EFFECTS OF DORMANT SEASON GRAZING ON HERBAGE PRODUCTION AND PLANT GROWTH. Sciences Department, NDSU, Fargo. NDSU, Hettinger, ND

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1 EFFECTS OF DORMANT SEASON GRAZING ON HERBAGE PRODUCTION AND PLANT GROWTH Kristy-Lyne Nelson 1, Kevin Sedivec 1, Jckie Olson 2, Mitch Fulkner 3, Tim Fller 4, Christopher Schuer 4 1 Grdute Student, Stte Extension Rngelnd Specilist, Animl nd Rnge Sciences Deprtment, NDSU, Frgo 2 Assistnt Professor of Agriculture, Dickinson Stte University, Dickinson, ND 3 Rnge Specilist, Nturl Resource Conservtion Service, Lincoln, NE 4 Director, nd Post-Doc Reserch Associte, Hettinger Reserch Extension Center, NDSU, Hettinger, ND Impct Sttement Preliminry dt indicted tht rief erly summer use of dormnt-seson pstures nd winter stocking rtes intended to chieve 5% utiliztion of stnding oveground iomss or 5% winter utiliztion of stnding oveground iomss hs similr or positive impcts on forge production nd plnt growth thn sesonlong grzing or 3% winter utiliztion with no summer use. Introduction Winter, or dormnt-seson grzing, is prcticed y mny North nd South Dkot livestock producers in n effort to lower winter feed costs. Dormnt-seson grzing, while not n exclusive winter-grzing period, is defined s grzing during tht time period etween plnt quiescence in lte fll nd green up in erly spring. Although dequte informtion exists regrding nutritionl mngement of winter grzing cttle, little is known out the ecologicl effects of these prctices on rnge or psture lnd in the upper Midwest nd northern Gret Plins. Furthermore, reserch emphsizing inferences for specific winter-grzing mngement is lcking. Vrious spects of dormnt-seson grzing hve een exmined in vriety of ecosystem types, nd conventionl wisdom dicttes tht defolition during winter months while plnts re dormnt hs little to no effect on plnt vigor (Riesterer et l. 2). Vllentine (21) stted tht determining when to hrvest stnding forge is dependent on plnt fctors, physicl site fctors, niml fctors, nd economic nd mngement fctors. Determining the effectiveness nd prcticlity of dormnt-seson grzing requires ssessing mngement prctices to ddress these four points. Reserch is undnt regrding the effects of grzing nd clipping on rngelnd condition nd productivity, niml production, nd economics during the growing seson, yet insufficient informtion exists regrding the effects of such prctices during the dormnt seson. Furthermore, with the implementtion of new grzing mngement techniques tht include seson-of-use chnges, differences in economic return, plnt growth nd vigor, nd susequent plnt-species composition cn e expected.

