Shallow mechanical loosening of a soil under dairy cattle grazing: Effectson soil and pasture

Shallow mechanical loosening of soil to 22 cm deep (aeration) was investiga ted as a method for ameliorating soil compaction caused by dairy cattle tre ading. Soil physical and pasture measurements taken over 46 weeks compared plots grazed under normal grazing practice (non-aerated) with plots under n ormal grazing practice where soil was mechanically loosened (aerated). Aera ted soil initially showed reduced (P < 0.05) penetration resistance, degree of packing, and bulk density, and increased (P < 0.05) hydraulic conductiv ity, total porosity, macroporosity, and proportion of small aggregates, com pared with non-aerated soil. However, after 40 weeks aerated soil showed so me reversion back to a non-aerated state, and only the most sensitive measu rements (penetration resistance, degree of packing, soil structure, and mac roporosity) showed significant (P < 0.05) treatment differences. Pasture he rbage yield, botanical composition, and root length were unaffected (P < 0. 05) by aeration, but aeration increased (P < 0.05) root dry weight and decr eased bare ground. This work suggests that timing of aeration with regard t o soil moisture and atmospheric conditions is vital for optimal soil and pa sture responses. The need to use methods which sample large volumes of soil and pasture to detect soil physical and pasture changes due to loosening i s also stressed.