Effects of Controlled Plant Spacing on Growth and Mortality of Three Range Grasses
1971
McGinnies, William J.
A new technique was devised to study effects of plant spacing on growth and morality of range grasses under semiarid conditions. Growing area per plant was controlled by establishing plants in sheetmetal pipes set vertically in the soil; the pipes restricted the plant roots to a predetermined surface area of soil. Pipes with diameters of 10.2, 15.2, 22.9, 30.5, and 45.7 cm simulated plant densities of approximately 123, 55, 24, 14, and 6 plants/m². Crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schult.), Russian wildrye (Elymus junceus Fisch.) and blue grama (Bouteloua gracilis (H.B.K.) Lag. ex Steud.) were grown in pipes for 6 years in northern Colorado. As growing space became more restricted: (a) seedstalk height decreased; (b) number of seedstalks/ plant decreased; (c) number of seedstalks/m² increased; and, (d) herbage yield/plant decreased. After 6 years, two sets of pipes of each species were dug out and the soil was washed off of the roots. As pipe diameter decreased, the root/shoot ratio increased for all species; and for crested wheatgrass and Russian wildrye, root yield/ha increased and the percentage of total root yield found in the surface 20 cm of soil increased. It was concluded that the use of sheetmetal pipes to restrict the area occupied by individual plants is a satisfactory technique for evaluating some effects of plant spacing under semiarid conditions.
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