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Horticulturae
Volume 6
Issue 3
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Horticulturae, Volume 6, Issue 3 (September 2020) – 21 articles

Cover Story (view full-size image): Current horticultural research aims at the environmentally safe production of fruits and vegetables. Therein, productive sustainable cultivation systems for high quality produce aim to preserve available resources. This includes a reduction in plastic and chemical inputs into cultivation systems. Mechanisation is one answer to these challenges, such as mechanical weeding and mechanical thinning. Mechanical thinning, as described by Lammerich et al., in contribution no. 6(3), is a prime example for stone fruit. View this paper
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9 pages, 1537 KiB  
Article
Fertilizer Rate and Substrate Water Content Effect on Growth and Flowering of Beardtongue
by Amanda Bayer
Horticulturae 2020, 6(3), 57; https://doi.org/10.3390/horticulturae6030057 - 16 Sep 2020
Cited by 2 | Viewed by 3008
Abstract
Research has shown that reduced irrigation and fertilizer rates can still produce good plant growth when irrigation is applied efficiently to reduce leaching. The impact of reduced irrigation and fertilizer rate on flowering and plant growth would provide additional information on the potential [...] Read more.
Research has shown that reduced irrigation and fertilizer rates can still produce good plant growth when irrigation is applied efficiently to reduce leaching. The impact of reduced irrigation and fertilizer rate on flowering and plant growth would provide additional information on the potential for reduced production inputs. The objective of this research was to quantify the impact of reduced irrigation and fertilizer rate on growth and flowering of Ruby Candle beardtongue (Penstemon × ‘Ruby Candle’). A soil moisture sensor automated irrigation system was used to maintain plants at 40% volumetric water content [VWC; well-watered (WW)] or 18% VWC (reduced irrigation, RI). A controlled release fertilizer was applied at 100%, 50%, and 25% of the bag rate (12 g/plant). There was not a significant treatment effect on any flower parameter. Average plant height was greatest for plants receiving the 50% fertilizer rate (75.9 cm) and was lowest for the 100% fertilizer rate (64.5 cm). Internode length was greater for WW plants (36.9 mm) than RI plants (32.4 mm). Well-watered plants had greater fresh weight (99.1 g) than RI plants (79.2 g) and 100% fertilizer rate (97.1 g) was greater than the 25% fertilizer rate (82.7 g). Full article
(This article belongs to the Section Floriculture, Nursery and Landscape, and Turf)
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13 pages, 786 KiB  
Article
Compositional Nutrient Diagnosis (CND) Applied to Grapevines Grown in Subtropical Climate Region
by Danilo Eduardo Rozane, Betania Vahl de Paula, George Wellington Bastos de Melo, Eduardo Maciel Haitzmann dos Santos, Edicarla Trentin, Carina Marchezan, Lincon Oliveira Stefanello da Silva, Adriele Tassinari, Lucas Dotto, Filipe Nunes de Oliveira, William Natale, Elena Baldi, Moreno Toselli and Gustavo Brunetto
Horticulturae 2020, 6(3), 56; https://doi.org/10.3390/horticulturae6030056 - 4 Sep 2020
Cited by 28 | Viewed by 4931
Abstract
Soil analysis is used to estimate nutrient availability, but nutrient concentrations are not always related to yield in most fruit plants, including grapevines. Thus, additional multivariate mathematical models, such as the compositional nutrient diagnosis (CND), which takes into account leaves nutrient concentration, and [...] Read more.
Soil analysis is used to estimate nutrient availability, but nutrient concentrations are not always related to yield in most fruit plants, including grapevines. Thus, additional multivariate mathematical models, such as the compositional nutrient diagnosis (CND), which takes into account leaves nutrient concentration, and yield, can contribute to estimating critical levels or sufficiency bands of elements, as well as to detect deficiency and/or excess of nutrients. The aim of the present study was to establish CND standards, and the critical level and sufficiency band of nutrients, in the grapevine Vitis vinifera L., grown in a subtropical climate region. Leaves were collected in 81 vineyards in the Campanha Gaúcha do Rio Grande do Sul region, Southern Brazil, and analyzed for macro- and micro-nutrient concentration. The yield of each vineyard was assessed. Grapevine nutritional status was calculated through the CND method. CND-r2 indices were effective in establishing the nutritional status of grapevines for macro- and micro-nutrients as sub-optimal, excessive, or balanced. The CND methodology established the critical level and sufficiency bands of nutrients more accurately than the current recommendations for grapevines. Multi-nutrient associations were more effective than the single nutrient determination in defining the threshold of a given nutrient that can reduce grapevine yield. Full article
(This article belongs to the Special Issue Fertilization Management of Horticultural Crops)
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12 pages, 755 KiB  
Article
Trichoderma spp. and Mulching Films Differentially Boost Qualitative and Quantitative Aspects of Greenhouse Lettuce under Diverse N Conditions
by Ida Di Mola, Lucia Ottaiano, Eugenio Cozzolino, Mauro Senatore, Adriana Sacco, Christophe El-Nakhel, Youssef Rouphael and Mauro Mori
Horticulturae 2020, 6(3), 55; https://doi.org/10.3390/horticulturae6030055 - 4 Sep 2020
Cited by 8 | Viewed by 3972
Abstract
The global increasing demand of lettuce is pushing farmers to boost their production through several technical means, including mulching and nitrogen fertilization. However, from an environmental protection perspective, the role of scientific research is to limit the excessive use of some chemical approaches. [...] Read more.
