High tunnels have been used successfully in many areas of the world to extend the growing season for numerous crops. However, very little research has been conducted to evaluate the season extension benefits offered by high tunnels to small fruit crops in high elevation growing areas such as the Intermountain West region of the United States. The use of high tunnels was investigated in North Logan, Utah (41.766 N latitude, 1405 m elevation, 119 freeze free days) to extend the growing season for both strawberries and raspberries. June-bearing `Chandler' strawberries in a fall-planted annual hill system were evaluated for early season production. High tunnels advanced spring strawberry production by approximately 3 weeks compared to field-grown plants. High tunnels were used for earlier planting and growth in a spring-planted day-neutral strawberry system. Day-neutral cultivars (`Albion', `Seascape', `Evie 2', and `Tribute') produced strawberries throughout the summer and into the fall with significantly higher yields from the high tunnel treatments than the field-grown plants. High tunnels also extended late-season strawberry production until mid-December. The floricane-fruiting red raspberry `Tulameen' was evaluated for early season production, and primocane-fruiting `Caroline' was evaluated for late season extension. High tunnels were unable to provide sufficient winter protection for the cold-tender `Tulameen' at this location. Results from late season extension indicated that high tunnels could extend late season raspberry production by as much as three weeks. However, peak yields for `Caroline' were before the first fall frost, and a later fruiting cultivar would be more suitable. In addition to research results, this thesis contains chapters on practical management considerations for commercial producers, and enterprise budgets to assist in evaluating the economic costs and returns of high tunnel strawberry and raspberry production.

High tunnels have been used for many years worldwide. However, there has been limited research about use of high tunnel technology in the southeastern United States and its popularity has recently increased in Mississippi. A planting date study of 'Roma'' tomato, 'Legend' tomato, 'Ichiban' eggplant, 'Sweet Banana' pepper, ‘Benary’s Giant’ zinnia and ‘Potomac Red’ snapdragon was conducted in spring 2010 in three high tunnels in Starkville, Mississippi. Results showed for most cultivars (tomatoes, eggplant and pepper) a 12 Mar. 2010 planting date did not differ in marketable yield from planting on 2 Apr. 2010. In 2011, a fertilizer study on Encore lettuce mix and Ovation green mix was conducted both in high tunnel and in the field. Results indicated there was no effect of vermicompost tea or fertilizer treatments on yields of salad mixes.

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Cary L. Rivard / As populations of cities continue to increases, communities in the United States are implementing urban food systems including locally-cultivated produce. Urban and peri-urban farmers apply intensive production systems, including high tunnels, to better utilize limited space. Grafting tomato with vigorous rootstocks provides the potential for higher yields. Our first objective was to identify tomato rootstocks that improve productivity in high tunnel environments with no soilborne diseases in the Central U.S. Eight replicated high tunnel trials were conducted at four sites in northeastern Kansas in 2013 and 2014. We selected 'BHN 589' scion for all sites and evaluated seven rootstocks. Grafting with ‘Maxifort’, ‘Multifort’, ‘Arnold’, ‘DRO 131’, and ‘Colosus’ rootstocks resulted in significant increases in total fruit yield, which ranged from 40% to 73% when compared to nongrafted plants (P<0.05). No significant increases in yield were observed for ‘RT-1028’ and ‘RST-04-106’ rootstocks. Our results suggested that tomato growers that utilize high tunnels should be strategic when selecting rootstocks. Our second objective was to develop simple propagation techniques that yield high quality grafted transplants for small-batch propagators. Formation of adventitious roots (AR) from the scion can result in poor quality plants and loss of rootstock function/benefit. Greenhouse studies were designed to investigate how leaf removal (LR) affects AR formation and plant growth post-grafting. We applied three treatments, 0% LR, 50% LR, and 90% LR, to the ‘BHN 589’ scion and then grafted them onto ‘Maxifort’ rootstock. The experiment included 4 replicated blocks and was conducted in three different healing chambers. Our results indicate that both 50% and 90% LR significantly decreased AR formation in the low humidity chamber, but only 90% LR reduced AR formation in the chambers with high humidity (P<0.05). We measured plant growth 24 to 52 days post-grafting to understand how leaf removal affects transplant quality, growth, and development. Plants with 90% LR had significant growth reduction at day 24 but at day 52, only had reduced stem diameter and height compared to 0% LR. Total flower count was the same for all treatments. Leaf removal during grafting may be a viable method for propagating high quality, grafted transplants.

