What are subsoil constraints?
Subsoil constraints (SSC) are a key dampener of crop yields on particular soils throughout the northern grains region. Where grain crops are grown on soils with subsoil constraints, root growth is restricted, reducing water uptake, and limiting crop performance. Constraints seen in particular soil types within the Queensland cropping region include: • Sodicity. Sodium ions (Na+) within the subsoil region (30-90 cm) can impair root elongation into the subsoil and lead to nutrient imbalances. Sodicity also leads to dispersion of soil particles, and the increased risk of compaction as finer particles move down the profile. Around 45% of Queensland soils are described as sodic (DNR 1997). • Salinity. An excessive concentration of salts within the profile can prevent roots from growing and accessing stored soil moisture. These dissolved salts include sodium, chloride (Cl-), calcium (Ca2+), magnesium (Mg2+), nitrate (NO32-), and sulphate (SO42-). Salinity is usually determined by techniques
