No abstract

Sphagnum moss, which has very different chemical and physical characteristics compared with other soilless media, is commonly used as a substrate to grow Phalaenopsis in countries such as Japan and Taiwan. Pour-through (PT) is a nondestructive, effective, and convenient medium extraction method developed for peat-based media. To know if PT can be applied to sphagnum moss and to set up a standard procedure, experiments were conducted to test the effects of volume and electrical conductivity (EC) of the displacing solution and the timing of leachate collection on leachate properties. Results demonstrated that applying distilled water with a volume less than 70 mL to 10.5-cm pots 1 h after fertigation did not influence leachate EC and pH. Applying displacing solution with EC between 0.001 and 0.93 dS·m−1 1 h after fertigation did not affect leachate EC or pH. Thus, in theory, a variety of solutions may be used for displacement. Leachate properties were found to remain consistent when collected between 20 and 160 min after fertigation. These results demonstrated that PT can be successfully used in Phalaenopsis cultivation with sphagnum moss. Furthermore, substrate EC obtained by PT extraction was highly correlated with that by the press method, confirming that PT is a feasible medium extraction method for sphagnum moss in Phalaenopsis cultivation.

Lime is regularly used to increase soil pH, which will increase boron (B) fixation in soils. The effects of raising pH on B adsorption and the reversibility of adsorbed B in acid soils are essential for soil B management. In this study, B adsorption and desorption in limited concentration as a function of pH were measured in five finetextured red soils. Immediately after adsorption of B, four consecutive desorption steps were carried out by successive dilution. The sorption results were described well by the Freundlich equation. Boron adsorption markedly increased as pH increased. This increase was more pronounced when Ca(OH) 2 , as opposed to NaOH, was used for pH adjustment. The presentation of desorption data was based on the traditional isotherm approach and on time-dependent isotherms. Apparent hysteresis was observed in that both derivational families of desorption isotherms deviated from the adsorption isotherm for the five soils at their original pH. Moreover, hysteresis coefficients, n des /n ads and L trad for the traditional approach, had a positive correlation with organic carbon content, but they had a negative correlation with free Fe 2 O 3 and free Al 2 O 3 content. As pH increased, the hysteresis diminished, and adsorbed B became more likely to be desorbed. This finding may be because B adsorption and raising pH increase the negative charge on the surface, which creates electrostatic repulsion and results in an increase in desorption as pH increases.

The ignition method and the perchloric acid (HClO 4 ) digestion method for the determination of total phosphorus (P) content in 65 agricultural soils of Taiwan were compared. The average amount of total P obtained by the ignition method was 4.3% less than that obtained by the HClO 4 method. There was a wide range of variation, from 37% less to 21% more in the ignition method than those results obtained by the HClO 4 digestion method. Because the ignition method can also be used for the estimation of soil organic P and is thus worthy of further study, it should be adopted as a routine procedure.