The global increasing demand of lettuce is pushing farmers to boost their production through several technical means, including mulching and nitrogen fertilization. However, from an environmental protection perspective, the role of scientific research is to limit the excessive use of some chemical approaches. This research aims to evaluate the possible effects of two mulching films (black polyethylene, PE, and brown photoselective film, BF) and two treatments with a plant growth-promoting product, containing Trichoderma spp., (non-treated, - Control and treated with RYZO PEP UP, - TR), on the productive and qualitative traits of lettuce grown under four regimes of nitrogen (0, 30, 60 and 90 kg ha−1, N0, N30, N60, and N90, respectively). The marketable yield increased at higher nitrogen levels, but without differences between the N60 and N90 doses. The photoselective film elicited marketable yield, with an 8% increase over PE. N fertilization also improved photochemical efficiency (higher Soil Plant Analysis Development and chlorophyllous pigments biosynthesis), as well as antioxidant activities (lipophilic—LAA and hydrophilic—HAA) and bioactive compounds (phenols and total ascorbic acid—TAA). Interestingly, Trichoderma spp. had a positive effect on these qualitative parameters, especially when combined with mulching films, where the increase generated by PE-TR treatment over the all other treatments was 16.3% and 16.8% for LAA and HHA, respectively. In all treatments, the nitrate leaves content was consistently always within the legal limit imposed by the European community. Overall, although Trichoderma spp. did not engender a marked effect on yield, probably due to the short crop cycle, its positive effect on some quality traits is an interesting starting point for further research. Full article
(This article belongs to the Special Issue Soil, Water and Nitrates Management in Horticultural Production)
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12 pages, 653 KiB  
Article
Salt Tolerance of Hydrangea Plants Varied among Species and Cultivar within a Species
by Genhua Niu, Youping Sun, Triston Hooks, James Altland, Haijie Dou and Christina Perez
Horticulturae 2020, 6(3), 54; https://doi.org/10.3390/horticulturae6030054 - 4 Sep 2020
Cited by 6 | Viewed by 4857
Abstract
A greenhouse study was conducted to assess the relative salt tolerance of 11 cultivars of hydrangea: Hydrangea macrophylla ‘Ayesha’, ‘Emotion’, ‘Mathilda Gutges’, ‘Merritt’s Supreme’ and ‘Passion’; H. paniculata ‘Interhydia’ and ‘Bulk’; H. quercifolia ‘Snowflake’; H. serrata ‘Preciosa’; and H. [...] Read more.
A greenhouse study was conducted to assess the relative salt tolerance of 11 cultivars of hydrangea: Hydrangea macrophylla ‘Ayesha’, ‘Emotion’, ‘Mathilda Gutges’, ‘Merritt’s Supreme’ and ‘Passion’; H. paniculata ‘Interhydia’ and ‘Bulk’; H. quercifolia ‘Snowflake’; H. serrata ‘Preciosa’; and H. serrata × macrophylla ‘Sabrina’ and ‘Selina’. Plants were treated with a nutrient solution at an electrical conductivity (EC) of 1.0 dS·m−1, and nutrient solution-based saline solutions at an EC of 5.0 dS·m−1 (EC 5) or 10 dS·m−1 (EC 10). The study was repeated in time (Experiments 1 and 2). In both experiments, by the fourth week after treatment, ‘Bulk’ plants in EC 10 exhibited severe salt damage with most of them dead. ‘Interhydia’ was also sensitive, showing severe salt damage in EC 10 with a high mortality rate by the end of the experiment. The leaf area and total shoot dry weight (DW) of all cultivars in EC 5 and EC 10 treatments were significantly reduced compared to the control. Leaf sodium (Na+) and chloride (Cl−) concentrations were negatively correlated with visual quality, leaf area and shoot DW. The salt-sensitive cultivars ‘Bulk’, ‘Interhydia’ and ‘Snowflake’ had inherently low leaf Na+ and Cl− concentrations in both control and salt-treated plants compared to other cultivars. Salt tolerance varied among species and cultivars within H. macrophylla. Among the 11 cultivars, H. macrophylla ‘Ayesha’ and two hybrids, ‘Sabrina’ and ‘Selina’, were relatively salt-tolerant. H. macrophylla ‘Merritt’s Supreme’ and ‘Mathilda’ were moderately tolerant. H. paniculata ‘Bulk’ was the most sensitive, followed by H. paniculata ‘Interhydia’, and then by H. serrata ‘Preciosa’ and H. macrophylla ‘Passion’, as evidenced by high mortality and severe salt damage symptoms. H. quercifolia ‘Snowflake’ and H. macrophylla ‘Emotion’ were moderately salt-sensitive. Full article
(This article belongs to the Section Floriculture, Nursery and Landscape, and Turf)
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15 pages, 1980 KiB  
Article
Measuring Camellia Petal Color Using a Portable Color Sensor
by Phillip C. Post and Mark A. Schlautman
Horticulturae 2020, 6(3), 53; https://doi.org/10.3390/horticulturae6030053 - 3 Sep 2020
Cited by 9 | Viewed by 5850
Abstract
The color of petals of flowering plants is often determined by comparing one or more of the petals to various Royal Horticultural Society (RHS) Colour Chart cards until a color match is found. However, these cards are susceptible to fading with age and [...] Read more.
