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Plastic mulches made from nonbiodegradable polyethylene (i.e., "PE mulch") are an integral tool for organic and conventional strawberry (Fragaria x ananassa) production due to their ability to optimize soil and crop microclimates, suppress weeds, and promote overall yield and fruit quality. Unfortunately, PE mulch is primarily single-use and seldom recycled, leading to large volumes of plastic waste, with some of the plastic mulch fragments residing in the soil or polluting the surrounding agroecosystem. Although soil-biodegradable plastic mulches are a promising mulch technology that aims to reduce waste generation, no commercial products are available that meet the National Organic Program's requirements. Hydromulches are an alternative mulch technology that is sprayable and can be formulated to meet organic requirements, but they have undergone limited testing. The objective of this study was to evaluate the effects of various hydromulch formulations on yield, fruit quality, and tissue nutrient status of day-neutral strawberries grown in two diverse environments. Hydromulches made with various formulations of paper, guar gum, or psyllium tackifiers were compared with PE mulch in Northwest Washington and North Dakota in 2022. Few treatment effects were observed throughout the experiment, and both strawberry yield and fruit quality were maintained. Slight variations in tissue nutrient concentrations were observed but not attributed to hydromulch treatments. Information resulting from this project demonstrates hydromulches maintain crop productivity and quality. Future research should evaluate the ability of hydromulches to suppress a spectrum of weed species, impacts on soil health, and economic viability. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Despite the growing interest in high tunnel organic vegetable production, limited information is available regarding optimizing nutrient management for organic leafy greens. This 3-year study examined the impacts of cowpea cover crop as well as different organic fertilizers and composts on yield, leaf mineral nutrient content, and phytochemical properties of organic leafy greens produced in high tunnels under Florida sandy soil conditions. The experiment was arranged in a split-split-plot design with three replications. The whole plots consisted of a cowpea (Vigna unguiculata 'Iron & Clay') cover crop and a weedy fallow control, with fertilization treatments in the subplots, including preplant application of granular fertilizer vs. weekly injection of liquid fish fertilizer at the same seasonal rates of nitrogen (112 kg/ha), phosphorus (9.8 kg/ha), and potassium (74.4 kg/ha). The sub-subplots included yard waste-based compost (22.4 Mt/ha), cow manure-based compost (22.4 Mt/ha), vermicompost (5.6 Mt/ha), and no compost control. Cowpea was broadcasted (112 kg/ha) in early July or mid-August and terminated 51 to 53 days after seeding. Pac choi (Brassica rapa var. chinensis 'Mei Qing Choi') was transplanted inmid-Sep. ormid-Oct. and harvested after 33 to 36 days. Baby spinach (Spinacia oleracea 'Corvair') or baby leaf lettuce (Lactuca sativa 'Outredgeous') was direct seeded subsequently as a catch crop. Each experimental unit remained in the same location across the 3 years of the study. Cover cropping had little influence on yields, leafmineral nutrients, ascorbic acid content, total phenolics, and total antioxidant capacity of pac choi and baby spinach/lettuce. Compared with preplant application of the granular organic fertilizer, weekly liquid organic fertigation improved pac choimarketable yield and dryweight by 16.8%and 5.4%on average, respectively, and enhanced leaf nitrogen and phosphorus contents on a dry weight basis. Relative to the no compost control, yard waste compost consistently improved marketable yields of pac choi by 11.6%on average and led to higher yields of the baby spinach/lettuce catch crop in years 1 and 3, suggesting that compost applications may enhance seasonal nutrient availability to better meet crop demand. However, compost application exhibited inconsistent effects on crop mineral nutrient and phytochemical contents across the years, which could be attributed to the different nutrient compositions of the composts applied in each season, as well as the legacy effects from the previous season. Furthermore, the compost benefits may be influenced by the fertilization programas indicated by their interaction effects observed in this study. [ABSTRACT FROM AUTHOR]

Grafted tomato (Solanum lycopersicum) production is popular, particularly in high tunnels, because grafted plants can mitigate soilborne disease incidence in highly infested soils and increase water and nutrient use efficiency and crop yield and quality. However, these potential benefits are not as well documented in open field production systems with less disease pressure. The objective of this study was to quantify the effect of tomato grafting on fruit yield, number, and size across 2 years (2018 and 2019) and three diverse open-field production environments in Nebraska (Lincoln, North Platte, and Dwight). At each location, a scion from one of two determinant fresh market tomatoes, ‘Nebraska Wedding’ (heirloom) or ‘BHN 589’ (commercial hybrid), were grafted onto one of two rootstocks, ‘Estamino’ and ‘Maxifort,’ and the nongrafted scion cultivars were controls. In year 2, a fertilizer treatment was introduced (0 and 50 kg·ha21 N). Ripe tomatoes were harvested weekly, sorted as marketable or cull, counted, and weighed fresh. No marketable or total yield benefits of grafting were observed in 2018 for any scion by rootstock combination across locations. Marketable yield of grafted plants was reduced by 32% in Lincoln. However, grafted ‘Nebraska Wedding’ plants (regardless of rootstock) in North Platte (with coarse-textured, lower organic matter soil) increased fruit number (but not yield) by 50% to 63%. In 2019, grafting ‘BHN 589’ to ‘Maxifort’ increased total tomato yield by 24% across all locations. The heirloom variety Nebraska Wedding did not benefit from grafting in 2019. ‘Estamino’ rootstock did not increase tomato yield, number, or size for either scion variety in either year. Nitrogen fertilizer increased yield as expected in 2019, but grafted plants did not perform better than nongrafted under reduced nitrogen fertility. Results from this study suggest that grafting is not consistently beneficial to ‘BHN 589’ and ‘Nebraska Wedding’ in open field production systems in Nebraska, particularly if there are no known soilborne disease issues. [ABSTRACT FROM AUTHOR]

