PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



143 



age in the summer and fall units as well as older 

 cattle. 



Lewis and others (21) compared season-long 

 grazing with ewes at three intensities with rest- 

 rotation grazing at a moderate intensity at An- 

 telope Range near Buffalo, S. Dak., for the pe- 

 riod of 1964-69. The average annual precipita- 

 tion is 34 cm., but it was above average during 

 this study period. Season of use was rotated on 

 the four rest-rotation units, and one unit was 

 rested each year. Time of ewe movement was 

 based on utilization (about 50 percent). Year 

 differences due to blizzards, spring storms, pre- 

 cipitation, and disease have contributed to a 

 greater variation in the results than the grazing 

 treatments. Contrary to results obtained during 

 a dry phase (7), ewe performance in this wet 

 phase under heavy grazing has been about equal 

 to that of ewes on lightly and moderately grazed 

 units. Rest-rotation grazing resulted in good 

 range improvement. However, ewe and lamb pro- 

 duction was lower with rotation grazing than 

 with any of the season-long treatments. Heavy 

 utilization in spots is a problem in all units. Com- 

 bination stocking with sheep and cattle may alle- 

 viate this problem. 



Southern Great Plains 



Several grazing systems were compared at the 

 Southern Great Plains Field Station near Wood- 

 ward, Okla. (24) ■ The average annual precipita- 

 tion is 58 cm., 70 percent of which occurs April- 

 September. The major plants are Artemisia fili- 

 folia Torr., Bouteloua gracilis, Sporobolus cryp- 

 tandrus (Torr.) A. Gray, Eragrostis trichodes 

 (Nutt.) Wood, Andropogon scoparius Michx., A. 

 hallii Hack.,- Panicum virgatum L., Paspalum 

 stramineum Nash, and Leptoloma cognatum 

 (Schult.) Chase. 



Continuous summer grazing (April-October) 

 was compared with three-division rotation graz- 

 ing at both heavy and moderate stocking rates 

 (23.) The steers were rotated among divisions at 

 2-month intervals in 1942 and at 1-month or 

 shorter intervals for 1943-51. Rotation grazing 

 in 1942 reduced steer gains 29 kg. per head at the 

 heavy rate and 17 kg. at the moderate rate. There 

 was no real difference between gains in the other 

 years when the rotation was shortened. The more 

 desirable tall grasses, and also some of the forbs. 



increased most under rotation grazing at both 

 rates. The less desirable Paspalum stramineum, 

 Leptoloma cognatum, and Bouteloua hirsuta Lag. 

 increased most under continuous grazing. How- 

 ever, Mcllvain and Savage (23) concluded that 

 this type of rotation could not be recommended 

 over continuous grazing as an improved manage- 

 ment practice. 



Mcllvain and Shoop (24-) concluded that the 

 following grazing systems have not proved su- 

 perior to continuous yearlong grazing at the same 

 stocking rates at Woodward: (1) summer and 

 winter grazing, (2) alternate-year grazing. (3) 

 three-unit rotations with rotations at 2-month, 

 1-month. 15-day, and 10-day intervals, (4) two- 

 unit, 6-week, one-herd rotation when grass is 

 growing, and (5) six-unit, 6-day, one-herd rota- 

 tion. They cited some major reasons for the suc- 

 cess of continuous yearlong grazing in the South- 

 ern Great Plains as (1) forage production is 

 primarily dependent upon summer rainfall — 

 and monthly forage production during the sum- 

 mer can vary from 22 to 672 kg./ha., (2) most 

 species are grazed by cattle at one time or an- 

 other; (3) many of the "increaser" species are 

 excellent grazing plants and they may be very 

 productive under certain conditions; (4) cattle 

 compete with natural losses of forages and with 

 other consumers; (5) young and regrowth for- 

 age is more palatable and more nutritious than 

 more mature forage; (6) grazed plants save soil 

 moisture for later green growth; and (7) favor- 

 able growing seasons combined with proper 

 management allow ranges to recover a desirable 

 species composition. Some additional reasons for 

 the success of yearlong-continuous grazing may 

 be (1) utilization during the growing season is 

 light, and (2) lighter stocking per unit area 

 means less soil compaction by livestock during 

 wet periods. 



Edwards Plateau 



Merrill (25) compared continuous yearlong 

 grazing at three intensities with deferred-rotation 

 grazing at a moderate rate near Sonora. Tex. 

 The major forage species is Hilaria belangeri 

 (Steud.) Nash with minor amounts of Tridens 

 pilosus (Buckl.) Hitchc. Aristida L. sp., Boute- 

 loua curtipendula (Michx.) Torr., B. hirsuta, 

 Bothriochloa saccharoides Rydb., Andropogon 



