Phosphorus and phosphorus stratification

In the grains-growing areas of south-east Australia, the bulk of plant nutrients in labile form usually occurs in the topsoil, with much lower amounts present in the subsoil. It is becoming increasingly evident that in environments where the nutrient-rich topsoil is prone to drying, nutrient uptake by crops is likely to be adversely affected despite the availability of water in the subsoil. This is likely due to impeded root growth in the dry topsoil or reduced diffusion of immobile nutrients to plant roots or both. Despite the numerous studies on vertical nutrient stratification, there is still limited information on the effectiveness of subsoil nutrition on yield productivity and also the efficiency of nutrient use. This paper reviews P cycling and budgeting in grain production systems with an emphasis on P stratification and the resulting consequences it has on crop P demand.