An experiment was conducted with ryegrass growing in pots containing soil from the 0-10 cm layer of a red-brown earth to determine how the grass should be managed to improve stable aggregation of the soil. The quickest way to stabilize aggregates was to grow ryegrass with ample water and to clip the tops at monthly intervals. Clipping appeared to stimulate the growth of hyphae. Stressing the plants by allowing them to wilt reduced the stability of aggregates. The mycorrhizal hyphae persisted for at least several months after the plants had died. Although the hyphae may not have been viable they continued to bind particles of soil in stable aggregates.