AbstractsBiology & Animal Science

An experiment was conducted to determine the best method to establish subterranean clover on medusahead infested ranges in Western Oregon. Secondary objectives of this study were to determind the effects of management treatments on (a) subterranean clover density, (b) density of medusahead and other vegetation, and (c) yield of subterranean clover. Four treatments for establishing subterranean clover were compared including two seeding methods superimposed over six old treatments for controlling medusahead. The results of this experiment are as follows: Subterranean clover density was found to be significantly higher early in the season in the sod plus broadcast seeded area, in all but the chemically treated areas, when compared with the sod seeded area. The number of subterranean clover plants per square foot in May was significantly higher in the sod plus broadcast seeded areas in all but the chemical treatment. There was a great loss of subterranean clover plants in both methods of seeding from March through April; this was due to poor nodulation. Vegetation density was significantly lower in the chemical-mowed and sheep-grazed treatments in May. Medusahead density was lower in only the chemical-mowed treatment. It appears that removing the old vegetation before applying paraquat makes the chemical more effective in controlling medusahead and other vegetation. The yield of vegetation other than subterranean clover ranged from 1,871 to 2,437 pounds per acre. The yield of vegetation in the chemical-mowed and sheep-grazed treatment was significantly lower than in the mechanical and control treatment. Subterranean clover yields, which were highest in the sod plus broadcast seeded areas, ranged from 22 to 397 pounds per acre. The chemical-unmowed treatment along with a previous control treatment had the highest yield: the lowest yield was obtained in the mechanical treatment combined with a late grazed treatment. Low yields of subterranean clover were attributed to lack of nodulation which probably was caused by dessication of rhizobja prior to sowing (a 24 hour delay in broadcast inoculated seed), drying after seeding because of poor coverage in drill rows and lack of available phosphorus. In establishing subterranean clover on similar sites, reduction of vegetation would be of prime importance. Prior grazing would be beneficial as shown, but because of the unpalatable and low nutritional value of annual grasses in summer and autumn, vegetation removal might depend on use of fire or mechanical means, with or without herbicides. For stand establishment sod- seeding was more effective than broadcasting the seed. A higher rate of seeding is suggested when surface broadcasting seed onto undisturbed soil. Continued work on establishing of subterranean clover on medusahead infested sites should include the variables mentioned above.