2 Winter grzing is n ppeling mngement option to mny rnchers. Producing hy or purchsing winter feeds is lor nd cpitl intensive, while winter grzing offers the potentil for flexiility in mking mngement decisions. Furthermore, this prctice llows for more efficient utiliztion of rnge resources. The ojectives of this study were to determine the impcts of winter grzing on herge production, growth rte of dominnt grss species (short-term), nd chnges in plnt species composition using vrious levels nd comintions of winter nd summer use (long-term susequent reserch). Study Are This study ws locted in Adms County, North Dkot nd Perkins County, South Dkot. The Adms County study site ws pproximtely 62 h nd locted 8 km southwest of Hettinger, North Dkot (El. 817m) on sections 16, T129N, R96W nd 25, R97W, T129N. The Perkins County study site ws pproximtely 58 h nd locted 25 km south of Lodgepole, South Dkot (El. 83m) on sections 13, T19N, R12E, nd 18, T19N, R13E. Climte Western North nd South Dkot re chrcterized y continentl, cool temperte, semi-rid climte with wrm summers nd cold winters. Averge nnul precipittion is out 41 cm/yr ner Hettinger, North Dkot nd Lodgepole, South Dkot (Oweny nd Enzell 1992). Approximtely 7% of the precipittion t oth loctions occurs during the growing seson occurring from April through erly Octoer. The study loctions receive frost-free d/yr (Omodt et l. 1968) with the wrmest month, July, verging 22º Celsius. Jnury is the coldest month with n verge temperture of 8º Celsius (Owensy nd Ezell 1992). Growing-seson precipittion ws 28.6 cm in 2, which ws 7.6 cm elow the nnul verge, with ll months except My nd July elow verge during the growing seson. The 21 growing seson ws chrcterized s dry spring nd wet July, with verge precipittion 4. cm elow the 3-yer verge. The fll nd winter of 2-1 received ove verge precipittion, however the fll nd winter of 21-2 received considerly less precipittion, prticulrly in Novemer nd Decemer. In 22, growing-seson precipittion ws cm, which ws 2.42 cm elow the nnul verge. All growing seson months were elow verge. Less-thn-verge precipittion ws received in Novemer nd Decemer of 22. Growing-seson precipittion received in 23 ws 6.68 cm elow the 3-yer verge, with only the months of My nd Septemer receiving ove verge precipittion during the growing seson. During the 24 growing seson, precipittion ws 11.6 cm elow the 3-yer verge. Only the months of July md Octoer were ove verge precipittion. Monthly verge tempertures were generlly ove the 3-yer verge in 2, with the exception of June, Novemer, nd Decemer. Wrmer-thn-verge tempertures chrcterized the winter of 21-22, s Novemer nd Decemer 21 nd Jnury nd Ferury 22 were sustntilly wrmer thn the 3-yer verge. The winter of lso hd wrmer-thn-verge tempertures compred to the 3-yer verge.

3 Spring nd summer tempertures were ner verge for ll four yers. The winter of 23-24, nd the 24 growing seson were chrcterized y wrmer thn verge tempertures. Vegettion The study res were found in the northern mixed-grss pririe nd descried s the Missouri Slope Vegettion Zone (SCS 1984). The plnt communities re descried s whetgrss-needlegrss vegettion type (Brker nd Whitmn 1994). Dominnt midgrss species were western whetgrss nd needle-nd-thred (Stip comt Trin. & Rupr.), nd dominnt short grminoid species were thred-lef sedge (Crex filfoli Nutt.) nd lue grm (Boutelou grcilis; Brker nd Whitmn 1994; Shiflet 1994). Plnt nmes were referenced from McGregor et l. (1986) nd USDA-USFS (22). Uplnds of the study res were represented y shllow ecologicl sites. The soils were modertely corse to modertely fine textured with restricting lyers of shles nd sndstone occurring t depths of 25 to 5 cm elow the soil surfce. This site is comprised of uplnd sedges (Crex spp.), little luestem, lue grm, pririe sndreed (Clmovilf longifoli (Hook.) Scrin. ), western whetgrss, pririe junegrss, fringed sgewort, nd numerous uplnd for species. Averge totl primry production on shllow ecologicl sites in the Dkots vries from 1,35 to 2, kg/h (Sedivec et l. 1991). Midlnd sites on the North nd South Dkot study res were comprised of lomy ecologicl site with well-drined, modertely deep nd medium to fine textured soils. Plnt communites were comprised of western whetgrss, needle-nd-thred, lue grm, Kentucky luegrss (Po prtensis L.), pririe junegrss, chetgrss (Bromus tectorum L.), uplnd sedges (Crex spp.), green needlegrss (Stip viridul Trin.) nd numerous for species. Averge totl primry production on these sites rnge from 1,7 to 3,15 kg/h (Sedivec et l. 1991). Mterils nd Methods Tretments: Two study res (locks) were selected in North nd South Dkot sed on similr rnge condition nd ntive plnt species composition. Ech study re ws locked nd divided into four pddocks with one of four tretments 1) 5% summerutiliztion (seson-long control; SL), 2) 25% summer use for 2 weeks in erly nd mid June nd 5% dormnt-seson utiliztion [flsh grzing (Hrt 21); FL], 3) 3% dormnt-seson utiliztion (DS 3), nd 4) 5% dormnt-seson utiliztion (DS 5) ssigned rndomly to pddock within lock. The SL tretment ws 32 h pddock nd the dormnt-seson-use tretments were ech 9 h pddocks in North Dkot. The South Dkot DS 3 nd SL tretment pddocks ech 12 h; the FL tretment ws 15 h; nd the DS 5 tretment ws 19 h. Stocking Rtes: Stocking rtes for the summer-use tretments were determined using the United Sttes Deprtment of Agriculture (USDA) Nturl Resource Conservtion Service (NRCS) Technicl Guide (21) for the Missouri Slope Vegettion Zone. Summer use pddocks were surveyed for ecologicl site composition using the USDA SCS soil

