Important components of water management for transplant production include water quality, the frequency and volume of water application, and the method of application. Water quality factors of concern are alkalinity, soluble salts including sodium absorption ratio (SAR), and ions at potentially toxic concentrations including boron and fluoride. The available water in individual transplant cells is influence by container size and geometry, medium particle size, medium moisture release characteristics, and wetting agents but is primarily determined by irrigation frequency and the amount of water applied at each irrigation. Irrigation scheduling can be done using several methods but is influenced by the crop stage, the water volume applied, and the frequency of drying desired. Transplants can be watered by hose and breaker, stationary sprinklers, traveling boom sprinklers, fog nozzles, or subirrigation. The outcome of experiments testing effects of transplant size, transplant age and fertilizer rates are all influenced by water management.
John A. Biernbaum and Natasha Bos Versluys
Responses to a 1993 survey showed that drip irrigation was used on 36,400 ha of commercial vegetables in the southeastern and mid-Atlantic United States. Florida led with 44% of total drip-irrigated vegetable area, followed by Georgia, North Carolina, and Pennsylvania, with about 10% each. Drip irrigation was used most commonly on tomato, pepper, and watermelon crops. The most-important benefits of drip irrigation were improved water and fertilizer delivery efficiencies compared to other irrigation systems, such as overhead sprinklers and subirrigation. Challenges with drip irrigation included high installation cost, emitter clogging problems, need for filtration, overirrigation problems, disposal of tubing, and lack of readily available expertise. Most drip irrigation was used with polyethylene mulch and most tubing was thin-wall disposable rather than thick-wall reusable. Eighty-one percent of the drip-irrigated vegetable acreage was fertigated with N and K. Survey responses indicated that drip irrigation use for vegetables is increasing.
Daniel I. Leskovar and Daniel J. Cantliffe
Transplants produced with overhead or subirrigation and plants from direct seeding using primed or nontreated `Jupiter' bell pepper (Capsicum annuum L.) seeds were evaluated for growth and yield in the field for 3 years. Early in development, overhead-irrigated (01) transplants had more basal root elongation than subirrigated (SI) transplants; however, root growth differences caused by irrigation systems in the greenhouse were minimized during late ontogeny in the field. Basal, lateral, and taproot dry weights accounted for 81%, 15%, and 4% of the total for transplants and 25%, 57%, and 18% of the total for direct-seeded plants. Direct-seeded plants maintained a more-balanced root, stem, leaf, and fruit dry matter partitioning than transplants, which allocated more dry weight (per unit of root growth) to stems, leaves, and fruits. Over all seasons, transplants exhibited significantly higher and earlier yields than direct-seeded pepper plants, and total yields were similar between SI and OI transplants and between primed and nontreated seeds.
M.S. Albahou and J.L. Green
The use of the halophyte Suaeda salsa as a salt absorber in saline soils has been exploited as an attempt to increase crop productivity in marginal saline soils. The shoot and root salt contents of this halophyte has been documented to reach up to 27% and 12% of dry weights. The sodium salinity stress of the growth media [peat:vermiculite (1:1 by volume)] may be alleviated by planting the Suaeda with tomato plant in the same root pouch of a completely closed root environment, referred to as the closed insulated pallet system (CIPS). The CIPS is a continuous sub-irrigation capillary system with water moving from reservoir to rootzone in response to plant uptake. In CIPS, fertilizer reserve is placed at the top surface of the root matrix, so fertilizer ions move downward by diffusion. The objective of the present research was to utilize the Suaeda salsa as a bio-desalinator, so salinity of the growth media is reduced, thus reducing the salt uptake by the tomato cv. `Pik Red'. Two salinity levels (control and 4 g/L NaCl in the sub-irrigation water) were imposed on tomato plants or tomato grown with Suaeda in the same pouch. Sodium contents were reduced 56.4% and 37.1% in the growth media and tomato foliage, respectively, in the presence of the halophyte during a 110-day growing period. Likewise, the electrical conductivity of the growth media was reduced by 31.1% with Suaeda companionship. The Suaeda had accumulated salts up to 4.1 mg/g dry weight tissues. The results seem promising; however, growth and yield of tomato plants grown with the halophyte were significantly decreased, probably due to competition for nitrogen and/or light. Research is underway for development of the CIPS to better accomodate crop companionship.
