Plug Transplants Research Articles

Flowering and fruiting of day-neutral and ever-bearing strawberry cultivars in high-elevation for summer and autumn fruit production in Korea

This study was conducted to evaluate the flowering and fruiting of day-neutral (DN) and ever-bearing (EB) cultivars in high-elevation in Korea. Six DN and five EB cultivars were established in bench-top substrate culture system in high tunnel. Plug transplants were planted on 5 May, 2011 and complete nutrition was supplied during the whole experimentation. Fruit harvest started in early June, and lasted until middle November. Fruit yield was significantly different among DN and EB, and individual cultivars. Generally, summer flower came out earlier and resulted in more summer yield for EB cultivars than for the DN cultivars. However, DN cultivars produced higher autumn yield than EB cultivars. Fruits of DN cultivars showed harder firmness, bigger size, less malformed fruits, deeper surface colors than those of EB cultivars. Fruit surface colors significantly varied with the progressive seasons and an interactive effect between cultivars and harvest time on fruit surface colors was found. Among DN cultivars, ‘San Andreas’ not only showed some typical DN characters such as big fruit and hard firmness, but also showed high values of color parameters. Among EB cultivars, ‘Charlotte’ and ‘Goha’ combination can realize even fruit supply in summer and autumn. Combination of DN cultivar and EN cultivar not only can realize even fruit supply but also can fulfill both fresh consumption and processing purposes in summer and autumn season.

Tolerance of Hooker’s Evening Primrose Transplants to Preemergence Herbicides

No research has investigated the phytotoxic response of hooker’s evening primrose (Oenothera elata) plug transplants to preemergence herbicides. Varied phytotoxic responses of common evening primrose (Oenothera biennis) to preemergence herbicides suggest that options may exist for the safe control of weeds present within hooker’s evening primrose when grown as an agronomic field crop. Enhanced weed control during early establishment may reduce competition for water and nutrients as well as increase seed yield and oil content. Therefore, the objective of this research was to determine the phytotoxic effect of preemergence herbicides on hooker’s evening primrose plug transplants grown in the greenhouse. Research was conducted in 2010 and 2011 at the Plant and Soil Science greenhouse complex at Texas Tech University in Lubbock, TX. Herbicide treatments were applied on 13 July 2010 and 5 Apr. 2011 and consisted of oxadiazon at 3 lb/acre, isoxaben at 0.5 lb/acre, oryzalin at 2 lb/acre, prodiamine at 1.5 lb/acre, dithiopyr at 0.5 lb/acre, s-metolachlor at 1.8 lb/acre, pendimethalin at 0.6 lb/acre, and isoxaben + trifluralin at 2.5 lb/acre. One 4-month-old hooker’s evening primrose plug (2 inches wide) was transplanted into each pot (3 gal) 2 days after treatment (DAT). Dithiopyr and s-metolachlor treatments exhibited similar lack of phytotoxicity as the untreated control 7 DAT. Phytotoxicity ≥13% was observed for trifluralin + isoxaben, pendimethalin, prodiamine, oryzalin, isoxaben, and oxadiazon 7 DAT, with the highest level of phytotoxicity (24%) exhibited by trifluralin + isoxaben treatments. Hooker’s evening primrose phytotoxicity decreased (plants grew out of the damage) for all treatments except trifluralin + isoxaben, pendimethalin, and oryzalin 28 DAT. Oryzalin (16%) and trifluralin + isoxaben (60%) were the only two treatments that did not exhibit similar phytotoxicity to the untreated control 28 DAT. There were no significant differences in aboveground or belowground biomass nor plant growth index (PGI) of any of the treatments when compared with the untreated control 28 DAT. Based upon the results of this trial, pendimethalin, prodiamine, dithiopyr, s-metolachlor, oryzalin, isoxaben, and oxadiazon may be used for preemergence weed control in hooker’s evening primrose without causing excessive phytotoxicity (>20%), potential yield loss, or both. Trifluralin + isoxaben treatments exhibited 60% hooker’s evening primrose phytotoxicity 28 DAT, which resulted in too low of an initial plant stand to warrant use.

