and water use efficiency ( Uva et al., 1998 ). Subirrigation is an alternative irrigation method whereby the applied irrigation water and dissolved fertilizer nutrients are applied to the bottom of the container through the use of capillary mats, ebb
Jinrong Liu, W. Roland Leatherwood, and Neil S. Mattson
Theo J. Blom and Brian D. Piott
Low volume drip (2 l/h) was compared with 2 subirrigation ('trough' and `ebb and flo') systems for production of poinsettias and chrysanthemums in 15 cm diameter (1.6 l) `azalea' pots. Irrigation frequency as well as fertilizer rates were the same for all systems. The drip system received 280 ml per watering.
Two plantings of poinsettias (fall) as well as two plantings of chrysanthemums (spring and summer) showed no differences in plant growth between the drip and the subirrigation systems. Water uptake by the medium was similar for all irrigation systems, but water and fertilizer application was 70% higher for the drip system. Nutrients, measured at 4 depths within the pot at monthly intervals, increased with time and was markedly more concentrated in the top layer, regardless of the irrigation system.
Trisha Blessington Haley and David Wm. Reed
Two experiments were conducted to investigate the effect of K fertilizer rates on growth of New Guinea impatiens (Impatiens Hawkeri Bull.), vinca (Catharanthus roseus (L.) G. Don) and petunia (Petunia ×hybrida Hort. Vilm.-Andr.) in a recirculating subirrigation system. Based on a variety of growth parameters, a broad range of K concentrations allowed maximum growth, notably 1 to 6 mM for New Guinea impatiens `Ovation Salmon Pink Swirl', 2 mm for New Guinea impatiens `Cameo' and `Illusion', 2 to 8 mm for vinca `Pacifica Apricot', and 2 to 16 mm for petunia `Trailing Wave Misty Lilac'. Thus, the lowest concentration that allowed maximum growth was 1 to 2 mm K. A third experiment compared the optimum K concentration and K balance of vinca grown with recirculating subirrigation versus top-watering. Based on a variety of growth parameters of vinca `Pacifica Red', the lowest concentration that allowed maximum growth was 2 mm K with recirculating subirrigation and 4 mm K with top-watering. The K balance demonstrated that subirrigated plants were twice as efficient in K use compared to the top-watered plants. Leachate loss was the major contributor to inefficiency in top-watered plants. Electrical conductivity (EC) of the growing medium remained below the recommended level of 1.2 dS·m-1 in both irrigation methods at K concentrations of 16 mm and below in the bottom layer and 8 mm and below in the middle layer. In the top layer of the growing medium, EC was above the recommended level at all K concentrations tested in subirrigation at all concentrations, and in top-watering at 16 mm and above.
Takafumi Kinoshita and Masaharu Masuda
The efficiency of nutrient and water use is generally higher with subirrigation than with drip irrigation because subirrigation greatly reduces water leaching ( Goodwin et al., 2003 ; Incrocci et al., 2006 ; Santamaria et al., 2003 ). For uniform
Nancy Morgan Todd and David Wm. Reed
New Guinea impatiens (Impatiens hawkeri Bull.) were grown in a recirculating ebb-and-flow subirrigation system under increasing levels of salinity stress from a mixture of NaCl and CaCl2 (1:1 equivalent ratio, 2:1 molar ratio) and recommended production levels of other nutrients. Growth and quality decreased as salinity level increased, with a 75% to 80% growth reduction at 18 mol·m-3 NaCl-CaCl2 compared to controls. Among controls, root mass distribution was 10%, 50%, and 40% in the top, middle, and bottom layers of the root zone, respectively. In the highest salinity treatment (18 mol·m-3 NaCl-CaCl2), most of the root mass was in the middle layer (80%), while the root mass in the top and bottom layers was reduced to 5% and 15%, respectively. The electrical conductivity (EC) of the growing medium was high in the top layer in all treatments, but only exceeded maximum recommended levels in the middle and bottom layers in the 4·mol·m-3 or higher treatments. Initial postproduction leaching caused the salts in the top layer to migrate to the middle and bottom layers, which in some experiments induced a rapid and transient wilting. Up to six leaching and drying cycles of a 0.20 leaching fraction were required to reduce EC in all layers to recommended levels. Overall, salable plants of good quality and size were produced with up to 2 mol·m-3 (total 152 mg·L-1) NaCl-CaCl2 in the recirculated nutrient solution.
