
Goals / Objectives
Objective 1:Validate integers and descriptive levels used to estimate the integrated effects of all 3 components of the Sandhills Defoliatioin Response Index System (SanDRIS),a grazing management decision-support tool. Objective 2:Determine critical levels of fall defoliation and soil water for western wheatgrass and needleandthread based on subsequent-year tiller density and herbage production on mixed-grass prairie. Objective 3:Quantify late summer through spring precipitation regime effects on net primary production of mixed-grass prairie. Objective 4:Quantify prescribed-burning by spring-grazing interaction effects on cheatgrass control and composition and/or yield of indigenous plant species on cheatgrass infested mixed-grass prairies. Objective 5:Quantify plant community and spring-soil-water effects on forb establishment and growth when wildflowers are re-introduced into existing native graminoid plant communties.
Project Methods
Objective 1:Eighteen 3.0 x 3.0-m rangeland plots with relatively uniform distribution of plant species will be permanently marked and blocked by species composition.Water will be applied to plots with passive application watering systems (PAWS)to bring the top 0.5,1.0,or 1.5m of the soil profile to field capacity in early April 2006 to initiate drought,average,and wet plant-year precipitation regimes.Ambient and wet-year main plots will not be covered during August 2005 to August 2006.drought and wet-year main plots will be watered with PAWS units at about 17 and 9-day intervals.during May though July to simulate 50% or 150%of long-term precipitation.Lawn mowers will be used to remove residual herbage to a 2-cm stubble during early April 2006 and to remove 0,40,or 80% of the current-year herbage from0.6 x 1.4-m subplots in late May,June,or July 2006.Lawn mowers will be used to harvest subsequent-year,peak standing herbage in late July 2007. Objective 2:Thirty-two 2.0 x
3.0-m plots with relatively uniform occurrance of western wheatgrass and needleandthread will be randomly assigned to treatment years,2005 or 2006.A 4x4 factorial array of treatments will replicated in consecutive years with main plots receiving 0,5,10,15,cm of supplemental water during early August and clipping treatments of 0,40,or 80% defoliation will be applied to 1.0 x 1.5-m subplots in early October. Objective 3:Precipitation regime treatments will be applied to 2.0 x 30-m plots.Thirty plots dominated by western weathgrass and 30 plots dominated by threadleaf sedge will be equally allotted to initiation years,2007 or 2008,at each of 2 ranches.Cattle will be excluded from study sites at the end of each preceding-year growing season.Rainout shelters and passive application watering systems will be used to simulate 5 precipitation rigimes,a dry fall (August-October) followed by an ambient or wet(135% of long-term average) spring (March-May),or a wet (135% of long-term average) fall
followed by a dry,ambient,or wet spring. Objective 4:Six 60 x 60-m mainplots will be marked at each of 2 locations.Half of the main plots will be randomly assigned to each initiation year,2005 or 2006.One half of each main plot will be grazed in the spring by yearling cattle.The other 30 x 60-m subplot will be nongrazed.Before grazing treatments are applied,each subplot will be divided into three 20 x 30-m sub-subplots to which fall burining (October),spring burning (late April to early May),or nonburned control will be randomly allocated. Objective 5:Heavy-wire cattle panels and wood posts will be used to construct 10 x 10-m exclosures in 4 cool-season graminoid-dominated and 4 warm-season grass dominated communities on a mixed-grass prairie sites.Cotrasting communities in the sandhills will be warm-season tallgrass dominated and warm-season shortgrass dominated.Spring mid-month applications of 5 cm of supplemental water in April and May,May only,May and June,or nonirrigated control
will be randomly allotted to four 4 x 4-m mainplots in each exclosure.Four native forb species will be randomly allotted to 4 1.0-m subplots in each mainplot.