Improved Sustainability through Novel Water Management Strategies for Strawberry Transplant Establishment in Florida, United States

Establishing bare-root transplants in Florida, United States, is an inefficient water-consuming activity. Between 3500 and 5500 m3/ha are applied with sprinkler irrigation to lower temperatures around the transplant crown and aid early root development, but more than 97% of the water volume runs off the polyethylene-covered beds. Research has been conducted to evaluate the feasibility of producing containerized (plug) short-day cultivar transplants under Florida conditions, the effect of continuous and intermittent low-volume sprinklers on transplant establishment and the use of kaolin clay to reduce stress on young transplants. Research results demonstrated that growers may have alternatives to reduce water use and pumping costs during strawberry transplant establishment by the following: (a) plug transplants can be produced from mother plants from Florida’s subtropical weather without chilling conditioning and still be competitive in the winter market; (b) using continuous and intermittent low-volume sprinkler irrigation saves between 16% and 33% of the water volumes for strawberry establishment; and (c) using kaolin clay showed to be a low-cost (US$63/ha plus application costs) investment to reduce irrigation volumes by at least 30%.

Multiplication of strawberry stock plants at different planting times

The objective of this research was to determine the effectiveness of the multiplication of micropropagated strawberry stock plants as a method for producing runner tips to be used in the production of plug transplants. Micropropagated stock plants of cultivars INIA-Arazá, INIA-Guenoa and INIA-Yvapitá were planted at October 1st, 2008. Runner tips emitted by the micropropagated stock plants were harvested and planted as multiplied stock plants at 37; 40; 46; 51; 58; 64; 67; 75 and 87 days after planting the micropropagated stock ones. Runner tips emitted by all plants between October, 2008 and April, 2009, were harvested and counted, the number of root nodules counted and the crown diameter measured. The number of runner tips decreased linearly on all stock plants by delaying planting time, while crown diameter and number of root nodules were not affected. Higher number of runner tips was produced by micropropagated stock plants. The cultivar INIA-Arazá was the most prolific. Multiplying stock plants may be a new propagation method than can be used for reducing the number of micropropagated stock plants required for the production of strawberry commercial plug transplants.

Crown size and transplant type on the strawberry yield

Strawberry (Fragaria x ananassa D.) yield is affected by vigor of transplants. Those young and vigorous at planting lead to plants reaching higher vegetative growth and fruit yield than weak or old ones. This study aimed at determining plant growth, development, and fruit yield of the strawberry plant from bare root and plug transplants with different crown diameters. Bare root transplants were produced by rooting stolons and plug transplants from runner tips collected and rooted in a substrate growing bed. Three classes of crown diameters were compared in a 2 × 3 factorial and randomized block experimental design, with four replications, 16 plants per plot and a density of 6.6 plants m-2. For bare root transplants, crown diameters were between 3.0 and 5.0 mm (class 1); 5.1 and 8.0 mm (class 2) and greater than 8.1 mm (class 3). For plug transplants, runner tips were screened between 2.0 and 3.9 mm (class 1); 4.0 and 5.5 mm (class 2) and 5.6 to 7.0 mm (class 3). Transplants of both types were planted at April 16th, 2008, and at this date, crown diameter, shoot and root dry mass and number of leaves were higher in all classes of plug transplants. Ripe fruits were harvested from June 15th to November 7th, 2008, and fresh fruit yield was determined. Plant growth and development were determined at last harvest. Higher growth, development and fruit yield were obtained in plants from plug transplants. For bare root transplants, crown diameters higher than 5.1 mm can be used while for plug transplants the crown diameter of runner tips does not affect plant growth and fruit yield.

