The Pour-Through Procedure for Monitoring Container Substrate Chemical Properties: A Review

The pour-through procedure is a nondestructive method commonly used by horticultural crop producers and research scientists to measure chemical properties and nutrient availability in container substrates. It is a method that uses water as a displacement solution to push the substrate solution out of the bottom of the container so it can be analyzed for pH, electrical conductivity, and nutrient concentrations. The method was first introduced in the early 1980s. Since then, research has been conducted to determine factors that affect the results of the pour-through including volume, nature and timing of application of the displacement solution, container size, and substrate stratification. It has also been validated against other common methods for determining container substrate pH, EC, and nutrient concentration, most notably the saturated media extraction procedure. Over the past 40 years, the method has been proven to be simple, robust, and consistent in providing crop producers and researchers valuable information on substrate chemical properties from which management decisions and experimental inferences can be made.

Response of Calceolaria ×herbeohybrida Cultivars to Substrate pH and Corresponding Leaf Tissue Nutrient Concentration Effects

Calceolaria (Calceolaria ×herbeohybrida) is a flowering potted greenhouse crop that often develops upper-leaf chlorosis, interveinal chlorosis, and marginal and leaf-tip necrosis (death) caused by cultural practices. The objectives of this research were to 1) determine the optimal incorporation rate of dolomitic and/or hydrated lime to increase substrate pH; 2) determine the influence of the liming material on substrate pH, plant growth, and leaf tissue nutrient concentrations; and 3) determine the optimal substrate pH to grow and maintain during calceolaria production. Sphagnum peatmoss was amended with 20% (by volume) perlite and incorporated with pulverized dolomitic carbonate limestone (DL) and/or hydrated limestone (HL) at the following concentrations: 48.1 kg·m−3 or 144.2 kg·m−3 DL, 17.6 kg·m−3 DL + 5.3 kg·m−3 HL, or 17.6 kg·m−3 DL + 10.6 kg·m−3 HL to achieve a target substrate pH of 4.5, 5.5, 6.5, and 7.5, respectively. Calceolaria ‘Orange’, ‘Orange Red Eye’, ‘Yellow’, and ‘Yellow Red Eye’ were grown in each of the prepared substrates. For all cultivars, substrate solution pH increased as limestone incorporation concentration and weeks after transplant (WAT) increased, although to different magnitudes. For example, as limestone incorporation increased from 48.1 kg·m−3 DL to 17.6 kg·m−3 DL + 10.6 kg·m−3 HL, substrate solution pH for ‘Orange’ calceolaria increased from 4.1 to 6.9 to 4.8 to 7.2 at 2 and 6 WAT, respectively. Substrate solution electrical conductivity (EC) and growth indices were not influenced by limestone incorporation, but total plant dry mass increased. Few macronutrients and most micronutrients were influenced by limestone incorporation. Leaf tissue iron concentrations for ‘Orange’, ‘Orange Red Eye’, ‘Yellow’, and ‘Yellow Red Eye’ calceolaria decreased by 146%, 91%, 71%, and 84%, respectively, when plants were grown in substrates incorporated with increasing limestone concentrations from 144.2 kg·m−3 DL to 17.6 kg·m−3 DL + 10.6 kg·m−3 HL (pH 6.5–6.9). Therefore, incorporating 144.2 kg·m−3 DL into peat-based substrates and maintaining a pH <6.5 will avoid high pH–induced Fe deficiency and prevent upper-leaf and interveinal chlorosis.

Methods of potassium contents evaluation in the substrate solution and gerbera leaves

