Evaluating Silicon Foliar Sprays as a Strategy to Improve Postproduction Performance of Potted Basil (Ocimum basilicum L.)

The objective of the study was to evaluate foliar silicon (Si) applications for effects on the growth and performance of container-grown basil during production and resistance to postproduction wilt in retail. Basil (Ocimum basilicum ‘Genovese’ L.) seedling plugs were transplanted into 10-cm diameter plastic containers with peat-based substrate and grown for 42 d in a polycarbonate greenhouse. Plants were irrigated with fertilizer solution consisting of a 17.0 nitrogen (N)-1.3 phosphorus-14.1 potassium water-soluble fertilizer dissolved in tap water at 150 mg∙L-1 N. Foliar sprays containing sodium silicate at 0, 50, 100, 200, and 400 mg∙L-1 Si mixed with deionized water were applied every 7 d. Spray solutions also contained a non-ionic surfactant at 0. 3 mL∙L-1, and a 100% deionized water spray treatment was included as a no-surfactant control. Data collection consisted of leaf SPAD chlorophyll content, shoot height, shoot fresh and dry mass, and Si concentration in dried shoot tissue for four replicates per treatment. Four remaining replicates per treatment continued for a simulated retail phase, during which all replicate containers were irrigated to saturation with clear (no fertilizer) water and placed an indoor environment. Plants were checked twice daily for visible wilt, and number of days until wilting was recorded. To minimize the variability in daily evapotranspiration caused by fluctuations in the retail environment and temperature, days to wilt was standardized by dividing the total water loss per replicate determined using gravimetric methods by the average daily water loss from evaporation pans. The 0 mg∙L-1 Si and no-surfactant control treatments were combined for greater statistical power as there were no differences in their effects. Single degree-of-freedom contrasts were used to compare the effects of each Si treatment to the non-silicon control. Leaf SPAD chlorophyll content was greater for each Si treatment compared to the control. Shoot dry mass was also greater when Si was applied at 400 mg∙L-1, but there was no effect on shoot fresh mass or height. Shoot Si content increased with spray concentration, ranging from 466 to 882 μg∙g-1 of dry tissue for 0 and 400 mg∙L-1 Si treatments, respectively. Foliar sprays of 200 and 400 mg∙L-1 Si increased the number of days until wilting by 2.2 and 2.5 d, respectively. Based on these results, foliar Si sprays applied during production may be a practical and effective strategy for growers to increase resistance to wilting during retail for basil, with minimal effects on plant growth and quality

Quantifying Temperature Effects on Plant Development Rates and Quality of Compact Container-grown Pepper

The mean daily temperature effects on plant development rates and quality of compact container-grown pepper were evaluated. Compact pepper cultivars Fresh Bites Yellow and Hot Burrito were grown in greenhouses at 18 to 26 °C (Expt. 1) and 20 to 30 °C (Expt. 2) under supplemental high-pressure sodium lighting and a 16-hour photoperiod. The number of days to first open flower, to first ripe fruit, and from flower to ripe fruit were measured and the development rates calculated by taking the reciprocal (e.g., 1/day). Temperature effects were predicted by fitting a nonlinear exponential function that included the base temperature (Tmin) and maximum developmental rate (Rmax) parameters. Plant quality attributes were measured during Expt. 2. As the temperature increased, the times to flower and fruit decreased (i.e., developmental rates increased) for both cultivars. The estimated Tmin was 13.3 °C for ‘Fresh Bites Yellow’, and that for ‘Hot Burrito’ was 9.3 °C, whereas the Rmax was similar between cultivars (averages of 0.0488 at flower, 0.0190 at fruit, and 0.0252 from flower to fruit). ‘Fresh Bites Yellow’ and ‘Hot Burrito’ grown at ≈25 °C had a relatively short crop time, compact canopy, large fruit size, and high number of fruits per plant at finish. Compact peppers are new crops being grown by greenhouse floriculture operations for their ornamental and edible value, and the information from this study can help growers schedule these crops to meet critical market windows and determine the impacts of changing the growing temperature on crop timing and quality

A Tunable Snapshot Imaging Spectrometer

A tunable snapshot imaging spectrometer has been demonstrated. A liquid crystal spatial light modulator (LC SLM) has been integrated into a computed tomographic imaging spectrometer (CTIS) to achieve tunability. The LC SLM allows for rapid, programmable, and non-mechanical alteration of its phase profile by the application of appropriate voltages to its transparent electrodes.The goal of this dissertation is twofold: (1) to integrate a liquid crystal spatial light modulator into a CTIS instrument and characterize its performance as a tunable CTIS disperser, and (2) to implement tunability by analyzing different CTIS configurations.The theoretical model of CTIS operation, calibration, reconstruction, and disperser design are covered in detail. The cross talk of the LC SLM forces the use of a feedback design algorithm rather than designing the desired phase profile a priori in the computer. The modifications to the current polychromatic linear inversion technique for use with the LC SLM in feedback are presented. The result of the modifications is the successful integration of a reprogrammable (i.e. tunable) disperser for the CTIS instrument.The implementation of tunability is explored by analyzing the spectral resolution of a reconstructed point source for different disperser configurations. A method for experimentally determining the CTIS spectral resolution is presented