English

During past mining activities the East Fork of the Arkansas River was diverted through a 2000-foot long concrete pipe where it crosses Climax Molybdenum Company's Climax Mine property at approximately 11,150 ft above mean sea level (3,400 m). In 2006, the mine initiated an ambitious project to daylight the river into a newly constructed channel. The goals of the project were to engineer a hydraulically stable and aesthetically pleasing stream channel and adjoining landform and to establish self-sustaining and diverse riparian and wet meadow plant communities and viable aquatic habitats. Revegetation was implemented in 2007 and 2008 after channel and adjacent topographic feature reconstruction was complete on the 15-acre site. Biosolids, composted on-site as a part of Climax's EPA award-winning program, were the only soil amendment added to the site. Composted biosolids were spread over the disturbance area at a rate of 400 cubic yards per acre and were incorporated into the mineral soil fill material to a depth of 12 inches. The upland areas adjacent to the river were seeded with a mixture of native subalpine species at a rate of 30 pure live seeds per square foot. Additionally, 120 Engelmann spruce and subalpine fir transplants, harvested on the property, were planted. Along the banks of the channel, around the lake, and in low-lying swales 108 willow and birch shrubs, over 500 willow stakes, and over 700 native wetland plug transplants were planted and a mixture of native subalpine wetland species was seeded at a rate of 50 pure live seeds per square foot. After 3 years vegetative cover averages 27.4% over the entire site with 28.2% cover in upland areas and 11.6% in wetland areas. Survival of transplanted willows, birches, and cinquefoil was 100%, and spruce survival was 73%. Willow stake survival was 68% and almost all wetland plugs survived.

Cell size in trays for the production of strawberry plug transplants

The objective of this work was to evaluate the influence of cell sizes used for strawberry plug production in trays compared to bare root transplants, regarding initial plant size, harvest timing, and total strawberry fruit yield. Plug transplants were produced from runner tips rooted in trays with cell sizes of 26.5, 50, 100 and 150 cm³ filled with Plantmax HA organic substrate. Bare root transplants (control) were produced in a closed soilless system using sand as substrate. A randomized block design was used, with four replicates with 16 plants per plot. Bare root transplants and plug transplants from 100-cm³ cells had larger crown and higher leaf and root dry mass. Early fruit yield was higher in plants propagated from plugs than in those propagated from bare root transplants. Spring and total fruit yield did not differ among treatments, with an average yield of 435 and 874 g per plant, respectively. Earlier strawberry fruit yield was obtained by using plug transplants, even from trays with small cells of 26.5 or 50 cm³.

Effects of ages of plug transplants and planting depths on the growth and yield of sweetpotato

Sweetpotato [ Ipomoea batatas (L.) Lam. cv. Beniazuma] plug transplants produced from single node leafy cuttings under artificial light in a closed-type growth chamber were planted with roots and substrate of 11- and 15-day old (ca. two to three unfolded leaves with 0.08 m shoot length and three to four unfolded leaves with 0.11 m shoot length, respectively). The plug transplants of both the 11- and 15-day old were planted with one and three nodes depth (ca. 4 and 25 mm deep, respectively) inside the soil ridges (called one- and three-node depth, respectively, hereafter). The conventional vine cuttings (ca. 0.3 m long with seven to eight unfolded leaves) without roots were planted as Control treatment to compare the growth and yield of sweetpotato with each of the treatments of plug transplant. The main objectives of the study were to see the effects of ages of plug transplants and depths of planting for greater growth and yield of sweetpotato in the field. The yield of storage roots 115 days after planting in the field was 33 t ha −1 when using 15-day old plug transplants planted with three-node depth and was 10 t ha −1 greater than that in the Control. The mean storage root length was about 259 mm when using 11-day old plug transplants planted with three-node depth and was 33 mm greater than that in the Control. The mean diameter of storage roots was 70 mm when using 11- and 15-day old plug transplants planted with one-node depth and was 21 mm greater than that in the Control. The plug transplants planted either 11- or 15-day old showed greater overall performances than those of the conventional cuttings. The plug transplants planted with three-node depth showed greater performances than did the plug transplants planted with one-node depth.