Colored shade nets are known to alter the light quality and quantity and thus can influence plant growth and nutritional quality of crops. Lettuce (‘Lollo Antonet’ and ‘Green Forest’) and basil (‘Aroma-2’ and ‘Genovese’) were grown in ebb-and-flow hydroponic tables for 4 weeks. Colored shade nets of aluminet, black, pearl, and red with 50% shading intensity along with a control (no-shade) were used in this experiment. Data for plant growth and leaf quality attributes were collected at harvest time. The no-shade treatment showed increased shoot fresh and dry weight, sugar, and relative chlorophyll content in both lettuce and basil cultivars, whereas plant height and net photosynthesis rates were increased under aluminet, pearl, and red nets. In basil, calcium and sulfur were greatest under no-shade, whereas zinc and copper were greatest under aluminet. Zinc, iron, calcium, magnesium, and manganese concentrations were greatest under no-shade in lettuce. The pearl-colored net increased leaf soluble solids content. No-shade produced the greatest starch values in basil, whereas pearl shade net produced the greatest starch in ‘Lollo Antonet’ in the fall. Light spectra varied with shade net resulting in 90%, 65%, 50%, 30%, and 70% of incident light occurring between 400 and 700 nm for no-shade, pearl, aluminet, black, and red shade nets, respectively. Overall, lettuce and basil plants under no-shade (daily light integral of 20 to 24 mol·m−2·d−1 and temperature of 26 to 30 °C) had increased plant growth and leaf quality in late spring and fall, compared with colored shade nets. [ABSTRACT FROM AUTHOR]

Growers have been searching for alternative horticultural growing media components because of their desire to use sustainable resources. Biochar is a carbonbased material that has been evaluated for use as an alternative aggregate in peatbased soilless substrates. Additionally, silicon (Si) has been examined as a beneficial element to promote plant growth and plant quality in a variety of crops. However, there has been limited research regarding the interaction of biochar as an aggregate and Si in soilless substrates. This study aimed to determine the impact of Si and biochar on plant growth and nutrient uptake for greenhouse-cultivated hemp (Cannabis sativa L.). Hemp plants were grown in one of 12 different substrate blends: with two rates of calcium silicate (CaSiO3), two aggregate types of biochar (medium or coarse) or perlite, and aggregate percentages of 85% peat + 15% aggregate and 70% peat + 30% aggregate. The cannabinoid concentration, plant height, diameter, or total plant biomass were similar across all substrate blends after 12 weeks of growth. Additionally, the use of CaSiO3 as a Si substrate amendment increased Si foliar concentrations, and the addition of biochar to peat-based mixes did not limit the Si availability for plant uptake. However, Si substrate amendments did not impact plant height, diameter, or total plant biomass. This suggests that the biochar tested during this study is suitable in peat-based substrates for C. sativa 'BaOx' production at rates up to 30% (by volume) in peat-based substrates with CaSiO3 amendments. [ABSTRACT FROM AUTHOR]

During California's broad experiment with fig cultivation, Ira J. Condit became known as the "High Priest of the Fig." Herein is a large set of fig attributes deemed agriculturally important by Ira J. Condit in his 1955 monograph. The attributes are divided into five categories and distributed across 717 cultivars. All data and software source code have been made available publicly on Figshare. [ABSTRACT FROM AUTHOR]

Anthocyanins are a group of human-health-promoting phenolic compounds that influence the pigmentation of red-leaf lettuce (Lactuca sativa). Ultraviolet A (UVA; 315-399 nm) and blue (B; 400-499 nm) light can increase the concentrations of phenolic compounds but also suppress cellular expansion, which can limit harvestable biomass accumulation. It is not known whether UVA or B light is more effective at increasing phenolic compound concentrations when they are each applied at the same photon flux density. Our objective was to evaluate the efficacy of UVA and B light when added during the end of production (EOP) at promoting phenolic compound synthesis and red-leaf coloration without limiting biomass accumulation. We grew red-leaf lettuce 'Rouxai' in a controlled indoor environment at an air temperature of 22°C under warm-white and red light-emitting diodes (LEDs). On day 24, 30 or 60 µmol·m-2·s-1 from UVA, B, UVA plus B, or red plus green LEDs was added during the last 6 days of the 30-day production period. UVA and B light, alone or combined, similarly increased leaf redness (by up to 72%), total phenolic concentration (by up to 92%), total anthocyanin concentration (by up to 2.7-fold), and relative chlorophyll concentration (by up to 20%) and did not inhibit growth, compared with lettuce grown without EOP supplemental lighting. Considering B light was as effective as UVA light at increasing leaf color and phytonutrient density and that B LEDs are more electrically effective, economical, and durable, an enriched blue-light spectrum at the EOP is a comparatively sustainable method to increase crop quality without suppressing biomass accumulation. [ABSTRACT FROM AUTHOR]

For many growers, established and newcomers, the determination of the optimal light spectrum for growing crops can be challenging and highly dependent on crop species and variety. With the increased popularity of LED lighting, the capability to fine- tune a light spectrum has never been greater. Here, we break down the fundamental roles of the major spectral regions (ultraviolet, blue, green, red, and far-red) and explain the effect on plant growth, yield, and crop quality (i.e., greenness, coloration, flavor) when applied in isolation or combination. The first part of this review examines plant responses to light stimuli and the potential benefits for growers. We also discuss how LED lighting can be used to manipulate plant growth and development to improve crop productivity and/or value. We suggest some basic LED light "recipes" that could be used by growers to deliver specific growth effects and provide an easy-to-use visual reference guide. The second part of this review explores the impact of light treatments on crop productivity. Increased productivity is weighed against the ongoing costs associated with various light treatments, modeled in the context of UK electricity pricing. [ABSTRACT FROM AUTHOR]

