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  • Author or Editor: Edward Carey x
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High tunnel strawberry (Fragaria × ananassa) production experiment was conducted in south central Kansas, which consisted of two cultivars and four tunnels. The same experimental design was conducted under field conditions. The objectives of this study were to compare strawberry production and quality under high tunnels to those grown in the field and to assess the potential for high tunnels for early-season strawberry production. Plug plants of `Sweet Charlie' and `Chandler' were planted October 18. Plants were spaced at 12” × 12 “in double rows on raised beds covered with black plastic mulch. Protected plants under high tunnels had 100% winter survival rate compared to 60% of the field plants. Yield and berry quality of the high tunnel plants were by far better than those of field grown plants. Plant growth under high tunnels was about three to four fold higher than the unprotected field plants. `Sweet Charlie' flowered in early February and produced berries one week earlier than `Chandler'. Both cultivars were harvest from early April through late May at weekly interval. `Sweet Charlie' in early April produced an average berry weight of 14 g, soluble solids of 8 °Brix, and the largest average berry weight was 15 g. `Chandler' harvested late April produced larger berries than `Sweet Charlie' with the largest average berry weight of 35 g compared to 31 g for `Sweet Charlie'. In mid May, `Chandler' produced 72% higher yield than `Sweet Charlie'. High tunnel not only produced higher yield and better quality berries than field strawberries but it has a potential to produce early crop and extend the season production of strawberry in Kansas.

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Plant growth, yield, and fruit quality of two strawberries (Fragaria ×ananassa Duch.)—`Chandler' and `Sweet Charlie'—grown under high tunnels (HTs) were compared with that of field plants during 2002–03 and 2003–04 growing seasons. Plug plants were planted in mid-October 2002 and mid-September 2003 on raised beds covered with black polyethylene mulch. Microclimate of the HTs protected strawberry crowns from winter damage and advanced fruit production 5 weeks earlier than that of plants grown under field conditions. From December to February, average minimum and maximum crown temperatures under the HTs were 5 and 12 °C warmer than those of the field crowns, respectively. The earliest HT fruit were harvested on 7 Apr. 2003 and 11 Mar. 2004. Yield and fruit quality under the HTs were superior to that of field-grown plants. HT plants, especially `Sweet Charlie', bloomed earlier than did field plants, but `Chandler' produced higher yield than `Sweet Charlie' late in the season. Larger fruit with higher soluble solids concentration (SSC) were produced inside the HTs than outside. HT `Sweet Charlie' fruit were sweeter than `Chandler' fruit, but `Chandler' produced larger fruit. Larger leaf area, greater number of leaves and shoot biomass, more branch-crowns, and fewer runners were developed under HTs than field conditions. Total leaf area, leaf production, total shoot biomass, and number of branch-crowns of HT `Chandler' were greater than HT `Sweet Charlie'. Results of this study indicate that strawberry plants under HTs were not only precocious, but also produced higher yields and superior quality to that of field plants. HT conditions suppressed runner growth, but enhanced branch-crown development.

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There is great interest by horticulture producers in the Central Great Plains in methods to extend the traditional growing season, increase value of crops and provide more locally grown produce. High tunnels are low-cost, unheated greenhouses that can accomplish these goals. In 2002, the Central Great Plains High Tunnel Project was initiated through funding support by the Initiative for Future Agriculture and Food Systems (IFAFS). The Univ. of Missouri, Kansas State Univ., and the Univ. of Nebraska have constructed 24 high tunnels to conduct research on vegetables, small fruits and cut flowers. Each year, a multi-state workshop is conducted along with several on-farm and research center tours. Growers are collaborating with extension personnel on projects ranging from high tunnel temperature management to pest management. A web site for high tunnel information has been constructed (www.hightunnels.org). Production guides on specific high tunnel crops have been printed. From 2002-03, a significant number of high tunnels have been constructed in the Central Great Plains.

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High tunnels, unheated greenhouses, have been shown to be a profitable season-extending production tool for many horticultural crops. Production of cool-season vegetables during hot summer months can be achieved using shaded high tunnels. Microclimate in high tunnels and open field was monitored during summer trials of leaf lettuce, in which unshaded tunnels and shaded tunnels (39% PAK white shadecloth) were used, respectively, in 2002 and 2003. Wind speed was consistently lower in high tunnels. Compared to open field, daily air temperature was about 0.7 °C higher in unshaded high tunnels, and 0.5 °C lower in shaded high tunnels. Relative humidity was slightly lower in unshaded tunnels, but tended to increase in shaded tunnels, in comparison to the open field. When using shadecloth, soil temperature was lowered by 1∼3 °C and the leaf surface temperature was significantly reduced by 1.5∼2.5 °C. In shaded high tunnels, PAR light dropped by at least 50% relative to the outside, where the maximum PAR light intensity reached 1800 μmol·m-2·s-1. Overall, shaded high tunnels resulted in higher quality lettuce, with less bolting and bitterness. Reference crop evapotranspiration (ET0) was estimated from meteorological data on a daily basis using the FAO-56 method. ET0 was lowest in shaded high tunnels, and highest in the open field. Relatively lower ET0 in high tunnels indicated a likely lower water requirement and therefore improved water use efficiency compared with the open field.

