• Blue Grama Response to Nitrogen and Clipping Under Two Soil Moisture Levels

      Reed, J. L.; Dwyer, D. D. (Society for Range Management, 1971-01-01)
      Effects of N-fertilization and clipping on production and water use of blue grama were evaluated under two soil moisture levels, field capacity and 1/5 available water. Nitrogen increased shoot production 77% on unclipped plants. Clipping decreased shoot production 287% below the control averaged across N levels. Soil moisture levels produced no differences in yields. Root weights were decreased an average of 253% below the control by clipping. No differences were observed in total water used between fertilized and unfertilized plants but clipping reduced water used by 95%. Unclipped plants fertilized with 80# N/acre used more water than unfertilized unclipped plants. The amount of water required to produce a unit of a shoot was reduced 37% when fertilized. Clipping lowered this water requirement an average of 98%. Nitrogen greatly increased seed stalk numbers and the increase in shoot production due to fertilization came primarily from increased numbers of seed stalks.
    • Cattle Utilization and Chemical Content of Winged Elm Browse

      Dalrymple, R. L.; Dwyer, D. D.; Webster, J. E. (Society for Range Management, 1965-05-01)
      Cattle browsed winged elm twigs most intensively during May 1 to late July, when the browse was succulent and higher in crude protein content. As the growing season progressed, upward trends were observed in percent dry matter, ether extract and crude fiber, while downward trends were observed in percent moisture, protein and nitrogen-free extract.
    • Clipping Height and Frequency Influence Growth Response of Nitrogen-Fertilized Blue Grama

      Bekele, E.; Pieper, R. D.; Dwyer, D. D. (Society for Range Management, 1974-07-01)
      A greenhouse study with two clipping heights (1- and 2-inch stubble heights) and two clipping frequencies (every 10 and 20 days) showed that blue grama was able to make use of nitrogen fertilizer much more efficiently when unclipped than when clipped. Both clipping heights and clipping intervals decreased shoot and root weights on fertilized plants compared to fertilized and unclipped plants. The effect of clipping on unfertilized plants was much less drastic than on fertilized plants.
    • Competition Between Forbs and Grasses

      Dwyer, D. D. (Society for Range Management, 1958-05-01)
    • Effects of One Year's Nitrogen Fertilization on Native Vegetation Under Clipping and Burning

      Gay, C. W.; Dwyer, D. D. (Society for Range Management, 1965-09-01)
      Burning and nitrogen fertilization in combination increased forage production significantly over any other treatment including fertilization alone. Forage production on plots burned and fertilized with 100 pounds of nitrogen increased forage production 59% over the control and 54% over plots unburned and treated with 100 pounds of nitrogen. Burning, fertilization, and their combination were effective in reducing forbs.
    • Fire Effects on Blue Grama-Pinyon-Juniper Rangeland in New Mexico

      Dwyer, D. D.; Pieper, R. D. (Society for Range Management, 1967-11-01)
      Study of an April 1964 fire in the blue grama-pinyon-juniper vegetation type of New Mexico showed that forage production was reduced significantly the first year on the burned area but recovered by the end of the second. Species composition of herbaceous vegetation was not significantly affected. Loss of live grass crowns was fully recovered by the second year. Litter was significantly less on the burned area all three years of the study. About 24% of the juniper and 13.5% of the pinyon pine were killed by the fire. Cholla less than one ft tall were damaged more by the fire than those 2 to 3 ft tall.
    • Forage Yield, Phenological Development, and Forage Quality of an Agropyron Repens x Agropyron spicatum Hybrid

      Perez-Trejo, F.; Dwyer, D. D.; Asay, K. H. (Society for Range Management, 1979-09-01)
      Studies were conducted to evaluate the potential of the Agropyron repens (L.) Beauv. × Agropyron spicatum (Pursh) Scrib. & Smith hybrid as a forage grass. The hybrid was compared with its parental species for phenological development, chemical composition, in vitro dry matter digestibility, and acceptance by sheep. The new species was highly productive, maintained a high nutritional value, especially in its fall regrowth, and was readily accepted by sheep. In most respects it was intermediate to its two parents. Results of these studies indicate the hybrid has potential as a forage species under certain rangeland conditions.
    • Pattern of Retrogression of Native Vegetation in North Central Oklahoma

      Sims, P. L.; Dwyer, D. D. (Society for Range Management, 1965-01-01)
      The pattern of retrogression due to grazing for native vegetation was established for the important plants of the loamy prairie range site. Total forb numbers increased as range condition declined but there were usually as many perennial forbs in high condition pastures as in low condition ones. Total available water was significantly greater in excellent condition than poor condition range.
    • Plants Emerging from Soils Under Three Range Condition Classes of Desert Grassland

      Dwyer, D. D.; V., E. A. (Society for Range Management, 1978-05-01)
      This research was conducted to determine emergence of seedlings from surface soil collected on black grama (Bouteloua eriopoda) grassland sites in good, fair, and poor condition classes. The species that emerged and their numbers were compared to the species actually found on the field locations. The following conclusions were drawn: (1) The fair condition site had more seedlings emerge than the other two and of these seedlings by far the most were grasses; (2) Mesa dropseed (Sporobolus flexuosus) was the most abundant grass species emerging from collected soil for all three condition classes, but it was much more abundant from fair condition soil; (3) Though black grama dominated the good condition range, emergence of black grama seedlings in the greenhouse from collected soil was much below expectations; (4) More plant species occurred in the field than emerged from collected soils; (5) Secondary successional patterns cannot be predicted accurately from techniques used in this study; (6) Mesa dropseed appears to be a key mid-successional species, filling a broad niche from low good to low fair range condition.
    • Preferences of Steers for Certain Native and Introduced Forage Plants