Potassium (K) is a critical plant nutrient that determines quality in a myriad of crops and increases production yields. However, excessive application of various types of K fertilizers can decrease both the food quality and yields, which translates as economic losses and food safety issues. The objectives of this study were to 1) elucidate the impacts of different application rates of various K fertilizers on garlic, with the aim to identify the optimal and most economical K fertilizer dosage and 2) compare the effects of applying two common K fertilizers (KCl and K2SO4) on garlic, to determine the optimal combination. From 2018 to 2020, we utilized two distinct Kfertilized fields to conduct our experiments. The results revealed optimal KCl fertilization increased the biomass and vegetation index in garlic, and promoted the transfer of nitrogen, phosphorus, and potassium nutrients from the stem and leaf to bulb, thereby increasing bulb production. The application of KCl fertilizer increased the number of cloves, the diameters of the cloves and bulbs, and reduced variations in bulb size. In addition, the application of KCl fertilizer improved the nutritional quality (Vitamin C, soluble sugar, soluble protein, and allicin) of the garlic and reduced the accumulation of nitrate. However, excessive KCl fertilizer cause decreased yields, appearance traits, and nutritional quality. Applying the same rate of K fertilizer in the form of K2SO4 in isolation increased the garlic yield by only 0.1% to 22.5% when compared with KCl fertilizer. However, the results were not always significant. In this study, the highest yields, appearance traits, and nutritional quality were achieved with the ratio of K2SO4: KCl =3:1. Consequently, to ensure the highest economic value (considering the market prices of K fertilizer, garlic sprouts, and bulbs), the authors recommend a K fertilizer rate of 252.5 kg·ha-1 K2O, with K2SO4 accounting for 61.6% for garlic production in field. [ABSTRACT FROM AUTHOR]

To determine whether supplemental blue light (B) or far-red light (FR) overnight can promote microgreen elongation to facilitate machine harvesting and improve microgreen quality and yield, two common microgreen species, mustard (Brassica juncea) and arugula (Eruca sativa), were grown in a greenhouse in Guelph, Ontario, Canada, during January 2019. Low-intensity (14 µmol·m-2·s-1) B or FR was applied to microgreens overnight from 1730 hr to 0630 hr, and no supplemental lighting (D) was used as a control. After 2 weeks of light treatments, B compared to D promoted stem elongation by 16% and 10%, respectively, and increased crop yield by 32% and 29%, respectively, in mustard and arugula. B compared to D also increased the cotyledon area in mustard and leaf mass per area in arugula and enhanced cotyledon color in both species despite having no effects on total chlorophyll, carotenoid, and phenolic contents. However, FR did not increase stem length or fresh weight compared with D, reduced plant height compared with B in both species, and reduced the cotyledon area in arugula. FR, compared with D and B, reduced the stem diameter and phytochemical contents of both species. Therefore, low-intensity B can be applied overnight for winter greenhouse microgreen production because of its beneficial effects on appearance quality and crop yield without negatively affecting nutritional quality. [ABSTRACT FROM AUTHOR]

Controlled environment (CE) food crop production has existed in the United States for many years, but recent improvements in technology and increasing production warranted a closer examination of the industry. Therefore, our objectives were to characterize historical trends in CE production, understand the current state of the U.S. hydroponics industry, and use historical and current trends to inform future perspectives. In the 1800s, CE food production emerged and increased in popularity until 1929. After 1929, when adjusted for inflation (AFI), CE food production stagnated and decreased until 1988. From 1988 to 2014, the wholesale value of CE food production increased from $64.2 million to $796.7 million AFI. With the recent increase in demand for locally grown food spurring an increase in CE production, both growers and researchers have been interested in using hydroponic CE technologies to improve production and quality. Therefore, we surveyed U.S. hydroponic food crop producers to identify current hydroponic production technology adoption and potential areas for research needs. Producers cited a wide range of technology utilization; more than half employed solely hydroponic production techniques, 56% monitored light intensity, and more than 80% monitored air temperature and nutrient solution pH and electrical conductivity. Additionally, the growing environments varied from greenhouses (64%), indoors in multilayer (31%) or single-layer (7%) facilities, to hoop houses or high tunnels (29%). Overall, producers reported managing the growing environment to improve crop flavor and the development of production strategies as the most beneficial research areas, with 90% stating their customers would pay more for crops with increased flavor. Lastly, taking historical data and current practices into account, perspectives on future hydroponic CE production are discussed. These include the importance of research on multiple environmental parameters instead of single parameters in isolation and the emphasis on not only increasing productivity but improving crop quality including flavor, sensory attributes, and postharvest longevity. [ABSTRACT FROM AUTHOR]