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High tunnels have been shown to be a profitable season-extending production tool for many horticultural crops. Production of cool-season vegetables during the hot summer months represents a challenge to market growers in the midwestern United States. Two experiments were conducted to investigate the microclimate and production of eight leaf lettuce (Lactuca sativa) cultivars in high tunnels and open fields, using unshaded and shaded (39% white shadecloth) tunnels in Summer 2002 and 2003, respectively. Wind speed was consistently lower in high tunnels with the sidewalls and endwalls open. An unshaded high tunnel resulted in an increase of daily maximum and minimum air temperatures by ≈0.2 and 0.3 °C, respectively, in comparison with the open field. In contrast, daily maximum air temperature in a shaded high tunnel decreased by 0.4 °C, while the daily minimum air temperature was higher than that in the open field by 0.5 °C. Using high tunnels did not cause a marked change in relative humidity compared with the open field. When using shadecloth, the daily maximum soil temperature was lowered by ≈3.4 °C and the leaf surface temperature was reduced by 1.5 to 2.5 °C. The performance of lettuce during summer trials varied significantly among cultivars. Unshaded high tunnels generally led to more rapid bolting and increased bitterness of lettuce compared with the open field. Lettuce grown in high tunnels covered by shadecloth had a lower bolting rate, but decreased yield relative to the open field. Based on our results, summer lettuce production would not be recommended in high tunnels or open fields in northeastern Kansas, although the potential of shaded high tunnels deserves further studies. Reference crop evapotranspiration (ET0) was estimated from meteorological data on a daily basis using the FAO-56 method. The ET0 was lowest in the shaded high tunnel and was the highest in the open field. Relatively lower ET0 in high tunnels indicated a likely lower water requirement and therefore improved water use efficiency compared with the open field.

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An experiment was conducted at Olathe, Kan., in Spring 2004 to investigate the influence of organic and conventional fertilizer sources and application rates on antioxidant levels of pac choi (Brassica rapa L. cv. Mei Qing) in open fields and poly-covered high-tunnel plots. Organic plots received pre-plant application of composted cattle manure and alfalfa (Hu-More 1–1–1) at 0 kg/ha N, 156 kg/ha N, or 314 kg/ha N, and conventional plots received preplant application of 13N–13P–13K at 0 kg/ha N, 78 kg/ha N, or 156 kg/ha N. Antioxidant levels were measured using the oxygen radical absorbance capacity (ORAC) assay. There were significant effects of fertilizer source and high-tunnel environment on the antioxidant capacity of pac choi. Organic fertilization significantly increased hydrophilic ORAC of pac choi in open field plots, but not in high tunnels. Regardless of the fertilizer source, pac choi grown in the open field had significantly higher hydrophilic ORAC than that grown in tunnels. Lipophilic ORAC was significantly increased by organic fertilization but was not affected by high-tunnel production. Total ORAC (hydrophilic + lipophilic) was significantly higher in pac choi from organic or open-field plots, compared to conventional and high-tunnel plots, respectively. Although fertilizer rate did not show significant impact on antioxidant level of pac choi, hydrophilic and total ORAC seemed to decrease as the fertilizer rate increased, especially under conventional fertilization, while lipophilic ORAC reached the highest level at the medium fertilizer rate. Differences in antioxidant levels were likely associated with the enhanced phytochemical content of pac choi from organically fertilized and open-field plots.

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This study characterized the influence of nitrogen (N) rates and variation in local availability on root architecture as measured by lateral root (LR) development attributes during the onset of the storage root (SR) initiation stage in ‘Beauregard’ sweetpotato adventitious roots (ARs). In N rate experiments, plants grown without fertilizer N showed significantly lower values for all measured LR attributes compared with fertilized plants. Total first- (1LR) and second-order LR (2LR) length increased by 78% and 2873%, respectively, as N was increased from 0 to 50 kg·ha−1. Total 1LR and 2LR number increased by 32% and 1465%, respectively. Increasing the N rates to 100 and 200 kg·ha−1 did not result in further increases for all LR attributes measured. There were no differences in AR number between untreated controls and plants fertilized with 50 kg N/ha. However, the number of ARs increased by 65% when fertilizer N was increased from 50 to 100 kg·ha−1. Increasing the rate to 200 kg·ha−1 did not result in further increases in AR number. In split-root experiments, roots grown in the compartment with 50 kg N/ha had 135% and 2916% increase in total 1LR and 2LR length, respectively, compared with roots grown in the compartment without fertilizer N. Total 1LR and 2LR number increased by 110% and 2114%, respectively. There were 111% more ARs in the fertilized compartment relative to the unfertilized compartment. There were no differences in LR attributes and AR number between compartments that received similar fertilizer N rates. In fertilizer placement experiments, there were no differences in LR attributes between pre-mixing fertilizer N and placement of fertilizer ≈4 cm below the surface of the growth substrate. There were also no differences between the unfertilized control and placement of fertilizer ≈4 cm from the bottom of the pot. Plants grown in substrate with pre-mixed N showed 38% and 342% increase in 1LR and 2LR length, respectively, relative to the bottom placement of N. Total number of 1LR and 2LR in the growth substrate with pre-mixed N increased by 30% and 312%, respectively, relative to the bottom placement of N. These results represent the first evidence for the association between sweetpotato root architectural attributes and variation in N rate and localized availability. These results are also consistent with findings in model systems in which local N presence is necessary for LR development. This information can be used to further optimize SR yield by helping to ensure the availability of N at the optimum rate across time and space.