4 surveys for Adms County, North Dkot (Ulmer 1987) nd Perkins County, South Dkot. (Wiesner 198). The stocking rte for the seson-long grzing tretment ws clculted for 4-month grzing period eginning June 1 nd ending Octoer 1. The North Dkot site ws stocked t.76 h/aum with ten 544 kg cows nd their clves. The South Dkot site ws stocked t.63 h/aum with seven 28 kg spyed heifers (Tle 3). Summer use of the flsh grzing pddocks ws trgeted for 25% utiliztion. The summer-use FL tretment grzing crrying cpcities were clculted y stocking for 5% use of the totl ville AUMs in June while considering tht 5% of the totl nnul production occurred y mid June, thus chieving 25% utiliztion of totl nnul iomss. The North nd South Dkot sites were stocked with ten nd sixteen 544 kg cows nd clves or 1.78 h/aum nd 1.69 h/aum, respectively, for two weeks. Stocking rtes for the winter grzing tretments were clculted fter determining drystnding plnt iomss on 15 Nov. 2. Ten rndomly plced.25m 2 frmes were clipped for ech ecologicl site (n=2) existing within given replicte (n=2). The USDA SCS (Wiesner 198, Ulmer 1987) soil survey mps nd technicl guides were used to estimte ecologicl site composition within ech pddock to clculte totl stnding iomss. Finl stocking rtes for ech tretment were computed y clculting 25% grzing-use efficiency with 5% disppernce (Lycock et l. 1972, Person 1975) nd dry mtter intke for 115 l non-lctting cow using the Beef Ntionl Reserch Council (1996) for eef cttle. The North Dkot DS 5 nd FL grzing tretments were ech stocked with four 544 kg cows, or 1.23 nd 1.22 h/aum, respectively, nd the DS 3 tretment ws stocked with three 544 kg cows, or 1.64 h/aum. The DS 5 tretment ws stocked with 11 cows or 1.2 h/aum, the FL tretment stocked with 8 cows or.95 h/aum, nd the DS 3 tretment stocked with 6 cows, or 1.2 h/aum t the South Dkot site. All South Dkot tretments were stocked with cows weighing n verge of 115 l. Winter grzing cttle were llowed d liitum ccess to white slt nd trce minerls nd were supplemented with 3l/dy on n s-fed sis of 3% crude protein ll-nturl cke. During the winter grzing period of 2-21, cttle grzed s snow cover llowed for 53 dys eginning Novemer 15 on oth the North nd South Dkot study sites. During the dormnt-seson grzing period of 21-22, cttle grzed on the North Dkot site for 53 dys eginning Novemer 15. The cttle on the South Dkot site grzed for 35 dys nd niml numers were incresed to meet set stocking rte guidelines, s turn out ws delyed until Jnury 12 due to mechnicl filures ffecting the wtering system. Cttle were llowed to grze t oth the North Dkot nd South Dkot sites for 53 dys eginning on Novemer 15 during the nd winter grzing period. Tle 1 reports h/aum comprisons of tretments nd percent reduction in crrying cpcities compred to the SL tretment (control). From perspective of utilized AUMs, the dormnt seson only grzing tretments hd reduced crrying cpcities reltive to seson-long use, however, the FL tretment numericlly incresed crrying cpcities slightly reltive to seson-long use (3.2 to 5.3%).

