Bijdrage tot de kennis van capillaire verschijnselen in verband met de heterogeniteit van den grond

The negative value of capillary pressure (D) was defined and its practical significance considered. The results of former research on rate and final value for capillary uptake were discussed.

The author constructed various meters for the measurement of capillary uptake. They were described and their dimensions and properties were compared with those used by other workers. The minimum and maximum values for D due to the heterogeneity of the soil material were tabulated for a series of sandy soils or soil fractions. These results were compared with those obtained in model experiments with perforated disks.

A series of new concepts was defined, concerning the forms and properties of isolated water in the soil profile. The terms 'sejunction' and 'funicular' and 'pendular' water were discussed. Their importance was demonstrated by a series of model experiments with sand fractions of different size grades. The distribution functions for the pores of these sands were calculated and compared with the experimental results. A few calculated examples were discussed on the importance of the isolated water for aeration of soil. Conclusions were derived for the presence of cracks in the soil profile and the influence of the distribution of rainfall on the amount of available water to plants.