Vegetable Transplant Production Research Articles

Evaluating the Soil Block Method and Growing Media in Organic Vegetable Transplant Production

Organic vegetable growers are interested in using the “soil block” method for transplant production as an alternative to plastic flats. The soil block method compresses growing media into a freestanding block in contrast to the cells of a plastic flat. Anecdotal evidence of soil block–grown transplants with increased vigor and root development exists, but limited research has been conducted to evaluate these claims. Furthermore, identifying commercial growing medium for certified organic transplant production is needed. The objective of this study was to compare growth parameters and root development of cucumber (Cucumis sativus) and pepper (Capsicum annum) transplants grown in soil blocks and plastic flats, in combination with four commercially available certified organic media (Beautiful Land Products “Soil Blocking Mix,” Purple Cow Organics “Seed Starter Mix,” Cowsmo “Green Potting Soil,” and Vermont Compost Company “Fort Vee”). A volume-based 50% peat, 25% compost, 12.5% perlite, and 12.5% vermiculite growing medium was also evaluated. A split-plot randomized complete block design with four replications was used with growing method as the whole plot factor and medium as the subplot factor. ‘Marketmore 76’ cucumbers and ‘Yankee Bell’ peppers were seeded in 50-cell flats and soil blocks made with Johnny’s Selected Seeds Stand-up 12 Soil Blocker. Data were collected on growth parameters by destructively sampling cucumbers 3 weeks after seeding, and peppers 5, 6, and 7 weeks after seeding. Root development was evaluated using WinRHIZOTM at the last sampling. Cucumber and pepper transplants performed differently in soil blocks and flats. Cucumbers grown in flats had a significantly greater dry weight than those grown in soil blocks, by 20% in 2022 and by 38% in 2023. In contrast, pepper transplants grown with the soil block method had between 50% and 130% greater dry weight in the final sampling in 2022. Cucumber and pepper transplants grown with Cowsmo “Green Potting Soil” performed poorly, with an up to 144% lower dry weight and up to 167% lower root surface area than transplants grown with the other media. Root development correlated with shoot development, without a specific advantage in soil blocks, although differences in root system architecture should be investigated. The evaluated Beautiful Land Products, Purple Cow Organics, and Vermont Compost Company media can all be considered suitable for growing certified organic vegetable transplants in both soil blocks and flats. Further research is warranted to better optimize the soil block technique, investigate optimum soil block bulk density, and inform growers of appropriate commercially available certified organic growing media for organic vegetable transplant production.

Compost from willow biomass (Salix viminalis L.) as a horticultural substrate alternative to peat in the production of vegetable transplants

Willow (Salix viminalis L.) is a species well adapted to the environment conditions of central Europe. It is mainly cultivated for energy purposes as solid fuel. In this study, an evaluation of its suitability for other purposes was made using a 4-year old short rotation coppice (SRC) willow regrowth to produce chipped biomass which was composted. Four composting methods were used: without additives (WC), with the addition of nitrogen to narrow the C:N ratio (WN), with the addition of mycelium (WPG) and with the addition of mycelium and nitrogen (WPGN). A mixture of WC and WPGN composts was also prepared at 75:25% and 50:50% by volume. Composts, different proportion (25, 50 and 75%) of peat (SM) were evaluated for suitability as a substrate for tomato and cucumber transplant production. Tomato transplants produced in the medium were prepared from mixtures of willow composts (WPGN + WC(1) and WPGN + WC(2) and these mixtures with peat (WPGN + WC(1):SM and WPGN + WC(2):SM) were characterised as having the best parameters: plant height, lateral leaf span and number of leaves. Similarly, for cucumber transplants, better growth conditions than in peat substrate were obtained in the variant WPGN + WC(1) and WPGN + WC(1):SM. The addition of nitrogen to the composted biomass positively influenced the composting process. N concentration in the substrate was too high and toxic for the growth of tomato and cucumber transplants. At the end of the tomato and cucumber experiment, the nitrate content was 1510 and 2260 mg dm−3, respectively, in the WN substrate. Similarly, the high N–NO3− content in the composted willow substrate with the addition of nitrogen and mycelium did not promote the growth of tomato and cucumber. Based on this research at least 25% of the mass of the peat can be replaced by different willow composts without having an adverse impact on seedling growth and with some of the willow compost mixtures this could be as high as 50%.

