. (1997) measured clay swelling behavior in situ. Like in soil studies, the physical properties of growing media used in horticulture are usually characterized by the water retention curve obtained during a drying process according to standardized
Guifang Qi, Jean-Charles Michel, Pascal Boivin, and Sylvain Charpentier
George Gizas, Ioannis Tsirogiannis, Maria Bakea, Nikolaos Mantzos, and Dimitrios Savvas
growing media originating from waste organic residues ( Nektarios et al., 2011 ). Posidonia oceanica (L.) Delile, which is a higher aquatic plant belonging to the family potamogetonaceae of the Monocotyledoneae class, is very common in the Mediterranean
Kurt A. Schekel and Paul S. Kaczmarczyk
The presence of the growth regulators paclobutrazol and uniconazole in leachate or distribution through media consisting of various proportions of Douglas fir bark, sphagnum peat and perlite was evaluated. Distribution through a column 25 cm deep occurred rapidly and growth regulators were found in the leachate the first day after drench application when perlite was in the mix. Movement was limited to a maximum of the top 60% of the column in bark and peat mixes without perlite. Leachate was collected daily over a 12 day period after drenches were applied. Paclobutrazol and uniconazol showed similar distribution patterns in the media.
Santakumari Mane, James Turner, and Stanley Kostka
Three soilless media of different composition (peat: vermiculite, bark: peat: vermiculite, peat: vermiculite: polystyrene) received one of three wetting agent treatments (AquaGro 160 at 60 ml or 120 ml·m–3; or AquaGro L at 120 ml·m–3) and were subsequently analyzed for wettability after storage for up to 4 months. The respective untreated media served as the controls. All media were stored in closed bags at 24 ± 4C. Water retention was greater in wetting agent-treated media than in controls. Both wetting agents facilitated uniform distribution of water in the media. Control media became more difficult to wet over time, whereas wetting agent treatments maintained uniform wettability of media throughout the storage period. Wetting agent chemistry, treatment rate, and media composition influenced wetting characteristics during media storage. All three wetting agent treatments improved wetting of the peat: vermiculite over the 4-month test period. In bark media, AquaGro 160 applied at 120 ml·m–3 enhanced wetting throughout the study. Media containing polystyrene were difficult to wet. AquaGro 160 applied at 120 ml·m–3 improved wetting for up to 2 months.
Brent K. Harbaugh
Symptoms of foliar chlorosis or bleaching, interveinal chlorosis of lower leaves, leaf edge and tip necrosis, stunted growth and delayed flowering of Eustoma increased as pH decreased below 6.5 in various peat-vermiculite based media for all cultivars tested. Symptoms were evident with or without microelement amendments in the media or fertilizer. A 5×5 factorial with pH of media and fertilizer solutions ranging from 5.1 to 7.5 indicated fertilizer pH did not negate plant response to low media pH. Leaf tissue levels of Zn were elevated at low media pH and negatively correlated to plant growth and flowering characteristics, while imbalances in tissue levels of N, P, K, Ca, Mg, Fe, Mn, Cu and B appeared to be less important. Symptomatic plants grown in media with a pH from 5.0 to 5.8 had tissue levels of Zn ranging from 200 to 1200 ppm, and plants without symptoms in media with a higher pH had leaf tissue levels from 40 to 100 ppm Zn.
Krishna Nemali* and Marc van Iersel
Monitoring moisture status of the growing medium is essential as growth and quality of greenhouse crops largely depend on the amount of available water. Recently, two new types of moisture sensors have been developed (ECH2 O, Decagon devices, Inc., Pullman, Wash.; Theta probe ML2X, Delta -T devices Ltd., Burwell, Cambridge, U.K.). We studied the performance of these sensors for measuring the volumetric water content (VWC) of a soilless growing medium. We also tested the sensitivity of these sensors to temperature and electrical conductivity (EC) of the growing medium. Our results indicate that these sensors can be calibrated and used effectively for measuring a wide range of moisture contents in the growing medium; however media specific calibration may be required. Regression analysis indicated that the output of ECH2 O probes was affected by changes in the EC and temperature of the growing medium. Effects of EC were too small to be of practical significance, while the measured VWC increased by 0.003 m3/m3 for each °C increase in temperature. The output from the Theta Probe was not affected by changes in the EC or temperature of the growing medium. In a comparison study, both probes were found to give similar estimates of the VWC of the growing medium within the common range seen under greenhouse production.
George Gizas and Dimitrios Savvas
gypsophila shoots when coarser particles (0 to 8 mm) were used. Fig. 3. Effects of particle size of pumice and cultivation method (placement of the growing media in pots or bags) on the vegetative growth and flower yield of gypsophila. Values are
Isabelle Lemay, Jean Caron, Martine Dorais, and Steeve Pepin
In Europe and North America, there is increasing pressure to partly or totally replace peat, coir, rockwool, perlite, and polystyrene components of growing media with sustainable materials such as organic industrial byproducts of local origin
Raul I. Cabrera and Pedro Perdomo
Hydrophilic polymer tubes (2.5 mm OD, 1.4 mm ID, 10-cm length, 0.1-mm pore diameter) attached to PVC hose were used to extract solution from soilless media at container capacity and analyzed for pH, EC, NO3-N and NH4-N. Media chemical properties were also analyzed by the Saturated Media Extract (SME) and Pour-Through (PT) methods. Extraction and analyses were conducted in peat: vermiculite (PV) and peat: perlite (PP) media irrigated for 1 week with Hoagland solution at 0.25, 0.5, 1, 2 and 4x. A 10-mL syringe was used as the vacuum source (48.1 ± 0.5 kPa) for the solution samplers (SS), yielding ≈2–5 mL of solution over a 3-min period. Simple correlation coefficients for EC, NO3-N and NH4-N between SS and SME and PT were high (>0.99). When measured by PT, these chemical properties were similar to SS (within 1% to 6%), whereas SME values were much lower than SS (12% to 15% and 35% to 38% in PV and PP media, respectively). Correlation coefficients for pH were lower than in other chemical properties, particularly in the PV medium. With an estimated life of ≈6 months in soil, SS are excellent monitoring tools for mineral nutrition research and horticultural crop production.