Application of compost is known to improve the hydraulic characteristics of soils. The objective of this study was to examine the seasonal and short-term effects of solid waste compost amendments on selected hydrophysical properties of soil during dry and rainy seasons and to explore any negative impacts of municipal solid waste compost (MSWC) amendments on soil hydrophysical environment concerning Agriculture in low-country wet zone, Sri Lanka. Eight (T1–T8) MSWC and two (T9, T10) agricultural-based waste compost (AWC) samples were separately applied in the field in triplicates at 10 and 20 Mg ha–1 rates, with a control (T0). Field measurements (initial infiltration rate, Ii; steady state infiltration rate, ISS; unsaturated hydraulic conductivity, k; sorptivity, SW) were conducted and samples were collected (0–15 cm depth) for laboratory experiments (water entry value, hwe; potential water repellency: measured with water drop penetration time, WDPT) before starting (Measurement I) and in the middle of (Measurement II) the seasonal rainfall (respectively 5 and 10 weeks after the application of compost). The difference in the soil organic matter (SOM) content was not significant between the dry and rainy periods. All the soils were almost non-repellent (WDPT = <1–5 s). The hwe of all the samples were negative. In the Measurement I, the Ii of the T0 was about 40 cm h–1, while most treatments show comparatively lower values. The ISS, SW, and k of compost amended samples were either statistically similar, or showed significantly lower values compared with T0. It was clear that all the surface hydraulic properties examined in situ (Ii, ISS, SW) were higher in the Measurement I (before rainfall) than those observed in the Measurement II (after rainfall). Water potential differences in soils might have affected the surface hydrological properties such as SW. However, water potential differences would not be the reason for weakened ISS and k in the Measurement II. Disruption of aggregates, and other subsequent processes that would take place on the soil surface as well as in the soil matrix, such as particle rearrangements, clogging of pores, might be the reason for the weakened ISS and k in the Measurement II. Considering the overall results of the present study, compost amendments seemed not to improve or accelerate but tend to suppress hydraulic properties of soil. No significant difference was observed between MSWC and AWC considering their effects on soil hydraulic properties. Application of composts can be considered helpful to slower the rapid leaching by decreasing the water movements into and within the soil.
This study explored the effect of soil water repellency (SWR) on soil hydrophysical properties with depth. Soils were sampled from two distinctly wettable and water repellent soil profiles at depth increments from 0–60 cm. The soils were selected because they appeared to either wet readily (wettable) or remain dry (water repellent) under field conditions. Basic soil properties (MWD, SOM, θ v) were compared to hydrophysical properties (Ks, Sw, Se, Sww, Swh, WDPT, RIc, RIm and WRCT) that characterise or are affected by water repellency. Our results showed both soil and depth affected basic and hydrophysical properties of the soils (p<0.001). Soil organic matter (SOM) was the major property responsible for water repellency at the selected depths (0–60). Water repellency changes affected moisture distribution and resulted in the upper layer (0–40 cm) of the repellent soil to be considerably drier compared to the wettable soil. The water repellent soil also had greater MWDdry and Ks over the entire 0–60 cm depth compared to the wettable soil. Various measures of sorptivity, Sw, Se, Sww, Swh, were greater through the wettable than water repellent soil profile, which was also reflected in field and dry WDPT measurements. However, the wettable soil had subcritical water repellency, so the range of data was used to compare indices of water repellency. WRCT and RIm had less variation compared to WDPT and RIc. Estimating water repellency using WRCT and RIm indicated that these indices can detect the degree of SWR and are able to better classify SWR degree of the subcritical-repellent soil from the wettable soil.