The color of petals of flowering plants is often determined by comparing one or more of the petals to various Royal Horticultural Society (RHS) Colour Chart cards until a color match is found. However, these cards are susceptible to fading with age and can also provide inaccurate results if lighting is not optimal. The cards also rely on the human eye to determine a match, which introduces the possibility of human error. The objectives of this study were to determine camellia (Camellia japonica L.) petal color using the RHS Colour Chart, to determine camellia petal color with the NixTM Pro color sensor (Nix Sensor Ltd., Hamilton, Ontario, Canada), and to compare these measurements using different color measuring approaches. Color measurements of camellia flower petals using the NixTM Pro color sensor were compared to published CIELAB values from the Royal Horticultural Society (RHS) Colour Chart. Forty-five petal color samples were collected from fifteen different camellia shrubs. The RHS Colour Chart was used for each of the petals, and the RHS identifications were recorded. Measurements using the NixTM Pro color sensor were compared to RHS-provided CIELAB values that corresponded with the recorded identification for each petal to determine accuracy. The NixTM Pro color sensor’s measurements were also compared to a mean of the values, multiple measurements on the same petal location, and multiple measurements on different petal locations to determine precision and variation. The Nix™ Pro color sensor’s readings were precise in petal color determination and provided more nuanced differences between petals of the same plant and plants of the same variety in each of the color categories. The RHS Colour Chart provided an accurate depiction of most petals, but it was difficult to use with petals that had wide color variation over the entire petal. The Nix™ Pro color sensor’s measurements appeared to have more variation in the b* color space. However, overall, the Nix™ Pro color sensor L*, a*, and b* values were highly correlated with the provided RHS values (p < 0.01), showing that the sensor can be used as an accurate and precise substitute for the RHS Colour Chart. The Nix™ Pro color sensor can be a useful, cost-effective tool to measure the petal color of camellia and other flowering plants and rectifies many of the problems associated with the RHS Colour Chart. Full article
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8 pages, 3707 KiB  
Article
Mechanical Crop Load Management (CLM) Improves Fruit Quality and Reduces Fruit Drop and Alternate Bearing in European Plum (Prunus domestica L.)
by Sebastian Lammerich, Achim Kunz, Lutz Damerow and Michael Blanke
Horticulturae 2020, 6(3), 52; https://doi.org/10.3390/horticulturae6030052 - 2 Sep 2020
Cited by 11 | Viewed by 3765
Abstract
(1) Background: With ca. 10 million tons of annual production worldwide, the plum (Prunus ssp.) ranks as a major fruit crop and can suffer from small fruit size, premature fruit drop and alternate bearing, which are addressed in this paper using [...] Read more.
(1) Background: With ca. 10 million tons of annual production worldwide, the plum (Prunus ssp.) ranks as a major fruit crop and can suffer from small fruit size, premature fruit drop and alternate bearing, which are addressed in this paper using a range of crop load management (CLM) tools. (2) Methods: Sixty 10-year-old European plum cv. “Ortenauer” trees on dwarfing St. Julien INRA GF 655/2 rootstock (slender spindle; 4.25 × 2.80 m) in a commercial orchard near Bonn (50°N), Germany, were thinned in 2 years and flower intensity assessed in the following year. Thinning was performed either mechanically (type Bonn/Baum) or chemically, with ATS (ammonium thiosulfate) or ethephon (Flordimex), or by a combination of mechanical and chemical methods, to improve fruit quality and the proportion of Class 1 fruit. Adjacent un-thinned trees served as controls. (3) Results: Natural fruit drop in June was reduced from 290 fruits per tree in the un-thinned controls to 265 fruits after ATS blossom treatment, and to 148 fruits after mechanical thinning at 380 rpm at a 5 km/h tractor speed at full bloom. The un-thinned control trees developed a large number of small, undersized fruits. The yield of Class 1 fruits increased per tree from 47% in the un-thinned controls, up to 69% after crop load management. Sugar content and fruit firmness were unaffected. (4) Conclusions: The study has shown that fruit quality (i.e., fruit size) and financial returns could be improved by either mechanical (380 rpm at 5 km/h) or chemical thinning, or a combination of both. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae)
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8 pages, 1481 KiB  
Article
Rapid In Vitro Multiplication of Non-Runnering Fragaria vesca Genotypes from Seedling Shoot Axillary Bud Explants
by Babul C. Sarker, Douglas D. Archbold, Robert L. Geneve and Sharon T. Kester
Horticulturae 2020, 6(3), 51; https://doi.org/10.3390/horticulturae6030051 - 1 Sep 2020
Cited by 2 | Viewed by 3702
Abstract
Fragaria vesca L. has become a model species for genomic studies relevant to important crop plant species in the Rosaceae family, but generating large numbers of plants from non-runner-producing genotypes is slow. To develop a protocol for the rapid generation of plants, leaf [...] Read more.
Fragaria vesca L. has become a model species for genomic studies relevant to important crop plant species in the Rosaceae family, but generating large numbers of plants from non-runner-producing genotypes is slow. To develop a protocol for the rapid generation of plants, leaf explants were compared to single axillary bud shoot explants, both from in vitro-grown Fragaria vesca seedlings, as sources of shoots for new plant production in response to benzyladenine (BA) or thidiazuron (TDZ) combined with indolebutyric acid (IBA) on Murashige and Skoog’s Basal Salt (MS) medium. BA at 2.0 and 4.0 mg L−1 and TDZ at 1.5 mg L−1 promoted the greatest number of shoots produced per shoot explant. There were no IBA effects or IBA interactions with BA or TDZ. Significant interactions between BA and IBA, but not TDZ and IBA, occurred in leaf explant callus formation and % explants with callus at 6 and 9 weeks of culture and on shoots per leaf explant at 9 weeks. TDZ treatments produced uniformly high levels of callus but low numbers of shoots. The treatment generating the most shoot production was BA at 4.0 mg L−1 plus IBA at 0.50 mg L−1. After 9 weeks of culture, leaf explants of the non-runner-producing genotype Baron Solemacher had generated 4.6 shoots per explant with the best treatment, while axillary bud explants had generated 30.8 shoots with the best treatment. Thus, in vitro culture of shoot axillary bud explants can generate high numbers of clonal shoots from a single seedling plant in vitro. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae)
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18 pages, 2307 KiB  
Article
Grapefruit Production in Open Hydroponics System
by Rhuanito S. Ferrarezi, Thiago A. R. Nogueira, Arun D. Jani, Alan L. Wright, Mark A. Ritenour and Randy Burton
Horticulturae 2020, 6(3), 50; https://doi.org/10.3390/horticulturae6030050 - 1 Sep 2020
Cited by 2 | Viewed by 3936
Abstract
Conventionally managed citrus orchards can be modified to incorporate advanced horticultural practices such as higher plant density and efficient water and fertilizer application known as open hydroponics system (OHS) to increase productivity under Huanglongbing (HLB) endemic conditions. A field study was conducted from [...] Read more.
