No description available.

Germination and establishment was evaluated in Arizona cottontop (Digitaria californica (Benth.) Chase), bush muhly (Muhlenbergia porteri Scribn.) and plains lovegrass (Eragrostis intermedia Hitchc.) from southern Arizona. Germination was determined in different aged seed harvested from native and irrigated plots of various populations. Results indicated variability in germination characteristics of study species that appeared unrelated to afterripening or dormancy. Germination ranged from 62 to 96% for Arizona cottontop, 34 to 99% for plains lovegrass, and 75 to 99% for bush muhly. Bush muhly had highest average velocity of germination (58.0 ± 4.1), followed by plains lovegrass (35.9 ± 1.91), and Arizona cottontop (31.4 ± 1.13). Effects of 3 surface treatments (furrows, gravel, litter) and 2 cultivation treatments on establishment of study species and yellow bluestem (Bothriochloa ischaemum (L.) Keng var. ischaemum) was investigated in the field. Bush muhly did not emerge and plains lovegrass had minimal emergence. Arizona cottontop had similar emergence in cultivated and uncultivated plots whereas yellow bluestem had greater emergence in cultivated plots. Litter promoted greater survival of Arizona cottontop. Lower survival in furrows may have resulted from fewer days with available soil moisture and interference from greater density of non-seeded species. Soil covers appear to positively influence survival rather than emergence. Effect of rainfall distribution on germination was investigated using 2 seed retrieval methods. Arizona cottontop and bush muhly germinated after at least 3 days of available soil moisture. Plains lovegrass seeds did not germinate in the field but retrieved seeds had 83% germination, possibly due to light exposure under laboratory conditions. Another study determined whether species have different density and cover under overstory species compared to open areas. Arizona cottontop had either greater, less, or no differences in density under canopied versus open areas. Cover of Arizona cottontop was greater or similar among canopied and open areas. Plains lovegrass had lower or similar density and cover under canopies than in open areas. Bush muhly had greater density and cover under canopies. Overall, studies suggested that species are easily germinated, but accept relatively narrow ranges of environmental conditions for establishment. Establishment may be enhanced by sowing species when rainfall is consistent, extending available moisture through use of soil covers, or mimicking microsites where a species occurs naturally.

The ability of different seedbed preparation treatments to enhance seedling establishment of 'Vaughn' sideoats graina (Bouteloua curtipendula (Michx.) Torr.), 'A-130' blue panic (Panicum antidotale Retz.), 'A-68' Lehmann lovegrass (Eragrostis lehmanniana Nees) and 'Cochise' Atherstone lovegrass (Eragrostis lehmanniana Nees X E. tricophera Coss and Dur.) was determined in field and greenhouse experiments. Field experiments compared seed burial and seedling emergence on undisturbed plots with that of plots lightly or heavily trampled by cattle, furrowed with a land imprinter or plowed. Seed burial was nearly always greatest in plots disturbed by these 3 latter treatments compared to undisturbed or light-trampled plots. Summer thunderstorms increased burial on treated and undisturbed plots. These seedbed treatments likewise increased seedling emergence of all species during a moderately-wet summer but not during a dry summer when emergence was limited. Sideoats graina emergence was low all 3 years. Seed burial and emergence of the small-seeded lovegrasses was high in a wet year even on undisturbed plots. Greenhouse experiments were designed to determine effects of seedbed microsites, sowing depth and soil water on emergence, survival and morphology of sideoats graina, blue panic and Cochise lovegrass. Emergence of all species was highest from seeds under gravel, followed by seeds under litter, seeds in cracks and finally seeds on the bare soil surface. Cochise lovegrass had high emergence under gravel for both continuously-wet and drying seedbeds. Cochise lovegrass had greater survival, followed by blue panic and then sideoats graina. All 3 species initiated permanent roots from nodes near the soil surface regardless of sowing depth. Seedlings from deeper-sown seeds had shallower primary roots and less survival than seedlings from shallow-sown seeds. Although seedbed treatments may increase the number of seeds buried and thereby increase seedling emergence when summer storms are frequent, treatments which bury seeds too deep may decrease seedling emergence. Seedbed treatments do not ensure successful emergence in a dry year.

Graduation date: 1997

No description available.

