Do subsoil amendments provide benefits for crop productivity and the environment?

Abstract

Subsoil properties that limit the infiltration of water into the B horizon are a common occurrence in the agricultural districts of South Australia, and can have impacts on both crop productivity and the environment. A field experiment on a sodosol at Stansbury, Yorke Peninsula, was used to assess the effect of subsoil amelioration on the soil properties that influence crop growth, water movement and soil water quality. Subsoil treatments applied at the field site in 2004 and 2007 at approximately 40 cm depth included: deep ripping with deep nutrients, gypsum, or organic matter. Crop growth, soil moisture and soil water quality were measured during the growing season. A post-harvest assessment of soil physical properties was also undertaken to identify the effects of the subsoil treatments on soil physical properties that are considered to influence the movement of water. In 2007, crops responded most significantly to deep ripping with liquid nutrients applied in 2007, and as a residual response to deep ripping with nutrients applied in 2004. Significant improvements in soil strength to the depth of the subsoil treatment were identified in all treatments that included deep ripping, but there was no change in bulk density or macroporosity. There was also no effect of subsoil amendment on soil water quality properties. The results suggest that crop growth responses are due largely to impacts of nutrient availability at depth and there was little evidence of impacts of treatment on water movement and soil water quality in 2007.