L. Trenholm, G.T. Dodds, C.A. Madramootoo, and K. Stewart
In a 2-year study, tomato plants (Lycopersicon esculentum Mill., cv. New Yorker), grown in a sandy loam in field lysimeters, were subjected to controlled water table treatments (CWTT) of 0.3, 0.6, 0.8, and 1.0 m from the soil surface, factorially combined, in a central composite design, with 5 K–Ca fertilization combinations, replicated four times. Final shoot mass, no. fruit/plant (yield), percent marketability, fruit dimensions, and the incidence and severity of catfacing and sunscald were measured. In the first, drier year, the two higher, better-irrigated CWTT (0.3 and 0.6 m) gave higher yields, larger fruit, and higher final shoot mass, whereas in the second, wetter year, the two lower, better-drained CWTT (0.8 and 1.0 m) were best. In the dry year, the best-yielding CWTT showed the poorest marketability, while, in the wet year, the best-yielding CWTT showed the best marketability. Severity of catfacing and sunscald did not show consistent variations with CWTT. Fertilizer effects were generally not significant. Results will be discussed in the context of the use of subirrigation in field tomato production.
William R. Argo and John A. Biernbaum
Four experiments were conducted with six liming materials of different particle sizes and six commercially available blended preplant nutrient charge (PNC) materials in the laboratory and in container culture with subirrigation for durations up to twenty-eight days. Liming material, particle size, and incorporation rate affected both the initial and final stable pH of one type of peat without an incorporated PNC. Saturated media extract (SME) Ca2+ and Mg2+ concentrations were below the acceptable recommended concentrations for both pulverized and superfine dolomitic lime at incorporation rates up to 7.2 kg·m-3. For the blended PNC materials, initial N, P, K+, Ca2+, and Mg2+ concentrations for five of the six PNC materials were at or above the optimal concentrations recommended for an SME, but did not remain persistent in the root zone. A large percentage of all nutrients tested moved from the root zone into the top 3 cm (top layer) of the pot within two days after planting. Nutrient concentrations in the top layer continued to increase even when nutrient concentrations in the root zone fell below acceptable levels for an SME. The importance of this fertilizer salt stratification within the pot lies in the reduced availability of nutrients to the plant.
Mohammed S. Albaho and James L. Green
To determine its effect on salinity of the growth medium and on tomato (Lycopersicon esculentum Mill.) growth and yield, the halophyte Suaeda salsa (L.) Pallas, or seepweed, was planted as a companion plant in the closed insulated pallet system (CIPS). In this production system, water moves from a bottom reservoir through capillary wicks to the medium in the root pouch in response to plant uptake. Fertilizers are placed at the top surface of the root matrix, so nutrient ions move downward to the roots by chemical ion diffusion to establish relatively stable chemical gradients within the matrix. Plants were subjected to capillary subirrigation water containing 0 or 4 g·L–1 NaCl. Sodium (Na+) concentration of the root medium at termination was 50% lower when S. salsa was grown in the same pouch with tomato. Sodium concentration was also significantly less in the tomato foliage, but S. salsa did not prevent suppression of growth of tomato plants by NaCl. Suaeda salsa plants reduced blossom end rot of tomato fruit but did not significantly affect fruit weight, number or yield.