Fruiting Responses and Economics of Containerized and Bare-root Strawberry Transplants Established with Different Irrigation Methods

Strawberry (Fragaria ×ananassa) crops were transplanted in two seasons in central Florida with bare-root and containerized (plug) plants under three transplant establishment-period irrigation methods to evaluate crop fruiting responses and production economics associated with the various establishment systems. Irrigation was not required to establish plug transplants in the field. Early (first 2 months) fruit yield with nonirrigated plug plants was greater than early yield with sprinkler-irrigated bare-root plants (the current commercial system) in one of two seasons and equal in a second season. Total-season yields were similar in each season between the two establishment systems. Large or medium plug plants led to greatest early fruit yields in one season while large plug plants resulted in greatest early yield in a second season. Total yield was greatest with medium plants in one season and large plants in another season. The extra cost for the plug plant system was $1853/acre. In one out of two seasons there was increased net income amounting to $1142/acre due to greater early yield associated with the plug plant cultural system. Strawberry plug transplants showed promise for earlier and more profitable crops in addition to substantial savings in water used for plant establishment in the field. The ability to establish strawberry crops without irrigation will be important in areas where growers are required to reduce farm water consumption.

Effect of Multiple Plants per Plug on Processing Tomato Yield in California

In recent years, an estimated 65% of processing tomato acreage has converted from direct seeding to transplanting the crop. Growers have been switching to transplants for a number of reasons, including land use efficiency, water conservation, and weed management. Field studies investigating plant spacing and multiple plants per transplant plug (cell) were initiated when observations by growers indicated that there were seemingly decreased fruit yields from transplanted crops. A transplant density experiment was established in 2004 in a commercial field of processing tomatoes grown on the west side of Fresno County in the San Joaquin Valley, the major tomato production area in California. The field trial investigated in-row spacing (37.5 cm and 75 cm), the number of plants per transplant plug (1, 2, or 3), on a medium vine size variety (Halley 3155) and a large vine size variety (AB2). Individual plots were large enough for mechanical harvest. Yield results indicate that these two varieties responded similarly to increasing plant density. In general, a spacing of 37.5 cm with 2 or 3 plants per plug yielded significantly more than 1 plant per plug, regardless of variety. There was no yield advantage in seeding 3 plants per plug when compared to yields with 2 plants per plug, regardless of variety or in-row plant spacing. A plant spacing of 75 cm with only 1 plant per plug yielded the least.

Potential Use of a 24-Hour Photoperiod (Continuous Light) with Alternating Air Temperature for Production of Tomato Plug Transplants in a Closed System

To evaluate the potential use of a 24-hour photoperiod for transplant production in a closed system, tomato (Lycopersicon esculentum Mill.) plug transplants were grown for 17 days either under a 24-hour photoperiod with a photosynthetic photon flux (PPF) of 200 μmol·m-2·s-1 or under a 16-hour photoperiod with a PPF of 300 μmol·m-2·s-1, resulting in the same daily integrated PPF (17.3 mol·m-2). Air temperatures were alternated between 28 °C during the first 16 hours and 16 °C for the subsequent 8 hours of each day. Fresh weight, dry weight and leaf area were 41%, 25%, and 64% greater, respectively, under the 24-hour photoperiod than under the 16-hour photoperiod. Physiological disorders (e.g., chlorosis and/or necrosis) were not observed under the 24-hour photoperiod, probably due to the alternating air temperature. Floral development of plants originating from both treatments did not differ significantly. Electric energy use efficiency of the closed system was 9% greater under the 24-hour photoperiod than under the 16-hour photoperiod. These results suggest that using a 24-hour photoperiod with relatively low PPF can reduce both initial and operational costs for transplant production in a closed system due to the reduction in the number of lamps.

