It can be quite difficult to check soil fertility and acidity (EC (electrical conductivity) and pH) levels in large, potted woody ornamentals periodically, to monitor what is going on inside the potting media of the container. Conditions change over time; your fertilizer levels decrease, the pH changes due to irrigation application and fertilizer release.
We did a field demonstration to show growers four different ways to check the fertility levels in a large container. We demonstrated a soil lysimeter, a pour-thru method, a leaching fraction method, and a two-to-one (water:soil) saturated media extract.
Some methods may be easier than others depending upon your nursery constraints such as labor, materials, and time. The key to successfully using this kind of data is to use a method that is exactly repeatable every time. Therefore a grower can compared the results over time and across plants. A grower needs to determine which method is more suitable depending upon factors such as how the fertilizer is incorporated in the container (top-dressed versus sub-dressed) or how irrigation is applied.
I posted a video looking at the methods of checking pH and EC regularly. You can watch it here. pH and EC BMP Video. This video is a quick overview of the methods to measure container potting media fertility. If you have specific questions regarding the methods or need more in depth information please contact Shawn Steed at Hillsborough County Extension Office.
Research is currently underway at the Gulf Coast Research and Education Center to compare and contrast these different methods. We will show how these methods compare with each other and how variable they are when using the data to make management decisions when the work is completed.