Use efficiency of applied nitrogen (N) is estimated typically to be <50% in most crops. In sandy soils and warmer climates particularly, leaching and volatilization may be primary pathways for environmental loss of applied N. To determine the effect of N fertilization rate on the N use efficiency (NUE) and apparent recovery of N fertilizer (APR), a replicated field study with ‘BHN 602’ tomato (Solanum lycopersicum) grown in sandy soils under a fertigated plastic-mulched bed system was conducted using ammonium nitrate as the N source at four different rates (0, 150, 200, and 250 lb/acre). Spring tomato was followed by fall tomato in the same field, a typical cropping sequence in north Florida. Fertigation of N fertilizer was applied weekly in 13 equal doses for both seasons. The highest NUE was 12.05% (spring) and 32.38% (fall), and the highest APR was 6.11% (spring) for the lowest rate of N applied (150 lb/acre). In the fall, APR was unaffected by fertilizer N rates and ranged from 12.88% to 19.39%. Nitrogen accumulation in tomato plants were similar among the three N fertilizer rates applied (150, 200, and 250 lb/acre), though compared with no N fertilizer application, significant increases occurred. Whole plant N accumulation, NUE, and APR declined or remained similar when N rates increased above 150 lb/acre. Additionally, a regression analysis and derivative of the quadratic fresh yield data showed that yields were maximized at 162 and 233 lb/acre N in the spring and fall seasons, respectively.
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Laura Jalpa, Rao S. Mylavarapu, George J. Hochmuth, Alan L. Wright and Edzard van Santen
Jasmine Jenji Mah, David Llewellyn and Youbin Zheng
One principle for reducing undesirable stem extension in greenhouse production is to counteract the decrease in red-to-far red ratio that occurs naturally during twilight periods. This study evaluated three lighting treatments on the morphology of easter lily (Lilium longiflorum): 1) a 1-hour end-of-day treatment providing 20 μmol·m−2·s−1 of monochromatic red light (EOD R), 2) blackout curtains closed 45 to 75 minutes before sunset and kept closed until 0 to 60 minutes after sunrise (BO), and 3) a control with natural twilight (CTRL). Plants under the BO treatment were 11% shorter than CTRL, while plants exposed to EOD R did not differ in height compared with BO or CTRL. There were no treatment effects on any other measured parameters, including aspects of flowering.
Anna J. Talcott and William R. Graves
Two species of North American shrubs in the genus Ptelea (Rutaceae), commonly known as eastern and western hoptree or wafer ash, have unfulfilled potential to increase the diversity of managed landscapes and support populations of pollinators and swallowtail butterflies. The white flowers of Ptelea are highly fragrant, and pistillate flowers give rise to clusters of distinctive samaras. The insufficiency of information about improving germination of seeds of Ptelea trifoliata and lack of recommendations for Ptelea crenulata prompted us to investigate effects of pericarp removal and cold (4 °C) stratification periods of 0, 4, 8, and 16 weeks on the germination of seeds of these two species. Samaras were collected from multiple plants of both species in the midwestern United States (P. trifoliata) and California (P. crenulata). The germination percentage of viable seeds, calculated after tests of viability with tetrazolium chloride of seeds that did not germinate, increased with longer stratification periods, with 100% germination for P. crenulata and 91% germination for P. trifoliata after 16 weeks of stratification. The germination value, a measure of the speed and uniformity of germination, and peak value also increased with longer stratification in both species. Pericarp removal increased the germination percentage of both species and increased the peak and germination value of P. crenulata. Propagators seeking to grow these species of Ptelea from seed should remove the pericarp and cold-stratify seeds for 16 weeks to improve germination success.
Leora Radetsky, Jaimin S. Patel and Mark S. Rea
Lighting from red and blue light-emitting diodes (LEDs) is common for crop production in controlled environments. Continuous application of red or blue light at night has been shown to suppress sporulation by Peronospora belbahrii, the causal organism of basil downy mildew (DM), but the suppressing effects of intermittent applications of red and blue LEDs have not been thoroughly researched. This study examined the effects of red (λmax = 670 nm) and blue (λmax = 458 nm) LED top lighting, at two photosynthetic photon flux densities (PPFD = ≈12 and ≈60 µmol·m−2·s−1), using continuous (10-hour) nighttime and two intermittent nighttime exposures, to suppress basil DM sporulation. The two intermittent treatments consisted of one 4-hour exposure and three 1.3-hour exposures spaced 3 hours apart. Continuous nighttime treatments with blue or red LED top lighting at ≈60 µmol·m−2·s−1 were able to suppress basil DM sporulation by more than 99%. At a given nighttime dose of light that did not completely suppress sporulation, continuous lighting was more effective than intermittent lighting, and for these partially suppressing doses, red LEDs were not significantly different from blue LEDs for suppressing sporulation. The present study showed that horticultural lighting systems using red and blue LEDs to grow crops during the day can also be used at night to suppress basil DM sporulation by up to 100%.