Italian ryegrass growth and production from positionally selective applications and sublethal rates of a nonselective herbicide were compared to growth and production when treated with diuron applied preemergence as a broadcast treatment and safened by activated carbon applied over the crop row. In the positionally selective treatments, herbicide spray was directed to leave an untreated zone over the crop row at planting. Growth analysis indicated no detectable differences when Italian ryegrass safened by directed spray was compared to Italian ryegrass safened by activated carbon. The major difference between systems was greater weed control in the crop row for carbon-safened treatments. The non-safened application superimposed sublethal diuron rates over Italian ryegrass and rattail fescue grown in varying densities and proportiors. Growth analysis of monoculture stands indicated differences due to planted density, species, and herbicide, whereas growth analysis of plants grown as space-planted individuals indicated difference due to species only. Diuron at the rates applied did not affect seed yield or above ground dry weight. Soil samples were taken in crop rows where diuron was applied as directed spray or broadcast spray safened by carbon. Samples were assayed and soil profile concentrations mapped. To assist future investigators' understanding of the role rainfall plays in herbicide movement from directed applications, elementary rainfall depth and occurrence models were examined. The Markov and mixed-exponential models adequately described rainfall occurrence and depth patterns for Corvallis, Oregon. / Graduation date: 1992

Chewings fescue [Festuca rubra L. subsp. fallax (Thuill.) Nyman] is a desired turfgrass with dense sod forming capabilities and superior shade tolerance. Thermal residue management (open-field burning) has traditionally been used to remove post-harvest residue and maintain seed yield over the life of the stand. However, alternative non-thermal residue management practices have been observed to produce adequate seed yields dependent upon cultivar. Strong creeping red fescue (F. rubra L. subsp. rubra) is desired for its prolific tillering capacity and creeping rhizomatous growth habit. In contrast to Chewings fescue, maintenance of seed yield in strong creeping red fescue has only been profitably produced under thermal residue management. Slender creeping red fescue [F. rubra L. var. littoralis (Vasey)] is a desired turfgrass with a compact, less rhizomatous growth habit, similar to Chewings fescue in desirable turf attributes. However, little is known about the effects of post-harvest residue management in slender creeping red fescue. The objectives of this study were: 1) to evaluate seed yield and yield components among different cultivars to thermal (open-burning), and non-thermal (flail low and flail high) post-harvest residue management; 2) to evaluate harvest index and percent cleanout to thermal and non-thermal residue management in different cultivars; and 3) and to provide an economic analysis of thermal and non-thermal residue management in all cultivars based on partial budgeting. Three post-harvest residue management treatments (burn, flail low and flail high) were applied over the course of two years. Seed yield components measured included: total dry weight, fertile tiller number, spikelets per panicle, florets per spikelet, and panicle length. Final seed yield in each cultivar and residue management treatment method was determined after seed harvest and conditioning. Seed yield component analysis was conducted over three production seasons. Chewings fescue, strong creeping red fescue, and slender creeping red fescue cultivars responded differently to residue management as indicated by a residue management by cultivar interaction. In 2003 and 2004, residue management by cultivar interactions were evident in seed number, seed weight, fertile tiller number, percent cleanout, harvest index, and seed yield. Residue management by cultivar interactions occurred in spikelets per panicle in 2003, whereas in 2004 a residue management by cultivar interaction occurred in panicle length and florets per spikelet. In 2004, non-thermal flail low, and thermal residue management resulted in significantly greater spikelets per panicle in all cultivars. Thermal residue management resulted in the greatest number of spikelets per panicle. Results indicate that thermal residue management best maintained seed yield in most subspecies and cultivars across both years. However, in 2003, non-thermal flail low residue management produced profitable seed yield in only Marker slender creeping red fescue. In contrast, thermal residue management resulted in poor seed yields in Marker slender creeping red fescue and enhanced yields in Seabreeze slender creeping red fescue in 2003. However, following the second year of thermal treatment in 2004, Marker and Seabreeze both had lower seed yields, thus exhibiting the only negative impact of thermal management among the cultivars tested in this study. Moreover, upon review of an economic analysis, Marker slender red fescue was the only cultivar that produced a positive net return of $78 and $4 ha⁻¹ under non-thermal residue management in 2003 and 2004, respectively. Furthermore, in 2003, thermal residue management net return increases ranged from $104 ha⁻¹ to -$996 ha⁻¹ in Barnica and Shademark, respectively. In 2004, thermal residue management net return increases ranged from $115 ha⁻¹ and $1,332 ha⁻¹ in Seabreeze and Shademark, respectively. Poor seed yields were observed in all strong creeping red fescue cultivars under non-thermal residue management across both years of the study. This may be attributed to an observed reduction in fertile tiller number and seed yield. In addition, percent seed cleanout was increased with non-thermal residue management. In 2004, as stand age increased, thermal residue management resulted in greater seed yields in all cultivars and species, except both cultivars of slender creeping red fescue. Thus, this study provided substantial evidence that thermal residue management has the potential to maintain or increase fine fescue seed yield as stands age as well as to maintain stand profitability. / Graduation date: 2005