5 Tle 1. Stocking rte comprisons mong grzing tretments in North nd South Dkot. SL FL DS 3 DS 5 N.D. H/AUM % Difference from SL S.D. H/AUM % Difference from SL SL = seson-long summer grzing, FL = 25% summer use for 2 weeks in erly nd mid June nd 5% dormnt seson utiliztion, DS3 = 3% dormnt seson utiliztion, DS5 = 5% dormnt seson utiliztion Herge Disppernce: The degree of disppernce of grminoids nd fors for ech tretment ws determined using pired-plot clipping technique (Milner nd Hughs 1968). Twenty cges were distriuted in ech psture during the tretment period. One plot within nd outside ech cge ws clipped using.25m 2 qudrt. Clipped herge ws seprted into grsses nd fors, dry mtter weights recorded, nd kg/h plnt iomss nd stndrd error of the men clculted for ech ecologicl site. Percent utiliztion nd stndrd errors of the men were clculted for grminoids nd fors comined nd grminoids lone. In the summer through winter periods of 2-21, 5 cges were systemticlly plced on ech of the 2 shllow ecologicl sites nd 2 lomy ecologicl sites efore grzing egn on ech tretment (n=2), with the exception of the South Dkot 3% tretment where only 5 cges were plced on shllow ecologicl site since this site mde up only 1% of the study re on the tretment. During the winter of 21 on the North Dkot sites, 5 plots were clipped for oth the lomy nd shllow ecologicl sites on the 3% tretment, 5 shllow plots were clipped on the 5% tretment, nd no plots were clipped on the FL tretment due to ice nd snow cover. On the summer tretments of 21, the 2 sites within ech psture selected for the tiller study were used to determine utiliztion. In 21-22, 22-23, nd ll plots from the winter grzing tretments were clipped since ice nd snow cover did not prevent clipping s it hd in In My 24, 3 cges were distriuted evenly cross the entire psture, regrdless of ecologicl differences. This creted more representtive smpling of the pstures. Lef Heights: A study exmining lef heights throughout the growing seson ws initited in My of 21 to determine the growth ptterns of western whetgrss, needlend-thred, thred-lef sedge, nd lue grm within ech tretment. The species were selected s they were descried s the predominnt forge se of the study region (Brker nd Whitmn 1994, Shiflet 1994). Furthermore, these species re descried s

6 commonly existing together in vrious successionl stges of rngelnd in western North Dkot (Hnsen nd Hoffmn 1988). Goetz (1963) monitored the growth nd development of ntive rnge plnts in western North Dkot nd used lef height s min indictor of plnt growth. Furthermore, reserchers hve correlted lef nd plnt height with plnt vigor, forge yield, competition, rnge condition nd trend, nd defolition levels (Short nd Woolfolk 1956, Buwi nd Trlic 1977). Twenty loctions indictive of the dominnt forge se were selected rndomly within ech tretment in My 21. On ech loction,.25 m 2 qudrt ws selected contining t lest 1 western whetgrss tillers, 5 needle-nd-thred tillers, 1 thred-lef sedge tillers, nd1 lue grm tillers. Cool-seson tillers were mrked with uniquely-colored rings upon the selection of ech site in mid My nd ech tiller mesured monthly until senescence ws oserved for ech species. Western whetgrss nd needle-nd-thred tillers were mesured mid monthly for lef height (height of tllest lef) from My to August. Thred-lef sedge ws mesured mid monthly for lef height from My to July. Blue grm ws the only wrm-seson grss investigted for growth, thus lef heights were mesured mid monthly during its growth period s descried y Goetz (1964), from June to Septemer. Needle-nd-thred nd thred-lef sedge were not mesured in 22 nd 23 to improve rndom distriution of the plots throughout the four tretments. Thirty loctions were selected in My 24 within ech tretment. On ech loction,.25 m 2 qudrt ws selected contining 1 western whetgrss tillers (cool seson) nd 1 lue grm tillers (wrm seson). Tillers were mrked with uniquely colored rings nd mesured monthly until senescence. Western whetgrss ws mesured from My until August nd lue grm ws mesured from June until Septemer. A generl liner model (GLM) ws used to test for etween-suject effects for tretmenty-dte interctions of lef heights for ech species. When interctions were detected (P.5), tretment y dte comprisons were mde using GLM model to determine differences etween tretments nd dte. When interctions were not detected, dt from ll periods nd replictes were comined nd GLM model ws used to determine differences mong tretments (P.5). Men seprtions were performed t P.5 using Tukey s Honesty Significnt Difference (HSD) procedure (Steele nd Torrie 198; SPSS 199). Results nd Discussion Herge Production: No differences in herge production were found etween loctions (P=.3). Following one yer of tretment, pek primry production on the winter-only tretments were not different (P>.5) thn the SL control tretment (Figure 1). Furthermore, herge production ws higher (P.1) on FL thn SL, DS 3, or DS 5 in 21. In 22, pek primry production on the SL control tretment ws lower (P<.5) thn FL nd DS 5. No differences (P>.5) in pek primry production were found on SL, FL, nd DS 3 following the third yer of tretment; however pek herge production ws lower (P<.5) on DS 5 compred to the other three tretments (Figure 1). In 23, pek primry production ws lower (P<.5) on DS 5 thn SL, FL, or DS

