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Soil probe samples were taken in the upper 1 m of the soil profile 0.5 and 1 m from the base of five blueberry cultivars (Vaccinium spp.) grown in a modified-pH soil. The samples were divided into 12 sections by depth: mulch, 0-5, 5-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, and 90-100 cm. Weights of the organic fraction of blueberry roots were determined by subtracting ashed weights from dry weights for each sample section. Duplicate soil probe samples were taken and soil pH determined at the 12 depths and two distances. Root weights were highest in the upper 20 cm of the soil profile at the 0.5 m distance for all cultivars. Soil pH was 5 and below in the upper 20 cm of the soil. Yield of 11 cultivars was obtained for five years (1988-1992). Total yield averaged over 5 years showed `Blueray' as the highest yielding cultivar with 4.43 kg/plant per year. `Patriot', `Elliott', and `Colville' were lower than `Blueray' but similar to each other, with yields of 3.42, 3.11, and 3.03 kg/plant per year, respectively.
Sustainable strawberry production depends on effective weed and soil management. Alternative weed management strategies are needed because few herbicides are registered for use in matted-row strawberry culture. Soil analyses are often measured in terms of chemical and physical properties alone. Measuring biological indicators of soil quality that are sensitive to changes in the environment can enhance these analyses. The experiment compared the effects of four weed management systems on weed growth, soil quality properties, and strawberry yield, growth, and development. Treatments were killed-cover crop mixture of hairy vetch (Viciavillosa) and cereal rye (Secalecereale); compost + corn gluten meal + straw mulch; conventional herbicide; and methyl bromide soil fumigation. Results indicated that there were no differences in percentage of weed cover or number of strawberry runners between the four weed management treatments in the planting year (July or Aug. 2004). The soil quality parameters, infiltration rate, soil bulk density, earthworm number, and total porosity were similar for all treatments. Plots that received the straw mulch treatment had a soil volumetric water content 20% higher and air-filled porosity that was 26% higher than the average of other treatments. Although treatment plots received similar N, leaf nutrient analysis showed that plants receiving the straw mulch + corn gluten meal treatment had a similar amount of total N when compared to the conventional and methyl bromide treatments, but was 21% higher than the killed-cover crop treatment.
A learning community was developed for first-year students majoring in horticulture at Iowa State Univ. in 1998. Learning communities are a curriculum design that schedules courses for both students and faculty to encourage community and connections among students, between students and faculty, and among faculty. Learning communities can offer students more opportunities for interactions among each other, academic assistance through supplemental instruction and/or group study sessions, and planned horticulture-related activities, all of which are important for success and retention of first-year students. First-year students in the horticulture learning community enrolled in the same courses and sections of five courses. The first-year English composition course was linked to the second-year principles of horticulture course that requires writing-across-the-curriculum activities. Faculty mentoring was provided through local field trips to horticultural sites of keen interest to the students. Academic environment survey results showed students rated their expectations highly for developing a network of other students as a resource group and for learning cooperatively in groups. Iowa State Univ. supports learning communities by providing faculty development and facilitating course registration, peer mentoring, supplemental instruction for challenging core courses, and academic and student services, to strengthen undergraduate teaching programs within and outside of the classroom.
Raspberry (Rubus idaeus L., `Heritage') fruit were harvested at six stages of color development to determine the relationship between quality attributes and physiological changes during ripening. Soluble solids concentration and fruit weight increased, whereas titratable acidity decreased during ripening. Fruit darkened and color saturation increased with maturity. Raspberry fruit exhibited a nonclimacteric pattern of respiration, and ethylene (C2H4) was detected only after red pigment developed. Respiration and C2H4 production of whole fruit were similar to those of drupes. Ethylene-forming enzyme activity commenced in drupes and receptacle tissue from fruit at the yellow and mottled stages, respectively. These data indicate that ripening in raspberry fruit is independent of C2H4 production and is nonclimacteric.
The purpose of this project was to investigate the use of evapotranspiration (ET) as a guideline for trickle irrigation timing in field-grown day-neutral `Tristar' strawberry. Proper management of trickle irrigation would allow optimum yields and quality with minimum water inputs. A randomized complete block field design with four replications was used at the ISU Horticulture Station in central Iowa. Irrigation treatments were based on % of ET and number of applications per week. The four treatments included: 30, 60, and 90 % of ET applied once per week (1X) and 30% of ET applied 3 times per week (3X). Total yield data (kg of fruit per season) indicated the 30% of ET (3X) treated plants yielded 15% more fruit than the 30% of ET (1X) plants. Berry number was 14% greater from plants receiving the 30% of ET (3X) treatment than from those receiving the 30% of ET (1X) treatment. Average berry weights for the entire growing season were similar among all treatments.