Alicia Sanchez-Escarcega and George C. Elliott
The potential for N mineralization or immobilization in potting media containing compost was investigated in experiments using sunflower (Helianthus annuus `Sunrich Yellow') as a test crop with potting media formulated from 3 aged pine bark: 2 sphagnum peat or compost: 1 vermiculite (by volume). Cropped and uncropped media in 350-mL pots were fertilized by subirrigation with complete nutrient solutions containing N at 2, 4, 6, 8 or 12 mmol·L–1 as ammonium nitrate. In control medium without compost, sunflower fresh mass increased linearly with increasing N. In one compost medium (C), growth was stimulated and with N at 6 mmol·L–1 was equal to growth with N at 12 mmol·L–1 in the control medium. With another compost medium (A), growth was inhibited and did not respond to increasing N. In medium C, saturated media extracts (SME) obtained before and up to 12 days after transplanting had higher concentrations of NH4 and NO3 than the control medium. In medium A, NH4 concentrations were similar to controls, but NO3 concentrations were lower. Nitrite concentrations were less than 0.2 mmol·L–1 and were highest in medium C. Nitrogen derived from compost in medium C substantially reduced the soluble fertilizer N requirement for sunflowers, while N immobilization by compost in medium A was not overcome by increasing fertilizer N.
Peter R. Hicklenton and Kenneth G. Cairns
Containerized Cotoneaster dammeri `Coral Beauty' and Forsythia `Northern Gold' were grown in a 2 bark: 1 peat: 1 sand (by volume) medium containing 5 kg·m–3 Nutricote 16N–4.4P–8.1K, Type 140, under four irrigation regimes: drip (DR; 20 min/day; two periods), overhead (OV; 90 min/day; two periods), overhead pulse (OP; 28 min/day; four periods), and subirrigation (SU). Volumes of 0.33, 0.35, and 0.14 liters·day–1 were delivered to each container in the DR, OV, and OP systems, respectively. SU was supplied from a geotextile-covered sand bed. End-of-season dry weights of Cotoneaster and Forsythia were 41% and 55% greater, respectively, in SU-grown plants compared to their OV-irrigated counterparts. Differences in growth between the other three regimes were minor for both species. Pre-dawn and dusk water potentials did not differ between plants in the four regimes, but midday potentials were slightly lower in SU- and DI-irrigated plants. End-of-season foliar N and P content differed only slightly between irrigation treatments, but K levels were significantly higher in SU plants. The reasons for better growth under SU remain obscure but may be related to improved medium nutrient retention and improved fertilizer use efficiency under an irrigation regime in which water moves upwards from the pot base to top.
William R. Graves and Hongyi Zhang
Air temperature and photosynthetically active radiation (PAR) effects on relative water content (RWC), rooting percentage, root count, and root mass of unmisted, subirrigated stem cuttings of two taxa were determined. Leaf RWC of `Charm' chrysanthemum [Dendranthema ×grandiflorum (Ramat.) Kitamura] decreased until roots initiated and then increased, was lower for cuttings at 23 °C photoperiod/14 °C dark than for cuttings at 31 °C photoperiod/22 °C dark, and was lower at 193 than at 69 μmol·m–2·s–1 PAR. Neither temperature nor PAR affected leaf RWC of `Dollar Princess' fuchsia (Fuchsia ×hybrida Hort. ex Vilm.), which increased linearly before and after root initiation. Rooting percentage and root count were higher with photoperiods at 31 °C than at 23 °C for chrysanthemum after 7 days and for fuchsia after 10 days. Although all cuttings of both taxa had rooted after 14 days, root dry mass was higher with photoperiods at 31 °C than at 23 °C regardless of PAR for fuchsia and at 69 μmol·m–2·s–1 PAR for chrysanthemum. Propagators wishing to use subirrigation instead of mist, fog, or enclosure can minimize the decline in leaf RWC before root initiation and increase the number and dry mass of roots of chrysanthemum by using 69 μmol·m–2·s–1 PAR and a 31 °C photoperiod/22 °C dark cycle. Root dry mass of fuchsia also can be increased by the use of high temperature, but differences in rooting were independent of changes in leaf RWC.