Evaluation of Organic Strawberry Runner Production

System requirements for organic strawberry (Fragaria × ananassa) runner production under cover were determined during the 2001-02 and 2002-03 seasons. In the field, yield and fruit quality were assessed for organically produced runners (plug and bare-rooted transplant) in comparison with barerooted conventionally produced runners under organic, BioGro certified production conditions. The preferred organic production system was the enhanced suspended system, where mother plants grew on benches in the tunnel house and the first two runners were potted into growth substrate. This system produced approximately 50 plug transplants/mother plant or 200 plug transplants/m2. The least preferred system was the nursery bed, where mother plants were allowed to produce runners that yielded approximately 100 bare-rooted runners or 100 transplants/m2. Tunnel house production of runners (plug transplants and bare-rooted) allowed earlier planting (March vs. May) compared to field-produced bare-rooted runner plants. The earlier planting date increased yield by approximately 181 g/plant. Under organic production conditions, organically produced runners (plug and bare-rooted transplants) performed at least as well as bare-rooted conventionally produced runners. Our results show that indoor production of organic strawberry runners is possible. We also showed that organically produced runners (bare-rooted and plug transplants) perform similarly in the field compared to bare-rooted conventionally produced runners. Generally, there were no differences in yield or fruit quality among runner sources.

Plug Tray Cell Volume Effects on Sweet Corn Transplant Root Architecture and Biomass Accumulation

Sweet corn (Zea mays L.) is difficult to transplant due to poor root regeneration. Despite reduced yields, growers are transplanting sweet corn to hasten maturity time to target profitable early markets in the Northeast. Researchers have ascribed the negative impacts on yield to restricted rooting volume. Therefore, the impacts plug cell volume had on sweet corn transplant root architecture and biomass accumulation were investigated. `Temptation' sweet corn was sown in volumes of 15, 19, 14, and 29 mL correlating to transplant plug trays with plug counts of 200, 162, 128, and 72 plugs per tray. Plug cells were exposed to three substrate environments; a dairy manure based organic compost media, a commercial soil-less germination mix, and the soil-less media supplemented 2X with 200 ppm soluble 3-3-3 organic fertilizer. A 4 × 3 factorial randomized complete-block experimental design with two blocks and five replicates per treatment was repeated twice in the greenhouse. For each experiment a total of three center cells were harvested from each replicate for analysis using the WinRhizo Pro root scanning system (Regent Instruments Inc., Montreal). Three cells per treatment were also transplanted into 8-inch pots to stimulate field transplanting. Based on mean separation tests (n = 30), increased cell volume before transplanting significantly increased root surface area, average diameter, and root volume after transplanting (n = 18). Mean root surface area for a 29-mL cell was 30% greater than a 15-mL cell before transplanting and 22% greater after transplanting. Plug cell volume also significantly impacted shoot and root biomass (P <0.0001). A 14-mL increase in cell volume resulted in a root and shoot dry weight increase of about 15%.

The Relative Merits of Native Transplant Plugs and Topsoil Islands in the Enhancement of Understory Biodiversity on Reclaimed Minelands

In northeastern Ontario, Canada, mine tailings and lands rendered barren by smelter emissions are commonly revegetated using a grass-legume mixture, then planted with native trees, mostly conifers such as Red, White and Jack Pine. Vigorous colonization by native pioneer tree species such as White Birch and Trembling Aspen occurs, as well as that of native herbs associated with forest openings, such as Asters and Goldenrods. However, it is rare for the herbs and shrubs found in the understory of a mature pine forest to colonize these artificially wooded sites. Native understory species have been transplanted from natural habitat at an experimental level over a number of years on grassed smelter-affected barrens and grassed tailings, to determine whether such transplants survive and spread. Small islands of forest topsoil have also been established on grassed tailings. The source of native plugs has been predominantly mature Jack, Red and White Pine forest, but species adapted to naturally exposed sites such as sand dunes have also been transplanted with success. Not surprisingly, the species that spread most readily are those possessing rhizomes or stolons, such as Canada Mayflower (Maianthemum canadense) and Starry False Solomon's Seal (Smilacina stellata) in the case of plugs, and Spreading Dogbane (Apocynum androsaemifolium) in the case of topsoil islands. Since results so far suggest that both approaches are valid, the relative advantages of each are critically appraised.