The changes of willow biomass characteristics during the composting process and their phytotoxicity effect on Sinapis alba L.

This study evaluated in 2019-2021 the use of willow chips for compost production and its effect on Sinapis alba L. germination index and seedling growth. Peatlands and peat are of very important economic but above all environmental significance. The conservation of peatland resources is one of the most crucial future challenges. Composts and other forms of lignin-cellulosic biomass are potentially the best renewable alternative to peat in its economic use. Composted lignin-cellulosic biomass can replace peat and be used as a substrate for vegetable transplant production. The impact of modifying the willow lignin-cellulosic biomass composting process has not been well analysed. A compost experiment with willow biomass was conducted to study its effect on selected compost indexes (particle size structure in %, bulk density (kg m-3), and total nitrogen content). The quality assessment of the willow composts was determined after six months of composting process based on the N content and morphological characteristics of tested plant in vegetative chamber. Sinapis alba L. was germinated on a water extract made from willow compost using the following additives to willow biomasses: W0-without additives, WN-with the addition of nitrogen, WF-with the addition of mycelium, WNF-with the addition of nitrogen and mycelium. During the composting process, samples were taken after each mixing of the biomass pile to assess their maturity through the use of a bioassay. Willow biomass did not have a negative effect on biological evaluation parameters, and in some indicators, such as the length of embryonic roots in the VI period of the measurements, it was stimulating (61-84% longer in W0 and WF than in the control). The addition of nitrogen during the composting process, especially in the initial composting period, had a strong inhibitory effect.

LIGHT EMITTING DIODES IN VEGETABLE PRODUCTION SYSTMES

LEDs have become the predominant future lighting system for greenhouse crop production. The LEDs are popularly applied in photoperiod lighting, vegetable transplant production, graft-healing, greenhouse production and quality enhancement. As the LED technology advances, they improve the quality of vegetable transplants and produces. The spectral control reduce production costs and increase the value of specialty crops with promoted flavor and sensory traits. The Horticultural LED will continue to grow more hardware configurations and control protocols. LEDs provide comprehensive tool for plant environment for manipulation of plant function.

Swine Lagoon Compost: Analysis as Transplant Substrate for ‘Traviata’ Eggplant, ‘Clemson Spineless’ Okra, and ‘Moneymaker’ Tomato

Composted swine (Sus domesticus) lagoon solids may provide a nutrient rich alternative to peatmoss (Sphagnum sp.) in a transplant substrate while dispersing the concentrated nutrients of this waste product in a cost effective, environmentally conscientious manner. The objective of this study was to evaluate the physical and chemical characteristics of swine lagoon solids composted with peanut (Arachis hypogaea) hulls and evaluate the utility of this substrate to support growth of vegetable transplants. Swine lagoon solids were composted in an in-vessel compost reactor with peanut hulls 15:85 v/v producing a transplant substrate, swine lagoon compost (SLC). A greenhouse study was conducted with three vegetable species: ‘Moneymaker’ tomato (Solanum lycopersicum), ‘Traviata’ eggplant (Solanum melongena), and ‘Clemson Spineless’ okra (Abelmoschus esculentus) grown in SLC, an organic potting mix (OM), and a peatmoss-based substrate (PEAT). ‘Traviata’ eggplant, ‘Clemson Spineless’ okra, and ‘Moneymaker’ tomato transplants produced in SLC substrate were significantly greater in height and dry weight than those produced in either the OM or PEAT. Based on these findings SLC can provide both the physical and chemical requirements needed for vegetable transplant production without additional amendments or fertilizers.

Compost Functions as Effective Replacement for Peat-Based Potting Media in Organic Greenhouse Transplant Production

Commercial horticulture in many regions of the world depends upon Sphagnum peat as a potting-media substrate, but extracting peat has serious environmental consequences. Composts may be able to serve as effective substitutes for peat and offer potential environmental advantages. The suitability of compost as potting media depends upon the raw materials as well as processing methods used. This study includes two related experiments—one with beet (Beta vulgaris L.) and the other with tomato (Solanum lycopersicum L.)—aimed at assessing the potential viability of farm-produced, food-residuals compost as a replacement for peat-based potting media in the production of organic vegetable transplants. The experiments were conducted in 2021 on the Berea College Farm in Kentucky, USA, a USDA certified organic farm. The results indicated that potting media composed of 75% to 100% compost performed as well as fertilized, peat-based growing media for plant growth. Further, although weeds were present in the compost, weed pressure was not severe enough to adversely affect crop growth. Thus, sterilization of compost, which did eliminate weeds in the compost, was not deemed necessary for using the compost as a partial or complete potting medium. Compost pasteurization was also assessed but was ineffective in destroying weed seeds.

