Crowns and tranplants of `Martha Washington' (MW) and `Jersey Prince' (JP) asparagus were planted in 1985. Plots were harvested for 0,2,4 weeks (traditional schedule); 1,2,6 weeks (moderate harvest pressure); or 2,4,8 weeks (severe harvest pressure) in 1986, 1987, and 1988, respectively. All plots were harvested for 8 weeks after 1988. An AOV was performed to test the main effects of cv, planting technique and harvest schedules and interactions on early and total season yield of large, medium-sized and total spears. MW produced a significantly higher yield of both early and total season large spears than JP in all years. Total yields did not differ between cvs. There was no significant effect of planting technique on yield in any year. Harvest schedules imposed in the first 3 years had significant long term effects on yield. Although severe harvest pressure produced larger yields than the other schedules in 1986-1988, from 1989-1991 yields were lowest in the severe harvest pressure plots. The traditional harvest schedule produced similar yields to the moderate pressure schedule. There were no consistent interactions between cultivar, planting technique and harvest schedule These data indicate that a slightly more aggressive harvest schedule in the early years of an asparagus planting would not have long term deterimental effect on yield. However, severe cutting pressure can reduce yields compared to traditional cutting schedules for at least 3 years after initial harvest pressure treatment
Darlene Wilcox-Lee and Daniel T. Drost
Darlene Wilcox-Lee and Daniel T. Drost
Seedlings of the asparagus cvs Mary Washington (MW) and Syn 4-56 (4-56) were grown at minimum soil matric potentials (SMP) of -0.05, -0.10, and -0.30, -0.50 or -1.5 MPa. Decreases in shoot dry weight leaf area, storage and fibrous root dry weights, and total root and plant dry weight were an exponential function of soil moisture in both cvs. Most of the growth inhibition occurred between the -0.05 and the -0.30 MPa levels of soil moisture, with little further response to SMP drier than -0.30 MPa. Consistent differences between the two cvs, regardless of SMP were apparent in leaf area, shoot dry weight, storage and fibrous root dry weights and root/shoot ratios. MW produced greater leaf area and shoot dry weights than did 4-56 at high SMP and exhibited greater inhibition of shoot dry weight by low SMP than did 4-56. Conversely, 4-56 produced greater storage root dry weight than MW at all SMP., although in mature field-grown plants, 4-56 produced greater fern weight, crown weight and number and stem numbers than MW. Root/shoot ratios generally increased with decreasing SMP. However, the root/shoot ratio of 4-56 was greater than that of MW over the entire range of soil moisture and increased more with decreasing SMP than did MW. Stomatal conductance (gs), fern xylem potential (), and net C02 assimilation rates decreased with decreasing SMP in a similar manner in both cvs. were
Darlene Wilcox-Lee and Daniel T. Drost
Asparagus officinalis L. cv. Centennial established with transplants in 1983 was maintained with tillage or a no-till (NT) system to evaluate effects of tillage on yield and plant growth in a mature asparagus planting. Metribuzin or metribuzin + napropamide at 1.12 and 1.68 kg a.i./ha, respectively, were used for weed control in both tillage regimes. Marketable yields were assessed for 5 years. In 1989, in addition to yield data, destructive harvests of entire plants were made every 3 weeks from March to November to evaluate the effect of tillage on fern, crown, and bud growth, and carbohydrate status. Yields were reduced by tillage from 12% to 50% from 1985 to 1989. There were no herbicide effects nor was there an effect on yield due to an interaction between herbicides and tillage. All indices of growth measured for NT exceeded those in tilled plots, although seasonal patterns of growth were similar in both. Crown and fern weight, bud cluster, and bud and fern counts were higher by 178%, 175%, 152%, 161%, and 195%, respectively, in NT than in tilled plots. The metribuzin + napropamide combination did not reduce fern fresh weight or yield, but significantly reduced the number of bud clusters, buds, and ferns when compared to metribuzin alone. Chemical names used: 4-amino-(1,1-dimethylethyl)-3-(methylthio)-l (metribuzin); 2,4-triazin-5(4H) -one, N,N-diethyl-2-(naphthalenyloxy)-propanamide (napropamide).