Conventionally managed citrus orchards can be modified to incorporate advanced horticultural practices such as higher plant density and efficient water and fertilizer application known as open hydroponics system (OHS) to increase productivity under Huanglongbing (HLB) endemic conditions. A field study was conducted from 2013 to 2018 to evaluate the effect of an OHS on “Ray Ruby” grapefruit (RR) production under HLB-endemic conditions. We tested a combination of different rootstocks [Sour orange (RR/SO) and US-897 (RR/897)], tree planting densities [standard (STD, 358 trees per ha) and high density staggered (HDS, 953 trees per ha)], fertilization methods (dry granular—dry and fertigation—fert), and irrigation systems (double driplines—DD and microsprinkler—MS), arranged in five treatments: RR/SO_STD_dry_MS, RR/SO_HDS_fert_DD, RR/897_HDS_fert_MS, RR/897_HDS_fert_DD, and RR/SO_HDS_fert_MS. All trees were infected by Candidatus Liberibacter asiaticus five years after planting. Trunk diameter and canopy volume increased over time and were higher under RR/SO_STD_dry_MS compared to other treatments. Total fruit number increased in 2016/17 compared to other seasons; however, 65% of fruit were classified as small (<100 mm). Fruit produced under RR/897_HDS_fert_DD had the highest amount (79%) of adequate size fruit (100–117 mm) compared to other treatments. Fruit yield was similar for both rootstocks planted at HDS using DD and MS fertigation, and 67% higher than the standard treatment (RR/SO_STD_dry_MS). Soluble solid contents (SSC), titratable acidity, and SSC-to-titratable acidity ratio were not affected by the treatments. HDS planting resulted in higher fruit yield, irrespective of rootstock and irrigation system, representing an important advance in grapefruit production. Overall, our results demonstrated that production of grapefruit in high-density using OHS can be used by citrus growers who aim to make the best water and fertilizer management under HLB-endemic conditions. Full article
(This article belongs to the Special Issue Advances in Citrus Horticulture)
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10 pages, 1109 KiB  
Article
Altered Carbohydrate Allocation Due to Soil Water Deficit Affects Summertime Flowering in Meiwa Kumquat Trees
by Naoto Iwasaki, Asaki Tamura and Kyoka Hori
Horticulturae 2020, 6(3), 49; https://doi.org/10.3390/horticulturae6030049 - 26 Aug 2020
Cited by 2 | Viewed by 2797
Abstract
The summertime flowers of the ever-flowering Meiwa kumquat (Fortunella crassifolia Swingle) are the most useful for fruit production in Japan; however, summertime flowers bloom in three or four successive waves at approximately 10 day intervals, resulting in fruit of different maturity occurring [...] Read more.
The summertime flowers of the ever-flowering Meiwa kumquat (Fortunella crassifolia Swingle) are the most useful for fruit production in Japan; however, summertime flowers bloom in three or four successive waves at approximately 10 day intervals, resulting in fruit of different maturity occurring on the same tree. Soil water deficit (SWD) treatment has been shown to reduce the flowering frequency and improve harvest efficiency; therefore, in this study, the effects of SWD treatment on the accumulation of soluble sugars in each tree organ above-ground were examined and it was discussed how SWD affects the whole-tree water relations and sugar accumulation by osmoregulation. The number of first-flush summertime flowers was higher in SWD-treated trees than non-treated control (CONT) trees (177.0 and 58.0 flowers, respectively), whereas the second- and third-flush flowers were only observed in CONT trees. The soluble sugar content was higher in SWD treated trees than CONT trees for all organs and tended to be higher in current-year organs than previous-year organs; however, when the sugar content of the current-year spring stems exceeded approximately 100 mg g−1 dry weight, the current-year leaf water potential decreased sharply and the rate of increase in the number of first-flush flowers also tended to decrease. SWD treatment significantly increased the total sugar content of the xylem tissue of the scaffold branches to three times the value in CONT trees (p = 0.001); however, the increase was observed even in sucrose, a disaccharide, similar to that in monosaccharides such as glucose and fructose. These results suggest that the increased sugar levels in the xylem tissue resulted from not only osmoregulation but also other factors as well; therefore, these sugars may affect whole-tree water relations as well as the development of flower buds. Full article
(This article belongs to the Special Issue Soil, Water and Nitrates Management in Horticultural Production)
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17 pages, 295 KiB  
Article
An Appraisal of Biodegradable Mulch Films with Respect to Strawberry Crop Performance and Fruit Quality
by Maria Giordano, Ciro Gianmaria Amoroso, Christophe El-Nakhel, Youssef Rouphael, Stefania De Pascale and Chiara Cirillo
Horticulturae 2020, 6(3), 48; https://doi.org/10.3390/horticulturae6030048 - 21 Aug 2020
Cited by 17 | Viewed by 3781
Abstract
Fragaria × ananassa is a fruit grown all over the world, appreciated for its organoleptic and nutraceutical properties. Together with other berry fruits, it is rich in bioactive molecules that make it a beneficial fruit for human health. However, strawberry cultivation is influenced [...] Read more.