Humic Substances Improve Vegetable Seedling Quality and Post-Transplant Yield Performance under Stress Conditions

Vegetable growers require vigorous transplants in order to reduce the period of transplant shock during early stand establishment. Organic media containing solid humic substances (HS) are amendments that have not been comprehensively explored for applications in containerized vegetable transplant production systems. In this study, HS (1% v/v) were applied to a peat-based growth medium to evaluate pre- and post-transplant growth modulation of four economically important vegetable species. Those were: pepper, tomato, watermelon, and lettuce. Seeding for all species was performed in two periods in order to evaluate their post-transplant yield performance under drought (water deficit vs. well-watered) and heat (hot vs. cool season) stresses. Compared with control, HS-treated plants had: (1) increased leaf and root biomass after transplanting due to faster growth rates; (2) lower root/shoot ratio before transplanting, but higher after 10 days of field establishment; and (3) increased root length and surface area. The negative effects of heat and drought stresses on crop yield were more prominent in control plants, while HS-treated transplants were able to mitigate yield decreases. The results clearly demonstrated the benefits of using solid HS as a management input to improve transplant quality in these crop species.

Supplemental Radiation Quality Influences Cucumber, Tomato, and Pepper Transplant Growth and Development

Supplemental lighting is required for the production of high-quality vegetable transplants in greenhouses when the photosynthetic daily light integral (DLI) is low. Light-emitting diodes (LEDs) are a promising alternative to high-pressure sodium (HPS) lamps. However, there are a limited number of studies that have evaluated how LED supplemental lighting spectral quality beyond blue (B) and red (R) radiation influences plant growth and development. Seeds of hybrid greenhouse seedless cucumber ‘Elsie’ (Cucumis sativus), tomato ‘Climstar’ (Solanum lycopersicum), and pepper ‘Kathia’ (Capsicum annuum) were sown and placed into a dark growth chamber until radicle emergence. Seedlings were grown in a greenhouse at a 25 °C constant temperature set point and under five lighting treatments. The supplemental lighting treatments delivered a total photon flux density (TPFD) of 120 μmol·m−2·s−1 for 16 h·d−1 based on an instantaneous threshold from HPS lamps or LEDs [three treatments composed of B (400–500 nm), R (600–700 nm), white, and/or far-red (FR; 700–800 nm) LEDs], and a control that delivered 25 μmol·m−2·s−1 from HPS lamps (HPS25). The LED treatments defined by their wavebands (TPFD in μmol·m−2·s–1) of B, green (G, 500–600 nm), R, and FR radiation were B20G10R75FR15, B25R95, and B30G30R60; whereas the HPS treatments emitted B7G57R47FR9 (HPS120) and B1G13R9FR2 (HPS25). Generally, cucumber, pepper, and tomato transplants under B30G30R60 and HPS120 supplemental lighting had the greatest stem diameter. Fresh weight and leaf area of all three species was greater when G radiation replaced R or B radiation. For example, leaf area and fresh weight of cucumber, tomato, and pepper increased (by 33%, 22%, and 49%; and 35%, 14%, and 56%, respectively) for plants under B30G30R60 supplemental lighting compared with plants under B25R95 supplemental lighting. The most compact cucumber and pepper transplants were those grown under B25R95 supplemental lighting, and the most compact tomatoes were those grown under the HPS25 (control) and B25R95 supplemental lighting. Tomato transplants under treatments providing ≥30 μmol·m−2·s−1 of G radiation had an increased incidence of leaf necrosis. From this study, we conclude that plant responses to supplemental lighting quality are generally genera-specific, and therefore high-wire transplants should be separated by genera to optimize production and quality. However, additional studies are required to provide complete LED supplemental lighting recommendations.

Growth and development of tomato seedlings in substrates containing distinct amendments of a novel calcium montmorillonite nanocomposite hydrogel.