Twenty petunia (Petunia 3hybrida) cultivars were grown at 14, 17, and 20 8C to quantify the impact of temperature on time to flowering, flowering and development rates, and crop quality parameters. Increasing temperature increased vegetative development rates and reduced time to flower (TTF) for all cultivars. Linear functions generated to describe the effects of temperature on the flowering rate (1/TTF) revealed considerable variability in the temperature sensitivity of flowering rates across cultivars. The minimum temperature for the rate of progress toward flowering (Tbase) ranged from 0.15 °C for 'Damask Purple' to 7.1 °C for 'Wave Purple'. The crop quality parameters plant height and branch and flower bud number were all influenced by interactions between cultivar and temperature. Plant height at flowering was unaffected by temperature for 13 of the 20 cultivars, whereas the height of five cultivars was lower at 20 °C compared with 14 °C, and two cultivars were shortest at 17 °C. The branch number of six cultivars was lower at 14 °C than at 17 or 20 °C, whereas three cultivars produced more branches at 17 °C compared with 20 °C. The branch number of 11 cultivars was not impacted by temperature. For 11 of the 20 cultivars, the flower bud number was greater at 14 °C than at 20 °C, whereas temperature did not influence the flower bud number for the other nine cultivars. The results of this work could help to improve production efficiency by allowing cultivars to be placed in temperature-response groups based on the temperature sensitivity of flowering time and/or crop quality parameters. [ABSTRACT FROM AUTHOR]

Low natural daily light integrals (DLIs) are a major limiting factor for greenhouse production during darker months (e.g., October to February in Canada). Supplemental lighting (SL) is commonly used to maintain crop productivity and quality during these periods, particularly when the supply chain demands consistent production levels year-round. What remains to be determined are the optimum SL light intensities (LIs) for winter production of a myriad of different commodities. The present study investigated the growth and yield of sunflower (Helianthus annuus L., 'Black oil'), kale (Brassica napus L., 'Red Russian'), arugula (Eruca sativa L.), and mustard (Brassica juncea L., 'Ruby Streaks'), grown as microgreens, in a greenhouse under SL lightemitting diode (LED) photosynthetic photon flux density (PPFD) levels ranging from 17.0 to 304 mmol⋅m-2⋅s-1 with a 16-hour photoperiod (i.e., supplemental DLIs from 1.0 to 17.5 mol⋅m-2⋅d-1). Crops were sown in a commercial greenhouse near Hamilton, ON, Canada (lat. 43814#N, long. 80807#W) on 1 Feb. 2018, and harvested after 8, 11, 12, and 12 days, resulting in average natural DLIs of 6.5, 5.9, 6.2, and 6.2 mol⋅m-2⋅d-1 for sunflower, kale, arugula, and mustard, respectively. Corresponding total light integrals (TLIs) ranged from 60 to 188 mol⋅m-2 for sunflower, 76 to 258 mol⋅m-2 for kale, 86 to 280 mol⋅m-2 for arugula, and 86 to 284 mol⋅m-2 for mustard. Fresh weight (i.e., marketable yield) increased asymptotically with increasing LI and leaf area increased linearly with increasing LI, in all genotypes. Hypocotyl length of mustard decreased and hypocotyl diameter of sunflower, arugula, and mustard increased with increasing LI. Dry weight, robust index, and relative chlorophyll content increased and specific leaf area decreased in kale, arugula, and mustard with increasing LI. Commercial microgreen greenhouse growers can use the light response models described herein to predict relevant production metrics according to the available (natural and supplemental) light levels to select the most appropriate SL LI to achieve the desired production goals as economically as possible. [ABSTRACT FROM AUTHOR]

Grafting is used in watermelon [ Citrullus lanatus (Thunb.) Matsum and Nakai] production as a means to combat soilborne diseases. To support the development of new rootstock cultivars in the United States, we screened cucurbit germplasm accessions for resistance to verticillium wilt (caused by Verticillium dahliae Kleb.) and for compatibility as watermelon rootstocks. Screening was done using a field naturally infested with V. dahliae [5 and 7.5 colony-forming units (cfu)⋅g-1 soil in 2017 and 2018, respectively], and plants were inoculated at transplanting (1.5 and 104 cfu of V. dahliae per plant in 2017 and 2018, respectively). In 2017, 56 germplasm accessions from three genera commonly used as rootstocks, Cucurbita, Lagenaria, and Benincasa, were sourced from the U.S. Department of Agriculture (USDA) National Plant Germplasm System and area under the verticillium wilt (disease) progress curve (AUDPC) values ranged from 16 to 397. The 14 accessions with the lowest AUDPC values and good germination (>40%) were used as rootstocks along with the commercial rootstock cv. Tetsukabuto (control), and all were grafted with watermelon cv. Secretariat as the scion in 2018. Grafted plant survival rate was greatest for 'Tetsukabuto' (90%) and the accession PI 381840 ( L. siceraria ) (89%), and ranged from 22% to 85% for all other accessions. All grafted treatments that produced mature fruit in 2018 tended to flower at the same time as nongrafted 'Secretariat', with first male and female flowers occurring in 45 to 50 days and 44 to 51 days after transplanting, respectively. There were no significant differences in AUDPC values due to grafting or when accessions were compared with 'Tetsukabuto'. Only six accessions produced mature fruit when grafted with 'Secretariat', indicating they were compatible for watermelon grafting. Fruit weight and number as well as total soluble solids, pH, lycopene content, rind firmness and thickness, and dry matter content were similar for all accessions and 'Tetsukabuto' grafted on 'Secretariat'. Only fruit flesh firmness differed and was highest for 'Secretariat' grafted on 'PI 491316' and lowest for 'Secretariat' grafted on 'PI 49174'. The six verticillium wilt-tolerant accessions that were compatible with watermelon could potentially be used as rootstocks or as sources of genetic resistance in rootstock breeding programs. [ABSTRACT FROM AUTHOR]

Plant growth and development relies on light and is influenced by light. Lightemitting diode (LED) technology is nowadays providing the possibility for regulating plant growth and development by modifying light spectral composition. Many researches have been carried out to figure out the effects of light quality on various aspects of plant behaviors, including plant morphology, physiology, and biochemistry. In this review, we summarized those research outputs, in order to give suggestion of light quality application for both research and production purposes, in the field of productional yield, productional quality for horticultural plants including vegetables or ornamentals in difference with cultivation goals. [ABSTRACT FROM AUTHOR]

