• Journal of Bio-Environment Control
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• v.20 no.2
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• pp.93-100
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• 2011

Maintenance of adequate soil water potential during the period of crop growth is necessary to support optimum plant growth and yields. A better understanding of soil water movement within and below the rooting zone can facilitate optimal irrigation scheduling aimed at minimizing the adverse effects of water stress on crop growth and development and the leaching of water below the root zone which can have adverse environmental effects. The objective of this study was to evaluate the feasibility of using a portable irrigation controller with an Watermark sensor for the cultivation of drip-irrigated vegetable crops in a greenhouse. The control capability of the irrigation controller for a soil water potential of -20 kPa was evaluated under summer conditions by cultivating 45-day-old tomato plants grown in three differently textured soils (sandy loam, loam, and loamy sands). Water contents through each soil profile were continuously monitored using three Sentek probes, each consisting of three capacitance sensors at 10, 20, and 30 cm depths. Even though a repeatable cycling of soil water potential occurred for the potential treatment, the lower limit of the Watermark (about 0 kPa) obtained in this study presented a limitation of using the Watermark sensor for optimal irrigation of tomato plants where -20 kPa was used as a point for triggering irrigations. This problem might be related to the slow response time and inadequate soil-sensor interface of the Watermark sensor as compared to a porous and ceramic cup-based tensiometer with a sensitive pressure transducer. In addition, the irrigation time of 50 to 60 min at each of the irrigation operation gave a rapid drop of the potential to zero, resulting in over irrigation of tomatoes. There were differences in water content among the three different soil types under the variable rate irrigation, showing a range of water contents of 16 to 24%, 17 to 28%, and 24 to 32% for loamy sand, sandy loam, and loam soils, respectively. The greatest rate increase in water content was observed in the top of 10 cm depth of sandy loam soil within almost 60 min from the start of irrigation.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.1
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• pp.30-37
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• 2009

Early enamel caries is commonly remineralized by the patient‘s improved oral hygiene or fluoridation, however the result is clinically unreliable. As an alternative, we tried to seal the lesions with low-viscosity light-curing resin. The aim of the present study was to search the proper methods of the adequate pretreatment prior to applying adhesive resin on natural proximal caries lesions. Thirty nine extracted deciduous molar teeth showing proximal early caries lesion were used for this study. They were divided into 5 groups : Group 1; only carefully cleaned with water, group 2; etched with 15% HCl for 15s, group 3; etched with 35% phosphoric acid for 15s, group 4; etched with 35% phosphoric acid for 30s, and group 5; cleaned with 0.5% NaOCl. Following results were obtained by evaluating with SEM and CLSM after applied with adhesive resin. 1. As a result of SEM evaluation, group 2 showed clearly removed surface layer, group 3,4 showed partially removed surface layer irregularly, group 5 showed slightly removed surface layer. 2. Group 2 showed the deepest infiltration depth, followed by group 4, group 3, group 5, group 1 and besides group 5, other groups showed significantly deep infiltration depth. (p < 0.01) In conclusion, the best methods of the adequate pretreatment on natural proximal caries lesion for deep infiltration of adhesive resin was to etch with 15% HCl for 15s.