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  • Author or Editor: Michael S. Douglass x
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Demand for local food, including strawberries (Fragaria ×ananassa), is increasing throughout the United States. Strawberry production in the midwestern United States can be challenging due to the relatively short growing season and pests. However, vertical, hydroponic, high tunnel production systems could extend the growing season, minimize pest incidence, and maximize strawberry yield and profitability. The objectives of this study were to 1) identify the best cultivars and growing media for vertical, hydroponic, high tunnel production of strawberries in the midwestern United States and to 2) assess potential strategies for replacing synthetic fertilizer with organic nutrient sources in hydroponic strawberry production. To accomplish these objectives, three experiments were conducted across 2 years and two locations in Illinois to compare 11 strawberry cultivars, three soilless media mixtures, and three nutrient sources. Strawberry yield was greatest when grown in perlite mixed with coco coir or vermiculite and fertilized with a synthetic nutrient source. Yield was reduced by up to 15% when fertilized with a bio-based, liquid nutrient source and vermicompost mixed with soilless media. Strawberry yield among cultivars varied by year and location, but Florida Radiance, Monterey, Evie 2, Portola, and Seascape were among the highest-yielding cultivars in at least one site-year. Results contribute to the development of best management practices for vertical, hydroponic, high tunnel strawberry production in the midwestern United States, but further research is needed to understand nutrient dynamics and crop physiological response among levels within vertical, hydroponic towers.

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We evaluated suitability of chemical indices of three media formulations or substrates (A, B, and C) consisting of composted pine bark, coconut coir pith, sphagnum peatmoss, processed bark ash, and perlite in varied proportions for growing northern red oak (Quercus rubra L.) seedlings. These substrates were ranked according to their ability to promote seedling growth. The low-yielding substrate (A) was devoid of pine bark and perlite and the medium-yielding substrate (B) contained no peatmoss or processed bark ash. The high-yielding substrate (C) contained all components. Additionally, we tested plant response to high nitrogen (N) fertilization on each substrate. Media EC, pH, and total dissolved solids measured at transplanting explained 68%, 43%, and 66%, respectively, of the variation in plant dry weight and 39%, 54%, and 46%, respectively, of the variation in shoot height. Vector diagnosis effectively ranked nutritional limitations on seedling growth as N > P > K. High N fertilization highlighted element deficiency in seedlings grown on substrate A, but resulted in element toxicity and antagonistic interactions in plants established on substrates B and C, respectively.

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Abrasive weeding is a nonchemical weed control tactic that uses small, gritty materials propelled with compressed air to destroy weed seedlings. Organic fertilizers have been used successfully as abrasive grits to control weeds, but the goal for this study was to explore the effects of fertilizer grit, application rates, and background soil fertility on weeds, plant available nitrogen (N) uptake, and crop yield. Field trials were conducted in organic ‘Carmen’ sweet red pepper (Capsicum annuum) and organic ‘Gypsy’ broccoli (Brassica oleracea var. italica) and treatments included organic fertilizer grit (8N–0.9P–3.3K vs. 3N–3.1P–3.3K), grit application rates (low vs. high), compost amendments (with and without), and weedy and weed-free controls. Weed biomass was harvested at 84 days and 65 days after transplanting for pepper and broccoli, respectively. Simulated total plant available N (nitrate + ammonium) uptake was measured with ion exchange resin stakes between 7 and 49 days after the first of two grit applications. Produce was harvested at maturity, graded for marketability, and weighed. The higher grit application rate, regardless of fertilizer type, reduced the weed biomass by 75% to 89% for pepper and by 86% to 99% for broccoli. By 5 weeks after the first grit application, simulated plant N uptake was greatest following grit application with the 8% N fertilizer, followed by the 3% N fertilizer, and lowest in the weedy control. The high grit application rate of 8% N fertilizer increased pepper yield by 112% compared with the weedy control, but it was similar to that of the weed-free control. Broccoli was less responsive to abrasive grits, with yield changes ranging from no difference to up to a 36% increase (relative to the weedy control) depending on the application rate and compost amendment. This is the first evidence indicating that the nutrient composition of organic fertilizer abrasive grits can influence in-season soil N dynamics, weed competition, and crop yield. The results suggest that abrasive weeding technology could be leveraged to improve the precision of in-season fertilizer management of organic crops.

Open Access