Nitrogen and potassium are two crucial nutrient elements that affect the yield and quality of crops. The aim of this study was to quantify the impacts of potassium on growth dynamics and quality ofmuskmelon, so as to optimize potassiummanagement formuskmelon in a plastic greenhouse, and develop a coupling model of nitrogen and potassium. For this purpose, four experiments (two experiments with different levels of potassium treatment and planting dates, and the other two experiments with different ratios of nitrogen and potassium, and planting dates) on muskmelon (Cucumis melo L. 'Nanhaimi' and 'Xizhoumi 25') were conducted in a plastic greenhouse located at Sanya from Jan. 2014 to Sept. 2015. The quantitative relationship between leaf potassium content and growth dynamics and yield of muskmelonwas determined and incorporated into a photosynthesis-driven crop growth model (SUCROS). Independent experimental data were used to validate the model. The critical leaf potassium content at the flowering stage for muskmelon 'Nanhaimi' and 'Xizhoumi 25' were 55.0 and 46.0 mg·g-1. The result showed that the coefficient of determination (r2) between the predicted and measured values of leaf area index (LAI), direct weight of shoot (DWSH), direct weight of stem (DWST), dry weight of leaf (DWL), dry weight of fruit (DWF), fresh weight of fruit (FWF), soluble sugar content (SU), soluble protein content (PR), vitamin C (Vc), and soluble solids content (SO) of potassiummodel were 0.93, 0.98, 0.83, 0.96, 0.98, 0.99, 0.94, 0.94, 0.89, 0.85, and 0.90, respectively; and the relative root-mean-squared error (rRMSE) were 10.8%, 19.6%, 30.3%, 21.1%, 11.9%, 17.2%, 13.9%, 27.8%, 20.6%, and 10.1%, respectively. The two ways of nitrogen and potassium coupling (multiplicative coupling and minimum coupling) were compared, and the multiplicative coupling was used in model development finally. The r2 between the predicted and measured values of LAI, DWSH, DWST, DWL, DWF, FWF, SU, PR, Vc, and SO of nitrogen and potassium coupling model were 0.78, 0.91, 0.93, 0.94, 0.83, 0.89, 0.92, 0.95, 0.91, and 0.93, respectively; and their rRMSE were 9.2%, 12.4%, 11.8%, 43.2%, 6.6%, 7.2%, 6.85%, 4.98%, 6.61%, and 4.35%, respectively. The models could be used for the optimization of potassium, nitrogen, and potassium coupling management for muskmelon production in a plastic greenhouse. [ABSTRACT FROM AUTHOR]

This study analyzed the effects of two ranges of drying down of substrate moisture content (SMC) before re-watering on plant growth and development, postproduction quality, and economic value of bedding plants grown in 1.67-L containers during greenhouse production. The two SMC treatments were wide-range (WR) SMC (WR-SMC) for dry-down from container capacity (CC) of 54% SMC dried down to 20% SMC or narrow-range (NR) SMC(NR-SMC) for dry-down from CC of 54%SMC dried down to 40% SMC. Six bedding plant cultivars were used [Solenostemon scutellarioides 'French Quarter' (coleus); Petunia 3hybrida 'Colorworks Pink Radiance' (petunia); Lantana camara 'Lucky Flame' (lantana); Impatiens 3hybrida 'Sunpatiens Compact Hot Coral' (SCC); 'Sunpatiens Spreading Lavender' (SSL) (impatiens); and Salvia splendens 'Red Hot Sally II' (salvia)]. Shoot dry weight was reduced with WR-SMC on petunia, lantana, impatiens SCC, and salvia at the end of production. With WR-SMC, the petunia and impatiens SCC root ball coverage percentages were greater on the bottom of the container, whereas those of impatiens SSL and salvia were reduced. TheWR-SMC increased petunia postproduction quality by increasing the flower number. Lantana and impatiens SCC inflorescence/flower and/or bud number were reduced with WR-SMC. The impatiens SSL flower number was unaffected by SMC treatment. Salvia grown with WR-SMC had increased postproduction quality. WR-SMC reduced postproduction water potential in petunia, lantana, and coleus, suggesting that plants with WR-SMC during production were acclimated to reduced irrigation administered during postproduction.WR-SMC saved labor due to less frequent watering and overhead-associated costs due to reduced bench space, with the exception of coleus and impatiens SSL, which used the same bench space as NR-SMC. Considering production and/or postproduction quality, using WR-SMC during greenhouse production is beneficial as an irrigation method for coleus, petunia, impatiens SSL, and salvia, but not for impatiens SCC or lantana grown in 1.67-L containers. [ABSTRACT FROM AUTHOR]

Spinach is an annual, cool-season, green leafy vegetable that in temperate areas can be grown year-round. However, different seasons can influence the quality and shelf life of the produce. The objective of this study was to investigate the influence of different seasons on the quality of baby spinach leaves during growing and postharvest storage. The study was initiated in early Nov. 2013 and culminated toward the end of Oct. 2014, then was repeated from Nov. 2014 until Oct. 2015. A 4 3 5 3 3 factorial experiment was laid out in a randomized complete block design with four replicates per treatment. The treatments were arranged as follows. In autumn, winter, spring, and summer, leaves were kept up to 12 d at three different temperatures: 4, 10, and 20 °C. Parameters recorded are weight loss, leaf length, total flavonoids, and antioxidant activity. Results of the study demonstrate that the level of antioxidants in winter remained stable during storage, specifically at 4 °C, followed by autumn and spring. In contrast, the summer season reflected the worse potential of retaining a level of antioxidants compared with the other seasons. On day 12, at a storage temperature of 4 °C, winter maintained 0.55 mg·g-1 dry weight (DW), whereas autumn, spring, and summer had 0.41, 0.40, and 0.11 mg·g-1 DW, respectively. In conclusion, it is recommended that baby spinach growers consider winter, autumn, and spring for growing baby spinach to manage the quality favorably during the postharvest storage period in South Africa. [ABSTRACT FROM AUTHOR]