Open-field burning has been an effective, economical, and widespread method of post-harvest residue management in creeping red fescue seed production in the Willamette Valley since the late 1940s. However, the use of field burning has been legislatively restricted due to air quality and safety issues. The foliar-applied plant growth regulator trinexapac-ethyl (TE), commercialized in the USA as Palisade, has been accepted by producers as a yield enhancing agent and is considered here as an alternative to open-field burning over a four-year period. The effects of open-field burning versus mechanical removal (flailing) of post-harvest residue, and spring versus fall applications of TE on seed yield, dry matter partitioning, and seed yield components were evaluated in a split-plot design. The response to the different treatment combinations differed across years. The young stand responded with a seed yield increase to spring TE applications, regardless of residue management treatment. However, as the stand aged, field burning became critical for maintaining high yields and, in 2003 and 2004, only spring TE applications resulted in seed yield increases in burned plots. The higher potential seed yield achieved in burned plots over flailed plots, as a result of a higher number of panicles per unit area and spikelets per panicle, was critical for maintaining high seed yields as the stand aged. Spring applications of TE, further increased seed yield over the untreated check by increasing the number of florets per spikelet, reducing fertile tiller height and lodging and consequently, favoring pollination and fertilization of the florets. Late spring TE applications also increased 1000-seed weight in 2003 and 2004. Although spring applications of TE were a promising alternative to open-field burning early during the life of the stand, as the stand aged they did not increase seed yield on flailed plots. Fall TE applications did not have a consistent effect on seed yield, dry matter partitioning or seed yield components, and were found not to be a viable management practice. / Graduation date: 2005

A greater than 10-fold increase in Canada goose (Branta canadensis) populations over the past several years has resulted in concerns over grazing impacts on grass seed production in the mid-Willamette Valley, Oregon. This study was designed to develop methods to quantify and statistically analyze goose-grazing impacts on seed yields of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.). Yield-mapping-system equipped combines, incorporating global positioning system (GPS) technology, were used to measure and map yields. Image processing of ground-level photography to estimate crop cover and other relevant observations were spatially located via GPS to establish spatial-temporal goose grazing patterns. We sampled each field semi-monthly from mid-winter through spring. Spatially located yield data, soils information, exclosure locations, and grazing patterns were integrated via geographical information system (GIS) technology. To avoid concerns about autocorrelation, a bootstrapping procedure for subsampling spatially contiguous seed yield data was used to organize the data for appropriate use of analysis of variance. The procedure was used to evaluate grazing impacts on seed yield for areas of fields with different soils and with differential timing and intensity of goose grazing activity. We also used a standard paired-plot procedure, involving exclosures and associated plots available for grazing. The combination of spatially explicit photography and yield mapping, integrated with GIS, proved effective in establishing cause-and-effect relationships between goose grazing and seed yield differences. Exclosures were essential for providing nongrazed controls. Both statistical approaches were effective in documenting goose-grazing impacts. Paired-plots were restricted by small size and few numbers and did not capture grazing impacts as effectively as comparison of larger areas to exclosures. Bootstrapping to subsample larger areas of yield for comparison was an effective method of avoiding autocorrelation of data while better representing impacts within a field. Occasional yield increases, ranging from 1 to 5 percent, were recorded following goose grazing. Goose grazing generally resulted in seed yield reductions, ranging up to 20 percent. Later and more intensive grazing tended to increase yield reductions. Newly seeded tall fescue tended to be the most sensitive to grazing. Established perennial ryegrass tended to be more resilient. / Graduation date: 2003