Abstract
A field experiment was carried out to investigate the effects of compost, sawdust and rice straw biomass on soil three-phase composition, soil resistance to penetration, bulk density, nearsaturated hydraulic conductivity, K(h), and soil water retention characteristics. The experimental design involved ten split blocks such that the non-amended one plot was considered as control and other nine plots were under each of compost, sawdust and straw treatments at application rates of 0.1,0.2 and 0.3 m3m-3 of apparent soil volume. Addition of compost, sawdust and straw showed potential for improvement of surface soil physical and hydraulic properties, then its effectiveness was partly dependent on amendment types and application rates. Three-phase composition of all amended soils showed solid-phase reductions and increase of total porosity. Generally, soil resistance and bulk density at all amendment plots were decreased, which was likely due to reduction in soil solid phases. A good correlation between soil resistance and bulk density was also observed. Except for sawdust applied at higher rate, the K(h) generally increased at any level of compost and straw incorporations, and this was attributed to the of
reduction in solid phase of amended soils. Soil water content was relatively high at higher suction for compost amended soils, while improvement in soil water retention was limited at lower suction for sawdust, and gradually increased from low to high suction for straw amended soils, respectively.
