How to Optimize the Uptake of Phosphorous In Potted Plants

Many greenhouse growers are using soluble multi-nutrient fertilizers with a high percent phosphorous (P₂O₅) content on their crops in addition to the phosphorous applied to the substrate as a pre-plant as superphosphate or treble superphosphate. Using potted chrysanthemum as the model plant and using a recirculating sub-irrigation system to control the nutrient inputs, we determined the effectiveness of the pre-plant and post-plant phosphorous on various plant parameters, and also how much phosphorous could be recovered from the P-inputs. For this purpose, we used four rates of pre-plant P and four rates of post-plant P in a completely factorial experiment.  Another aspect of the study has been to compare a number of phosphorous sources as a pre-plant on the water soluble phosphorous concentration in the substrate over time and on growth parameter of the chrysanthemums. P-recovery by the plant relative to the P-input will be discussed.