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Open access

Natalie Yoder and Jessica G. Davis

Selecting supplemental nitrogen (N) fertilizer for use on certified organic farms can be difficult and confusing. There are many options commercially available to farmers with similar N concentrations but widely different ingredients. Experiments were conducted in a certified organic field and high tunnels near Fort Collins, CO in 2013 and 2014 to evaluate the impact of organic fertilizers on yield and nutrient concentrations of three kale (Brassica oleracea and Brassica napus) cultivars. This study includes an organic fertilizer (cyano-fertilizer), which is produced on-farm by growing N-fixing cyanobacteria (Anabaena cylindrica) in raceway ponds. The three fertilizer treatments were hydrolyzed fish emulsion, alfalfa (Medicago sativa) meal, and cyano-fertilizer. These were applied at rates calculated by subtracting soil nitrate concentration from a target 50 mg·kg−1 to the depth of 6 inches of soil. Cyano-fertilizer and hydrolyzed fish emulsion were applied in liquid form, while the alfalfa meal was incorporated dry into the soil before planting. Biweekly measurements of plant height were taken on three cultivars of kale: Dinosaur, Red Russian, and Winterbor. Leaf weight, leaf area, and N, iron (Fe), and zinc (Zn) concentrations were measured during three to four monthly harvests each year. Organized in a split-plot experimental design, there were three treatment replications with subplots of different kale cultivars. Fertilizer treatment did not significantly affect plant height, leaf weight, leaf area, or plant N, Fe, and Zn concentrations. However, there were cultivar differences in plant height, leaf area, and yield. Kale cultivar choice had a larger impact on yield and plant nutrient concentrations than fertilizer choice, because fertilizers were applied at similar N rates.

Open access

Santiago García-Martínez, Adrián Grau, Aranzazu Alonso, Pedro Carbonell, Juan F. Salinas, José A. Cabrera and Juan J. Ruiz

Open access

Shana G. Brown and James E. Klett

Stock plant productivity is an important concern for growers of ‘Snow Angel’ coral bells (Heuchera sanguinea) because this variety produces a limited number of basal cuttings. The objective of the study was to determine the best growth substrate and container size combination to maximize productivity of stock plants. A secondary objective was to determine if the stock plant treatments influenced the rooting of vegetative cuttings. The study used three different container sizes (2.8, 11.4, and 14.6 L) and four commercial soilless substrates that were primarily composed of the following: bark, peat, and perlite (substrate 1); bark, peat, and vermiculite (substrate 2); bark, peat, and coarse perlite (substrate 3); and peat (substrate 4). Two stock plant experiments were conducted using the same 12 treatment combinations, and a subset of those stock plants was randomly selected for the rooting studies that immediately followed each stock plant experiment. Stock plants responded to substrate treatments differently depending on the batch of substrate in which they were grown. The most successful stock plants, which produced more cuttings per plant and per square foot, as well as larger cuttings, were those grown in substrate 3 (Expt. 1) and substrate 2 (Expt. 2). Regardless of the substrate, the highest number of cuttings per square foot was obtained from stock plants grown in 2.8-L containers, indicating that the smaller containers allow for the most efficient use of space when growing ‘Snow Angel’ stock plants for 6 to 8 months. The rooting of vegetative cuttings was successful (98% to 100% of cuttings rooted after 4 weeks under mist) for all treatment combinations, although higher numbers of visible roots were produced during the second study and may be due to larger fresh weights of cuttings.