Fragaria × ananassa is a fruit grown all over the world, appreciated for its organoleptic and nutraceutical properties. Together with other berry fruits, it is rich in bioactive molecules that make it a beneficial fruit for human health. However, strawberry cultivation is influenced by pre- and post-harvest factors. Being a small plant, its fruit comes into direct contact with the soil and, as such, can quickly decompose. To reduce this inconvenience, farmers have used different strategies to mulch the soil, and the most useful method is polyethylene mulch films that are not biodegradable. The focus on environmentally sustainable agriculture can be represented by a transition to biodegradable mulch films. In our study, ten biodegradable mulch films were used to understand their effectiveness in covering the soil during the cultivation cycle of strawberry cv. Rociera. Polyethylene film was considered the control. The best yield and the highest number of fruits with greatest size and quality were obtained on polyethylene, BioFlex® (P2), Bio 6, and Bio 7 films. On BioFlex® (P2) and Bio 3 biodegradable films, strawberries showed a higher calcium and magnesium content, respectively. These results may encourage growers toward the use of eco-sustainable agricultural practices, such as biodegradable mulch films. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae)
15 pages, 1653 KiB  
Article
Soil-Biodegradable Plastic Mulches Undergo Minimal in-Soil Degradation in a Perennial Raspberry System after 18 Months
by Huan Zhang, Markus Flury, Carol Miles, Hang Liu and Lisa DeVetter
Horticulturae 2020, 6(3), 47; https://doi.org/10.3390/horticulturae6030047 - 20 Aug 2020
Cited by 12 | Viewed by 5008
Abstract
Soil-biodegradable plastic mulches (BDMs) are made from biodegradable materials that can be bio-based, synthetic, or a blend of these two types of polymers, which are designed to degrade in soil through microbial activities. The purpose of BDMs is to reduce agricultural plastic waste [...] Read more.
Soil-biodegradable plastic mulches (BDMs) are made from biodegradable materials that can be bio-based, synthetic, or a blend of these two types of polymers, which are designed to degrade in soil through microbial activities. The purpose of BDMs is to reduce agricultural plastic waste by replacing polyethylene (PE) mulch, which is not biodegradable. Most studies have evaluated the breakdown of BDMs within annual production systems, but knowledge of BDM breakdown in perennial systems is limited. The objective of this study was to evaluate the deterioration and degradation of BDMs in a commercial red raspberry (Rubus ideaus L.) production system. Deterioration was low (≤11% percent soil exposure; PSE) for all mulches until October 2017 (five months after transplanting, MAT). By March 2018 (10 MAT), deterioration reached 91% for BDMs but remained low for PE mulch (4%). Mechanical strength also was lower for BDMs than PE mulch. In a soil burial test in the raspberry field, 91% of the BDM area remained after 18 months. In-soil BDM degradation was minimal, although the PSE was high. Since mulch is only applied once in a perennial crop production system, and the lifespan of the planting may be three or more years, it is worth exploring the long-term degradation of BDMs in perennial cropping systems across diverse environments. Full article
(This article belongs to the Section Fruit Production Systems)
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11 pages, 789 KiB  
Article
The Effects of Gibberellic Acid and Emasculation Treatments on Seed and Fruit Production in the Prickly Pear (Opuntia ficus-indica (L.) Mill.) cv. “Gialla”
by Lorenzo Marini, Chiara Grassi, Pietro Fino, Alessandro Calamai, Alberto Masoni, Lorenzo Brilli and Enrico Palchetti
Horticulturae 2020, 6(3), 46; https://doi.org/10.3390/horticulturae6030046 - 17 Aug 2020
Cited by 4 | Viewed by 4766
Abstract
Prickly pear (Opuntia ficus-indica (L.) Mill. 1768) is cultivated in several dry and semi-dry areas of the world to produce fresh fruit, bioenergy, cosmetics, medicine, and forage. One of the main production constraints is the presence of many seeds within the fruit, [...] Read more.
Prickly pear (Opuntia ficus-indica (L.) Mill. 1768) is cultivated in several dry and semi-dry areas of the world to produce fresh fruit, bioenergy, cosmetics, medicine, and forage. One of the main production constraints is the presence of many seeds within the fruit, which can negatively influence both the fresh-fruit market price and industrial transformation processes. In this study, different gibberellic acid (GA3) concentrations were tested for their ability to produce well-formed and seedless fruits. Different application methods (injection and spraying) and concentrations of GA3 (0, 100, 200, 250, and 500 ppm) combined with floral-bud emasculation were applied to a commercial plantation in southern Italy to evaluate their effects on the weight, length, and diameter of the fruits, total seed number, hard-coated viable seed number, and seed weight per fruit. The results indicated that the application of 500 ppm GA3 sprayed on emasculated floral buds was the most effective method for reducing seed numbers of prickly pear fruits (−46.0%). The injection method resulted in a very low number of seeds (−50.7%) but produced unmarketable fruit. Observed trends suggest the need to investigate the impact of higher GA3 concentrations and the applicability of a maximum threshold. Further studies are needed to increase our understanding of the physiological effects of the gibberellic acid pathway through productive tissue in terms of organoleptic and fruit quality. Full article
(This article belongs to the Special Issue Horticultural Crop Response to Different Environmental and Nutritional Stress)
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17 pages, 1302 KiB  
Article
Deficit Irrigation and Arbuscular Mycorrhiza as a Water-Saving Strategy for Eggplant Production
by M. A. Badr, W. A. El-Tohamy, S. D. Abou-Hussein and N. S. Gruda
Horticulturae 2020, 6(3), 45; https://doi.org/10.3390/horticulturae6030045 - 11 Aug 2020
Cited by 23 | Viewed by 4423
Abstract
Crop production in arid regions requires continuous irrigation to fulfill water demand throughout the growing season. Agronomic measures, such as roots-soil microorganisms, including arbuscular mycorrhizal (AM) fungi, have emerged in recent years to overcome soil constraints and improve water use efficiency (WUE). Eggplant [...] Read more.