INCREASING WINTER STRAWBERRY PRODUCTION IN NORTH-CENTRAL FLORIDA USING PASSIVE VENTILATED GREENHOUSES AND HIGH PLANT DENSITIES

Winter production of strawberry (Fragaria x ananassa Duch) under protected structures can give several advantages to producers over field production. The objective of this research was to determine how increasing plant densities (10.8, 11.7, 12.7, 14, 16.9, 18.3, 20, and 22 plants per m 2 ) of 'Sweet Charlie' strawberry grown in a passive ventilated greenhouse might improve yield Without adversely affecting fruit quality. Plant densities were derived with four between-row spacings (65, 60, 55, and 50 cm center-to-center) and two within-row spacings (17.5 cm and 35 cm plant-to-plant). Strawberry plants were grown in a 'Hanging Bed-Pack' trough system (Polygal Industries, Ramat Hashofet, Israel) that were suspended 1.8 m above the ground level and filled with 6.5 cm 2 sieved pinebark. Marketable yield per m 2 increased linearly with an increase in plant density throughout the season. Early yield per plant was not affected by plant density, however, total yield per plant decreased as plant density increased. Regardless of treatment, the average berry size for early and total yield was 20 g and more than 90 percent of the yield was marketable. A cost threshold was developed by comparing the value of higher early yields when prices are highest, to increased cost of plug transplants at high plant densities. A plant density of 16.9 plants per m 2 led to break-even yields while higher plant densities from 18.3 to 22 plants per m 2 led to increased profits. Thus, high plant populations were required to maximize profits from strawberries grown in passive ventilated greenhouses.

GROWTH CONTROL IN PROCESSING TOMATO SEEDLINGS

The use of high density plug transplants in processing tomato production has considerably increased in commercial growing areas in recent years. Seedling height control in this growing technique seems to be more challenging than that of the conventionally grown seedlings. Several control measurements of seedling height were tested on high density plug transplants by using two processing tomato cultivars. Brushing at 40 strokes per day reduced stem height by 25 %, which was similar to that obtained by Paclobutrazol application once every 15 days. When both treatments were combined stem length was reduced up to 35 %. Increasing cool air movement around the seedling was less effective in controlling stem height and remained at a reduction rate of 18-19 %. The possibilities in replacing chemical treatments with more environmental friendly techniques were discussed.

閉鎖型苗生産システムと開放型苗生産システムの夏季におけるトマトセル成型苗の品質と資源消費量の比較例

Tomato (Lycopersicon esculentumMill., cv. Momotaro) plug transplants were grown in a closed-type (CTPS) and an open-type (OTPS ; i.e., greenhouse) transplant production systems during summer (11-15 August to 1 September, 2000) . The quality of transplants and water consumption in the CTPS were compared with those in the OTPS. Electric energy consumption per transplant was estimated in the CTPS. The CTPS was a system designed to produce transplants under artificial light in a relatively airtight structure with thermally insulated walls, and to produce high quality transplants using minimal resources. The CTPS employed a sub-irrigation system. Air temperature in the CTPS was maintained at 28°C during a 16 h photoperiod and at 19°C during an 8 h dark period by using an air conditioner. The OTPS employed an overhead irrigation system. Air temperature in the OTPS was partly controlled by using roof and side ventilators, but varied from 23 to 43°C depending on the weather conditions. The quality of transplants was higher in the CTPS than in the OTPS. Electric energy consumption per transplant in the CTPS was 0.7 MJ (0.2 kWh), which corresponded to a cost of 2.9-3.2 Japanese Yen. The amount of water consumed during the transplant production period in the CTPS was 1/12-1/16 of that in the OTPS. These results suggested that value-added transplants could be produced at a lower water consumption of resources in the CTPS than in the OTPS at low electricity consumption.