Several authors report that potassium (K) is the nutrient absorbed in greater amounts by gerbera plants. Thus, objective of determining the concentration of Kin the solution of substrates for growing potted gerbera, quantified by the Cardy Horiba C-131 and an atomic absorption spectrophotometer, correlating them with each other and with the plant leaf content. The experiment was carried out in a greenhouse. The experimental design was in randomized complete blocks using a 5×2 factorial scheme (5 substrates/2 cultivars) and four replications. Cherry and Red gerbera cultivar seedlings with four final leaves were transplanted into pots, filled with the substrates and acclimated for 30 days. After acclimation, the K content in the substrate solution extracted by the “PourThru” methodology was evaluated every two weeks using the Cardy Horiba C-131 portable ion meter and an atomic absorption spectrophotometer, as well as the K content in the leaves of gerbera plants. The solution of the commercial substrate had higher concentrations of K in relation to the others in the two forms of measurement, which is directly related to the high initial contents of the nutrient in this substrate. This is directly related to the high initial K contents in the substrate. Greater values of K were obtained for the cultivar Red, both in the solution and in the leaves. The K concentration of the substrate solution cultured with gerbera plants quantified by the Cardy Horiba C-131 and atomic absorption spectrophotometry correlated significantly with each other and showed a low correlation with the content of this nutrient in the plant tissue.

THE EFFECTS OF PROPOLIS HONEY CANDY CONSUMPTION ON MYELOPEROXIDASE ACTIVITY IN STIMULATED SALIVA

Objective: Propolis is a natural product that contains flavonoids and has antibacterial effects that could decrease myeloperoxidase (MPO) activity inthe saliva. Propolis honey candy is currently being developed and to analyze the effects of propolis honey candy on MPO activity in stimulated saliva.Methods: Stimulated saliva samples were collected from individuals who met the inclusion criteria before and after consumption of propolis honeycandy twice a day for 7 days. Salivary samples were centrifuged to separate the supernatant and pellet. A 100-μl aliquot of the supernatant wasdirectly added to the wells of a 96-well plate and mixed with 100 μl of substrate solution containing 3,3’-diaminobenzidine, guaiacol, dapsone, andTris-HCl buffer. After incubation for 30 min at room temperature, MPO activity was measured by subtracting the absorbance value (wavelength of450 nm) of the saliva samples from that of the blank control (distilled water).Results: The absorbance value of MPO activity of propolis honey candy was 0.071 before consumption and 0.076 after consumption.Conclusion: MPO activity significantly increased after the consumption of propolis honey candy (Wilcoxon signed-rank test, p<0.05).

Oxygenation of Irrigation Water during Propagation and Container Production of Bedding Plants

Oxygen supply to the root zone is essential for healthy plant growth, and one technology that can potentially supply additional oxygen is the injection of purified oxygen (oxygenation) into irrigation water. The objective was to evaluate whether oxygenation of irrigation water affected plant growth and substrate dissolved oxygen (DO) levels during mist propagation of unrooted cuttings and subsequent growth in containers. Dissolved oxygen measured at source tanks for ambient tap water (averaging 7.1 mg·L−1) or oxygenated tap water (31.1 mg·L−1) was pumped through fine (69 µm) mist nozzles for propagation of Calibrachoa ×hybrid ‘Aloha Kona Dark Red’ and Lobelia erinus ‘Bella Aqua’. There were no measured differences in root length or root dry mass for Calibrachoa and Lobelia propagated using oxygenated water compared with ambient water because DO of ambient or oxygenated water reached ≈100% oxygen saturation in water (8.7 mg·L−1) after passing through mist nozzles. To evaluate subsequent growth without the effect on DO of fine emitters, rooted cuttings of these two plant species and Pelargonium ×hortorum ‘Patriot Red’ were grown in 10.2-cm diameter pots. The plants were irrigated with either ambient (6.0 mg·L−1) or oxygenated (27.7 mg·L−1) nutrient solutions, delivered by top watering or subirrigation when the substrate dried to ≈45% of container capacity (CC), measured gravimetrically. Oxygenated water did not enhance root or shoot growth compared with ambient water for the three bedding plants. In addition, Pelargonium growth was not enhanced when irrigated at high moisture level (maintained at 80% CC) with oxygenated water compared with ambient water. In container substrate without plants, it was possible to increase DO of the substrate solution by 68% when a high volume of oxygenated water (200% container volume or 850 mL) was applied by top watering because existing substrate solution was displaced. In contrast, when containers were subirrigated at 45% CC, the smaller 180-mL volume of oxygenated water was absorbed by the substrate and did not increase DO compared with ambient water. Overall, irrigating with oxygenated water did not enhance root or plant growth of three bedding plants grown in porous, peat-based substrate. To increase oxygen supply to roots in container production, growers should focus on having adequate air porosity in substrate and avoiding overwatering.