Liming Chen, Matthew Wallhead, Michael Reding, Leona Horst and Heping Zhu
Laser-guided variable-rate intelligent spray technology is designed to significantly reduce pesticide use with a positive impact on the environment. However, there have been no reports on applying this technology to commercial fruit farms. Comparative experiments of intelligent variable-rate and conventional constant-rate spray applications for pesticide use and pest control were conducted at a fruit farm in Ohio during two consecutive growing seasons. Apple (Malus pumila), peach (Prunus persica), blueberry (Vaccinium section Cyanococcus), and black raspberry (Rubus occidentalis) were used for the tests. Pest severity of codling moth (Cydia pomonella), oriental fruit moth (Grapholitha molesta), scab (Venturia inaequalis), and powdery mildew (Podosphaera leucotricha) in apple; oriental fruit moth, brown rot (Monilinia fructicola), and powdery mildew (Podosphaera pannosa) in peach; spotted wing drosophila (Drosophila suzukii), mummy berry (Monilinia vaccinii-corymbosi), and phomopsis (Phomopsis vaccinii) in blueberry; and anthracnose (Elsinoe veneta) in black raspberry were assessed. There was equal severity of pests between intelligent and conventional spray applications, whereas the intelligent spray reduced pesticide use by 58.7%, 30.6%, 47.9%, and 52.5% on average for apple, peach, blueberry, and black raspberry, respectively. These results illustrate that intelligent spray technology is more environmentally friendly than conventional standard spray technology and equally or more effective for control of insect and disease pests in fruit production.
Kristine M. Lang, Ajay Nair and Kenneth J. Moore
Growing colored bell peppers in high tunnels enhances fruit quality and accelerates ripening. While there are benefits to high tunnel pepper production, increased heat inside the structures can lead to plant stress, blossom drop, sunscald, and reduced marketable yields. The objective of this study was to test shadecloth treatments placed on high tunnels to mitigate heat stress and improve colored bell pepper yield and fruit quality, while also identifying cultivars that perform well within Midwest high tunnel systems. Research was conducted at the Iowa State University Horticulture Research Station (Ames, IA) from 11 May to 11 Oct. in 2017 and 3 May to 9 Oct. in 2018. Six single-poly passively ventilated Quonset high tunnels were used for the experiment. The shade treatments (no shadecloth, 30% light-reducing shadecloth, and 50% light-reducing shadecloth) were applied in June of each season. Within each shade treatment, there were three randomized complete blocks of the seven colored bell pepper cultivars (Archimedes, Delirio, Flavorburst, Red Knight, Sirius, Summer Sweet, and Tequila). Data were collected on yield, fruit quality, and plant growth characteristics. Environmental parameters were monitored throughout the growing season. Both the 30% and 50% shadecloth treatments reduced monthly average and maximum air temperatures within high tunnels, with the largest differences occurring in the months of July and August. The use of a shadecloth reduced the incidence of sunscald by 59% between no shade and 50% shadecloth treatments. While there was no difference between 30% and 50% shade treatments, the use of 50% shadecloth caused a decrease in both marketable number (32%) and weight (29%) of pepper fruit compared with the control. ‘Tequila’, ‘Delirio’, and ‘Flavorburst’ had more marketable fruit per plant. Shade treatments did not affect fruit soluble solids content (SSC), pH, or total titratable acidity (TTA). Shade treatments had no effect on Soil Plant Analysis Development (SPAD) readings, shoot biomass, the number of leaves per plant or the total leaf area per plant; however, plant height increased by an average 14.5 cm for plants under shadecloth treatments. Average leaf size was 11.2 cm2 larger on plants grown under the 50% shadecloth, compared with the control. Several cultivar differences existed for each fruit quality and plant growth parameter. While differences in fruit quality and plant growth parameters were limited among shade treatments, decreasing marketable yield is concerning. Our research suggests that Midwest growers should not exceed 30% light-reducing shadecloth on their high tunnels for colored bell pepper production.
