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Marvin P. Pritts

A course was developed at Cornell University for the purpose of attracting nonmajors from across the university, instilling in them an appreciation for horticulture and then encouraging them to take additional horticulture and plant science courses. The course incorporates many engaging and interesting horticultural activities, with scientific concepts and horticultural techniques conveyed almost exclusively through hands-on instruction using the campus as a laboratory. Experiential learning and culinary experiences are key components of the course. Student evaluations are very high (5-year average of 4.94/5.00 with five representing “excellent”), and the class fills to capacity each spring semester with diverse students from across campus. Enrollment in other horticulture classes has increased since the course has been offered. Forty-three percent of students who took Hands-On Horticulture as a freshman, sophomore, or junior subsequently enrolled in at least one other plant science course. Participating horticulture faculty also find the class to be fertile ground for recruiting research and field assistants. Students report an increase in well-being and reduction in stress while taking the course, and write about how their worldview has changed after the course experience. This class has allowed students to discover or rediscover their role and connection to nature while simultaneously providing them horticultural skills and understanding of scientific principles.

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Marvin P. Pritts

Strawberry (Fragaria ×ananassa) is a perennial plant with a compressed woody crown that responds to the environment in a similar way as other temperate fruit crops. Nutrient management practices are also similar, with a few exceptions. Levels of preplant amendments are determined based on soil test results, and are used to increase nutrient availability and modify pH as needed. Once plants are established, soil tests, coupled with foliar tissue analysis and observations of plant growth, are the best indicators of plant nutrient status and limitations. Drip irrigation is more efficient than granular applications for supplying soluble nutrients such as nitrogen (N). While most temperate fruit crops respond well to N in spring when growth resumes after winter, applications of spring N in strawberry can cause excessive vegetative growth, reduce fruit quality, and have only a marginal impact on yield. N is most efficiently taken up by plants when conditions favor root growth, and N applied in summer or fall is more effective at increasing yield the following spring, assuming that the carbohydrate status of the plant is good. However, if carbohydrate status is poor, supplemental N late in the season can reduce yield by requiring additional carbon (C) for N uptake. Many questions remain to better understand how to manage nutrients optimally in perennial strawberry.

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Marvin P. Pritts

Non-chemical methods for weed management are becoming important as fewer herbicides are labelled for use and as the market demands pesticide-free produce. We have studied the use of interplanted cover crops in strawberry plantings as an alternative/supplement to chemical weed management. Several different cover crops (tall fescue, marigold and sudangrass) were seeded between rows of newly planted strawberries in late June as runnering was commencing. An additional seeding of sudangrass was made in late July. For comparison, untreated plots and diphenamid treated plots were included in the experimental design. Measurements were taken throughout the season of soil moisture, light levels, crop nutrient concentrations, nematode numbers in soil and crop roots, runner biomass, and weed composition and biomass. Cover crops were incorporated in late fall and the planting was mulched. The following spring, crop nutrient concentrations, nematode numbers in soil and crop roots, weed composition and biomass, yield, individual fruit size, and aboveground strawberry biomass was assessed. The marigolds were too competitive for moisture to be an effective companion cover crop. The early planting of sudangrass was too tall, and fescue was too competitive for nutrients. The untreated plots contained many more weeds than other treatments, nematode levels were higher in the strawberry roots in these plots, and harvesting fruit was very difficult. The late seeding of sudangrass, however, provided significant weed control while not reducing yield relative to herbicide-treated plots.

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Marvin P. Pritts

This LISA project involves four state universities and the USDA, and has the objective of developing and evaluating non-conventional production and pest management strategies for raspberries and strawberries. Production goals are divided between cropping systems and pest management. The evaluation of trellising systems for cropping efficiency, ease of harvest, and spray distribution is an example of a production related objective. Groundcover management systems for strawberries are being evaluated for their effects on both the pest complex and production system. Biological control strategies for root diseases are also being studied. Evaluations involve field performance, economics, and impacts on pesticide use. In addition, grower attitudes towards adoption of non-traditional production practices have been assessed. The project supports the publication of a newsletter that is distributed to 450 growers. The major goal of our work has been to improve production efficiency and provide growers with economical, dependable tools that can be used to prevent pest problems before chemical intervention is required.

