Phosphorus deficiency (P)
In vegetables, a lack of phosphorus often becomes apparent at the very beginning of the vegetative period. Plant stems as well as older leaves will show dark-green discolouration, which will later typically turn bluish-grey and reddish-violet (anthocyanin colouration). Vegetable growth will be extremely weak. Plants suffering from a lack of phosphorus have a reduced number of leaves and only limited fruit set. Particularly root growth will be stunted. In case of prolonged phosphorus deficiency, younger and new shoots will also be affected. If the situation is not addressed, plants will shed their leaves.
Tomatoes will exhibit spindly stalks; leaves have a tendency to shrivel and drop. Cabbages suffering from phosphorus deficiency will show delayed development in comparison with healthy plants.
The focus should be on preventing a lack of phosphorus. Depending on the phosphorus content of the soil, an application of 50-80 kg P2O5 ha-1 has shown to be appropriate for bell peppers, while for tomatoes 90-150 kg P2O5 ha-1 has proven to be sufficient. Part of this total quantity should be applied as a starter dressing. Phosphorus-containing foliar fertilisers may help to reduce yield losses, but are not appropriate for addressing a deficiency.