This research assessed fruit load management and production techniques for cultivating indeterminate tomatoes in a high tunnel under intensive organic management. The successful production of high-quality, high-yielding crops is important for fruit and vegetable producers, especially growers using high tunnels. High tunnels are well-suited to organic farming and can be used to grow many valuable specialty crops. Fruit load management is practiced in fruit production (e.g., apples, peaches, and grapes), but there is lack of consensus concerning the effectiveness of fruit cluster pruning on tomato (Solanum lycopersicum) and its impact on fruit yield, quality, and marketability. In addition, there is no published research on tomato cluster pruning in certified organic systems or intensively managed high tunnels (e.g., densely planted, trellised, vegetatively pruned plants) for the Front Range of Colorado. In 2016 and 2017, a randomized complete block design was used to test the effects of cluster pruning within a high tunnel on certified organic land at Colorado State University's (CSU's) Agricultural Research, Development, and Education Center, South. Two treatments and three tomato cultivars were selected for the study; the treatment--cultivar combinations were replicated six times within a high tunnel. The treatments involved reducing fruit loads to three fruit and six fruit per cluster, whereas plants with unpruned clusters, which naturally developed as many as 10 fruit, served as the control. Tomato cultivars evaluated were 'Cherokee Purple', a widely studied heirloom, and two hybrids: 'Jet Star' and 'Lola'. Parameters measured included total yield, individual fresh fruit weight, soluble solids content (SSC), marketable yield, and nonmarketable yield. Individual fresh fruit weight increased for both hybrids in the three-fruit treatment, averaged over two growing seasons. 'Cherokee Purple' did not respond to the cluster pruning treatments. There was no decrease in total yield, across all cultivars, between treatments and the unpruned control. However, 'Jet Star' yielded more than the other two cultivars. In addition, SSC and marketability measurements were more influenced by cultivar than cluster pruning treatments. 'Lola' had a significantly greater SSC than the other two cultivars. 'Jet Star' had the greatest marketable yields of all cultivars tested whereas 'Cherokee Purple' produced greater nonmarketable (cull) yields. Cluster pruning produced larger organic tomatoes without reducing yield or quality for two of the three cultivars used in the study. Cultivar selection remains one of the greatest factors in determining yield, quality, and marketability of a crop. [ABSTRACT FROM AUTHOR]

The use of plastic biodegradable mulch (BDM) in many vegetable crops such as tomato (Solanum lycopersicum L.), broccoli (Brassica oleracea L. var. italica), and pepper (Capsicum annuum L.) has been proven to be of equal benefit as polyethylene (PE) mulch. However, there are limited research findings on the performance of BDMwith a large fruited crop such as pumpkin (Cucurbita pepo L.)where the fruit can rest directly on themulch for an extended period. To investigate whether heavy fruit might cause the mulch to degrade more quickly than expected, thereby, influencing weed control, fruit yield, and fruit quality including mulch adhesion on fruit, we carried out a field experiment in 2015 and 2016 at two locations in the United States with distinctive climates, Mount Vernon, WA and Knoxville, TN. Three plastic mulches marketed as biodegradable (BioAgri, Organix, and Naturecycle), one fully biodegradable paper mulch (WeedGuardPlus), and one experimental plastic BDM consisting of polylactic acid and polyhydroxyalkanoates (Exp. PLA/PHA) were evaluated against PE mulch and bare ground where 'Cinnamon Girl' pie pumpkin was the test crop. There was significant weed pressure in the bare ground plots at both locations over both years, indicating viable weed seed banks at the field sites. Even so, weed pressure wasminimal across mulch treatments at both locations over both years because the mulches remained sufficiently intact during the growing season. The exceptionswere Naturecycle in 2015 at both locations because of the splitting of the mulch and consequently higher percent soil exposure (PSE), and the penetration of all the plasticmulches atKnoxville by nutsedge (Cyperus sp. L.); nutsedge did not penetrateWeedGuardPlus. At Mount Vernon, overall pumpkin yield across both years averaged 18.1 t·haL1, and pumpkin yield was the greatest with PE, Exp. PLA/ PHA, BioAgri, and Naturecycle (19.9-22.8 t·haL1), intermediate with Organix and Weed- GuardPlus (15.3-18.4 t·haL1), and the lowest for bare ground (8.7 t·haL1). At Knoxville, overall pumpkin yield across both years averaged 17.7 t·haL1, and pumpkin yield did not differ because of treatment (15.3-20.4 t·haL1). The differences in yield between treatments at Mount Vernon were likely because of differences in the soil temperature. At 10 cm depth, the average soil temperature was 1 8C lower for bare ground and WeedGuardPlus as compared with PE mulch and plastic BDMs (20.8 8C). In contrast, soil temperatures were generally higher (25.2 to 28.3 8C) for all treatments at Knoxville and more favorable to crop yield compared with Mount Vernon. Forty-two percent to 59% of pumpkin fruit had mulch adhesion at harvest atMount Vernon, whereas only 3%to 12%of fruit had mulch adhesion at Knoxville. This difference was because of the location of fruit set--atMount Vernon,most of the fruit set was on the mulch whereas at Knoxville, vine growth was more extensive and fruit set was mostly in row alleys. Fruit quality differences among treatments were minimal during storage across both locations and years except for total soluble solids (TSS) in 2016, whichwas lower for bare ground andWeedGuardPlus compared with all the plasticmulches. Taken overall, these results indicate that pie pumpkin grown with BDMhas fruit yield and quality comparable to PE mulch; however, adhesion of some BDMs on fruit could affect marketable yield. Furthermore, paper mulch appears to prevent nutsedge penetration. [ABSTRACT FROM AUTHOR]