Crop production in arid regions requires continuous irrigation to fulfill water demand throughout the growing season. Agronomic measures, such as roots-soil microorganisms, including arbuscular mycorrhizal (AM) fungi, have emerged in recent years to overcome soil constraints and improve water use efficiency (WUE). Eggplant plants were exposed to varying water stress under inoculated (AM+) and non-inoculated (AM−) to evaluate yield performance along with plant physiological status. Plants grown under full irrigation resulted in the highest fruit yield, and there were significant reductions in total yield and yield components when applying less water. The decline in fruit yield was due to the reduction in the number of fruits rather than the weight of the fruit per plant. AM+ plants showed more favorable growth conditions, which translated into better crop yield, total dry biomass, and number of fruits under all irrigation treatments. The fruit yield did not differ between full irrigation and 80% evapotranspiration (ET) restoration with AM+, but a 20% reduction in irrigation water was achieved. Water use efficiency (WUE) was negatively affected by deficit irrigation, particularly at 40% ET, when the water deficit severely depressed fruit yield. Yield response factor (Ky) showed a lower tolerance with a value higher than 1, with a persistent drop in WUE suggesting a lower tolerance to water deficits. The (Ky) factor was relatively lower with AM+ than with AM− for the total fruit yield and dry biomass (Kss), indicating that AM may enhance the drought tolerance of the crop. Plants with AM+ had a higher uptake of N and P in shoots and fruits, higher stomatal conductance (gs), and higher photosynthetic rates (Pn), regardless of drought severity. Soil with AM+ had higher extractable N, P, and organic carbon (OC), indicating an improvement of the fertility status in coping with a limited water supply. Full article
(This article belongs to the Special Issue Soil, Water and Nitrates Management in Horticultural Production)
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13 pages, 486 KiB  
Article
Integrating Greenhouse Cherry Tomato Production with Biofloc Tilapia Production
by Jeremy M. Pickens, Jason J. Danaher, Jeff L. Sibley, Jesse A. Chappell and Terry R. Hanson
Horticulturae 2020, 6(3), 44; https://doi.org/10.3390/horticulturae6030044 - 4 Aug 2020
Cited by 13 | Viewed by 5187
Abstract
Integration of intensive aquaculture systems with greenhouse plant production has been shown to improve aquaculture water quality conditions and improve plant nutrient use efficiency. The majority of the focus of integrated systems has involved raft culture or true hydroponics. Little work has been [...] Read more.
Integration of intensive aquaculture systems with greenhouse plant production has been shown to improve aquaculture water quality conditions and improve plant nutrient use efficiency. The majority of the focus of integrated systems has involved raft culture or true hydroponics. Little work has been done on soilless culture utilizing drip irrigation. This study investigates the feasibility of integrating biofloc Nile tilapia (Oreochromis niloticus) production with greenhouse cherry tomato production (Solanum lycopersicum var. cerasiforme). Nile tilapia (157 g/fish) were stocked at 40 fish/m3 and grown for 149 days. The cherry tomato cvs. “Favorita” and “Goldita” were grown with aquaculture effluent (AE) waste and compared to plants grown with conventional fertilizer (CF) in soilless culture. Plants were grown for 157 days. Few differences in yield occurred between treatments until fish harvest (117 DAT). Post fish harvest, there was an 18.4% difference in total yield between CF and AE at crop termination for “Favorita”. Differences in yield between AE and CF were observed for “Goldita” at fish harvest (117 DAT) and crop termination (157 DAT). Results from this study suggest the potential for successful integration of cherry tomato grown in a substrate-based system with AE from a tilapia biofloc production system. Full article
(This article belongs to the Special Issue Advances in Knowledge of Hydroponic and Aquaponic Systems II)
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9 pages, 355 KiB  
Article
The Effect of Leaching Fraction-Based Irrigation on Fertilizer Longevity and Leachate Nutrient Content in a Greenhouse Environment
by Claire E. Krofft, Jeremy M. Pickens, Adam F. Newby, Jeff L. Sibley and Glenn B. Fain
Horticulturae 2020, 6(3), 43; https://doi.org/10.3390/horticulturae6030043 - 3 Aug 2020
Cited by 8 | Viewed by 2912
Abstract
An experiment was conducted to evaluate the effects of leaching fraction (LF) on the longevity of controlled-release fertilizer (CRF) and leachate nutrient content in a pine bark substrate. The effect of LF-based irrigation was evaluated under six target LFs of 0.05, 0.15, 0.25, [...] Read more.
An experiment was conducted to evaluate the effects of leaching fraction (LF) on the longevity of controlled-release fertilizer (CRF) and leachate nutrient content in a pine bark substrate. The effect of LF-based irrigation was evaluated under six target LFs of 0.05, 0.15, 0.25, 0.35, 0.45, and 0.55. The 2.72 L nursery pots were filled with 100% pine bark substrate amended with dolomitic lime at a rate of 2.97 kg/m3 and Harrell’s 16-6-13 POLYON® applied at a rate of 6 g per container. Fertilizer was encased in vinyl-coated fiberglass mesh bags and subdressed 2.5 cm under the substrate surface for recovery at the end of 10 weeks. The total amount of nutrients leached from the container was greater at higher LFs, with twice as much inorganic nitrogen leached at a LF of 0.55 than a 0.15 LF. The amount of dissolved nutrients left in the substrate decreased as the LF treatments increased. There were 29.6% more inorganic nitrogen and 37.7% more phosphorus left in the substrate irrigated with a 0.15 LF as compared to a 0.55 LF. This suggests that at lower LFs, more dissolved nutrients may be available for plant uptake. No differences were seen in the amount of nutrients lost from the CRF or remaining in the prills. Results indicate that reducing the LF did not influence the longevity of POLYON® CRF in a pine bark substrate, but that a lower LF may be useful in reducing nutrient runoff into the environment. Targeting a lower LF also resulted in a larger pool of plant-available nutrients, allowing nursery producers to potentially reduce fertilizer rates. Full article
(This article belongs to the Section Floriculture, Nursery and Landscape, and Turf)
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9 pages, 224 KiB  
Brief Report
Total Coliform and Generic E. coli Levels, and Salmonella Presence in Eight Experimental Aquaponics and Hydroponics Systems: A Brief Report Highlighting Exploratory Data
by Daniel L. Weller, Lauren Saylor and Paula Turkon
Horticulturae 2020, 6(3), 42; https://doi.org/10.3390/horticulturae6030042 - 30 Jul 2020
Cited by 8 | Viewed by 5200
Abstract
Although many studies have investigated foodborne pathogen prevalence in conventional produce production environments, relatively few have investigated prevalence in aquaponics and hydroponics systems. This study sought to address this knowledge gap by enumerating total coliform and generic E. coli levels, and testing for [...] Read more.
