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MISCELLANEOUS PUBLICATION 1271, U.S. DEPARTMENT OF AGRICULTURE 



seoparius, Leptoloma cognatum, and Stipa leuco- 

 tricha Trin. & Rupr. There is an overstory of 

 Juniperus L. sp. and Quercus L. sp. There is also 

 a variety of forbs under certain weather condi- 

 tions. The average annual precipitation is 61 cm. 

 The average monthly precipitation is highest in 

 spring and fall. Midsummer can be droughty. In 

 the four-unit rotation system, each unit is grazed 

 12 months, then rested 4 months. Thus, during 

 a 4-year cycle, each unit is deferred once during 

 each of the 4-month periods. Stocking was with 

 a combination of cattle, sheep, and goats. The 

 study was initiated in 1949. After 11 years, the 

 stocking rate of the units in the deferred-rota- 

 tion system has increased 33 percent from 12.4 

 animal units/km. 2 to 16.6 animal units/km. 2 {26). 

 These units carried the increased grazing pres- 

 sure and at the same time made greater range im- 

 provement than any of the units grazed continu- 

 ously. Average annual net returns for 1959-65 

 were $1.78, $2.91, and $1.63 per ha. with con- 

 tinuous stocking at the rate of 6-, 12-, and 19- 

 animal units/km. 2 . The average net return for 

 the same period on the rotation units was $4.15/ 

 ha. {26). 



A two-unit rotation, a four-unit rotation, and 

 yearlong-continuous grazing were compared near 

 Barnhart, Tex. {17). The most abundant grasses 

 are Bvthloe dactyloides (Nutt.) Engelm., Hilaria 

 belangeri, and H. mutica (Buckl.) Benth. There 

 are also other perennial and annual grasses and 

 forbes, and an overstory of Prosopis julifora 

 (Sw.) DC. The mean annual precipitation is 

 about 46 cm. with about the same average sea- 

 sonal distribution as Sonora. The four-unit rota- 

 tion is the same as the one described by Merrill 

 {25). In the two-unit rotation, the units are alter- 

 nately grazed and deferred for 3- and 6-month 

 periods ( for example, one unit is deferred March 

 1-June 1, grazed June 1-December 1, and de- 

 ferred December 1 -March 1). During a 2-year 

 period each unit was deferred 12 months with 

 deferment during each season. All treatments 

 were stocked with cattle and sheep at 10-animal 

 units/km. 2 During 1959-65, the average annual 

 net- returns per animal unit were $30.63, $39.03, 

 and $41.71 for continuous, four-unit rotation, and 

 two-unit rotation grazing, respectively {17). 

 Huss and Allen {17) found that combination 

 use of cattle and sheep was more profitable than 



grazing either class alone. Merrill {26) also 

 found that combination grazing with cattle, 

 sheep, and goats was more profitable at Sonora 

 than using sheep alone or cattle alone. 



Southern Rolling Plains 



Fisher and Marion {6) compared rotation and 

 continuous grazing at a moderate rate at Spur, 

 Tex. The major forage species are BucKLoe dac- 

 tyloides, Hilaria mutica, and Panieum obtusum 

 (H. B v K.). The average annual precipitation is 

 54 cm. The average monthly precipitation is well 

 distributed from April-October. The remainder 

 of the year is drier. The grazing season was about 

 May 1-October 1. The rotation system consisted 

 of grazing each of three units for one month and 

 deferring it for two months for the 1942-49 

 period. Fisher and Marion {6) concluded that 

 (1) rotation grazing did not improve the vege- 

 tational composition from 1942 to 1947; (2) ro- 

 tation grazing increased differential use of Buch- 

 loe and Hilaria as the season progressed or in 

 drought, and in some instances resulted in less 

 moisture penetration on sites occupied by the 

 more desirable species; and (3) gains of yearling 

 steers grazing on the rotation units were slightly 

 lower than those grazing on the continuous units. 



Various grazing systems were compared at the 

 Texas Experimental Ranch near Throckmorton 

 during 1960-68 {20). The major plant species are 

 Stipa leucotricha, BucKloe dactyloides, Bouteloua 

 curtipendula, Prosopis julifora, and Condalia ob- 

 tusifolia (Hook.) Weberb. There is a wide variety 

 of other plants in the flora. The average annual 

 precipitation is 63 cm. There is a tendency for 

 the precipitation to be distributed in the spring 

 and fall with a slight depression in midsummer 

 and in the winter. A moderate stocking rate with 

 cows and supplemental feeding level of 0.7 kg./ 

 day of cottonseed cake during winter were used 

 in comparing grazing systems. The three systems 

 were yearling-continuous, two-unit rotation sim- 

 ilar to that studied at Barnhart, Tex., by Huss 

 and Allen {17), and a four-unit rotation similar 

 to that studied at Barnhart by Huss and Allen 

 and at Sonora by Merrill {25). Calf production 

 per animal unit averaged 200, 208, and 221 kg. 

 for the moderate continuous, two-unit rotation, 

 and four-unit rotation, respectively, for the 8 