Estimation of crop evapotranspiration supports efficient irrigation water management, which in turn supports water conservation, mitigation of groundwater depletion/ degradation, energy savings, and crop quality maintenance. Past research in California has revealed strong relationships between fraction of the ground covered by photosynthetically active vegetation (Fc), crop coefficients (Kc), and evapotranspiration (ET) of cool-season vegetables and other specialty crops. Replicated irrigation trials for iceberg lettuce and broccoli were performed during 2012 and 2013 at the USDA Agricultural Research Station in Salinas, CA. The main objective was to compare crop yield and quality from ET-based irrigation scheduling with industry standard practice. Sprinkler irrigation was used to germinate and establish the crops, followed by surface drip irrigation during the treatment period. Each experiment compared three irrigation treatment schedules replicated five times in a randomized block design. Two decision-support models were evaluated as follows: 1) an FAO-56-based algorithm embedded in NASA's prototype Satellite Information Management System (SIMS) based on observed Fc, and 2) CropManage (CM), an online database-driven irrigation scheduling tool based on modeled Fc. Both methods used daily reference ETo data from the California IrrigationManagement Irrigation System (CIMIS) to translateKc to crop ET, with a target of 100% replacement of water use during the drip irrigation phase. A third treatment followed an irrigation schedule representing grower standard practice (SP) at 150% to 175% ET replacement during the drip irrigation phase. No significant treatment differences were seen in lettuce head weight or total biomass. Marketable yields of lettuce (near 45.4 Mg·ha-1) and broccoli (near 17.4 Mg·ha-1) were in-line with industry averages during both years and all treatments. During 2012,CMyieldwas below lettuce SP, and above broccoli SP, while in 2013 no treatment differences were detected for either crop. No significant differences were detected between SIMS and SP yields during any trial. [ABSTRACT FROM AUTHOR]

Implementing nutrient management strategies in soilless culture, which improve water use efficiency (WUE) and limit the loss of eutrophying elements without affecting crop performance, is a priority for the floriculture industry. The aim of the current research was to assess the effect of two nutrient management strategies, based on electrical conductivity (EC) or nitrate-nitrogen (N-NO3–) concentration control on plant growth, ornamental quality, plant–water relations, mineral composition, and WUE of greenhouse Hippeastrum grown in semiclosed soilless system. The recirculating nutrient solution was discharged whenever a threshold EC value of 3.0 dS·m–1 was reached (ECbased strategy), or when N-NO3– concentration decreased below the limit of 1.0 mol·m–1 (nitrate-based strategy). There were no significant differences in terms of plant growth parameters, stomatal resistance, leaf water relations, and macronutrient composition in plant tissues between the two nutrient management strategies. In the EC- and the nitratebased strategies, the recirculating nutrient solution was flushed 10 and 5 times, respectively. The water loss (WL) and the total water use (Wuse) in the EC-based strategy were significantly higher by 261.1% and 61.5%, respectively, compared with the N-NO3–-based strategy. In contrast with the EC-based strategy, the adoption of the N-NO3–-based strategy significantly minimized the nitrate, phosphate, and potassium emissions to the environment. The effective WUE of the system (WUES) recorded in the N-NO3–-based strategy was higher by 55.9% compared with the one recorded with the EC-based strategy. [ABSTRACT FROM AUTHOR]

Multilayer vertical production systems using sole-source (SS) lighting can be used for the production of microgreens; however, traditional SS lighting methods can consume large amounts of electrical energy. Light-emitting diodes (LEDs) offer many advantages over conventional light sources, including high photoelectric conversion efficiencies, narrowband spectral light quality (LQ), low thermal output, and adjustable light intensities (LIs). The objective of this study was to quantify the effects of SS LEDs of different light qualities and intensities on growth, morphology, and nutrient content of Brassica microgreens. Purple kohlrabi (Brassica oleracea L. var. gongylodes L.), mizuna (Brassica rapa L. var. japonica), and mustard [Brassica juncea (L.) Czern. 'Garnet Giant'] were grown in hydroponic tray systems placed on multilayer shelves in a walk-in growth chamber. A daily light integral (DLI) of 6, 12, or 18 mol·m-2·d-2 was achieved from commercially available SS LED arrays with light ratios (%) of red:green:blue 74:18:8 (R74:G18:B8), red:blue 87:13 (R87:B13), or red:far-red:blue 84:7:9 (R84:FR7:B9) with a total photon flux (TPF) from 400 to 800 nm of 105, 210, or 315 µmol·m-2·s-2 for 16 hours. Regardless of LQ, as the LI increased from 105 to 315 μmol·m-2·s-2, hypocotyl length (HL) decreased and percent dry weight (DW) increased for kohlrabi, mizuna, and mustard microgreens. With increasing LI, leaf area (LA) of kohlrabi generally decreased and relative chlorophyll content (RCC) increased. In addition, nutrient content increased under low LIs regardless of LQ. The results from this study can help growers to select LIs and LQs from commercially available SS LEDs to achieve preferred growth characteristics of Brassica microgreens. [ABSTRACT FROM AUTHOR]

