An irrigation system for monitoring and controlling soil moisture tension in the root zones of potted plants using computer and solid-state tensiometer technologies was evaluated in a commercial greenhouse on 'V-14 Glory' poinsettias over a 10 week period. Replicated benches with separate drip circuits controlled by the computer maintained the soil moisture tension of the potted poinsettia plants between 1 kPa and 5 kPa. The amount of water used by each bench and the amount leached was compared to benches with separate drip circuits that were manually operated by the grower according to standard commercial practice. There was a 65% savings in the total amount of water used for the computer-controlled system and an average weekly reduction of 98.6% in leachate. The differences were significant and there was no measurable reduction in plant quality, even though soil analyses showed slightly elevated EC levels.
Julie P. Newman, J. Heinrich Lieth, and Ben Faher
Kazuhiro Fujiwara, Toshinari Sawada, Yoshikatsu Kimura, and Kenji Kurata
A light-emitting diode (LED)-low light irradiation (LLI) storage system was developed for suppressing the change in dry weight and maintaining the quality of green plants during long-term storage. In this system, the carbon dioxide (CO2) exchange rate was maintained at zero by automatically adjusting the photosynthetic photon flux density (PPFD) with a proportional-integralderivative (PID) controller. The voltage supplied to the LEDs was controlled by the difference between the inflow (400 μmol·mol-1) and outflow CO2 concentrations in the storage case. Grafted tomato (Lycopersicon esculentum; scion = `House Momotaro'; rootstock = `Anchor T') plug seedlings were stored at 10 °C for 35 days under four different LLI conditions as a system operating test: fixed red light irradiation at 2 μmol·m-2·s-1, PID-controlled red light irradiation with no blue light, and PID-controlled red light irradiation with blue light at 0.2 or 1.0 μmol·m-2·s-1. The results showed that the automatic PPFD control during LED-LLI helped suppress changes in dry weight during storage as expected. Furthermore, it was found that addition of a low percentage of blue light improved the morphological appearance of the seedlings and reduced the PPFD required to suppress the change in dry weight.
N. Lallu, J. Burdon, D. Billing, D. Burmeister, C. Yearsley, S. Osman, M. Wang, A. Gunson, and H. Young
There are three main systems for the removal of carbon dioxide (CO2) from controlled atmosphere (CA) stores: activated carbon (AC) scrubber, hydrated lime scrubber, and nitrogen (N2) flushing. Each system is likely to have a different effect on the accumulation of volatiles other than CO2 in the store atmosphere, and these volatiles may influence the storage performance of the produce. `Hayward' kiwifruit (Actinidia deliciosa) were stored at 0 °C (32.0 °F) under 2% oxygen (O2) and 5% CO2 in CA rooms fitted with one of the three systems. In a fourth CA room, fruit were stored at 0 °C under air conditions. All four stores had their atmosphere scrubbed for ethylene. The store atmospheres and fruit firmness were monitored at intervals up to 27 or 14 weeks of storage in the 1999 or 2000 season, respectively. At the end of CA storage, and after an additional 4 weeks of air storage at 0 °C, fruit were evaluated for rots and physiological pitting. Linear discriminant analysis (LDA) showed the three CO2 removal systems altered the volatile profiles of the store atmospheres differently. CA storage delayed fruit softening markedly, and once returned to air, softening resumed at a rate equivalent to that of fruit of equivalent firmness that had not been CA stored. There was little effect of CO2 removal system on the fruit softening during storage. Although CA storage resulted in a higher incidence of rots, there was little difference among CO2 removal systems compared to the main effect between air and CA storage. Similarly, CA storage delayed the appearance of physiological pitting, although the incidence increased rapidly during an additional 4 weeks of storage in air, and was higher than for fruit stored throughout in air. Among the CO2 removal systems, N2 flushing resulted in fruit with the lowest incidence of physiological pitting. It is concluded that different CO2 removal systems alter room volatile profiles but may not consistently affect the quality of `Hayward' kiwifruit during CA storage.
Kimberly A. Klock-Moore and Timothy K. Broschat
Growth of hand-watered and subirrigated `Ultra Red' petunia (Petunia ×hybrida Hort.) and `Super Elfin Violet' impatiens (Impatiens wallerana Hook.f.) plants were compared when grown using four controlled-release fertilizer rates and four fertilizer placements in the pot. Furthermore, the amount of NO3-N leached from hand-watered plants was compared to amount captured by subirrigation system. Before planting, Osmocote (14N-6.2P-11.6K) (4 month release) was either topdressed (TD), layered in the middle of the pot (M), layered at the bottom of the pot (B), or incorporated throughout (I) the substrate at 1.25, 2.5, 5.0, or 7.5 kg·m-3 (oz/ft3). Shoot dry mass of petunia plants was similar between both irrigation systems and among the four fertilizer placements. Subirrigated petunias fertilized with 2.5 kg·m-3 had similar shoot dry mass as hand-watered petunias fertilized with 7.5 kg·m-3. Hand-watered impatiens had greater shoot dry mass than subirrigated impatiens. Hand-watered impatiens also had greater shoot dry mass in pots with fertilizer at TD, M, or I than with fertilizer at B, but no difference in growth was observed in subirrigated impatiens among the different fertilizer placements. Finally, significantly more NO3-N was leached from hand-watered plants than was captured with the subirrigation systems.
