Search Results

You are looking at 1 - 10 of 17 items for

  • Author or Editor: Jack W. Buxton x
Clear All Modify Search
Author:

The controlled water table irrigation system (CWT) consists of a capillary mat placed on a level bench so one side extends over the edge of the bench into a trough containing a nutrient solution maintained at a controlled distance below the bench. The nutrient solution is drawn by capillarity up to and over the bench surface. As plants use the nutrient solution or as water evaporates from the media, it is replaced from the trough. The automatic system maintains a constant air/water ratio in the growing media. Study 1: Geraniums were grown in 15-cm pots at 0, 2, and 4 cm CWT. Geraniums at 0 and 2 cm CWT had the greatest leaf area and dry weight. Plants at 0 and 2 cm CWT were more than 25% greater at 4 cm CWT. The roots of plants at 0 cm CWT were concentrated at 2 to 4 cm above the bottom of the container; whereas roots at 2 cm CWT uniformly extended from the center to the bottom. Study 2: Water potential in a coarse and fine textured media was determined at the bottom, middle and top of the container at 0, 2, and 4 cm CWT every 2.5 h during the light period. Water potential was about the same in each media within each CWT treatment. At the container bottom at 0 CWT water potential was 0; whereas the water potential at 2 and 4 CWT was lower. The water potential from top to bottom decreased slightly about mid afternoon on a sunny day when water demand was the greatest. The CWT system is potentially a commercially adaptable irrigation system for container crops. It also is a cheap, reliable tool for studying water stress on the crop growth and quality.

Free access

Abstract

A method is described for determining glucose metabolism by the C-6/C-1 ratio. After an initial lag period to allow for equilibration of labelled glucose, an increase of accumulated 14CO2 in rose petals was linear with time. By taking the limit of the ratio of the C-1 and C-6 lines, one can arrive at the C-6/C-1 ratio as a ratio of the slopes of the lines. The slope of each of the lines can be calculated with 2 determinations within a relatively short time period. This method reduces metabolic recycling of the glucose and other problems associated with the traditional method of determining the C-6/C-1 ratio.

Open Access

The relationship between initial total non-structural carbohydrate concentration (TNCi) in marigold seedlings, night temperature, and night length were evaluated. Seedlings containing an average of 7.2, 18.1, and 23.5 mg/100 mg dwt of nonstructural carbohydrate (TNC) at sunset were treated with night temperatures of low (10°C), medium (17°C), and high (24°C). Starch and soluble sugars were determined at intervals during the night. TNC concentration at the end of the night is a function of the night temperature, TNCi concentration at sunset, and the night length. A model describing the relationship of these variables and their interactions was derived to estimate TNC concentration at any time during the night. This model when solved for temperature (t) establishes a temperature that will regulate the metabolic rate so the TNC concentration is metabolized efficiently to some minimum concentration by the end of the dark period. t = (–2.93 + 1.14 TNCi + 0.74 T – TNC – 0.48 TNCi * T)/(–0.18 + 0.011 TNCi + 0.04*T), R 2 = 0.88**). Thus, by knowing TNCi (possibly by near-infrared spectroscopy), the length of the night, and, assuming some minimum concentration for TNC by the end of the dark period, the night temperature is established.

Free access

Natural-light growth chambers constructed within a greenhouse compartment were equipped with a ventilation/circulation system, two stages of heating, and evaporative cooling. Air drawn from the greenhouse compartment continuously ventilated the chambers; the air was heated or cooled to the set-point temperature. A computer-controlled environmental system maintained uniform temperatures within the chambers and maintained the temperature within ±1C of the set point at night and during periods of low solar radiation; during higher solar radiation periods, control was not as precise. Carbon dioxide concentration was accurately maintained, and the photosynthetic photon flux from supplemental high-pressure sodium lamps was ≈200 μmol·m-2·s-1. The natural-light growth chambers provide a means for studying the interactive effects of temperature, light, and other environmental variables in experiments to increase production efficiency.

Free access
Authors: and

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.

Free access

Maintaining adequate water for container plants in outdoor sales areas is difficult during the late spring and summer. In mass marketing areas employees are uninformed about the water requirements of plants under various environmental conditions. Plants often are severely stressed and over all quality reduced. A system was developed to automatically irrigate container plants in an outdoor sales area. The system is a modification of the Controlled Water Table (CWT) irrigation system developed at the Univ. of Kentucky (U.K.). The sales area consisted of 2 shelves each 2.44 m long and 0.28 m wide. A trough was constructed from a 5-cm diameter pipe with a 1/4 slot; it was attached to the back side of the shelf. One side of a capillary mat, placed on the shelves, was suspended in the trough containing water. Two systems were used to maintain the level of water in the trough. One was a small float valve installed in a 10-cm PVC pipe which was attached to the 5-cm PVC pipe. The float was adjusted to maintain the water in the trough 2 cm below the top of the shelf. The water reservoir consisted of a 20-cm diameter PVC pipe, 1.22 m long that held 70 L of water. A second system maintained a constant water level in the trough using Torricellian tube principle. The water reservoir was the same as above except it was tightly sealed so no air could leak from the system. The water table was maintained 2 cm below the bench surface by rotating a hole in small cap. A variety of plants in containers, ranging from 10 cm to 5 L pots were maintained without water stress, in a greenhouse environment as well in an outdoor environment for several weeks.

Free access
Authors: and

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.

Free access

Through control of light intensity and CO, concentrations, three levels of starch (low, medium and high) in marigold seedlings existed at sunset. The range in starch concentration represented that encountered under average greenhouse conditions. For each starting starch concentration, an optimum temperature was initially determined based on first and second order reactions on the corresponding starch decline curve. Every day, during seedling growth in the greenhouse, the starch concentration at sunset was predicted based on primarily the quantity of light received throughout the day; the night temperature was adjusted to the predicted optimum night temperature setting. Based on these studies a significant improvement in seedling growth can be achieved with significantly less heating cost.

Free access

Abstract

The pentose phosphate shunt (PPS) was shown to be active in roses (Rosa hybrida L.). The C6/C1 ratio indicated that possibly as much as 50% of the glucose oxidized in the rose flower is through the PPS. However, the activity of the PPS in relation to the Embden-Meyerhof-Parnas pathyway-tricarboxylic acid cycle (EMP-TCA) pathway did not change significantly throughout the cut life of the rose. There was a drop in the respiratory rate of petals throughout the cut flower life. The inner petals exhibited a consistantly higher respiratory rate than did outer petals regardless of whether the flower was kept in water or preservative.

Open Access

To prevent rooting into an irrigation mat, five water porous materials, perforated black plastic, perforated ground cover, polyester, woven polypropylene and porous plastic, were evaluated as mat covers. Only polyester, woven polypropylene and porous plastic prevented penetration of roots of marigold seedlings into the mat. Under high moisture stress, root tips were killed at the cell drainage hole; however, under low moisture stress the roots formed a mat on top of these mat covers. To prevent root penetration out the drainage hole, polyester and porous plastic were glued over the hole. No difference in shoot growth was observed between the control (only polyester mat cover) and seedlings produced in drainage hole covered cells. Total root growth of plug seedlings with drainage hole covered were greater than the control. Ten days after transplanting, seedlings that had been produced in plugs, with covered drainage holes, were larger.

Free access