Open access

James A. Schrader, Diana R. Cochran, Paul A. Domoto and Gail R. Nonnecke

Increasing interest in grape (Vitis sp.) and wine production in the upper midwest region of the United States has created a need for science-based information that characterizes the potential of cold-climate cultivars to produce quality grapes with acceptable yields. We evaluated the yield and quality (composition) of grapes from 12 cold-climate, interspecific-hybrid grape cultivars (northern hybrids) grown in a randomized and replicated field plot in central Iowa. The grape trial was planted in 2008, and crop performance of cultivars was evaluated from 2012 through 2017 (yield) and 2014 through 2017 (berry composition). The trial included two established cultivars, five newer cultivars, and five advanced selections. The established cultivars included in the study as controls were Frontenac and St. Croix. The newer cultivars evaluated in this study were Arandell, Corot Noir, La Crescent, Marquette, and Petit Ami, and the advanced selections were MN 1189, MN 1200, MN 1220, MN 1235, and MN 1258. Yield and productivity were characterized by measuring yield per vine, number of clusters per vine, average cluster weight, and pruning weight. The fruit composition indices were soluble solids concentration (SSC), pH, titratable acidity (TA), and sugar:acid ratio (SSC ÷ TA). On the basis of their strong results for both yield and fruit composition measures, ‘Marquette’, MN 1235, and MN 1220 ranked as the top-performing cultivars in Iowa’s climate, followed by Petit Ami and St. Croix. ‘Petit Ami’ had slightly lower yield consistency and slightly lower results for SSC than did the top performing cultivars, and St. Croix had among the highest and most consistent yields of the trial but showed lower results for SSC and sugar:acid ratio than many of the other cultivars. ‘La Crescent’ had midrange yields and high SSC, but the high TA of ‘La Crescent’ fruit resulted in a low sugar:acid ratio at harvest. Two cultivars (MN 1258 and MN 1200) had relatively low yields in Iowa’s climate but achieved good results for composition indices. ‘Frontenac’ had high, consistent yields and achieved high SSC, but the very high TA of ‘Frontenac’ fruit resulted in a very low sugar:acid ratio compared with most other cultivars. The remaining three cultivars (Corot Noir, MN 1189, and Arandell) performed poorly in Iowa’s climate, showing both low yield and undesirable fruit composition indices compared with the other cultivars in the trial. An itemized summary of the relative ratings for yield and fruit composition is provided to aid growers in selection and management of grape cultivars for use in Iowa and other areas of similar climate.

Open access

Asma Alhussein Alawaadh, Yaser Hassan Dewir, Mona S. Alwihibi, Abdulhakim A. Aldubai, Salah El-Hendawy and Yougasphree Naidoo

The present study aimed to optimize the micropropagation of lacy tree philodendron using shoot tip explants. Axillary shoot regeneration was investigated in Murashige and Skoog (MS) medium with different types and concentrations of plant growth regulators, varied levels of MS medium salt strength, sucrose concentration, and light intensity and culture type. Adding 6-benzylaminopurine (BAP; 1 mg·L−1) significantly increased shoot multiplication compared with other cytokinins, and the combination of cytokinins and auxins [indole-3-butyric acid (IBA) and naphthalene acetic acid (NAA)], yielded more shoots than cytokinins alone, with the greatest number of axillary shoots (11.4 per explant) obtained using both BAP (1 mg·L−1) and IBA (0.5 mg·L−1). In addition, the use of half-strength salt concentrations significantly reduced shoot multiplication, and high sucrose concentrations (>30 g·L−1) reduced explant growth. High light intensity also reduced shoot multiplication and growth, owing to photoinhibition, and shoot multiplication was more efficient in gelled culture, whereas shoot growth was greater in liquid/bioreactor culture. The best rooting success (100%) and greatest root number and fresh weight were obtained using MS medium supplemented with NAA (1–2 mg·L−1). The resulting plantlets were successfully acclimatized, with a survival rate of 100%, and were morphologically similar to the mother plant.

Open access

Seon-Ok Kim, Yun-Ah Oh and Sin-Ae Park

This study was conducted to compare the concentration and emotional condition of elementary school students performing an intensive assignment in the presence or absence of foliage plants, using electroencephalography (EEG) and a modified semantic differential method (SDM). In a crossover experimental design, 30 elementary students performed a 3-min intensive age-appropriate arithmetic assignment in the presence or absence of foliage plants. Continuous EEG monitoring in the frontal lobe was performed using a wireless dry EEG device. Immediately thereafter, subjective evaluation of emotions was performed using the SDM. The concentration of the male elementary students was significantly higher when the assignment was performed in the presence vs. absence of plants as evidenced by the increase in the ratio of spectral edge frequency of 50 and a decrease in the relative theta power spectrum in the right frontal lobe. The SDM results revealed a significant psychological relaxation when the assignment was performed in the presence of plants. Therefore, the presence of foliage plants in the space where the elementary students performed the intensive assignment led to positive effects on concentration and emotional condition.