Sensory and objective attributes of fresh fruit of five locally grown day-neutral strawberry (Fragaria × ananassa Duch.) cultivars (Tristar, Tribute, Mrak, Yolo, and Selva) were compared to those of California-grown strawberries available in the Iowa markets. `Tristar' and `Tribute' fruit were redder and more sour than fruit of other day-neutral cultivars, and `Tristar' fruit were the most juicy of the berries evaluated. `Tristar' and `Tribute' fruit had higher titratable acidity and lower Hunter L (lightness) values than those of other evaluated fruit. Sensory panelists rated the California-grown berries as the least red.
Yield of strawberry grown continuously on the same site often declines over time as a result of proliferation of weed seeds and pathogenic organisms in the soil. Plots were established and maintained in seven different cover crops and as continuous strawberry or continuous tillage for 10 years (1996 to 2005) in a site that was previously in strawberry production for 10 years (1986 to 1995). Cover crops included blackeyed Susan (Rudbeckia hirta L.), sorghum Sudangrass [Sorghum bicolor (L.) Moench], marigold (Tagetes erecta L.), big bluestem (Andropogon gerardii Vitman), perennial ryegrass (Lolium perenne L.), switchgrass (Panicum virgatum L.), and Indiangrass [Sorghastrum nutans (L.) Nash]. Treatments were ended in 2005 and plots were planted with ‘Honeoye’ strawberry in a matted row. Effectiveness of soil pretreatments in reducing weed populations and enhancing strawberry production was evaluated for four growing seasons by quantifying weed growth by type and biomass and strawberry plant density and yield. The results indicate that matted-row strawberry production plots that were either in continuous tillage or established in S. bicolor, P. virgatum, or A. gerardii before planting strawberry had lower weed biomass and greater strawberry plant establishment and yield than plots established in L. perenne or R. hirta or that had supported continuous strawberry production.
Abstract
Soil mulches (clear, white, or white-on-black polyethylene or straw) were evaluated for their effects on growth and development of day-neutral ‘Fern’ and ‘Tristar’ strawberry (Fragaria × ananassa). Plants mulched with straw or white-on-black polyethylene flowered and yielded more than plants mulched with clear or white polyethylene. Conversely, more crowns per plant, runners per plot, and greater leaf, crown, and root dry weights were associated with plants mulched with clear polyethylene than with those mulched with straw or white-on-black polyethylene. In midsummer, late-afternoon soil temperatures were highest under clear followed by white, white-on-black, and straw mulches. The results suggest that flowering is most profuse and vegetative growth least when day-neutral cultivars are grown on mulches that moderate soil temperatures.
A 200-level course at Iowa State Univ., Principles of Horticulture, has included a communication across the curriculum assignment for the past seven semesters involving ≈425 students. Each undergraduate student develops and writes an individual student newsletter on topics and for an audience of the student's choice. The semester-long project motivates students to practice a professional communication task, and teaches technical horticultural material and writing skills. The newsletters contain at least two separate articles for an intended audience, providing the students with an opportunity to learn technical information in subjects in which they are intensely interested, but may not be taught in a principles course. Drafts of the articles and newsletter project are peer-reviewed by the students to model the professional review process, provoke critical thinking, and provide students with more feedback than they would otherwise receive from the instructor alone. Additionally, peer-review facilitates writing intensive courses for the instructor who wishes to focus course activities on writing, but has limited time or resources for reviewing writing assignments. Student newsletter articles are selected to be included in quarterly department and extension newsletters, providing students with a real-world use of a communication across the curriculum assignment.
'Honeoye' (June-bearing) and 'Tristar' (day-neutral) strawberries were harvested, graded, and then stored for 7 days et 2C or 21C in air (control) or each of these 8 modified atmospheres: 1.5% O2, 3.5% O2, 15% CO2, 25% CO2, 1.5% O2 + 15% CO2, 1.5% O2 + 25% CO2, 3.5% O2 + 15% CO2, and 3.5% O2 + 25% CO2; all balance N2. When compared with storage at 21C, storage at 2C reduced weight loss and gray mold growth in all corresponding sets of storage atmosphere treatments. The combination of increased CO2 and decreased O2 controlled weight loss and gray mold growth more effectively than treatment with reduced O2 alone. Storage at 2C (versus 21C) reduced respiration of both cultivars. Respiration decreased as the O2 concentration decreased. 'Tristar' did not produce C2H4 at either temperature, whereas `Honeoye' produced more C2H4 at 21C than it did at 2C. Increased CO2 and/or decreased O2 concentrations in the storage atmosphere are not satisfactory substitutes for proper low-temperature storage of strawberries.