7 3. In 24, oth SL nd FL tretments hd lower (P<.5) pek herge production thn the DS 5 nd 3 tretments. On verge, full use dormnt-seson grzing tretments did not effect herge production, which corresponds with dt reported y Coughenour (1991) who found incresed nitrogen in live nd ded grsses nd fringed sgerush on winter grzed res. Increses in vrious spects of rngelnd productivity under moderte growing-seson grzing use versus light or no grzing use were reported y Mnley et l. (1995). Comprisons of grzed nd ungrzed rnge in Wyoming reveled elevted levels of C nd N in susurfce soil on grzed res. This phenomenon is ttriuted to the reduction of litter nd stnding plnt iomss s these sources immoilize significnt mount of N nd C. Furthermore, incresed niml trffic my enhnce physicl rekdown of residul plnt mteril nd soil incorportion. Likewise, Schcht et l. (1998) oserved tht mowing dormnt rnge of switchgrss, little luestem, nd ig luestem resulted in higher yield of nnul growth thn non-mowed control. Engle et l. (1998) lso reported which grzing strtegies emphsizing defolition during the dormnt seson tht decresed proility of multiple defolitions during the growing seson were less detrimentl thn those tht incresed the proility of multiple defolitions, such s the FL tretment in this study. Relevnt reserch y Auen nd Owensy (1988), Coughenour (1991); Engle et l. (1998), Schcht et l. (1998) nd Reisterer et l. (2) indicte dormnt-seson hrvesting of grsses hd little or no negtive effect on susequent herge production. kg/h f m y g m y fg m x g n x SL FL DS 3% DS 5% Tretment Figure 1. Pek herge production (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormntseson use (DS 5) in 21. Tretments with the sme letter re not significntly different (P>.5). fg Tretments with the sme letter re not significntly different (P>.5). mn Tretments with the sme letter re not significntly different (P>.5). xy Tretments with the sme letter re not significntly different (P>.5).

