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Browsing by Author "Schiffner, Sydney"

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    Do water limitation and species divergence affect physiological traits in Quercus oleoides?
    (2014-12) Schiffner, Sydney; Ramirez-Valiente, Jose A.; Cavender-Bares, Jeannine
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    Effects of Agronomic Treatments on Silphium integrifolium, a Potential Perennial Oilseed
    (2018-08) Schiffner, Sydney
    Silphium integrifolium (silflower) is a potential perennial oilseed crop that can enhance ecosystem services and provide economic return. The objectives of the first study were to determine the effects of planting density and nitrogen rate on silflower biomass production, seed yield, and seed yield components. The planting density experiment established silflower at five planting densities and at two locations (Becker and St. Paul, MN) in 2015, and plant measurements were collected in 2016 and 2017. The second experiment tested nitrogen (N) fertilization at five different rates (0, 22, 45, 90, and 179 kg N ha-1) and two planting densities (11881 and 23762 plants ha-1) at Becker, MN. At Becker in 2016, seed, oil, and biomass yields responded quadratically to planting density, and had an agronomically optimum planting density (AOPD) ranging from 39,000 to 42,857 plants ha-1. Planting density had no effect on yields at Becker in 2017. Planting density had a positive linear effect on biomass production at St. Paul in 2016 and 2017, but no effect on either seed or oil yields in either year. In all locations and years, increased plant density decreased the number of seeds and seed heads produced per plant. Nitrogen had a positive, linear effect on seed, oil and biomass yields in 2016, with no optimum rate within the range tested, but only affected biomass yields in 2017. Planting density and N rate interacted to influence the number of seeds per plant in 2016 and seed mass per seed head in 2016 and 2017. Seed yields averaged 365 kg ha-1 within the planting density study in Saint Paul and 1043 kg ha-1 within the same study in Becker, and reached the largest yields under the highest nitrogen rate and density tested as a part of the nitrogen rate experiment at Becker in 2016. Oil yields ranged from 95 to 218 kg ha-1 on average, and biomass yields ranged from 6.1 to 10.6 Mg ha-1. Relative to annual oilseed crops, seed and oil yields for this new perennial oil species are low, but under optimal production conditions, the potential is seen to be as high as traditional sunflower, and with germplasm improvement, gains should continue. Both Thinopyrum intermedium (intermediate wheatgrass; IWG) and Silphium integrifolium (whole-leaf rosinweed; silflower) are emerging perennial seed crops that do not produce seed within their establishment year. The second study considered here sought to examine the effects of seeding date on IWG and silflower. To induce flowering in both species, IWG and silflower were sown at multiple dates in the fall into the following spring, to determine the effect of planting date on biomass and seed production, establishment and development. This experiment was performed at one location, St. Paul, MN, for 2015-16 and two locations, St. Paul, MN and Salina, KS, over 2016-17 for IWG. The experiment was performed at St. Paul, MN over 2015-16 and 2016-17 for silflower. The planting dates for each of these species ranged from September 1 2015 to May 1 2016 in the first year’s experiment, then ranged from August 15 2016 to June 1 2017 in the second year’s experiment. Within the silflower experiment, nine different populations were used each year to quantify the effect of selection and seeding date on plant establishment. At the end of each growing season, seed and biomass yields were collected for both species. Height was also collected for IWG, and number of individuals and stage were collected for silflower. Over all years and locations, earlier planting dates resulted in higher biomass and seed yields, and taller heights for IWG at St. Paul, MN. Optimal seeding dates for IWG were determined to be early-October at Salina, KS and mid-August at St. Paul, MN. Accumulated growing degree days were also examined as a way to predict biomass and seed yields based on seeding date, and each location and year had a similar relationship with growing degree days and the response variables. For silflower in the first year’s experiment, only rows planted in September 2015 produced seed during the following year, indicating some amount of prior growth from the year beforehand being necessary for seed development. However, for 2016-17 these trends were less consistent. September-seeded plots still produced seeds, but a small amount of seed was produced by plants seeded at later dates as well, with plants growing to more intermediate growth stages than were seen in the previous year’s study, reflecting this lack of consistency. Growing degree days was also used as a predictor variable to explain variation of biomass yields and developmental stage in silflower. The second year’s planting did not achieve as many growing degree days as the first year’s, therefore explaining the lack and increased variability in seed and biomass production. However, there may be other considerations to take into account for production of reproductive tissues in silflower than solely accumulated growing degree days such as photoperiod and underground biomass requirements for flowering.