Master of Science / Department of Horticulture and Natural Resources / Cary L. Rivard / Tomatoes and peppers are the most popular and profitable high tunnel crops. However, year-round intensive cultivation and extensive monocropping can lead to a loss of soil quality and the buildup of soilborne pathogens. Many growers are considering grafting to help address the drawbacks of covered agriculture and improve yields. Although many trials have been conducted that examine the ability of rootstock to increase yield or reduce disease, the effect of scion cultivar has yet to be tested, and few studies have attempted to quantitatively assess scion compatibility. In 2016 and 2017, we evaluated ten hybrid, determinate, red slicing tomato scion cultivars for compatibility with ‘Maxifort’ rootstock in a three-season high tunnel in Olathe, KS. While all ten varieties were compatible with ‘Maxifort’, only ‘BHN 589’, ‘Red Deuce’, ‘Skyway’, and ‘Tasti Lee’ were “highly compatible” and showed significant improvements in marketable yield when grafted. Additionally, when ranked by yield, differences between grafted and nongrafted populations suggest that relative compatibility may be inconsistent between varieties. However, a significant inverse relationship between the yield of the nongrafted plants and the percent yield benefit from grafting indicates that the effect of a rootstock like ‘Maxifort’ may not be synergistic, with higher performing nongrafted scion varieties benefitting less from grafting than lower performing varieties. ‘Red Deuce’ and ‘BHN 589’ are productive, and highly compatible grafted varieties with potential for commercial high tunnel production. ‘Primo Red’ benefitted the least from grafting but was the highest performing nongrafted variety (outperforming four of the grafted combinations). Compared to tomatoes, published reports on grafted peppers have been limited and it is unclear whether they provide any advantage in the absence of soilborne disease or environmental stress. Additionally, the use of rootstocks from other solanaceous species outside the Capsicum genus for pepper grafting has not been well explored, though the pool of available rootstock options for peppers would be substantially increased if such graft unions proved to be compatible. The goals of a second project were to identify the utility of grafted pepper (C. annum) plants for commercial high-tunnel production and to explore the potential for graft compatibility between the Capsicum and Solanum genera. We grafted ‘Karisma’ bell peppers onto two Solanum cultivars (‘Maxifort’ and ‘Sweetie’) and three pepper rootstocks (‘Scarface’, ‘Meeting’, and ‘Yaocali’). Five trials were conducted in 2016-2017 and utilized a randomized complete block design in all locations. Plants grafted onto Solanum rootstocks displayed symptoms of delayed incompatibility, including significant (78%-89%) reductions in yield (by weight), 59%-93% less plant growth, and 58% less marketability, as well as malformations at the graft union and higher in-field mortality rates. These symptoms were likely due to differences in mature stem anatomy. Plants grafted to ‘Scarface’ produced 32% greater marketable yield, 15%-18% larger fruit, and 9-12% higher marketability than nongrafted ‘Karisma’. The results for ‘Yaocali’ were similar to ‘Scarface’, though less conclusive. While ‘Yaocali’ and ‘Scarface’ rootstocks may be useful for improving yield in low-stress environments, the use of ‘Meeting’ may be more beneficial for combatting disease.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Rhonda R. Janke / The goal of this study is to clarify the influence of organic fertilizer sources on vegetable crop yield under different production systems. This research hypothesized that organic soil amendments will produce healthy and vigorous plants with similar or higher yields while improving soil organic matter levels compared to conventional amendments. Applying organic fertilizer sources can be cost-prohibitive; moreover, synchronizing timing of crop nitrogen demand with soil plant available nitrogen is essential to maximizing yield and reducing nitrogen pollution to the environment. The objectives of this study are to evaluate yield in relation to soil fertility status at different fertility rates for organic and conventional management in field and high tunnel production systems, to measure plant nutrient status in crop petioles and compare it to available mineral N levels in soil at different growing stages, and to determine the effect of nitrogen availability of organic compared to conventional fertilization on plant available nitrogen and crop yield under both systems. A latin square experimental design was conducted from 2008 to 2010 at Kansas State University Research Center in Olathe KS to evaluate an organically managed vegetable rotation of tomato (Solanum lycopersicum L. ‘Bush Celebrity’) and pac choi (Brassica rapa L. ‘Mei Qing’) under three fertility rates; control, low (composted poultry manure), and high (composted poultry manure and fish hydrolyzate) in contrast with conventionally managed soils under two production systems (field and high tunnel). The effect of these four contrasting systems was measured on plant and soil nutrient status. All plots had cover crops of rye during the winter and buckwheat in the summer between pac choi crops. Soil nitrate-N (NO₃-N) and ammonium-N (NH₄-N) were measured, as well as petiole sap nitrate (NO₃⁻). In tomato, additional soluble fertilizers had no direct effect on yield in both field and high tunnel. Compost application had a positive effect on organic matter. In pac choi, additional liquid fertilizer helped organic field plots obtain maximum yield. Soil mineral nitrogen were affected by production system and fertility source, but statistical significance varied by crop and stage. Petiole sap reflected treatment regimens but not necessarily soil N status at each plant stage. The study also addressed long term management practices on organic and conventional available nitrogen. An incubation study on the soil at the conclusion of the field experiment explored the relationship between N mineralization from potentially mineralizable nitrogen (PMN) compared to Illinois Soil Nitrogen Test (ISNT) in control and pre-plant application fertility treatment for both field and high tunnel systems. The results indicated that ISNT concentration values for all soils were below the proposed value for corn crop suggested by (Khan, 2001). ISNT correlated with PMN with the stronger correlation being in field plots. ISNT also correlated with OM in field. Fertility rate showed a significant effect on total carbon and total nitrogen in organic systems of both field and high tunnel plots. This study supports composted poultry manure to improve the fertility status of the soil and to obtain a yield equal to that of conventionally managed soil.