8 Lef Heights: No differences (P<.5) in western whetgrss lef heights were detected etween tretments for the months of My nd June 21. In July, western whetgrss lef heights in the DS 3 tretment were shorter (P<.5) thn the SL tretment nd in August oth the FL nd DS 3 tretment lef heights were shorter (P<.5) thn the SL tretment (Figure 2). Negtive effects of grzing tretment on lte growing seson plnt production were lso oserved y Trent et l. (1988). Fll grzed winter whet plnts relied on photosynthesis lter in the growing seson thn non-grzed whet plnts, s they were unle to drw from crohydrte reserves during grin filling. Similrly, Buwi nd Trlic (1977) found hevy quiescent defolition of western whetgrss reduced TNC reltive to non-defolited control. Furthermore, moderte nd hevy dormnt defolition of western whetgrss reduced oth herge yield nd plnt height when compred to the control. No difference (P<.5) in western whetgrss lef heights were detected etween tretments for the months of June nd August in 22. In My, lef heights in the SL nd DS 3 tretments were shorter (P<.5) tht the FL tretment. The lef heights in the SL tretment were shorter (P<.5) thn the DS 5 in July (Figure 3). In 23, no differences (P<.5) in western whetgrss lef heights were detected mong ny tretment within ll months (Figure 4). In 24, only July showed no differences (P<.5) in tretments for western whetgrss lef heights. In My, lef heights in the SL nd FL tretments were shorter (P<.5) thn the DS 3 nd DS 5 tretments. The lef heights in the FL tretment were shorter (P<.5) thn the DS 5 in June, nd the SL tretment lef heights shorter (P<.5) thn the DS 5 tretment in June nd August (Figure 5) SL FL DS3 DS5 5 My June July August Month Figure 2. Western whetgrss lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormnt-seson use (DS 5) in 21. Tretments with the sme letter re not significntly different within ech month (P>.5).

9 SL FL DS3 DS5 My June July August Month Figure 3. Western whetgrss lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormnt-seson use (DS 5) in 22. Tretments with the sme letter re not significntly different within ech month (P>.5). Height (cm) SL FL DS3 DS5 5 My June July August Month Figure 4. Western whetgrss lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormnt-seson use (DS 5) in 23. Tretments with the sme letter re not significntly different within ech month (P>.5).

10 Height (cm) c c SL FL DS 3 DS 5 5 My June July August Month Figure 5. Western whetgrss lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormnt-seson use (DS 5) in 24. c Tretments with the sme letter re not significntly different within ech month (P>.5). Light winter use (DS 3) resulted in shorter lef heights thn hevy winter use for needlend-thred, thred-lef sedge, nd lue grm in 21. Light winter use lso resulted in lower needle-nd-thred nd lue grm lef heights thn SL. These dt suggest incresed utiliztion during the dormnt period result in incresed herge yield the following yer. Tretment y dte interctions were not detected (P<.5) for lue grm in 21, thus monthly lef height dt were comined. However, in 22 nd 24 there were tretment y dte interctions (P<.5) in July. No tretment y dte interction ws detected (P<.5) in 23. Blue grm lef heights in 21 were not different (P<.5) etween the SL, FL, nd 5% tretments; however, the SL nd FL tretments were higher (P<.1) thn the DS 3 tretment (Figure 6). In July 22, Blue grm lef heights were shorter (P<.5) in the SL tretment thn the FL nd DS 5 tretments. No differences (P<.5) in lef heights were detected in August nd Septemer (Figure 7). There were no differences found (P<.5) in lue grm lef heights in 23 (Figure 8). In July nd Septemer 24, the SL tretment lue grm lef heights were shorter (P<.5) thn the FL, DS 3, nd DS 5 tretments. In My, the FL tretment lef heights were shorter (P<.5) thn the DS 3 nd DS 5 tretments, nd the SL tretment heights were shorter (P<.5) thn the FL tretment. In August, 24, the SL tretment ws shorter (P<.5) thn the DS 5 tretment (Figure 9).

11 SL FL DS3 DS5 Tretment Figure 6. Blue grm lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormntseson use (DS 5) in 21. Tretments with the sme letter re not significntly different (P>.5) SL FL DS3 DS5 2 July August Septemer Month Figure 7. Blue grm lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormntseson use (DS 5) in 22. Tretments with the sme letter re not significntly different (P>.5).

12 June July August Septemer Month SL FL DS3 DS5 Figure 8. Blue grm lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormntseson use (DS 5) in 23. Tretments with the sme letter re not significntly different (P>.5). Height (cm) c c c c SL FL DS 3 DS June July August Septemer Month Figure 9. Blue grm lef height (men ±S.E.) on the seson-long (SL), June flsh nd 5% dormnt-seson use (FL), 3% dormnt-seson use (DS 3), nd 5% dormntseson use (DS 5) in 24. c Tretments with the sme letter re not significntly different (P>.5).