Although many studies have investigated foodborne pathogen prevalence in conventional produce production environments, relatively few have investigated prevalence in aquaponics and hydroponics systems. This study sought to address this knowledge gap by enumerating total coliform and generic E. coli levels, and testing for Salmonella presence in circulating water samples collected from five hydroponic systems and three aquaponic systems (No. of samples = 79). While total coliform levels ranged between 6.3 Most Probable Number (MPN)/100-mL and the upper limit of detection (2496 MPN/100-mL), only three samples had detectable levels of E. coli and no samples had detectable levels of Salmonella. Of the three E. coli positive samples, two samples had just one MPN of E. coli/100-mL while the third had 53.9 MPN of E. coli/100-mL. While the sample size reported here was small and site selection was not randomized, this study adds key data on the microbial quality of aquaponics and hydroponics systems to the literature. Moreover, these data suggest that contamination in these systems occurs at relatively low-levels, and that future studies are needed to more fully explore when and how microbial contamination of aquaponics and hydroponic systems is likely to occur. Full article
(This article belongs to the Special Issue Aquaponics: Circular Sustainability for Food Security)
16 pages, 1893 KiB  
Article
Optimizing Fruit-Thinning Strategies in Peach (Prunus persica) Production
by Mary Sutton, John Doyle, Dario Chavez and Anish Malladi
Horticulturae 2020, 6(3), 41; https://doi.org/10.3390/horticulturae6030041 - 22 Jul 2020
Cited by 17 | Viewed by 4201
Abstract
Fruit size is a highly valued commercial trait in peach. Competition among fruit and among other sinks on a tree reduces potential growth rate of the fruit. Hence, crop-load management strategies such as thinning (removal of flowers or fruit) are often practiced by [...] Read more.
Fruit size is a highly valued commercial trait in peach. Competition among fruit and among other sinks on a tree reduces potential growth rate of the fruit. Hence, crop-load management strategies such as thinning (removal of flowers or fruit) are often practiced by growers to optimize fruit size. Thinning can be performed at bloom or during early fruit development and at different intensities to optimize fruit growth responses. Responses to thinning may be cultivar and location specific. The objective of the current study was to fine-tune thinning strategies in the southeastern United States, a major peach producing region. Timing and intensity of thinning were evaluated across multiple cultivars over three years. Thinning at bloom or at 21 d after full bloom (DAFB) improved fruit size in comparison to unthinned trees in ‘Cary Mac’ and ‘July Prince’, respectively, in one year. Bloom-thinning reduced fruit yield (kg per tree) in the above cultivars in one year, suggesting that flower thinning alone may not be a viable option in this region. Intensity of thinning, evaluated as spacings of 15 cm and 20 cm between fruit, did not differentially affect fruit weight or yield. However, fruit diameter decreased quadratically with increasing fruit number per tree in ‘Cary Mac’, ‘July Prince’ and ‘Summer Flame’. Similarly, fruit weight decreased quadratically in response to increase in fruit number per tree in ‘Cary Mac’ and ‘July Prince’. Further, yield-per-tree decreased with increasing fruit size in ‘Cary Mac’ and ‘July Prince’. Importantly, these relationships were cultivar specific. Together, the data suggest that achieving a target fruit number per tree is an effective strategy for crop-load management to optimize fruit size in southeastern peach production. The target fruit number per tree may potentially be achieved through a combination of flower and fruit-thinning during early fruit development. Such an approach may provide flexibility in crop-load management in relation to adverse weather events. Full article
(This article belongs to the Section Fruit Production Systems)
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10 pages, 231 KiB  
Communication
Sole-Source LED Lighting and Fertility Impact Shoot and Root Tissue Mineral Elements in Chinese Kale (Brassica oleracea var. alboglabra)
by T. Casey Barickman, Dean A. Kopsell, Carl E. Sams and Robert C. Morrow
Horticulturae 2020, 6(3), 40; https://doi.org/10.3390/horticulturae6030040 - 18 Jul 2020
Cited by 4 | Viewed by 3195
Abstract
The current study investigated the impacts of light quality and different levels of fertility on mineral nutrient concentrations in the shoot and root tissues of Chinese kale (Brassica oleracea var. alboglabra). “Green Lance” Chinese kale was grown under: (1) fluorescent/incandescent light; [...] Read more.