Several results demonstrate that the correct use of hydrogels in adequate situations can increase seedling survival rates, plant growth and water-retention capacity of the soil. A technique of producing a nanocomposite hydrogel using calcium montmorillonite (NC-MMt) was recently developed. However, research results are still necessary in order to validate this innovative hydrogel, particularly for the production of vegetable crop transplants. In this context, the main objective of the present study was to evaluate the growth and development of ‘BRS Nagai’ tomato seedlings in substrates containing different amendments of NC-MMt. The trial was conducted in a 3 x 3 factorial design, with three replications. The substrates (peat moss – T1, pine bark – T2, and coconut peat based – T3) represented the first factor and three rates of hydrogel NC-MMt (0% – R1, 1.5% – R2 and 2.0% – R3, on a w/w basis) represented the the second factor. Each plot was composed of 16 plants that were compared after three weeks in all the treatments. Root diameter (means of 2.40 mm²), number of leaves (means of 12 leaves per plant), and plant emergency percentage – PEP (means of 86.8% at seven days after sowing – DAS) did not differ significantly amongst all factors. PEP at 14 DAS, plant height, plant height/shoot dry weight ratio, root dry weight, shoot dry weight/root dry weight ratio, leaf area, and Dickinson quality index were responsive to substrates, mainly T1. Root superficial area (RSA) and root volume (RV) were significantly affected by the distinct rates of NC-MMt. Treatments R2 (1.5%) and R3 (2.0%) differ significantly compared to control – R1 (0%). Positive responses for two factors (T1 substrate; R2 and R3 NC-MMt rates) were achieved for stem diameter (SD), RSA, RV values. In addition, no phytotoxic effects were observed. Therefore, tomato seedlings of the cultivar ‘BRS Nagai’ can be efficiently produced by means of one of these combinations.

Tomato transplant growth and leaf nutrient uptake using different nutrient solutions in the tropics

The use of a proper nutrient solution is a key factor in achieving production of vigorous transplants and subsequently obtaining profitable yields. It is true indeed when the grower says: “a good transplant is 50% of the production”. However, management of vegetable transplants' nutrition in Venezuela and in most tropical countries is seldom practiced, or it is carried out empirically, without any planning. The influence of different nutrient solutions on the growth of tomato transplants and leaf nutrient uptake was investigated in an experiment performed at a commercial nursery farm located in Quibor, Lara state, Venezuela. The treatments were: (1) tap water alone (TW); (2) conventional grower nutrient solution (C); (3) wye nutrient solution (W); and (4) W+TW (dW; concentration of 50%), using individual 200-plastic transplant trays filled with a combination of peat and coir (60 and 40%, respectively). It was found that all the transplant growth parameters evaluated (height, number of leaves, leaf area, stem diameter and shoot and root dry weights were significantly higher in W and dW solutions than in the C and control (TW) solutions. Similar responses were observed regarding leaf nutrient uptake. Plant tissues accumulated more nitrogen, phosphorus, potassium, calcium, and magnesium when W and dW were used. The lack of observed differences between C and TW could be associated to some nutrients supplied mainly from peat. Results from the study suggest that introducing new and balanced nutrient solutions is a crucial horticultural practice for the production of vegetable transplants. Besides, further research on integrated and planned transplant fertilization using other nutrient solutions (organic and mineral) and alternative substrates are recommended.

Organic Vegetable Crop Production in Controlled Environments Using Soilless Media

Organic vegetables produced in greenhouses and other controlled environments may fill a unique market niche as consumers demand local, high vegetables year round. However, limited technical information supports these production systems and more research is needed to provide recommendations for appropriate substrate mixes and nutrient management. Compost can be used as a substitute for peat-based media, and research results vary widely based on feedstock, compost method, and proportion used in mixes. Most studies consider compost in terms of peat-substitute or replacement and not as a source of fertility in soilless systems. Common challenges in using compost in soilless media are due to immaturity of the compost, poor water holding capacity, and unbalanced salinity and pH. It is possible to certify organic soilless production systems; however, the National Organic Program (NOP) of the U.S. Department of Agriculture has not yet provided clear rules and requirements supporting these systems. The objective of this article is to review the literature on soilless organic vegetable production, summarize results from the more widely studied topic of vegetable transplant production, and point to future research for organic agriculture.

