The Effect of Hydraulic Characteristics of Volcanic Materials on Yield of Roses Grown in Soilless Culture

Abstract

<jats:p>Rose (<jats:italic>Rosa</jats:italic> sp.) plants (`Mercedes') were grown in yellow tuff (YT) (volcanic ash, scoria) and pumice from Italy (PI) and Greece (PG) for which physical and hydraulic characteristics were determined. The differences among the measured retention curves of these materials result in significant differences among their relative hydraulic conductivity functions. The hydraulic conductivity of YT is much higher than that of PI, which is higher than that of PG. The plants were subjected to optimal growth and nutrition conditions. Irrigation was controlled using electronic tensiometers, at suction values well within the range of easily available water: 13 cm for YT and 8 cm for the two pumice types. Nonetheless, yields were significantly higher in YT than in PI; yields were even lower in PG. We suggest that the limiting factor was the dynamic water availability to the plants, which is affected mainly by the unsaturated hydraulic conductivity. The relative hydraulic conductivity of YT at 13 cm is more than an order of magnitude higher than that of PI at 8 cm. The relative hydraulic conductivity of PG at 8 cm is two orders of magnitude lower than that of YT at 13 cm. It seems that the current concept of easily available water, based on a predetermined suction range, independent of the hydraulic characteristics of the media, is not an appropriate parameter for irrigation management in soilless culture. The unsaturated hydraulic conductivity, being a characteristic function of the medium and highly sensitive to moisture variation, indicates better the actual availability of water to the roots. Therefore, it should be used for irrigation control in containers filled with porous substrates.</jats:p>

Growth and Irrigation Requirements of Croton in Substrates Amended with Pre-Charged Zeolitic Tuff

“…This may be attributed to the capability of zeolites to increase water retention [3] and improve cation-exchange capacity [23] of the substrate. Increased water availability in the root medium may be attributed to increased unsaturated hydraulic conductivity, [25] which is enhanced in substrates with relatively high volume of water-filled pores or CC as was the case with peatmoss-perlite (Table 2). [23] This feature makes zeolites widely used as water saver and slow-release fertilizers.…”

Pore network and water retention characteristics of volcanic porous media

“…Likewise, Tolk () indicated a correspondence between water content at −1471.50 kPa and wilting point estimated by the sunflower method. Results clearly suggested that hydraulic conductivity was a driving factor in the wilting process (Raviv et al , ). It is probable that hydraulic conductivity decreased in large aggregates and water content at wilting point increased accordingly.…”

Growing Plants in Soilless Culture: Operational Conclusions

“…Some typical examples are listed in Table 13.1. Kemble et al, 1994;di Benedetto and Klasman, 2004 Lettuce and other leafy vegetables Long season vegetables (tomato, pepper) 9-12 months Hydroponics 1-2 l Peterson et al, 1991a Perennial cut flowers (rose) 3-5 years 5-10 l Raviv et al, 1999; Tree saplings one year Transportation required ∼5 l Salifu et al, 2006 One common practical consideration for growers that dictates the root-zone volume is the interval between irrigation events. While it would be ideal to tailor the irrigation schedule to the needs ot the plants, many growers set the irrigation schedule for convenience or to take advantage of available capacity for irrigation.…”