A Method of Measuring Vigor of Range Grasses

After several years of intensive study of midwestern prairies, their degeneration under grazing was given careful consideration (Weaver and Fitzpatrick, '32, '34; Weaver and Hansen, '41). It was ascertained that the intelligent use or careless abuse of these grasslands had resulted in pastures and ranges which could logically be grouped into four classes. These were excellent, good, medium, and poor. The first consisted almost entirely of climax grasses and an abundance of nutritious forbs which, as is almost universally found, were of the highest grazing value (Bews, '29: 298). In good pastures many of these persisted, but there was a strong trend toward loss of vigor and decrease in abundance of the best grasses and forbs. About half of the vegetation consisted of the less productive Kentucky bluegrass (Poa pratensis) 2 or short grasses. In pastures of medium grade, climax grasses and the most palatable forbs had all but disappeared. Here bluegrass, blue grama (Bouteloua gracilis) or buffalo grass (Buchloe dactyloides) were the dominants. Usually bluegrass alone was in control east of the Missouri river and the short grasses westward, but in the transitional area it was not unusual for both types to occur in alternes. Poor pastures were characterized by broken cover, more or less isolated patches of bluegrass or short grasses, much bare soil or soil supporting a stand of various, mostly annual, weeds. Since the great drought, medium and poor pastures of sand dropseed (Sporobolus cryptandrus) and western wheat grass (Agropyron srnithii) also occur. Similar classification of pastures have now been made in widely separated grassland areas (Costello and Turner, '44; Humphrey and Lister, '41; Renner and Johnson, '42; and numerous mimeographed articles by U. S. Forest Service and Soil Conservation Service). Such classification is a valuable aid to the range examiner, range conservationist, or county agent in pointing out definitely to the rancher or farmer the grade and condition of his range. He then may explain how it may be kept in the excellent or good class or if degenerated to a medium or poor type how it may be brought back to its former good or excellent condition. The several characteristics or indicators of each grade of pasture are well known to range technicians. They are understandable when explained to an intelligent layman. Once comprehended, the actual present state of the pasture in relation to what it could and should be stands out clearly. This is a valuable aid in promoting proper range and pasture management. Pastures of low grade, which result from too early use, too frequent use, and too close removal of the forage (but also sometimes from continued drought), are usually by far the most abundant. The rate at which many excellent native pastures have deteriorated into poor ones is alarming. Degeneration from virgin prairie to poor pastures has repeatedly been observed to occur within a period of 3 to 4 years. Much of this overstocking and continuous grazing is unintentional on the part of the farmer or range operator, simply because he is unfamiliar with the fundamental physiological activities of plants. If the average stockman notices the "eaten out" bunches and general reduced vigor of plants at all, he thinks of it as a normal result of grazing. He does not realize that health and vigor of plants are almost synonymous with forage production. He does not know how to determine whether the vegetation will 1 Contribution from the Department of Botany, University of Nebraska, No. 151. 2Nomenclature is according to Hitchcock's Manual of the Grasses of the United States.