Lyn A. Gettys and Kimberly A. Moore
, 0.45, 0.91, or 1.83 g/pot N). Plants were divided into two groups that received either overhead irrigation or subirrigation. Plants receiving overhead irrigation were grown on nursery benches in a completely randomized design with respect to
Jeff Million, Tom Yeager, and Claudia Larsen
irrigation, capillary wick irrigation reduced cumulative irrigation volume 86% without sacrificing plant growth. Traditional subirrigation systems such as ebb-and-flow and flood-floor irrigation ( Barrett, 1991 ; Neal and Henley, 1992 ) are closed systems
Lyn A. Gettys and Kimberly A. Moore
transplanting. Plants were randomly selected for placement into either overhead irrigation or subirrigation treatments. Plants receiving overhead irrigation were grown on greenhouse benches in a completely randomized design with respect to substrate type and
Hongvi Zhang and William R. Graves
Use of subirrigation to root stem cuttings was compared to using mist, and effects of fertilization during subirrigation were determined. All cuttings of Dendranthema ×grandiflorum (Ramat.) Kitamura `Charm' and Coleus ×hybridus Voss. rooted, but misted D. ×grandiflorum `Charm' had a higher mean root mass than subirrigated cuttings. Percentage rooting and mean root mass of subirrigated Acer rubrum L. `Franksred' were 95% and 321 mg, whereas mean root mass of the 21% of cuttings that rooted with mist was 38 mg. Percentage cuttings with callus, mean callus diameter, rooting percentage, and mean root mass of Syringa retuculata (Blume) Hara were 77%, 124 mm, 21%, and 52 mg with subirrigation and 45%, 63 mm, 0%, and 0 mm with mist. Subirrigation with <7 mol N/m3 improved rooting of Impatiens hawkeri Bull. `Celebration Bright Scarlet' and A. rubrum `Franksred'. Subirrigation can replace mist, and effects of fertilizer in subirrigation solution vary among taxa.
Kimberly A. Klock-Moore and Timothy K. Broschat
Two experiments were conducted to compare the growth of `Ultra White' petunia (Petunia ×hybrida) plants in a subirrigation system versus in a hand-watered system. In Expt. 1, petunia plants were watered with 50, 100, or 150 ppm (mg·L-1) of N of Peter's 20-10-20 (20N-4.4P-16.6K) and in Expt. 2, Nutricote 13-13-13 (13N-5.8P-10.8K) type 100, a controlled release fertilizer, was incorporated into the growing substrate, prior to transplanting, at rates of 3, 6, or 9 lb/yard3 (1.8, 3.6, or 4.5 kg·m-3). In both experiments, there was no difference in petunia shoot dry mass or final flower number between the irrigation systems at the lowest fertilization rate but differences were evident at the higher fertilization rates. In Expt. 1, shoot dry mass and flower number of subirrigated petunia plants fertilized with 100 ppm of N was greater than for hand-watered plants fertilized at the same rate. However, subirrigated petunia plants fertilized with 150 ppm of N were smaller with fewer flowers than hand-watered petunia plants fertilized with 150 ppm of N. Substrate electrical conductivity (EC) concentrations for petunia plants subirrigated with 150 ppm of N were 4.9 times greater than concentrations in pots hand-watered with 150 ppm of N. In Expt. 2, subirrigated petunia plants fertilized with 6 and 9 lb/yard3 were larger with more flowers than hand-watered plants fertilized at the same rates. Although substrate EC concentrations were greater in subirrigated substrates than in hand-watered substrates, substrate EC concentrations of all hand-watered plants were about 0.35 dS·m-1. Subirrigation benches similar to those used in these experiments, appear to be a viable method for growing `Ultra White' petunia plants. However, the use of Peter's 20-10-20 at concentrations greater than 100 ppm of N with subirrigation appeared to be detrimental to petunia growth probably because of high EC concentrations in the substrate. On the other hand, the use of subirrigation with Nutricote 13-13-13 type 100 incorporated at all of the rates tested did not appear to be detrimental to petunia growth.