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Marvin P. Pritts

Manipulating light, temperature, moisture, and nutrients to favor plant growth and productivity is an important component of horticulture. The technology required to achieve such manipulation ranges from inexpensive, basic practices to elaborate, costly approaches involving the latest engineering advances. For example, pruning and mulching are relatively low-tech methods for improving light interception and soil moisture status in small fruit plantings. At the opposite extreme are glass houses with supplemental lighting, CO2 enrichment, and nutrient film hydroponic systems Of greatest value to small fruit growers, however, is technology that ran be applied in field situations, such as the use of overhead irrigation for maintaining soil moisture status, frost protection, and evaporative cooling. One of the greatest challenges to small fruit growers and rcsearchers is integrating new technology into production systems. The introduction of a new technique for environmental modification usually has indirect effects on other aspects of management, which may require additional technology to compensate for adverse changes while maintaining the favorable change. In addition, unique macro- and microclimates demand and market opportunities, specific solutions, and the result is a dynamic, diverse collage of production systems used by growers throughout the world.

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Marvin P. Pritts and Travis Park

Most institutions that offer a degree in horticulture have established a set of learning outcomes for the major or are in the process of doing so. Because horticulture programs are being subsumed into larger entities, and because there is no process for providing consistency of expectations for horticulture majors, a group of horticulture administrators from across the United States initiated an effort to develop a common set of learning outcomes that would be appropriate for any four-year horticulture program. The intent was to identify learning outcomes that could be made more specific for an institution’s local conditions and capacities, or expanded to accommodate broader plant science-type majors. Five outcomes with specific goals were identified. An increasing level of higher-order thinking skills is associated with later learning outcomes. The outcomes are knowledge acquisition; knowledge integration; synthesis, creativity and problem-solving; communication; and demonstration of professionalism and proficiency. Adopting these learning outcomes can provide students with guidance in choice of major, faculty with a tool for curriculum development and program assessment, and employers with expectations for new horticulture graduates.

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Ian A. Merwin and Marvin P. Pritts

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Norman A. Gundersheim and Marvin P. Pritts

A factorial arrangement of 48 treatments was used to evaluate the effects of cane density, time of cane density adjustment, primocane tipping, and cane or branch length on yield components in `Royalty' purple raspberry [(Rubus occidentals × R. idaeus) × R. idaeus] over 2 years. Yield was positively related to cane density and length, while fruit size and fruit count per lateral were negatively related to cane and branch length. When branches on tipped canes were shortened in late winter, more buds became fruitful at the proximal end of the branch, but fruiting laterals did not have more flowers or fruit. Fruiting laterals were longer on shortened canes, resulting in a decrease in the fruit: wood ratio. Plants performed similarly whether floricane density was adjusted in late winter orprimocane density was adjusted in late spring. Although potential yield was higher when primocanes were tipped in late spring, harvesting was more difficult because of branch orientation, and the incidence of cane blight infection was higher. Our study suggests that maintaining at least 12 canes per meter of row, avoiding primocane tipping, retaining full cane length, and providing adequate light, moisture, and nutrient levels can result in high yields of large fruit.

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Laura Elisa Acuña-Maldonado and Marvin P. Pritts

Early spring growth of perennial strawberry (Fragaria ×ananassa Duch.) plants is supported by the carbohydrate and nitrogen (N) reserves accumulated from the previous growing season. The limitations of these reserves on the initial spring growth and yield of perennial strawberries have not been studied in detail, particularly the influence of N reserves. Differential N fertigation (0 to 20 mm N) was applied to potted strawberries during the growing season and a supplemental foliar urea application was applied to a portion of the plants in the fall to modify reserve N during dormancy. Plant N content and spring vegetative growth the year after fertigation increased nearly twofold with increasing N fertigation. Photosynthesis per unit leaf area also increased up to 10 mm of fertilizer N and then stabilized through 20 mm. Foliar urea application in fall further increased total plant N content and size, decreased carbohydrate concentration, and also decreased yield in plants with the most total N. Nitrogen fertigation was resumed on a portion of these plants in early spring, but new growth and subsequent yield were unaffected by spring N application. In a second experiment, CO2 enrichment with and without soil and foliar N application in the fall was used to vary carbon (C) and N reserves. CO2 enrichment in fall increased plant size and yield the next July by ≈20%, but total nonstructural carbohydrate and N concentrations were unaffected. Foliar urea application also increased N and C reserves (but not concentration) as well as yield in both enriched and unenriched plants. Although foliar urea in fall decreased carbohydrate concentration, total reserve levels were unaffected because treated plants were larger. In this experiment, spring N increased plant size by ≈50%, but yield was increased only 12%, suggesting that yields are mostly dependent on reserves. Increasing N reserves with a late fall foliar application is one strategy growers can use to efficiently enhance growth and yield in low to moderately fertilized plants.