Dissertation (Ph.D.)--Auburn University, 2008. / Abstract. Vita. Includes bibliographic references.

Master of Science / Department of Horticulture and Natural Resources / Jason Griffin / Cary L. Rivard / Sweetpotatoes [Ipomoea batatas (L.) Lam.] are nutritious, easily stored and marketed, well-adapted to organic production, and fit large or small farming operations. Commercial production of propagules for sweetpotato, vine cuttings known as slips, is concentrated among a few coastal states. Consequently, growers in the Central United States have limited access to planting material. Considering the crop’s sensitivity to cold climates and the increasing use of high tunnels (HTs) in the region, the implementation of HT production systems could be a viable mechanism for increasing the distribution of sweetpotato nurseries across the US. The goal of this project was to investigate the production of slip propagation beds in HT systems at two research stations in Northeast and South Central Kansas. Trials were conducted in 2016 and 2017 to compare yield and quality of organic slips grown in HTs and the open-field (OF). Additionally, a split-plot design was utilized inside the HT to compare slip yields for three planting densities (45, 65 and 85-seed roots/m²). Slips grown in the two systems (HT and OF) were field-planted to elucidate the impact of the system on subsequent root tuber yields and grade. HT enterprise budgets were developed to determine what the potential economic impact is for growers that wish to implement this system and to identify the appropriate planting density based on cost and return. In 2016, the HT plots produced more slips than in the OF (P < 0.05), and the overall average slip number was 226.7 in the HT and 147.8 in the OF across both years. However, slips grown in the HT had significantly fewer nodes, less foliage, and compactness (P < .001). The field performance study showed slightly greater average marketable storage root yield from slips produced in the OF (P = NS), but the quantity and distribution of graded storage roots were similar between slips grown in the HT and OF treatments. Increased planting density treatment corresponded with greater average slip yield across all harvests, but was only statistically significant during 1st harvest of 2016. The positive correlation between slip yield and planting densities plateaued between 65 and 85-seed roots/m². When using foundation seed roots the optimum profit for enterprise budgets was achieved at the 65-seed root planting density. The use of 25% foundation and 75% on-farm produced seed roots at 85-seed root density generated $1.05/ft² profit in HT—using the more manual cultural practices and equipment of two case studies. The results of these trials suggest that slip production in HTs may provide growers in the Central and Northern regions of the U.S. a viable technology for developing their own sweetpotato propagation schedule, without compromising plant yield or storage root production. When compared to other common HT crop budgets, our data suggest that HT slip production is an economically-viable system for growers who wish to incorporate slip propagation beds into their HT rotations.

