Water-suspensible solids and structural stability

The water suspensibility of a number of particle/microaggregate sizes (< 60, < 20, < 6 and < 2 μm) were examined from the ploughed layer of a structurally weak soil (sieved to > 106 μm). After a period of saturation of approximately 1 min. significant amounts of water-suspensible material (WSM) < 106 μm in size were observed. After a 10-min period of saturation, the quantity of WSM < 60 μm doubled. whilst no significant change occurred in other sizes. No further WSM of < 60 μm was produced over a saturation period of 1000 min. The input of energy into the saturated soil by shaking produced significantly more WSM of all sizes. The WSM < 60 μm as a percent of the total soil in that size class was considerably greater than for other sizes. It is shown that WSM < 60 μm as opposed to WSM < 2 μm is a more important size in the stability of structure for certain soils and deserves more attention. Results are discussed in connection with furrow irrigation and soil strength. © 1991.