This post was contributed to by Lauren Vanderlingen, OMAFRA Summer Student and Christoph Kessel, OMAFRA Soil Fertility Specialist – Horticulture.
If you are using Saturated Paste Extract (SPE) to assess soil nutrients for in-ground grown cut flowers, you may be underestimating plant available nutrients and applying fertilizers that aren’t needed.
Many greenhouse growers use SPE analysis when testing growing media in the greenhouse for nutrient levels. Typically, SPE tests are used in soilless or peat-based growing substrates, the kind we usually see used in potted plant production. However, if you are growing cut flowers in a mineral soil, either in the greenhouse or outdoors, SPE is not giving you a complete report on nutrients available to your crop.