Biochar Rate and Transplant Tray Cell Number Have Implications on Pepper Growth during Transplant Production

Biochar, a carbon-rich material derived from the pyrolysis of organic matter, exhibits beneficial chemical and physical properties when added to a soilless medium. Research on the use of biochar to improve plant productivity and growth has increased over the past decade, and has focused on using biochar as an alternative to sphagnum peatmoss. However, little work has been done to determine whether biochar can be used to partially replace commercially available sphagnum peatmoss–based greenhouse medium in vegetable transplant production. This study investigated the potential for supplementing a greenhouse growing medium with biochar for ‘Paladin’ pepper (Capsicum annuum) transplant production. Biochar was added to a soilless mix at rates of 0%, 20%, 40%, 60%, or 80% (by weight). Pepper seedlings were grown for 56 days in 50-, 72-, or 98-cell transplant trays at each of the five levels of biochar concentration. Germination increased in the 50- and 72- cell trays with 20%, 40%, and 60% biochar; however, biochar had no effect on germination in the 98-cell tray. Seedling height and dry weight decreased as biochar concentration and cell number increased. Seedling stem diameter also decreased with increasing cell number and biochar concentration. Leaf SPAD readings (indirect measurement of chlorophyll) decreased with increasing biochar rate. Medium pH increased with increasing biochar application rates. Higher rates of biochar (60% and 80%) increased pH well beyond 7.0 and negatively affected transplant growth. Overall results indicate positive effect of biochar in sphagnum peatmoss–based growing mix on seedling growth characteristics; although higher biochar concentrations could negatively affect seedling growth. Biochar can successfully replace up to 40% of sphagnum peatmoss–based growing medium and serve as a sustainable alternative medium in vegetable transplant production.

Guar, jantar, wheat straw, and rice hull composts as replacements for peat in muskmelon transplant production

The demand for soilless media for vegetable transplant production is increasing. Economic constraints paired with concerns over the sustainability of peat mining have necessitated the replacement of peat with renewable and regionally abundant alternatives. The aim of this study was to develop from composts complete or partial substitutes for peat. Composted guar (Cyamopsis tetragonoloba), jantar (Sesbania aculeata), wheat (Triticum aestivum) straw, and rice (Oryza sativa) hulls adjusted to 10% air-filled porosity (AFP) were blended on a volumetric basis with peat moss at discrete levels (0–50%). Total water-holding capacity, shrinkage, dry and wet bulk density, pH, electrical conductivity, N, P, K, FE, B, and Zn concentrations of each compost, their blends, and a peat control were measured. The experimental media were used to grow muskmelon (Cucumis melo) plants in a greenhouse. Seed germination, shoot fresh weight, shoot height, leaf area, stem diameter, root length, and mineral nutrient concentrations of transplants were quantified. After transplanting in the field, the growth rates and yields were measured. Nonparametric regression was used to analyze the data. The physiochemical parameters measured for most of the experimental media fell within the recommended range for growing media; however, pH for all media exceeded the recommended range. Media-containing guar and jantar composts generally contained more nutrients than media-containing rice hull or wheat straw composts. Fresh weight, height, and root length were generally greater for seedlings grown in media-containing rice hull compost than for those grown in media-containing other composts. Seedlings grown in media-containing guar or jantar composts generally had greater tissue nutrient concentrations. All blends produced acceptable seedlings; however, the largest seedlings, and greatest post-transplant growth rate and yield were produced in media containing 30–50% rice hull compost.

Effect of flood fertigation on yield of greenhouse lettuce grown in different substrates

The hydroponic system is very often used for greenhouse vegetable production. The flood irrigation on a bench or on the flood floors is applied in the production of ornamental plants and vegetable transplants. This system is environmentally friendly, since fertigation is used in a closed system using the recirculation of nutrient solution. The aim of this study, conducted in 2010-2012, was to determine the effect of flood fertigation with different concentrations of nutrient solution (EC: 1.0; 2.0; 3.0; 4.0 mS cm-1) on the yield and quality of the butterhead lettuce cultivar Natalia grown in different substrates (coconut coir, peat and rockwool). The experiment was conducted in the spring and autumn cycle. The highest marketable yield at each concentration of the nutrient solution was achieved in the cultivation in rockwool, both within the spring and autumn. The highest nitrate content in lettuce in terms of both cultivation cycles was found in the lettuce grown in the nutrient solution concentration of EC 4 mS cm-1, and the lowest one was achieved in the nutrient solution concentration of EC 1.0 mS cm -1. Significantly less of nitrates was in lettuce grown in spring than in autumn. Higher levels of EC significantly increased the content of P and K in lettuce leaves during in both growing cycles, while the content of Ca and Mg was not significantly different. The applied substrates had a significant impact on the content of K, P, Ca and Mg in leaves of lettuce. The best concentration of the nutrient solution used for flood fertigation of greenhouse lettuce was EC 3.0 mS cm-1 for the spring cultivation and EC 4.0 mS cm-1 for the fall crop.