13 These findings re consistent with the pek herge production oservtions nd studies y Coughenour (1991) nd Mnley et l. (1995) who reported positive effects on herge production with incresed levels of herge removl during the dormnt seson. If dormnt-seson defolition is not detrimentl to needle-nd-thred, lue grm, nd thred-lef sedge, removl of stnding-ded plnt mteril nd the corresponding reduction in litter on the soil surfce my e importnt to susequent herge production nd plnt growth. Removl of stnding ded plnt mteril hs een reported to elevte soil tempertures, thus ccelerting decomposition nd minerliztion in the spring. Furthermore, nutrient turnover rtes re ccelerted under grzed systems y returning minerl nitrogen to the soil in redily decomposle form, therey ypssing slower plnt litter decomposition pthwys (Coughenour 1991). Summry During the months of My through Novemer in 2, sesonl forge vilility declined considerly etween the time of pek production nd the eginning of the winter grzing seson. Considering these losses, stockpiling of forge throughout the growing seson for use in lte fll or winter results in lost herge production potentil. Furthermore, AUMs/h for winter-only grzing res were severely reduced reltive to seson-long grzing use. Incorporting rief erly-summer grzing period on winter pstures cn increse lnd use nd reduce economic loses y incresing stocking rtes (AUMS/h). From n ecologicl nd lnd-use efficiency perspective, dormnt-seson grzing system tht incorportes moderte erly summer use comined with winter stocking rtes utilizing 5% of the stnding plnt iomss or winter stocking rtes utilizing 5 % of the stnding iomss lone. These methods yielded greter herge production thn other tretments nd resulted in greter needle-nd thred nd thred-lef sedge lef heights thn the seson-long or DS 3 grzing tretments. This method reduced western whetgrss lef heights lte in the growing seson in 21, however, western whetgrss nd lue grm lef heights were not ffected in 22, 23 nd 24 compred to summer grzing lone or n increse s seen in the 24 5 % dormnt seson grzing lonr tretment. If the conclusion is mde tht dormnt-seson defolition hs little effect on these grsses, limiting litter ccumultion on stockpiled pstures y ensuring t lest moderte utiliztion (5%) of stnding plnt iomss my positively ffect susequent herge production. Furthermore, SL grzing my hve more negtive ffect on needle-nd-thred, thred-lef sedge, western whetgrss, nd lue grm growth thn winter use t higher (5%) utiliztion levels. The direct effects of dormnt-seson grzing on individul plnt species versus conventionl SL use, t present, is undistinguished in relevnt literture. This reserch indictes western whetgrss nd lue grm were generlly unffected y dormnt-seson grzing or enefitted. Literture Cited Auen, L.M. nd C.E. Owensy Effects of dormnt-seson herge removl on Flint hills rngelnd. J. Rnge Mnge. 41:

14 Brker, W.T. nd W.C. Whitmn Rngelnd cover types of the northern Gret Plins. In: Shiflets, T.N., Rngelnd cover types of the United Sttes. Soc. for Rnge Mnge., Denver, CO. 154pp. Buwi, M. nd M.J. Trlic Multiple defolition effects on herge yield, vigor, nd totl nonstructurl crohydrtes of five rnge species. J. Rnge Mnge. 3: Coughenour, M.B Biomss nd nitrogen response to grzing of uplnd steppe on Yellowstone s northern winter rnge. J. Appl. Ecol. 28: Engel, R.K., J.T. Nichols, J.L. Dodd, nd J.E. Brummer Root nd shoot responses of snd luestem to defolition. J. Rnge Mnge. 51: Goetz, H Growth nd development of ntive rnge plnts in the mixed grss pririe of western north Dkot. M.S. Thesis. North Dkot Stte Univ., Frgo. 165pp. Hnsen, P.L. nd G.R. Hoffmn The vegettion of the Grnd River/Cedr River, Sioux, nd Ashlnd Districts of the Custer Ntionl Forest: hitt type clssifiction. Gen. Tech. Rep. RM-157. Fort Collins, CO: U.S. Deprtment of Agriculture, Forest Service, Rocky Mountin Forest nd Rnge Experiment Sttion. 68p. Hrt, R.H. 21. Where the ufflo romed-or did they? Gret Plins Res. 11: Lycock, W.A., H. Buchnn, nd W.C. Krueger Three methods for determining diet, utiliztion, nd trmpling dmge on sheep rnges. J. Rnge Mnge. 25: Mnley, J.T., G.E. Schumn, J.D. Reeder, nd R.H. Hrt Rngelnd soil cron nd nitrogen responses to grzing. J. Soil nd Wter Cons. 5: McGregor, R.L., T.M. Brkley, R.E. Brooks, nd E.K. Schofield Flor of the Gret Plins. University Press of Knss. Lwrence, K.S.. Milner, C. nd R.E. Hughes Methods of the mesurement of primry production of grsslnd. Blckwell Sci. Pu. Oxford, Englnd. Ntionl Reserch Council Nutrient requirements for eef cttle (7 th ed.) Nt. Acd. of Sciences-NRC, Wshington, D.C. Omodt, H.W., G.A. Johnsgrd, D.D. Ptterson, nd O.P. Olson The mjor soils of North Dkot. Dept. of Soils, Ag. Exp. St. North Dkot Stte Univ., Frgo. Bull. No pp. Oweny, J.R. nd D.S. Ezell Monthly sttion normls of temperture, precipittion, nd heting nd cooling degree dys , North Dkot. Climtogrphy of the United Sttes No. 81. NOAA, Ntionl Climtic Dt Center. Asheville, NC. 6pp. Person, H.A Herge disppernce nd grzing cpcity determintions of southern pine luestem rnges. J. Rnge Mnge. 28: Riesterer, J.L. M.D. Csler, D.J. Undersnder, nd D.K. Coms. 2. Sesonl yield distriution of cool-seson grsses following winter defolition. Agron. J. 92: Schcht, W.H., A.J. Smrt, B.E. Anderson, L.E. Moser, nd R. Rsy Growth responses of wrm-seson tllgrsses to dormnt-seson mngement. J. Rnge Mnge. 51:

15 Sedivec, K.K., D.L. Dodds, nd D. Gult Rnge Site Identifiction. N.D. Stte Univ. Ext. Serv. Bull. R-58 (Revised). N.D. Univ. Frgo. 7 pp. Shiflet, T.N Rngelnd cover types of the United Sttes. Soc. Rnge Mnge. Denver, CO. 152 pp. Short, L.R. nd E.J. Woolfolk Plnt vigor s criterion for rnge condition. J. Rnge Mnge. 9: SPSS. 2. Sttisticl procedures for socil science. Mrketing Dept. SPSS. Inc. Chicgo, Ill. Steel, R.G.D nd J.H. Torrie Principles nd Procedures of Sttistics. (2 nd Edition), McGrw-Hill, New York Compny. New York, NY. Trent, J.D., L.L. Wllce, T.J. Svejcr, nd S. Christinsen Effects of grzing on growth, crohydrte pools, nd mycorrhize in winter whet. Cn. J. Plnt Sci. 68: Ulmer, M.G Soil survey of Adms County, North Dkot. U.S. Gov. Print Off. Wshington, D.C. 174p. United Sttes Deprtment of Agriculture Nturl Resource Conservtion Service. 21. Rnge Technicl Guidelines. Bismrck, ND. United Sttes Deprtment of Agriculture Forest Service, Rocky Mountin Reserch Sttion, Fire Sciences Lortory 22. Fire Effects Informtion System, [Online]. Aville: [22, Ferury]. Vllentine, J.F. 21. Grzing Mngement. Acdemic Press. Sn Diego, CA.. Whitmn, W.C., D.W. Bolin, E.W. Klostermn, K.D. Ford, L. Moomw, D.G. Hog, nd M.L. Buchnn Crotene, protein, nd phosphorus in grsses of western North Dkot. N.D. Agr. Exp. St. Bull. No. 37. Frgo. 55p. Wiesner, H.C Soil survey, Perkins County, South Dkot. U.S. Gov. Print Off. Wshington, D.C. 195p.