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Lettuce was produced using a new concept of hydroponics. The system is based on maintaining a constant water table (CWT). Plants grew on a flat surface and obtained the nutrient solution from capillary matting. One end of the mat was suspended in a trough containing the nutrient solution. The distance between the nutrient solution in the trough and the bench top was kept constant with a water level controller. The nutrient solution was resupplied from a larger reservoir. A ground cover on top of the capillary mat provided nutrient movement to the roots but prevented root penetration. Lettuce seedlings, germinated in small plug trays, were placed in holes cut in a 2.5-cm-thick styrofoam sheet. The styrofoam provided seedling support as well as protected the roots. Roots grew on the surface of the ground cover and were easily removed at harvest. The CWT could be adjusted by changing the height of the water level controller. The CWT concept of hydroponic production does not require pumps nor large storage reservoirs. No runoff occurs; the only nutrient solution used is that required by plants and a minimum amount of evaporation from the ground cover surface. Disease potential should be less than in other systems.
The controlled water-table irrigation (CWT) system was evaluated for vegetable seed germination and transplant growth. The system is a modification of capillary mat irrigation except that the mat along one side extends over the edge of the bench into a narrow trough running along the side of the bench. The nutrient solution level in the trough is controlled by a liquid level controller, so it is at a fixed distance below the bench surface. The nutrient solution is drawn by capillarity from the trough upward to the bench surface and then moves by capillarity to the opposite side of the bench. The system automatically maintains a constant air: water ratio in the growing media. Seeds of broccoli, tomato, and pepper were germinated in a 96-cell plug tray and grown to transplanting stage with the CWT system. A factorial experiment consisted of two growing media combined with CWT treatments of 2 and 4 cm. Excellent germination and high-quality seedlings were produced with all treatments. No differences were observed in growth of seedlings at 2 vs. 4 cm or between the two growing media. The CWT system is capable of maintaining a constant uniform water: air ratio in all plug cells on a commercial growing bench. Nutrient solution does not run off the bench. The CWT potentially is an excellent system for the irrigation of vegetable transplants.
Commercial quality cut-roses were produced in a single-stem production system from single node cuttings. A significant advantage to single-stem rose production is that specific environments can be used for specific developmental stages of rose growth. In stage 1 (propagation), cuttings were treated with a 5-second dip in 500 ppm IBA/250 ppm NAA solution, placed in growing media in 8-cm pots, and placed under intermittent mist (5 second every 5 minutes) with growing medium temperature of 35°C. In stage 2 (axillary budbreak and stem development to visible pea size flower bud), rooted cuttings moved to benches (200 stems/m2) in a greenhouse at 14 to 16°C night, and plants received 12 hours supplemental light at 80 to 100 mol·m–2s–1. In stage 3 (stem elongation and flower bud development), small rose plants (30 to 35 cm tall with a pea-size flower bud) were moved to 100 stems/m2 in a greenhouse at 14 to 16°C night with ambient light. Through seven sequential crops of rose cuttings grown from Feb. through May 1995, rooting required a mean of 16 days, flower buds were visible in 42 days, and flower harvest required a mean of 58 days. Accumulated radiation and average temperatures through the spring had significant effects on the number of days in each developmental stage of rose growth.
Commercial quality cut-roses were produced in a single-stem production system from single-node cuttings. Single-node cuttings from cut stems of `Lady Diana' rose were characterized by the location of the node of origin in numerical sequence from the flower and initial stem size, large (thick stems, long length, many nodes), moderate (moderate thickness, moderate length, and node number), and small (generally not commercial quality). Cuttings were treated with a 5-second dip in 500 ppm IBA/250 ppm NAA solution, placed in growing media in 8-cm pots and placed under intermittent mist (5 second every 5 minutes) with growing medium temperature of 35°C. Seven sequential crops of rose cuttings were grown from Feb. through May 1995. The initial node of origin was significantly correlated to the final stem length of the single-stem rose and to the number of days for axillary budbreak on the cutting. The number of days to rooting was not effected by the initial node of origin of the cutting. The correlation with initial stem size had variable results.
Cabbage seed was germinated and grown to transplanting size in a 98-cell tray using an automatic irrigation system based on the principle of maintaining a constant water table (CWT) relative to the growing medium in transplant trays. Seedlings obtained a nutrient solution from a capillary mat with one end suspended in a trough containing the solution. The distance between the nutrient solution surface and the transplant tray bottom was regulated with a water level controller. The nutrient solution was resupplied from a larger reservoir. A polyester material on top of the capillary mat allowed solution movement to the roots but prevented root penetration into the mat. The water table placement below the tray determined the water content in the growing medium. Seedling growth was evaluated using two growing media combined with two water table placements. Excellent quality seedlings were produced; the CWT irrigation system satisfactory provided water and nutrients for the duration of the crop. The only problems observed were dry cells, less than 2%, because of no media–mat contact and algae growth on the media surface using the higher water table. The CWT irrigation system is adaptable to existing greenhouse vegetable transplant production systems. It is automatic and can provide a constant optimum amount of moisture for seedling growing. It can be adjusted for phases of seedling growing such as more water during germination and can create water stress near transplanting time to either harden off or hold plants because of unfavorable planting conditions.
The automatic subirrigation system consists of a capillary mat placed above a constant water level in a reservoir. The optimum mat height above the water level was established by slanting a flat surface so the difference in vertical height from one end of the surface to the other was 25 cm. A ground cover providing water movement but not root penetration was placed over the mat. The capillary mat extended beyond the lowest end of the slopped surface and into the reservoir, the mat at the lowest end of the slopped surface was at the same vertical height as the water in the reservoir and remained constantly saturated. Plug trays were placed at intervals of 2.5 cm in vertical height above the water level. An average of 96-100% germination was obtained with marigold, tomato, impatiens and pepper seed in trays placed 5-7.5 cm in vertical height above the water level. These seedlings continued to develop and reached transplanting stage quicker than other trays. The rate and % germination was less in trays placed on the surface nearer to the height of the water in the reservoir. Germination in trays above 12.5 cm was greatly reduced and seed that did germinate did not develop and eventually died.
Tomato and pepper seedlings were grown in six controlled environmental chambers with three different temperature levels (high:24/16°C, medium:20/12°C, and low:16/8°C) and two CO2 levels (1500 ppm and ambient) after cotyledons had unfolded. After 4 weeks, seedlings were planted into 15 cm pots. After 4 weeks, another set were transplanted to the field on 5/13 and arranged with 4 replications in a randomized complete block design. Only temperature treatment had a significant influence on the number of flowers developed in greenhouse experiments. However, for field transplanted seedlings, CO2 enrichment had a significant effect on flower formation and increased total flower numbers and fruit numbers in the early growth stages in field. Temperature also influenced seedling height. In other experiments, cold treatments were given to tomato and pepper seedlings. Seedlings were treated with 13°C temperatures for 0, 1 or 2 weeks after cotyledons unfolded. Results indicate that tomato seedlings with either 1 or 2 weeks of cold treatment had greater dry weight and leaf numbers and larger and more mature flower buds than those given no cold treatment. Pepper seedlings receiving 2 weeks of cold treatment showed similar increases compared to those receiving 0 or 1 weeks of cold treatment. The earliest flower initials were observed microscopically when tomato had only one visible leaf and pepper had 8 or 9 visible leaves. These results indicate that cold treatments should be started as soon as the cotyledons have unfolded to hasten flower formation.