STUDIES ON ONION SEEDS GERMINATION: 1- EFFECT OF MOIST-CHILLING ON GERMINATION OF ONION SEEDS STORED FOR TWO DIFFERENT PERIODS AND SUBSEQUENT SEEDLING GROWTH.

Onion seeds rapidly lose its viability and vigor after short time of harvest, and therefore its germinability largely decline. Consequently, the present investigation was carried out during the period from 2010-2012 in both Plant Tissue Culture Laboratory, Vegetables & Ornamentals Department, Faculty of Agriculture, Mansoura University and greenhouse of a private nursery in production of vegetable transplants, Qlabasho village, El-Dakahlia Governorate to study the effect of Moist-chilling (cold stratification) treatment for four periods (0, 5, 10 and 15 days) at 5 ± 1 0C on improvement of the germination parameters in the laboratory (germination percentage, seedling length, fresh and dry weight and vigor index) of onion seeds cv. “Red Beheri” stored for one or two years and enhancing growth characters (bulblet diameter, transplant length, fresh and dry weights and vigor index) of the subsequent transplants. The obtained results clearly indicated that all germination parameters of onion seeds stored for one or two years (except mean germination time) and also all obtained transplant characters except leaves number were significantly increased in all moist-chilling treatments than control one. The best treatment in this regard was moist-chilling for 15 days whereas the lowest one was control (non chilled seeds).

Organic Substrates of Tropical Origin for Use as Growing Media for Vegetable Transplant Production

Organic Substrates of Tropical Origin for Use as Growing Media for Vegetable Transplant Production

Yield and Nutrient Content of Bell Pepper Pods from Plants Developed from Seedlings Inoculated, or Not, with Microorganisms

The effectiveness of microorganisms applied in production of vegetable transplants has had mixed results. Bell pepper (Capsicum annuum L.) transplants were grown in a greenhouse using organic methods and the organic-certified potting mix was inoculated, or not, with beneficial bacteria or arbuscular mycorrhizal (AM) fungi, or both. Other transplants were grown in the same greenhouse with a conventional potting mix, which was not inoculated. Transplants were established in the field at various planting dates in a Bernow or Stigler soil and grown using conventional or organic methods. Pod yield and nutrient contents were determined. Yields of organically grown plants were similar to those of conventionally grown plants when both were grown on the Bernow soil. When grown on both soil types, yield was higher for the Bernow than for the Stigler soil. Treatment had little effect on pod mineral content. Chlorophylls, total carotenoid, and vitamin C contents of pods from plants grown on the Stigler soil were generally lower than those from plants grown on the Bernow soil. Average pod fresh weight for plants developed from seedlings inoculated with beneficial bacteria or AM fungi was greater than that from plants developed from conventionally grown seedlings. Inoculation did not improve fresh pod weights over that from plants developed from organically grown, but not inoculated, seedlings. Amending potting mix with the microorganisms tested did not provide extraordinary benefit or detriment for use in production of bell pepper.

N AND CA CONCENTRATION OF PRE TRANSPLANT NUTRIENT SOLUTION EFFECTS ON THE STAND ESTABLISHMENT RATE OF PEPPER (C. ANNUM. L) SEEDLINGS UNDER SALINE CONDITIONS

N AND CA CONCENTRATION OF PRE TRANSPLANT NUTRIENT SOLUTION EFFECTS ON THE STAND ESTABLISHMENT RATE OF PEPPER (C. ANNUM. L) SEEDLINGS UNDER SALINE CONDITIONS

