SHORT-TERM DECREASE IN SOIL STRUCTURAL STABILITY FOLLOWING BROMEGRASS ESTABLISHMENT ON A CLAY LOAM SOIL

The improvement in soil structural stability when grasses are grown in an unstable soil is well documented. Laboratory and field experiments have confirmed, however, that the introduction of bromegrass (Bromus inermis L.) can cause a significant short term decrease in stability. The decrease in stability was not related to changes in the redox potential, carbohydrate content or pH. The decrease in stability did correlate, however, with an increase in root length. The decrease in stability on introduction of bromegrass appears to be caused by physical fragmentation of aggregates by root penetration and/or by weakening of aggregates by enhanced wetting and drying.