Open access

Baojun Zhao, Feng Liu, Yonghong Gong, Dongsheng Li, Yahui Chang and Yunfei Wang

Open access

Yuji Nakata and Hidemi Izumi

‘Minomusume’ strawberries were stored in high CO2 atmospheres (20%, 30%, and 40%) by means of a controlled atmosphere (CA) and active modified atmosphere packaging (MAP) for 10 days at 5 °C. The CA of 20% to 40% CO2 was effective in delaying an increase in fungal count and preventing the external formation of mold mycelia, but a CA of >30% CO2 induced black discoloration on the surface of strawberry due to CO2 injury. When strawberry fruit were stored in a MAP flushed with either air or high CO2, all packages approached an equilibrium of ≈20% CO2 and 2% O2 by the end of storage. Fungal counts of strawberry fruit stored in a MAP remained constant throughout the storage period and the diversity of fungal flora was partially similar regardless of the difference in the MAP method. Visual quality (mold incidence and severity of black discoloration) and physicochemical quality (weight loss, firmness, pH, and total ascorbic acid content) were unaffected by CO2 atmospheres as the flushing gas during active MAP storage, except that the fruit in a MAP flushed with 20% and 30% CO2 were firmer than those with air and 40% CO2. After transfer to ambient conditions for 6 days at 10 °C, however, external formation of mold mycelia identified as Botrytis cinerea and surface black discoloration were induced in strawberry fruit in MAP flushed with 30% and 40% CO2.

Open access

Ling Li, Takashi Watanabe, Atsuko Uragami, Hiroaki Kitazawa and Xiangyou Wang

To control asparagus harvest timing, we investigated the effects of short-term low (5%) oxygen (O2) treatment in the cultivation area on asparagus growth and yield using a closed cultivation system. During 120 days of cultivation, low O2 treatments were initiated at 0 to 4, 20 to 24, and 40 to 44 days after planting (DAP). The sprouting spears and control crown yield gradually decreased with increasing DAP. However, low O2 treatment at 0 to 4 DAP significantly delayed the decrease until 80 DAP, although the total yield did not change during cultivation. In contrast, low O2 treatments at 20 to 24 and 40 to 44 DAP did not affect yield performance. Taken together, short-term low O2 treatment immediately after planting can change the harvest timing of white asparagus and can be used for effective asparagus culturing in a closed system, such as a plant factory.

Open access

Bryan K. Sales, David R. Bryla, Kristin M. Trippe, Jerry E. Weiland, Carolyn F. Scagel, Bernadine C. Strik and Dan M. Sullivan

Biochar, a carbon-rich, fine-grained residue obtained from pyrolysis of biomass, is known to improve soil conditions and to suppress infection by soilborne pathogens. However, its use as a soil amendment has received relatively little attention by the horticulture industry. Two 12-week experiments were conducted in a greenhouse to determine the potential of using biochar, produced from mixed conifers during conversion of wood to energy, as a soil amendment for highbush blueberry (Vaccinium hybrid ‘Legacy’). Plants in the first experiment were fertilized once a week with a complete fertilizer solution, whereas those the in the second experiment were fertilized once a month with a solution of ammonium sulfate. In both cases, the plants received the same amount of N in total and were grown in pots filled with unamended soil (sandy loam) or soil amended at rates of 10% or 20%, by volume, with biochar or a 4:1 mix of biochar and bokashi (biochar-bokashi). The bokashi was produced from fermented rice (Oryza sativa L.) bran and was added to increase nutrients in the amendment. Half of the plants in each soil treatment were inoculated with Phytophthora cinnamomi Rands, which causes root rot in blueberry. Although pH of the raw biochar was high (8.5), soil pH averaged 4.5 to 5.5 in each treatment. In the absence of P. cinnamomi, plants grown with 20% biochar or 10% or 20% biochar-bokashi had greater leaf area and 30% to 70% more total dry weight than those grown with 10% biochar or in unamended soil. Biochar also improved soil aggregation and increased root colonization by ericoid mycorrhizal fungi. The percentage of roots colonized by mycorrhizal fungi was 54% to 94% in plants grown with the amendments, but was ≤10% in those grown in unamended soil. Plants inoculated with P. cinnamomi were stunted and showed typical symptoms of root rot. Root infection by the pathogen was unaffected by biochar or biochar-bokashi and negated any growth benefits of the amendments. Overall, amending soil with biochar appears to be a promising means of promoting plant growth and mycorrhizal colonization in blueberry, but it may not suppress phytophthora root rot.