Abstract:
High spatial and temporal variability is an inherent feature of dryland cereal crops over much of the southern cereal zone. The potential limitations to crop growth and yield of the chemical properties of the subsoils in the region have been long recognised, but there is still an incomplete understanding of the relative importance of different traits and how they interact to affect grain yield. Measurements were taken in a paddock at the Minnipa Agriculture Centre, Upper Eyre Peninsula, South Australia, to describe the effects of properties in the topsoil and subsoil on plant dry matter production, grain yield and plant nutrient concentrations in two consecutive years. Wheat (Triticum aestivum L. cv. Worrakatta) was grown in the first year and barley (Hordeum vulgare L. cv. Barque) in the second. All soil properties except pH showed a high degree of spatial variability. Variability in plant nutrient concentration, plant growth and grain yield was also high, but less than that of most of the soil properties. Variation in grain yield was more closely related to variation in dry matter at maturity and in harvest index than to dry matter production at tillering and anthesis. Soil properties had a stronger relationship with dry matter production and grain yield in 1999, the drier of the two years. Colwell phosphorus concentration in the topsoil (0?0.15 m) was positively correlated with dry matter production at tillering but was not related to dry matter production at anthesis or with grain yield. Subsoil pH, extractable boron concentration and electrical conductivity (EC) were closely related. The importance of EC and soil extractable boron to grain yield variation increased with depth, but EC had a greater influence than the other soil properties. In a year with above-average rainfall, very little of the variation in yield could be described by any of the measured soil variables. The results suggest that variation in EC was more important to describing variation in yield than variation in pH, extractable boron or other chemical properties.