Rothamsted Studies of Soil Structure Iv.

Summary Porosity and gas diffusion have been measured within dry crumbs sieved from the horizons of one soil from each of the Hanslope, Ragdale, Evesham, Denchworth, Flint and Salop series. Crumb porosities, ɛc, ranged from 0.19 to 0.33, dimensionless gas diffusivities, D c /D 0 , from 0.015 to 0.098, and the effectiveness of unit pore space for diffusion, given by α c = (D c /D 0 )/ɛ c , from 0.06 to 0.29. Values of ɛ c and D c /D 0 were used to calculate complexity factors k c for the crumb pores. The results are discussed in terms of soil texture, pore size, ease of soil management, and the frequency and intensity of wetting and drying of the soil in each horizon. None of the results suggests why the soils of the Ragdale, Denchworth and Salop series should be more difficult to manage than the others.