Rui Wang, Yuqing Gui, Tiejun Zhao, Masahisa Ishii, Masatake Eguchi, Hui Xu, Tianlai Li and Yasunaga Iwasaki
Floral initiation is an important transition point from vegetative growth to reproductive growth in tomatoes and is known to be affected by light intensity, temperature, and nutrients. However, the regulation between flower formation and environmental factors, including nutrient conditions, due to source–sink dynamics (supply and demand of photoassimilates) is seldom documented. To evaluate the effects of light intensity and nutrition conditions on prefloral formation and development, dynamic floral characteristics during development were fitted with sigmoidal logistic curves under four light treatments with shading nets in two nutrient conditions. Source activity and sink strength were altered, which caused differences in the floral positions, length of floral shoots, floral initiation dates, and leaf numbers under the different treatments. Accumulated light acts upstream of nutrition supply during the formation of buds and leads to the accumulation of carbohydrates in source organs. Leaf area reached ≈500 cm2, and dry matter weights reached ≈3 g in each treatment until the flowering day, revealing that some level of photoassimilates are necessary for floral initiation. Both days to flowering and bud number were highly correlated with daily light integral (DLI) from 6 to 12 days before anthesis, which means this period is important for anthesis in tomato. Our results highlight regulation of the transition from vegetative growth to reproductive growth by tomato seedlings due to environmental factors and nutrients. A better understanding of communication between source organs and sink organs during floral initiation response to different environments is expected to provide management strategies for greenhouse tomato production.
Verónica De Luca, Diego Gómez de Barreda, Antonio Lidón and Cristina Lull
Due to restrictions on pesticide and nitrogen use in high-input European agricultural systems, many of the biostimulants used in horticulture are being incorporated into turfgrass management programs—although often with little understanding. A set of experiments was carried out on perennial ryegrass (Lolium perenne) cultivated in pots in a greenhouse in 2013 and 2014 to test the effect of three biostimulants: two composed of nitrifying bacteria (B1 and B2), and the other a mixture of amino acids, polysaccharides, nitrogen, and micronutrients (B3). Apart from the biostimulant treatment, nutritional stress was incorporated into the study to demonstrate if biostimulants could temporarily replace the fertilization role and so lessen the environmental impact. Turfgrass treated with B1 resulted in an increase in quality compared with untreated turf, and the positive effect lasted 2 and 3 months in 2013 and 2014, respectively. Additionally, an extended benefit was observed when the B1 interval application was longer, even temporarily replacing fertilization when applied on stressed turfgrass. The B2 produced similar results to B1, the effect was longer, and the turf exhibited a darker color—although it caused phytotoxicity at the tip of the leaves. The B3 led to a beneficial effect on turfgrass, especially under nutritional stress; it showed a better quality, darker green color, and more growth and yield than untreated turf (despite adding less nitrogen than during either mineral fertilizer treatment). Overall results show that the tested biostimulants increase turfgrass quality even when inducing a nutritional stress.
Clydette Alsup-Egbers, Patrick Byers, Kelly McGowan, Pamela B. Trewatha and William E. McClain
Commercial garlic (Allium sativum) is a relatively new crop for Missouri growers. While U.S. production is primarily in California, Oregon, Washington, and New York, little information is available regarding growing garlic in Missouri’s climate and soil conditions. Therefore, research is needed to investigate the optimum planting date for garlic in southwest Missouri. Comparisons between one spring and four fall planting dates using two garlic cultivars (Inchelium Red and German White) and the leek (Allium ampeloprasum) known as elephant garlic (A. ampeloprasum ssp. ampeloprasum) were planted at two replicated sites. Postharvest data were collected on bulb weight and diameter and clove weight and quantity. Although the numbers were not always statistically different, the overall results indicated that earlier planted garlic (September and early-October) had higher yields in 2016–17 than garlic planted later; however, in 2017–18, garlic planted in mid-October and early-November out-yielded garlic planted in September and early-October. Fall planting is preferred based on the results of our study, but spring-planted garlic can still yield a profitable crop for commercial growers. Future research on a variety of planting dates will give producers a better choice on when to plant in southwest Missouri.
Frederic B. Ouedraogo, B. Wade Brorsen, Jon T. Biermacher and Charles T. Rohla
Pecan (Carya illinoinensis) trees were pruned using varying intensities at planting to determine the effect of pruning on trunk development and shoot growth. Data on trunk diameter, number and length of shoots, as well as the total shoot growth were recorded annually from a completely randomized design experiment that assigned 0%, 50%, and 75% pruning of above-ground height to single-trunk transplants. The results suggest that pruning intensity has little effect on trunk diameter. The pruned trees had fewer shoots initially and more growth per shoot, leading to a difference of 7 cm/shoot higher for the 50% pruning group than the control group and to a difference of 11 cm/shoot higher for the 75% pruning group compared with the control group. The total length of all shoots was not significantly different across treatments. Because previous research has sometimes shown that pruning increases tree survival and this research shows that trees can recover from pruning, there is no need to change the current recommendation of pruning seedlings at planting.