Samples of soil were air dried for 7–14 days after which aggregate size distribution was determined by gently sieving a 25 g homogenised check details sub-sample through nine sieves: 4000, 2000, 1000, 500, 425, 300, 212, 106 and 53 μm. The mass retained on each sieve was weighed, recorded and the percentage mass in each fraction calculated. From aggregate size distributions, the coefficient of uniformity (Kézdi 1974) was used to numerically illustrate the differences in distributions where large and small aggregates co-existed. Aggregate stability was determined by the fast wetting (slaking) technique developed by Le Bissonnais (1996) and expressed

as mean weight diameter (MWD). Aggregate hydraulic properties were measured by a miniaturised infiltrometer (Leeds-Harrison et al., 1994 and Hallett and Young, 1999). Further sub-samples of the air dried soil SB431542 solubility dmso were sieved to 2–5 mm,

prior to oven drying at 40 °C for 24 h. The infiltration device was constructed with capillary tubing, glass tubing (3.5 mm internal diameter) and a 200 μl pipette tip. In order to assess the hydraulic conductivity, the sorptivity of water flowing into soil aggregates at five different heads of water was measured (0, −10, −20, −30 and −40 mm). Water repellency (R) was determined through measurements of the ethanol (Se) and water sorptivity (Sw) at the −20 mm head. Ethanol infiltration is not affected by hydrophobic substances and hence isolates the influence of the pore structure on wetability. Amino acid The repellency index (R) of individual aggregates was calculated from: R=1.95SeSwwith the constant accounting for the differences in surface

tension and viscosity. Soil structural analysis was undertaken non-destructively using a Venlo H series, X-ray CT Scanner (H 350/225 CT; X-TEK, Tring, Hertfordshire, UK). A 2 mm primary copper filter was placed near the X-ray source to eliminate X-ray scatter, in addition to a 4 mm secondary copper filter placed at the detector to prevent detector saturation (i.e. when the input to the detector exceeds the total capacity) and beam hardening (Taina et al. 2008). Gain and offset correction was applied to all of the diodes within the detector by applying a black (offset) and white (gain) reference to adjust for exposure variations. Macrocosms were scanned at 175 kV and 3 μA, with an exposure time of 90 ms. The samples were placed 145 mm away from the detector and scanned to collect a single image at 6 pre-determined depths according to each particular experimental layout. Images were processed using AnalySIS® (Soft Imaging Systems (SIS), Münster, Germany) to segment pore space. The image resolution was 65.4 μm pixel−1. Initial images were cropped to 52.97 mm × 50.69 mm (810 pixel × 775 pixel), to remove the sides of the macrocosm from the image, in addition to boundary effects such as cracks that occasionally ran down the edges of the macrocosm.