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Previously the use of direct observation of soil pore structure in assessing tillage trials has been restricted by the slowness of specimen preparation and data generation. It is desirable that pore structure assessment be performed within a similar time‐scale required for other routine chemical and physical measurements. This would aid the interpretation of routine measurements and enhance the ability to make management decisions in the same growing season as sampling. A method developed for rapid analysis of soil pore structure is presented in two parts. In this paper, a new technique for production of an undisturbed planar face through soil with pore space in the field condition is described. Field impregnation with opaque epoxy resin, that will cure in moist soil, is followed by sawing, laboratory impregnation of the exposed face, and grinding back beyond the original surface to a smooth finish. Grinding is followed by digitization, and digital grey‐level image segmentation to produce a binary image. Methods of image production are described, explained, and illustrated. Samples of Vertisols from a tillage and fallow management trial are shown as examples of the technique. The method can be completed in 4 d for a single specimen. It is emphasized that high quality binary images should be used for image measurement. The discipline of mathematical morphology is used to ensure this quality. This paper finishes with production of high quality digital images that provide graphic illustration of the nature of the pore structure in the vertical plane under the different tillage treatments.

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The stability in water of soil from 3 contrasting Vertisols was measured using5 tests. Two end-over-end shaking procedures, the Loveday & Pyledispersion test, and the relatively rapid SOILpak procedure of Daniells & Larsen were assessed. The latter method has been modified to deal with severaldeficiencies such as its lack of score subdivisions; the new procedure isreferred to as the ‘aggregate stability in water’ (ASWAT) test. Wecorrelated data from all the tests under consideration to provide definitionsof the ‘critical’ point at which dispersion becomes a problem forland managers. Three soil management zones have been defined provisionallyusing data from the ASWAT and end-over-end ‘aggregate stability’tests. The scheme allows appropriate surface soil management strategies to bepredicted using the ASWAT test. The relationship between data from the ASWATtest and exchangeable sodium percentage indicated that factors other thanexchangeable sodium strongly influence dispersibility of the samples underconsideration.

Erosion and excessive runoff from a crusting and hard-setting red-brown earth may he ameliorated1 with suitable management. A field trial, near Cowra, New South Wales, to assess the long-term effect 01 different tillage systems was used to compare the effect of direct drilling with conventional district cultivation practices under continuous wheat. The soil was sampled in the eighth year for assessment of the soil macropore structure, measurement of bulk density and hydraulic conductivity under tension. Vertical faces were prepared from resin impregnated blocks and the macropore structure described mathematically and visually using digital images and data generated from these images. Infiltration, bulk density and imagc: analysis data all lead to the same conclusions about changes in pore structure. Under direct drilling no crust was evident, and there was greater macroporosity (> 0.175 mm diameter in section). 'The treatment effects appeared to be significant to about 30 to 35 mm depth at the time of sampling. Greater root and faunal activity were observed under direct drilling.