      Dwyer, D. D.; Sims, P. L.; Pope, L. S. (Society for Range Management, 1964-03-01)
    • Range and Livestock Characteristics of Paraguay

      Fretes, R. A.; Dwyer, D. D. (Society for Range Management, 1969-09-01)
      Paraguay, located in the central part of South America, has an area of 157,000 square miles (40.7 million hectares). The country is divided into two geographic-physiographic areas: the eastern area with 40 percent of the land and relatively high precipitation; and the western or Chaco region with 60 percent of the land area and a semi-arid type climate. The economy of the country is based primarily on livestock and forest products. The efficiency of beef production in Paraguay is lower than in many other countries because improved management techniques are still being developed. The rangelands have a high potential for forage production, but many are overgrazed and subjected to improper burning. In general, the future of the ranching enterprise in Paraguay is bright. With added technical assistance and more and better trained Paraguayans, Paraguay has the potential of becoming a leading agricultural nation in South America./Paraguay, localizado en la parte central de America del Sur tiene una superficie de 400,000 kilometros cuadrados. El pais se divide en dos unidades geograficas-fisiograficas; (1) la Region Oriental, con una superficie que abarca el 40% de las tierras del pais, con topografia ondulada y buenas precipitaciones durante el año y (2) la Region Occidental, o Chaco, que ocupa el 60% de las tierras, con una topografia plana y un clima semiarido. La economia del pais esta basada en la agricultura, ganaderia y produccion forestal. La ganaderia, de la cual la explotacion de bovinos es la mas importante, posee el potencial necesario para una mayor expansion y desarrollo.
    • Range Management Training in Developing African Nations

      Smith, A. D.; Dwyer, D. D. (Society for Range Management, 1981-01-01)
      Assistance programs in range management to developing countries in Africa by the U.S. Agency for International Development historically have had a training program for nationals for the host countries as part of the package. These have been extremely valuable and, in the long run, are likely to provide the major benefits to recipient nations. They could become even more effective if closer coordination between U.S. universities, host government officials, and USAID personnel were achieved. This would result in more varied educational programs tailored to suit the needs of each student trainee and each host country, thus saving time and money.
    • Research Needs on Western Rangelands

      Klemmedson, J. O.; Pieper, R. D.; Dwyer, D. D.; Mueggler, W. F.; Trlica, M. J. (Society for Range Management, 1978-01-01)
      A brief history of rangelands leading to the current status of range research in the western United States is reviewed. Five categories of new or unresolved problems needing research are identified. Ranked by priority, the five are: (1) dynamics of individual plants and plant communities; (2) identification, classification, and inventory of range ecosystems; (3) improvement of rangelands for increased productivity and stability; (4) short- and long-term grazing impacts; and (5) influence of economic, social, and political constraints on management of range resources. Recommendations are made for some redirection of current research and for organizing, administering, and coordinating research activities.
    • Responses of Crested Wheatgrass and Russian Wildrye to Water Stress and Defoliation

      Mohammad, N.; Dwyer, D. D.; Busby, F. E. (Society for Range Management, 1982-03-01)
      Crested wheatgrass (Agropyron desertorum, Fisch Schult) and Russian wildrye (Elymus junceus, Fisch) plants were subjected to three levels of water stress (13, 2.6, and 1.8% soil moisture), in interaction with 4 defoliation levels (0, 40, 60, and 80% defoliation). Plants were clipped biweekly using the height-weight ratio method to determine the assigned defoliation level and leaf water potential $(\Psi _{1})$ was measured by pressure bomb. Following the final clipping at ground level a 40-day recovery period was allowed while maintaining plants at field capacity (13% soil moisture). Leaf water potential measurements showed significant differences between species, among three water stress levels, and within four defoliation levels. Water stress and defoliation levels significantly affected foliage yield, root biomass, and plant recovery. Heavy defoliation (80%) resulted in a 100% death loss for both species at wilting point (1.8% soil moisture). Light defoliated (40% at field capacity) produced more total dry matter than undefoliated plants maintained at field capacity or wilting point. Maximum root biomass was found in undefoliated plants of crested wheatgrass grown at field capacity. Significant differences in root production were also found among water stress and defoliation treatments. No plant recovery occurred among plants maintained at wilting point and defoliated at 80%. However, plants defoliated at 40 and 60% under 13 and 2.6% soil moisture exhibited considerable regrowth. In general crested wheatgrass out-yielded Russian wildrye in every treatment and was more resistant to defoliation and water stress.
    • Root and Shoot Growth of Five Range Grasses

      Dalrymple, R. L.; Dwyer, D. D. (Society for Range Management, 1967-05-01)
      Five range grasses were studied at relatively young ages. Sideoats grama had the most rapid root and shoot increase and produced the most quantity. Root growth of all species was initially rapid. Root: shoot ratios were consistently above 1.0 for all grasses.
    • Vegetational Responses Following Winged Elm and Oak Control in Oklahoma

      Dalrymple, R. L.; Dwyer, D. D.; Santelmann, P. W. (Society for Range Management, 1964-09-01)
      Total herbage production increased significantly following 92 to 100 percent control of winged elm, oak, and hickory trees. This increase, however, was mostly in less desirable grass and forb plants, even on reseeded plots. Natural recovery of desirable grasses after brush control on this type in Oklahoma appears to be a slow process. Reseeding may speed up forage plant establishment, but more research is needed.