The demand for local sustainably grown produce and flowers has increased (Low et al., 2015), and stimulated a growing interest in high tunnel production. The goal of this research project was to evaluate the production of cut flowers in high tunnel structures and in the field in the Northern Great Plains (NGP) region. The NGP offers unique climatic and environmental challenges based on its continental climate. Specialty cut flower cultivars Karma Irene and Chocolate dahlia (Dahlia x hybrida), Potomac White and Rocket Mix snapdragon (Antirrhinum majus), and Mariachi Misty Blue, Echo Blue and ABC2 lisianthus (Eustoma grandiflorum) were planted in both field and high tunnel environments at two soil temperature setpoints in the NGP to determine which of the selected crops are best suited for cut flower production. Our results indicate higher yields and more consistent quality in the high tunnel; however, the field was suitable for all species investigated.

High tunnels are used to modify the crop environment by trapping solar energy, providing protection from unfavorable weather events, and extending the growing season in temperate regions. This project assessed yield and quality in three independent cultivar trials of warm-season crops tomato (Solanum lycopersicum L.), bell pepper (Capsicum annuum L.) and cucumber (Cucumis sativus L.) grown under high tunnel production compared with an outdoor field in eastern and western North Dakota. Tomato yields in the high tunnel were increased by 1.4 times over the field trial yields. Yields from the pepper cultivar trials both inside the high tunnel and outside field were comparable to one another at 1.24 kg plant-1 and 1.06 kg plant-1, respectively. Cucumber yields in the high tunnel were increased by 1.7 times over the field trial yields. Results indicate that in North Dakota, high tunnels extended the growing season, and increased production relative to field conditions.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Edward E. Carey / A series of four investigations was conducted from 2005 to 2007 focusing on vegetable or high tunnel production. In the first study (chapters 1 & 2), the effect of high tunnels on soil quality was investigated. Grower perceptions of soil quality were assessed from 81 responses to a questionnaire. Indicators of soil quality were evaluated at two KSU research centers. Soil quality was then quantified in high tunnels and adjacent fields at 79 farms, where high tunnels ranged in age from two to fifteen years. Particulate organic carbon as a fraction of soil total carbon was used as an indicator of soil quality. At 80 % of locations, particulate organic matter carbon was greater under high tunnels than adjacent fields. Soil quality was not adversely affected by the continuous presence of high tunnel covering. Management and cropping history in high tunnels was also collected and reported as this information is of interest to growers and the universities and agricultural industries that serve them. Tomato was the most common high tunnel crop. It was grown by 86 % of survey respondents in the previous four year period. Organic soil amendments were applied by 89 % of growers; 35 % use organic soil amendments exclusively. In the second study (chapter 3), two microbial tea solutions were applied to collard green (Brassica oleracea L. var. acephala cv. Top Bunch) or spinach (Spinacea oleracea L. cv. Hellcat) crops at Olathe and Haysville, Kansas, without significant effects on crop yield or soil microbial biomass. Finally, preliminary results from two studies were formatted for reporting as extension publication (chapters 4 and 5). Autumn production, over-wintering, and spring bolting were assessed for 26 spinach cultivars in a 3-season multi-bay Haygrove high tunnel. Also, the effect of autumn planting date on harvest date and yield was observed for two spinach cultivars (cv. Avenger and PVO172) planted on six dates in October and November, under high tunnels at Olathe, Kansas. Spinach planted in the first half of October was harvested in the winter, without loss of spring yield for both cultivars.