Prevention and Management of Diseases on Vegetable Transplants

The use of disease-free greenhouse-grown plug transplants for the establishment of field plantings of many vegetable crops in the arid west and southwestern regions of the United States has become a very important part of the agricultural system in these areas. The development of effective disease-control programs for use in the greenhouse involves a broad knowledge of production systems, water management, growing media, cultural techniques, etc., as well as knowledge of the discipline of plant pathology. The consultant in this field also must know the people and organizations with whom he is working. His goal is not simply the passing on of technical information, but also assisting in the incorporation of that information into the total growing program. Good communication skills and the development of an atmosphere of trust between all parties concerned are a vital part of the consultant's work.

Temperature Conditioning and Container Size Affect Early Season Fruit Yield of Strawberry Plug Plants in a Winter, Annual Hill Production System

The demand for plug transplants by the Florida winter strawberry (Fragaria ×ananassa Duch.) industry may increase as water conservation during plant establishment becomes more important and the loss of methyl bromide fumigant makes the production of bare-root transplants more problematic. A study was conducted during the 1995-96 and 1996-97 seasons to determine the effect of container size and temperature conditioning on the plant growth and early season fruit yield of `Sweet Charlie' strawberry plants. Plants in containers of three sizes (75, 150, and 300 cm3) were grown in one of two temperature-controlled greenhouses (35 °C day/25 °C night or 25 °C day/15 °C night) for the 2 weeks just prior to transplanting into a fruiting field at Dover, Fla. Plants exposed to the 25/15 °C treatment had significantly higher average root dry weights at planting in 1995 and 1996 than did plants exposed to the 35/25 °C treatment. Plants exposed to the 25/15 °C treatment also had higher average fruit yields than the plants exposed to the 35/25 °C treatment (48% and 18% higher in 1995-96 and 1996-97, respectively). The effect of container size on plant growth and yield was variable. Plants propagated in the 150- and 300-cm3 containers tended to be larger (at planting) than the plants propagated in the 75-cm3 containers, but the larger container sizes did not result in consistently higher yields.

Sweetpotato Growth and Yield from Plug Transplants of Different Volumes, Planted Intact or Without Roots

Single‐node leafy cuttings of sweetpotato [Ipomoea batatas (L.) Lam. cv. Beniazuma] plants can be used to produce low‐cost, pathogen‐free sweetpotato plug transplants. This study was conducted to determine the effects of plug volume and root removal on sweetpotato growth and yield after planting in the field. The yield and growth of sweetpotato plants from transplants with 4 to 6 unfolded leaves (about 0.14‐m shoot length) produced in 55‐ or 35‐mL multicell plug trays, then planted intact or without roots were compared with a control treatment of unrooted conventional cuttings (about 0.3‐m‐long terminal vine cutting with 7 to 8 unfolded leaves). The plug transplants were grown from single node leafy cuttings under artificial light. Intact plug transplants (35 or 55 mL) produced 39 to 40 Mg ha−1 of storage roots 128 d after planting in the field, 11 to 12 Mg ha−1 greater than the control treatment. After 128 d of field growth, plug transplants (35 mL, with roots) gave a percent harvest index of 79%, 7% greater than the control. The maximum length and diameter of storage roots were, respectively, 271 and 68 mm when plug transplants were used (35 mL, with roots), and were, respectively, 58 mm longer and 18 mm wider than the control. Overall, growth and yield from plug transplants were significantly higher than from conventional cuttings, regardless of the plug volume or root removal. Plug transplants with intact roots produced greater growth and yield regardless of plug volume than did plug transplants without roots.