Soils with a very strong texture contrast pose significant crop production challenges due to limited water- and nutrient-holding capacity of the sandier topsoil. In dry years, plant establishment, growth and yield can be severely curtailed due to these constraints.
Here, we examine the effect of delving and surface applications of gypsum and feedlot manure, on the productivity of a hyper-texture contrast Sodosol. This sodosol is comprised of between 0.35 and 0.5 m of loamy sand and sand (5-8% clay) overlying a sodic light-medium clay subsoil (>40% clay).
Two weeks prior to delving, the gypsum, feedlot manure and gypsum+feedlot manure amendments were surface applied in strips across the experimental field at rates of 2.5 t/ha, 10 t/ha and 2.5 and 10 t/ha, respectively. Approximately 20 ha of this 24 ha sodosol field was delved, with the delve lines running perpendicular to the amendment strips. Two years post-delving, dual-purpose winter wheat was grown in 2023 and then again in 2024. In 2024, the wheat was harvested for grain after mid-season grazing events and yield was mapped across the entire field.
The wheat yield data indicated that the delved parts of the field outperformed the un-delved parts. Further, delved soil with a combined gypsum and manure treatment achieved the greatest average yield, followed by un-delved combined gypsum and manure treatments and delved manure sites, respectively. Both delving and the amendments, particularly manure, had a positive effect on wheat yield in this soil.
The effects of the delving on the sodosol included increasing the water-holding capacity, cation exchange capacity and sodicity of the sandy topsoil; although delving is often discouraged in these soils due to the risk of exacerbating sodicity-mediated soil structural issues, in this case the negative effects of topsoil sodicity were outweighed by the positive effects of greater water- and nutrient-holding capacity