Phosphorus and phosphorus stratification

Abstract

Take Home Message
Phosphorus (P) stratification can impact on the critical P requirements of grain crops. In northern NSW and Queensland placing P at 20cm below the soil surface resulted in significant grain yield responses (~13% increase in wheat) (Bell et al., 2016). These findings are worth further consideration in other regions of the Australian grain belt particularly where soil P values in the 10 - 30cm layer are very low (Colwell P < 5mg/kg soil) and surface soils (> 10cm) experience extended periods of low soil moisture that limits P uptake by roots.
Testing the extent of P stratification on-farm (surface 0–10cm and subsoil 10–30cm) can assist in P budgeting as the lack of subsoil P can be offset by higher concentrations of surface P in most soils provided soil moisture conditions are adequate for P uptake.
The extent to which P stratification impacts grain yield is influenced by; (i) the Colwell P values for 0–10cm and 10–30cm layers, (ii) the probability of poor crop P uptake due to low soil moisture at 0–10cm, and (iii) the crop type. The current understanding of these components for southern cropping systems is inadequate to provide any precise recommendations.