Developing Custom Fertilizer Strategies Recirculating Hydroponic Systems

Hydroponic systems recirculate nutrient solution to reduce the amount of water used in leafy green production. However, the rootzone of the nutrient solution is complex and influenced by interacting factors such as plant uptake demand, irrigation water quality, supplied fertilizer salts and nutrient concentrations, environmental conditions, and injection of mineral acids/bases to control solution pH. A common strategy for managing nutrients in commercial production is to select a hydroponic solution formulation (i.e. recipe) to supply and maintain a target pH and electrical conductivity (EC) in the recirculating solution over time by automatic injection of mineral acids/bases and concentrated fertilizer stock solutions. During nutrient replenishment of the recirculated solution, nutrients are resupplied at the same ratios at which they are supplied in the initial solution. Often with this approach, the resupply of nutrients is not balanced with plant uptake demand, resulting in root zone nutrient imbalances which can cause yield reductions and motivate growers to dump and replace solution. The objective was to develop a novel strategy for managing nutrients in recirculating solutions designed to supply and maintain optimal macronutrient concentrations and solution pH with basil (Ocimum basilicum) and lettuce (Lactuca sativa) as model crops. The strategy consisted of custom formulating species-specific initial and replenishment solutions formulated using a combination of data on plant tissue nutrient concentrations, previously published nutrient management guidelines and peer-reviewed research, and common grower tools and experience. The custom initial solution for each species was intended to supply macronutrient concentrations at near optimal ratios whereas the custom replenishment solution was intended to replace the nutrients taken up and maintain the concentrations/ratios in the initial solution. The custom strategy was evaluated with basil and lettuce grown for 56 d in deep water culture (DWC) systems and compared to a control strategy consisting of a common 2-part fertilizer formulation for both the initial and replenishment solution. Overall, the custom strategies for basil and lettuce resulted in macronutrients remaining near the initial concentrations supplied whereas the control strategy resulted in macronutrients, particularly calcium and sulfur, which deviated substantially from the initial concentrations. A separate experiment evaluated the custom nutrient management strategy with basil grown in hydroponic nutrient film technique (NFT) systems, where nutrient solutions were formulated using two sources of irrigation water differing in soluble salts and alkalinity. Overall, solution macronutrient concentrations remained more stable over time with the custom strategy compared to the control strategy for both irrigation water qualities. Yield was greatest for basil grown in hydroponic solutions formulated using the high alkalinity irrigation water as a result of the additional nitrogen (N) supplied by nitric acid (HNO3) injection used to neutralize the water alkalinity and adjust solution pH

Tim Tebow

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Developing Custom Fertilizer Strategies Recirculating Hydroponic Systems

Hydroponic systems recirculate nutrient solution to reduce the amount of water used in leafy green production. However, the rootzone of the nutrient solution is complex and influenced by interacting factors such as plant uptake demand, irrigation water quality, supplied fertilizer salts and nutrient concentrations, environmental conditions, and injection of mineral acids/bases to control solution pH. A common strategy for managing nutrients in commercial production is to select a hydroponic solution formulation (i.e. recipe) to supply and maintain a target pH and electrical conductivity (EC) in the recirculating solution over time by automatic injection of mineral acids/bases and concentrated fertilizer stock solutions. During nutrient replenishment of the recirculated solution, nutrients are resupplied at the same ratios at which they are supplied in the initial solution. Often with this approach, the resupply of nutrients is not balanced with plant uptake demand, resulting in root zone nutrient imbalances which can cause yield reductions and motivate growers to dump and replace solution. The objective was to develop a novel strategy for managing nutrients in recirculating solutions designed to supply and maintain optimal macronutrient concentrations and solution pH with basil (Ocimum basilicum) and lettuce (Lactuca sativa) as model crops. The strategy consisted of custom formulating species-specific initial and replenishment solutions formulated using a combination of data on plant tissue nutrient concentrations, previously published nutrient management guidelines and peer-reviewed research, and common grower tools and experience. The custom initial solution for each species was intended to supply macronutrient concentrations at near optimal ratios whereas the custom replenishment solution was intended to replace the nutrients taken up and maintain the concentrations/ratios in the initial solution. The custom strategy was evaluated with basil and lettuce grown for 56 d in deep water culture (DWC) systems and compared to a control strategy consisting of a common 2-part fertilizer formulation for both the initial and replenishment solution. Overall, the custom strategies for basil and lettuce resulted in macronutrients remaining near the initial concentrations supplied whereas the control strategy resulted in macronutrients, particularly calcium and sulfur, which deviated substantially from the initial concentrations. A separate experiment evaluated the custom nutrient management strategy with basil grown in hydroponic nutrient film technique (NFT) systems, where nutrient solutions were formulated using two sources of irrigation water differing in soluble salts and alkalinity. Overall, solution macronutrient concentrations remained more stable over time with the custom strategy compared to the control strategy for both irrigation water qualities. Yield was greatest for basil grown in hydroponic solutions formulated using the high alkalinity irrigation water as a result of the additional nitrogen (N) supplied by nitric acid (HNO3) injection used to neutralize the water alkalinity and adjust solution pH