Abstract
This study was conducted to investigate the changes of physicochemical properties of root zone soil based on sand blending with locally collected sandy loam (SL) and loamy sand (LS) upland soils for mainly a school playground. After categorizing the collected soils according to basic chemical property and particle size distribution, soil mixtures were prepared as follows; sand 100% (S), mixture 1 with 67% sand and 33% soil (SSL1: S 67%+SL 33%; SLS1: S 67%+LS 33%), mixture 2 with 50% sand and 50% soil (SSL2: S 50%+SL 50%; SLS2: S 50%+LS50%) and upland soil 100% (SL or LS). The pH of SSL or SLS soil was related to blending ratio with SL or LS where 100% sand only showed pH 6.8, with tending to lowering pH with mixing with more SL or LS portion. All the physical criteria including total porosity, capillary porosity, air-filled porosity and hydraulic conductivity of S, SSL1, SSL2, SLS1 and SLS2 were found to meet the USGA standard. The higher blending ratio of SL or LS for root zone soil increased significantly the air-filled porosity and total porosity (P<0.001), and decreased capillary porosity and hydraulic conductivity (P<0.001). These results indicated that mixtures with properly prepared SL and LS as root zone soil alternatives based on sand were improved soil physical characteristics such as porosity and hydraulic conductivity alleviating long-term soil compaction in school playgrounds, and expected that SL and LS might replace some soil amendments.
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