Soil arthropod responses to subsoil manuring in irrigated vegetable and rainfed grain production

Diverse soil biology is being increasingly recognised as important for productive soils. Subsoil manuring – the process of placing organic materials underground using a modified deep ripper – has been used to improve the structure and productivity of texture contrast soils. Using soil arthropods as indicator species, this study investigated the soil biology responses of the subsoil manuring approach. Different organic materials were placed in the upper zone of a clay subsoil at field sites used for irrigated vegetable and rainfed grain production. Soil samples were taken from the topsoil and from the depth of organic material placement and processed to extract soil arthropods. Of three suborders of soil arthropods recorded, mesostigmatid mites showed the most notable increases in abundance in response to subsoil manuring. The placement of organic materials at depth resulted in elevated abundance of soil arthropods at depths that are not the normal habitat of these organisms. Abundance and richness were both suppressed under irrigated production compared to rainfed, although it is acknowledged that a number of management practice differences between the two production systems could contribute to the differences observed.