The current study investigated the impacts of light quality and different levels of fertility on mineral nutrient concentrations in the shoot and root tissues of Chinese kale (Brassica oleracea var. alboglabra). “Green Lance” Chinese kale was grown under: (1) fluorescent/incandescent light; (2) 10% blue (447 ± 5 nm)/90% red (627 ± 5 nm) light emitting diode (LED) light; (3) 20% blue/80% red LED light; and (4) 40% blue/60% red LED light as sole-source lighting at two different levels of fertility. All plants were harvested 30 days after seeding and shoot and root tissues were analyzed for mineral nutrients. Lighting and fertility interacted to influence kale shoot and root mineral nutrient concentrations. The results indicate that sole-source LED lighting used in production can impact the mineral nutritional values of baby leafy greens now popular for the packaged market. This is evident in the current and previous studies in which lighting affects biomass and indirectly affects mineral nutrient concentrations. Full article
(This article belongs to the Section Plant Nutrition)
11 pages, 2628 KiB  
Article
Use of In Situ Soil Solution Electric Conductivity to Evaluate Mineral N in Commercial Orchards: Preliminary Results
by Elena Baldi, Maurizio Quartieri, Enrico Muzzi, Massimo Noferini and Moreno Toselli
Horticulturae 2020, 6(3), 39; https://doi.org/10.3390/horticulturae6030039 - 8 Jul 2020
Cited by 8 | Viewed by 3709
Abstract
The aim of the present experiment was to evaluate the effectiveness of soil electrical conductivity (EC) measurement as a fast tool to assess mineral nitrogen (N) in orchards, in order to define precise N inputs that can help farmers to reduce useless fertilizer [...] Read more.
The aim of the present experiment was to evaluate the effectiveness of soil electrical conductivity (EC) measurement as a fast tool to assess mineral nitrogen (N) in orchards, in order to define precise N inputs that can help farmers to reduce useless fertilizer application. During one vegetative season, seven orchards of different species, supplied with mineral or organic fertilization, were monitored. Nitrate soil concentration was measured monthly by laboratory analyses, while soil EC and moisture were recorded continuously by soil probes. Nitrate and EC were positively correlated, laying the foundation for the identification of a fast and reliable index. However, while some dates showed a high Pearson correlation coefficient, no correlation was found for others. The correlation was not affected by type of fertilizer, and was higher in silty-clay-loam than in loam soils. Pooling all of the data, a significant correlation with a Pearson coefficient of 0.75 was found. The soil optimal nitrate N availability was defined by an EC in the range of 0.3 to 0.6 mS cm−1. Although these are only preliminary results, our data are promising, showing a good suitability of soil EC measurement as a means to monitor soil mineral N availability. Full article
(This article belongs to the Special Issue Fertilization Management of Horticultural Crops)
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25 pages, 2064 KiB  
Review
The Potential of Introduction of Asian Vegetables in Europe
by Jungha Hong and Nazim S. Gruda
Horticulturae 2020, 6(3), 38; https://doi.org/10.3390/horticulturae6030038 - 3 Jul 2020
Cited by 25 | Viewed by 8709
Abstract
Increasing longevity, along with an aging population in Europe, has caused serious concerns about diet-related chronic diseases such as obesity, diabetes, cardiovascular diseases, and certain cancers. As recently noted during the coronavirus pandemic, regular exercise and a robust immune system complemented by adequate [...] Read more.
Increasing longevity, along with an aging population in Europe, has caused serious concerns about diet-related chronic diseases such as obesity, diabetes, cardiovascular diseases, and certain cancers. As recently noted during the coronavirus pandemic, regular exercise and a robust immune system complemented by adequate consumption of fruit and vegetables are recommended due to their known health benefits. Although the volume of fresh vegetable consumption in the EU is barely growing, demand for diversified, nutritious, and exotic vegetables has been increasing. Therefore, the European market for fresh Asian vegetables is expected to expand across the EU member states, and the introduction of new vegetables has enormous potential. We conducted this review to address the high number and wide range of Asian vegetable species with a commercial potential for introduction into the current European vegetable market. Many of them have not received any attention yet. Four Asian vegetables: (1) Korean ginseng sprout, (2) Korean cabbage, (3) Coastal hog fennel and (4) Japanese (Chinese or Korean) angelica tree, are further discussed. All of these vegetables possess several health benefits, are increasingly in demand, are easy to cultivate, and align with current trends of the European vegetable market, e.g., vegetables having a unique taste, higher value, are decorative and small. Introducing Asian vegetables will enhance the diversity of nutritious horticultural products in Europe, associated with all their respective consumption benefits. Future research on the Asian vegetable market within Europe is needed. In addition, experimental studies of Asian vegetables under practical conditions for their production in different European environments are required. Economic, social, and ecological aspects also ought to be considered. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae)
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40 pages, 495 KiB  
Review
Biochar—A Panacea for Agriculture or Just Carbon?
by Elvir Tenic, Rishikesh Ghogare and Amit Dhingra
Horticulturae 2020, 6(3), 37; https://doi.org/10.3390/horticulturae6030037 - 3 Jul 2020
Cited by 26 | Viewed by 9067
Abstract
The sustainable production of food faces formidable challenges. Foremost is the availability of arable soils, which have been ravaged by the overuse of fertilizers and detrimental soil management techniques. The maintenance of soil quality and reclamation of marginal soils are urgent priorities. The [...] Read more.
The sustainable production of food faces formidable challenges. Foremost is the availability of arable soils, which have been ravaged by the overuse of fertilizers and detrimental soil management techniques. The maintenance of soil quality and reclamation of marginal soils are urgent priorities. The use of biochar, a carbon-rich, porous material thought to improve various soil properties, is gaining interest. Biochar (BC) is produced through the thermochemical decomposition of organic matter in a process known as pyrolysis. Importantly, the source of organic material, or ‘feedstock’, used in this process and different parameters of pyrolysis determine the chemical and physical properties of biochar. The incorporation of BC impacts soil–water relations and soil health, and it has been shown to have an overall positive impact on crop yield; however, pre-existing physical, chemical, and biological soil properties influence the outcome. The effects of long-term field application of BC and how it influences the soil microcosm also need to be understood. This literature review, including a focused meta-analysis, summarizes the key outcomes of BC studies and identifies critical research areas for future investigations. This knowledge will facilitate the predictable enhancement of crop productivity and meaningful carbon sequestration. Full article
(This article belongs to the Special Issue Feature Papers in Horticulturae)
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