ORGANIC TOMATO TRANSPLANT PRODUCTION IN COMPOST-AMENDED SUBSTRATE

There is limited information available about organic fertilization of vegetable transplants. The availability and release of the mineral nutrients from organic fertilizers is not fully understood. The objective of this study was to determine the effect of compost rate and chicken manure on the growth of tomato transplants. Tomato transplants were grown in an organic peat-based substrate (Garden Safe® Organic Potting Mix) amended with six rates of either compost (0% to 50%, by weight) or chicken manure (0% to 40%, by weight). The results showed that plant dry weight was minimally affected by compost rates, suggesting that compost provided only a minimal amount of nutrients to the plants. However, since transplants produced with compost-amended substrate were of similar quality compared to those produced exclusively with the substrate, it suggests that compost may be used to partially replace peat-based substrates used for transplant production. Shoot, root and plant dry weight increased with increasing rates of chicken manure (applied prior to seeding) reaching a maximum at 10%-20% (by weight) and then declined at 40% rate. Thus, chicken manure mixed with the substrate appeared to provide enough nutrients to tomato transplants. INTRODUCTION Organic vegetable growers are increasingly faced with reduced supply and poor quality transplants (plugs). Vegetable transplants produced organically are often of low quality because of poor fertilization management. There is limited information available on fertilization of organic production of vegetable transplants. A major challenge in organic production is the uncertainties in bio-availability of macro and micro nutrients contained in organic fertilizers or amendments. In most instances the essential nutrients are in unavailable forms or need to be chemically modified to be available to plants. Thus, it is usually difficult to determine optimum application rates of organic fertilizers based only on the chemical composition of organic amendments. Chicken manure has a higher mineral nutrient content and higher rates of N mineralization compared to compost (Eklind et al., 2001). The objective of this study was to determine the effect of compost rate and chicken manure rate on growth and development of tomato plugs grown organically. MATERIALS AND METHODS The study was conducted in a greenhouse at the Horticulture Farm, Coastal Plain Experiment Station, Tifton, Ga, during the fall of 2006. Tomato (Solanum lycopersicum L.) ‘Florida-47’ transplants were grown in organic substrate (Garden Safe® Organic Potting Mix) amended with different rates of either compost or chicken manure. The design was a randomized complete block with four replications (replication = one 200cell tray) and six treatments (rates of compost or chicken manure). In the compost trial, the treatments were 0%, 10%, 20%, 30%, 40%, or 50% (by weight). Compost (Longwood Plantation, Newington, Georgia) was prepared from cotton gin waste, chicken litter, and a small amount of peat humus, mixed, and composted for a minimum of 10 weeks. In the Proc. IV IS on Seed, Transplant and Stand Establishment

Biological Amendment, Fertilizer Rate, and Irrigation Frequency for Organic Bell Pepper Transplant Production

Use of biological amendments in vegetable transplant production may affect plant development. Rhizosphere bacteria can alter conditions in the root zone and affect plant growth even if root tissue is not colonized. Arbuscular mycorrhizae (AM) affect plant development through symbiotic relations. Abiotic factors may mediate effects of biotic amendments. Organically certified potting medium was inoculated with a mix of Sinorhizobium sp. bacteria or a mix of AM fungi. Controls consisted of no amendment. Bell pepper, Capsicum annuum L., cv. Jupiter, seed were sown in the medium and irrigated either twice a day for 3 minutes per application or three times a day for 2 minutes per application. Seedlings were treated with 8, 16, 24, or 32 mL·L–1 of an organically certified liquid fertilizer beginning 3 weeks after sowing. Use of bacteria improved plant height and dry weight. Interactions of bacteria and fertilizer rate or irrigation regime affected plant height or dry weight. When irrigated twice a day, plants were tallest when provided 16 mL·L–1 fertilizer, and heaviest when provided 24 mL·L–1 fertilizer. When irrigated three times a day, plants were taller at the lower rates of fertilizer and heaviest at the highest rate of fertilizer. Use of AM had little effect on plant height and dry weight. Most of the responses when AM was the amendment were the result of fertilizer rate and irrigation regime. When irrigated twice a day, AM-treated plants were tallest and heaviest when provided at least 24 mL·L–1 fertilizer. Regardless of biological amendment, plant heights were correlated with plant dry weights over fertilizer rates and irrigation regime. Use of Sinorhizobium sp. appeared to provide a benefit to the development of bell pepper transplants.