it is expected that little, if any, of the potential 

 acreage will be used for grazing. Grazing use is not 

 likely because of the large annual variations in the 

 diverted acreage and because of the increased 

 demand for other uses of cropland. Thus, it is 

 expected that no more than 84 million acres of crop- 

 land will be used for pasture in future years. 



Pasture acreage. — It is possible to convert croland 

 to pasture and thereby increase the acreage and pro- 

 duction of grazed roughages from pastures. Conver- 

 sion of cropland to pasture to meet livestock feed 

 needs, however, is not feasible under the alternative 

 situations projected. Crop production must increase 

 by 50 to 97 percent to meet basic food needs during 

 the same time that Hvestock roughage production is 

 increasing. In addition, because of nonagricuhural 

 uses, less total cropland will be available. Since the 

 conversion of cropland to pastureland is not likely to 

 occur in a significant amount in the future in this 

 analysis, the pasture acreage is assumed to remain 

 constant through the 1976 to 2030 period.''^ 



Crop aftermath. — Crop aftermath is that portion 

 of the plant left in the field after the primary harvest. 

 The amount available depends on the crop, produc- 

 tion systems, and the demand for that crop rather 

 than any response to the need for livestock feed. Pro- 

 duction of hay, for example, results in considerable 

 aftermath grazing while production of corn silage 

 yields very little aftermath. At present, grazing of 

 aftermath is a common practice in many areas and 

 expansion of aftermath grazing does represent an 

 opportunity to provide additional feed as feed pro- 

 duction costs and demands for feed increase. The role 

 of aftermath grazing in production of cattle and 

 sheep is uncertain. Changes in the supply of after- 

 math available for grazing are a function of the crop- 

 producing system and is not derived by the demand 

 for grazing. Currently, an estimated 14 million 

 AUM's of grazing in the form of aftermath, or 2 per- 

 cent of all nonrange grazing, are consumed. The in- 

 creased quantity of aftermath grazing is assumed not 

 to exceed 5 percent (60 million AUM's) of nonrange 

 grazing by 2030.^9 



Increasing pasture and cropland pasture yields. — 

 Because the acreages of pasture and cropland pasture 



■"The analysis does not consider the conversion of range to 

 pasture. Increased outputs from range are considered as a function 

 of range improvements and not as a conversion to pasture. 



■" Higher estimates of aftermath grazing are available. A huge 

 quantity of roughage from corn, milo, wheat, etc., remains in the 

 fields. However, removal of this roughage requires replacement of 

 nutrients by fertilizers of increasing cost or the roughage may 

 become an energy source. Existence of these factors prompted use 

 of a conservative estimate of livestock use of crop aftermath in this 

 analysis. 



are very unlikely to increase, greater amounts of 

 roughages from nonrange sources must be achieved 

 through increased yield per acre. Increased herbage 

 yields from pasture and cropland pasture are feasible. 

 The production of dry matter on grazing lands in the 

 humid, temperate climates of the United States can 

 be increased as much as three times by improved 

 practices. ^°^' 



Increased production from grazed roughages can 

 also be achieved by better management of the live- 

 stock and livestock use of the grazing lands as well as 

 through improved quality. '2 However, all such im- 

 provements are included in this analysis as an 

 increase in dry matter per acre and, hence, as in- 

 creased animal unit months of grazing per acre. 



Cropland pasture on 84 million acres produced 385 

 million AUM's of grazing in 1976 with an average 

 yield per acre of 4.6 AUM's of grazing (table 5.14). 

 Projected increased yields per acre of 70 and 79 per- 

 cent by 2000 and 2030 are assumed. The high yield 

 level of cropland pasture, both current and projected, 

 reflects the high productive capacity of cropland rela- 

 tive to other pasture. Cropland pasture also includes 

 irrigated cropland pasture. Because of the basic 

 higher productive capacity of cropland pasture, irri- 

 gation, and the availability of the means to further 

 increase production via irrigation and fertilization, it 

 is expected that cropland pasture will yield higher 

 amounts of forage. 



Pasture is the permanent grazing area which is not 

 classified as range. Pasturelands are generally more 

 productive than range but generally less productive 

 than the croplands and the average yield per acre in 

 1976-78 was only 70 percent of the cropland pasture 

 yields. It is estimated that pasture yields could be 

 increased threefold, to over 8 AUM's of grazing per 

 acre under intensive management and fertilization. ^^ 

 This estimate is optimistic because it was estimated 

 during a period when the cost of fertilization was low. 

 Because the higher costs of energy are reflected in 

 fertilizer prices, the feasible level of fertilization will 

 be lower than previously estimated. Pasture yields are 

 expected to increase during the 1976-78 to 2030 

 period but at a slower rate than cropland pasture. 



'"Bula, R. M., U. L. Lechtenberg, D. A. Holt. Potential of 

 temperate zone cultivated forages for ruminant animal production. 

 In: Potential of the world's forages for ruminant animal produc- 

 tion. 91 p. Winrock International Livestock Research and Training 

 Center, Morrilton, Ark. p. 14, 15, and 27. September 1977. 



51 Martin, J. H., W. H. Leonard, D. L. Stamp. Principles of field 

 crop production, McMillan, N.Y. p. 272. 1976. 



" Hodgson, Harlow J. Food from plant products — forage. 

 Proceedings of Symposium on complementary roles of plant and 

 animal products in the U.S. food system. November 29-30, 1977. 

 National Academy of Sciences, Washington, D.C. p. 56-74. 1977. 



53 Hodgson, op cii. 



183 