Eun Young Yang*, Hye Jin Lee, and Yong-Beom Lee
The application of a closed hydroponic system for rose poses some horticultural problems. The nutrient uptake by the plants changes constantly depending upon environmental conditions and growing stages, which results in the imbalanced composition of the drained solution and aggravates root environmental conditions. This research was aimed to observe the effect of mineral nutrient control method on the nutrient solution management in a closed hydroponic system. Single-node cutting rose `Versillia' was grown in aeroponics and DFT system and was irrigated with the nutrient solution of the Univ. of Seoul (NO3 -N 8.8, NH4 -N 0.67, P 2.0, K 4.8, Ca 4.0, and Mg 2.0 me·L-1). Recirculated nutrient solution was managed by five different control method: macro- and micro-element control in aeroponic system (M&M); macroelement control in aeroponic system (M); nutrient solution supplement in aeroponic system (S); electrical conductivity (EC) control in aeroponic system (EC-A); EC control in deep flow technique system (EC-D). In the EC control method, the concentration of NO3 -N exceeds optimal range whereas P and Mg decreased at the later stage of plant growth. The overall mineral nutrient content increased with S. On the other hand, the nutrient content of root environment was maintained optimally with M&M and M.
Lavesta C. Hand, Wheeler G. Foshee III, Tyler A. Monday, Daniel E. Wells, and Dennis P. Delaney
( Brandenberger et al., 2005 ). Cover crops have been used in numerous cropping systems to improve weed control. In addition to providing weed suppression, benefits of growing a cover crop include improved soil structure, preservation of soil moisture, erosion
Daphne L. Richards and David Wm. Reed
New Guinea impatiens (Impatiens hawkeri Bull.) `Illusion' were grown in a recirculating subirrigation system under various rates and placements of 14N-6.1P-11.6K (Osmocote; Scotts-Sierra, Marysville, Ohio) resin-coated, controlled-release fertilizer (CRF). Four CRF placements (incorporated, top-dressed, bottom, and dibble) were tested. Incorporated placement yielded slightly greater dry weights than the other placements. A rate experiment tested incorporating from 0.5 to 2 times the fertilizer manufacturer's recommended rate of 7.11 kg·m-3. All shoot growth parameters (height, leaf number, shoot, and root fresh and dry weight) exhibited a significant quadratic response, as exemplified by shoot dry weight, where shoot dry weight increased up to the 1.5× rate, after which shoot dry weight decreased. A quadratic response surface model revealed that the optimum rate response ranged from 1.16× rate for height to 1.47× rate for shoot dry weight. The lower bound of the 95% confidence interval (CI) would be the lowest rate at which one could expect maximum growth response. The lower bound of the 95% CI varied from 0.56× rate for height to 1.30× rate for shoot dry weight. Thus, the lowest rate that would be within the 95% CI for all growth parameters, and thus yield maximum growth response, would be the 1.30× rate. Electrical conductivity (EC) of the growing media increased significantly with increasing CRF rate. At all rates, EC was significantly greater in the top layer than in the middle and bottom layers. Only in the 1.75× and 2× rates did EC exceed the recommended EC levels in the middle and bottom layer. All rates >0.75× exceeded recommended EC in the top layer. Release characteristics and total nutrient balance of the CRF was compared in subirrigated and top-watered systems. There was no significant difference between top-watered and subirrigated treatments for the amount of K recovered in plant tops and released from prills. By day 84, in subirrigation, 46% of the K was still in the prills, 41% was recovered in the plant tops, and 22% was recovered in the medium. Similar results were obtained in the top-watering treatment, except that a lesser amount was recovered in the medium (9%) and a small amount (4%) was recovered in the leachate. The uptake of K by plants and release of K by the CRF were inversely proportional and linear with respect to time. Of the K released from the prills, 77% and 83% were recovered in the plant tops for subirrigation and top-watering, respectively, indicating very high fertilizer use efficiency.
Jialin Yu, Nathan S. Boyd, and Zhengfei Guan
markets, and increased production costs ( Suh et al., 2017 ). The combination of increased production costs, lower prices, and volatile markets threatens the industry. The situation suggests that an alternative production system that increases grower
Jung Eek Son, Sung Kyu Kim, Sung Bong Oh, and Yin Ji Lu
The uptake of water and nutrient in potted plants is greatly affected by irrigation conditions, and it influences the plant growth. This study aimed to examine the correlations between basic environmental parameters and plant growth in potted plants (kalanchoe) and to develop the models for adequate irrigation control. Growth chambers were developed for the experiments, and four levels of photosynthetic photon flux (PPF) were treated by using different numbers of shading films and lamps. Kalanchoe blossfeldiana cv. New Alter, grown in the nutrient-flow wick culture (NFW) system, was used. The 7-cm pots were filled with a 7:3 mixture of peat moss and perlite medium (v/v). The initial water content was set at about 26%. A total of 150 pots and plants with different growth stage were prepared for 4 weeks. A wick [12 × 1 cm (L × W)] was used in each pot. Leaf areas of plants and surface areas of the medium were analyzed by a plant image analysis system. For measuring the water losses of plants and pots during the growth stage, the initial water content of the substrates was maintained at about 55%. Water losses were measured at 9, 11, 13, 15, and 17 hours for all experiment periods by using an electron balance. Two models were developed for estimating water losses by evapotranspiration and water intake by water absorption. Finally, a model for estimating water content in the medium was tried. Growth and environment parameters showed high correlations with transpiration and evaporation, respectively. There was an interactive effect of VPD and PPF on the change of evapotranspiration. The amount of absorption was increased by time and decreased with increase of initial water content.