A 2-year study (2012-13 and 2013-14) was conducted to evaluate the effect of plant growth regulator's (PGRs) on plant growth, yield, and quality of hydroponically grown sweet peppers. In 2012-13, sweet pepper plants were subjected to two levels of gibberellic acid (GA3) (10 and 15 mg⋅L-1), two levels of naphthalene acetic acid (NAA) (15 and 30 mg⋅L-1), and four combinations of NAA and GA3 (10 mg⋅L-1 GA3 + 15 mg⋅L-1 NAA, 10 mg⋅L-1 GA3 + 30 mg⋅L-1 NAA, 15 mg⋅L-1 GA3 + 15 mg⋅L-1 NAA, and 15 mg⋅L-1 GA3 + 30 mg⋅L-1 NAA) applied to plants at flower initiation in a nontemperature-controlled tunnel. This PGR application was repeated 60 days after transplanting (DAT). In 2013-14, in addition to previously mentioned treatments, two levels of 4-chlorophenoxyacetic acid (4-CPA), at 30 and 45 mg⋅L-1, were applied at flower initiation followed by three additional applications of the latter treatments at 20-day intervals in a temperature-controlled tunnel. Marketable and total yield were markedly reduced by application of 4-CPA at 30 and 45 mg⋅L-1. Plant height was increased by application of GA3, and GA3 in combination with NAA, compared with application of 4-CPA, 30 mg⋅L-1 NAA, and the control. Results also showed that application of GA3 at 10 and 15 mg⋅L-1 or in combination with NAA increased plant fresh and dry mass as well; however, this had no beneficial effect on the yield of sweet pepper fruit. The application methods and concentrations of various PGRs needs further investigation under different growing conditions on sweet pepper cultivars. [ABSTRACT FROM AUTHOR]

Twelve cacao (Theobroma cacao) clones propagated by grafting and orthotropic rooted cuttings of somatic embryo-derived plants were grown on an Ultisol soil at Corozal, Puerto Rico, and evaluated for 6 years of production under intensive management. Year, variety, year X variety, and propagation treatment x variety interactions indicated significant effects for dry bean yield, number of pods produced, pod index, plant height, and stem diameter. Propagation treatments had a significant effect on dry bean yield and pod index but not on number of pods produced. Average yield across varieties for both propagation treatments was 2087.9 kg⋅ha-1 per year of dry beans. There was a highly significant variety effect. 'UF-668' was the top yielder averaging 2536.7 kg⋅ha-1 per year of dry beans; however, this yield was not significantly different from the average yield of varieties 'TARS-30', 'TARS-1', 'TARS-13', 'TARS14', and 'TARS-2', which averaged 2427.0 kg⋅ha-1 per year. Except for 'UF-668', the TARS varieties were released in 2009 as high-yielding selections. Propagation treatments had a significant effect on dry bean yield. Dry bean yield of varieties propagated by grafting was 7% higher (2166.7 kg⋅ha-1 per year) than those propagated by orthotropic rooted cuttings of somatic embryo-derived plants (2009.2 kg⋅ha-1 per year). This yield difference could not be attributed to grafted plants being more vigorous nor by differences in root architecture. The lowest pod index value in both propagation treatments was obtained by 'UF-668'; however, pod index for this variety did not differ significantly from values for 'TARS-2' and 'TARS-23' in grafted plants and from 'TARS-2', 'TARS-23', and 'TARS-1' in plants propagated by orthotropic rooted cuttings of somatic embrvo-derived plants. With few exceptions, flavor characteristics were not significantly affected by propagation treatments. Although there were significant differences between plant propagation treatments for some of the variables measured in this study, these were not of a magnitude that would preclude the use of somatic embryogenesis as a viable propagation system for cacao. [ABSTRACT FROM AUTHOR]

In protected environments, temperature is often regulated to produce ornamental crops for specific market dates. Temperature primarily controls plant developmental rate and thus production time, but it can also interact with light quantity to affect crop quality attributes such as flower number, branching, and biomass accumulation. We quantified how mean daily temperature (MDT) between 14 and 26 °C influenced quality characteristics of 15 common bedding plant crops. American marigold (Tagetes erecta)., cup flower (Nierembergia caerulea), diascia (Diascia barberae), flowering tobacco (Nicotiana alata), geranium (Pelargonium xhortorum), globe amaranth (Gomphrena globosa)., heliotrope {Heliotropium arborescens), nemesia (Nemesia foetans). New Guinea impatiens (Impatiens hawkeri), osteospermum (Osteospermum ecklonis), pot marigold (Calendula officinalis), snapdragon (Antirrhinum majus), stock (Matthiola incana), and torenia (Torenia fournieri) were grown under two mean daily light integrals (9.0 and 18.0 mol⋅m-2⋅d-1) in five environmentally controlled greenhouse compartments with a 16-h photoperiod. As MDT increased from 14 to 26 °C, flower or inflorescence number decreased for nearly all crops. In six crops, flower or inflorescence size decreased as MDT increased, whereas in five crops, there was an initial increase in flower size with an increase in MDT and then a subsequent decrease at MDT greater than 20 °C. In 10 of the crops, shoot weight at flowering decreased linearly or quadratically with an increase in MDT. Branch number was inversely related with MDT in eight crops and was positively correlated with an increase in flower number. We conclude that in a majority of the crops studied, plant quality decreased as the MDT increased, which can at least partially be attributed to earlier flowering at the higher MDTs. Therefore, there is often a tradeoff between faster crop timing and higher plant quality, especially for plants with a low estimated base temperature (Tmin) for development. [ABSTRACT FROM AUTHOR]