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Compost teas, made using an aerated brewing process, have been reported to have potential for controlling a range of plant diseases and improving crop health. Septoria leaf spot of tomato, caused by the fungus Septoria lycopersici, is a common and destructive disease of tomato in Kansas. A field trial was conducted at Wichita, Kansas during Summer 2003 to evaluate the potential of pre-plant compost, and compost tea applied as a foliar spray or through drip fertigation, to control Septoria leaf spot of tomato. The experimental design included three factors: Pre-plant application of 13N-13P-13K or vermicompost; fertigation with CaNO3 or compost tea; and foliar spray with compost tea, fungicide (Dithane) or water. A split plot design was used with fertigation treatments as main plots and the other two factors as sub-plots. There were 3 replications. Tomato cultivar Merced was used and individual plots consisted of 5 plants grown on beds covered with red plastic mulch and supported by stake and weave system. Aerated compost tea was brewed weekly using a vermicompost-based recipe including alfalfa pellets, molasses, humic acid, fish emulsion and yucca extract and applied to plots starting 2 weeks after transplanting. Disease incidence and severity were recorded weekly for 3 weeks following the appearance of disease. Plots were harvested twice weekly and counts of No. 1, No 2 and cull grade tomatoes were recorded. There were no effects of pre-plant or fertigation treatments on Septoria leaf spot disease, but there was a significant effect due to foliar sprays, with mean severity of compost-tea-sprayed plots (26.3%) and fungicide-sprayed plots (31.9%) significantly lower than water-sprayed plots (45.9%) at trial termination.

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Implications of dietary phenolic compounds for human health and disease prevention have been indicated by a body of literature. A greenhouse pot study was performed to investigate the impacts of fertilizer source and preventive insecticide application on phenolic compound levels in pac choi [Brassica rapa (L.) cv. Mei Qing]. A two-way randomized complete-block design with five replications was used in this experiment. Fertilizer source consisted of two levels: conventional fertilizer (pre-plant application of Osmocote slow-release fertilizer), and organic fertilizer (pre-plant application of vermicompost and fertigation with compost tea and fish emulsion). Insecticide application consisted of three levels: organic (pyrethrin) vs. conventional (permethrin), and a plain water control. At harvest, total phenolics and individual phenolic compounds in pac choi leaves (blades) were analyzed by Folin assay and HPLC, respectively. Head weight of pac choi was significantly higher under conventional fertilizer treatment, while it was not affected by insecticides. Total phenolic content of pac choi was significantly increased by organic fertilizer treatment. HPLC results indicated that organic fertilizer treatment resulted in significantly higher levels of individual phenolic compounds, including chlorogenic acid and ferulic acid. In contrast, preventive insecticide application showed little effect on the phenolics in pac choi. Correlation analysis excluded the influence of plant size (head weight) on phenolic content in pac choi. Differential N-forms, rates of nutrient release, and/or variable nutrient content in organic and conventional fertilizer treatments may contribute to elevated phenolic content in organically fertilized pac choi.

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Consumers of organic food tend to believe that it tastes better than its conventional counterpart. However, there is a lack of scientific studies on sensory analysis of organic food. A consumer taste test was conducted to compare the acceptability of organically and conventionally grown spinach. Spinach samples were collected from organically and conventionally managed plots at the Kansas State University Research and Extension Center, Olathe. One hundred-twenty-two untrained panelists (80 female and 42 male) participated in this consumer study. Fresh and 1-week-old spinach leaves were evaluated by 60 and 62 consumers, respectively, using a 9-point hedonic scale (9 = like extremely, 5 = neither like nor dislike, 1 = dislike extremely). The ANOVA results showed that fresh organic spinach had a higher preference score than corresponding conventional spinach, although not at a significant level (P = 0.1790). For the 1-week-old spinach, the difference diminished, and instead, conventional spinach had a higher preference rating. Among 61 consumers who made comments regarding the sensory evaluation, 29 claimed that organic spinach was more tasty and flavorful; 19 consumers thought conventional spinach was better; 13 consumers could not tell the difference. Even though this consumer study did not reveal significant differences in consumer preference for organic vs. conventional spinach, further well-designed sensory tests are warranted given the trends indicated in our study. Assessment of sensory attributes of organic vegetables after storage also deserves further attention. Ideally, both consumer tests and descriptive analysis using trained panelists will be considered.

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