Nathan C. Phillips, Steven R. Larson, and Daniel T. Drost
Three wild onion species native to the intermountain west in the United States—Allium acuminatum, A. brandegei, and A. passeyi—show horticultural potential, but little is known about patterns of genetic diversity among localized populations and geographical regions. We examined amplified fragment length polymorphisms (AFLP) within and among five Allium acuminatum, four A. brandegei, and three A. passeyi collection sites in Utah. These three congeners with contrasting abundance and distribution patterns provide an opportunity to investigate the role of geographic distance, altitude, and rarity in patterns of genetic divergence. The collection sites were selected along an altitudinal gradient to reflect ecogeographic variation. Individual plants from each of the 12 sites were genotyped using six AFLP primer combinations detecting DNA variation within and among all three species. Genetic differences between species were high enough to render comparisons among species impractical, so each species was analyzed separately for differences between populations and variability within populations. Similarity coefficients were significantly greater within collection sites versus among collection sites indicating divergence between populations. Within-population genetic diversity was not correlated with elevation for any of the three species. Analysis of molecular variance revealed that 66% (A. acuminatum), 83% (A. passeyi), and 64% (A. brandegei) of observed variation is found within populations. Genetic divergence among populations (ФST) was higher in the widely distributed species, suggesting that interpopulation gene flow may be negatively correlated with range size. Allium acuminatum and A. brandegei individuals cluster into groups corresponding strictly to collection sites based on neighbor-joining analysis of the total number of DNA polymorphisms between individual plants. Allium passeyi populations, however, had less overall genetic variation between populations. Genetic isolation by distance appeared responsible for much of the variability among populations, although there was one notable exception showing significant differences between two geographically close populations in A. acuminatum.
Nathan C. Phillips, Steve R. Larson, and Daniel T. Drost
The genus Allium is distributed worldwide and includes about 80 North American species, with at least 13 occurring in Utah. Our study focuses on the population dynamics of three Allium species native to Utah; Allium acuminatum, A. brandegei, and A. passeyi. In conjunction with our studies of life history, growth characteristics, demographics, and habitat, we are interested in determining the levels of genetic variation in these species. This study examines amplified fragment length polymorphism (AFLP) within and among five Allium acuminatum, four A. brandegei, and three A. passeyi populations native to Utah. These species have contrasting abundance and distribution. The study populations were selected along an elevation gradient to represent within-species habitat differences. About 10–20 plants from each of the 12 populations were genotyped using six AFLP primer combinations, which detect DNA variation within and among all three species. These data will be used to compare levels of genetic variation and isolation among populations and species.
Tiffany L. Maughan, Kynda R. Curtis, Brent L. Black, and Daniel T. Drost
Strawberry production in the U.S. Intermountain West is limited by harsh climatic conditions and competition from domestic producers and imports. Using season extension methods to combat climatic conditions may be effective but generally increases production costs. This study evaluates the economic returns to implementing high tunnels, low tunnels, and in-ground supplemental heating to strawberry production (Seascape and Chandler cultivars) in northern Utah. The high tunnel provided a net return of $1,943.57 or $15,548.56 per hectare assuming eight high tunnels per hectare. The addition of low tunnels within the high tunnel led to a positive increase in net returns for ‘Seascape’ but not for ‘Chandler’ production. Supplemental in-ground heating increased net returns by up to 50% for both cultivars, primarily as a result of higher pre-season yield and market pricing. Study results find that season extension technologies can successfully increase net returns to strawberry production through early and increased yields, when strawberries are sold primarily through local direct markets.
Nathan C. Phillips, Daniel T. Drost, Bill Varga, Leila Shultz, and Susan E. Meyer
Seed germination timing strategies and seedling growth characteristics in wild populations have evolved in response to their life history, ecology, and habitat. In this study, we examined the ecophysiological aspects of seed germination and growth in three Allium species native to the Intermountain West (A. acuminatum, A. brandegei, and A. passeyi). Three populations of each species were studied along an elevation gradient resulting in low, mid, and high elevation sites for each species. We investigated seed dormancy patterns within and among species and their relation to habitat. Seeds collected at the study sites were subjected to cold (3 °C) moist stratification in low light to simulate the natural winter environment under snow. Stratification periods ranged from 0 to 24 weeks. After stratification, seeds were placed in lighted growth chambers at 8 °C to simulate the natural spring environment. Germination was observed for 4 weeks. Germinated seeds were then grown at either 12 °C or 16 °C until leaf senescence. Destructive sampling occurred at 2, 4, and 8 weeks. Bulb mass and water content were also assessed after leaf senescence. In the germination experiment, all species responded favorably to cold moist stratification, suggesting physiological seed dormancy. Germination percentages among species varied greatly with 98% germination in A. acuminatum, but only 33% in A. brandegei. Seedling survival and growth varied among species and in response to growing temperature. Observed patterns in seed germination and growth are typical of survival strategies in other spring ephemerals. Seed dormancy traits and seedling growth characteristics in these species have evolved to allow optimal success for their specific habitat.