Andreas Neuhaus, James Easton
Research projects around Australia have diagnosed subsoil constraints including nutrient deficiencies that cause yield limitations. This study reports the mapping of subsoil phosphorus (Colwell P) and potassium (Colwell K) values to generate awareness of these subsoil constraints among advisors and growers. Surface (0-10cm)- and subsoil analytical results (10-20 cm and 20-30 cm) from CSBP’s laboratory have been used to highlight P and K availability The maps identified a heterogenous soil nutrient profile, revealing subsoil limitations of P and K in many areas of Western Australia. A trend towards a higher contrast of P levels at depth was noted especially for the heavier textured soils in the medium to high rainfall zone. More subsoil or plant tissue testing is recommended to confirm the decline in P and K availability from subsoils. Regular soil sampling of the top 30cm of soil that contains the main root volume for nutrient uptake of most broadacre crops grown in WA is recommended to better understand nutrient requirements.