Suction Cup Lysimeter Method for Extracting Pine Bark Substrate Solution

The objective of this study was to determine the effectiveness of suction cup lysimeters (SCL) in extracting substrate solution from pine bark substrates. Lysimeter types tested were 4.8-cm diameter with a ½ or 1-bar air-entry value (AEV) and 2.2-cm diameter also with a ½ or 1-bar AEV. Sufficient volume could be obtained when a vacuum pressure of 30, 40 or 50 cb was applied to lysimeters with a minimum extraction time of five minutes. The 2.2-cm lysimeters were found to be suitable for extracting solution if smaller sample volumes were needed. To determine effect of vacuum pressure and extraction time on volume extracted, the 4.8-cm ½-bar lysimeters were installed in containers with pine bark substrate and Quercus phellos L. (willow oak) trees. Volumes extracted were somewhat erratic and not strongly dependent upon centibars of vacuum or extraction time. Lysimeters immersed in water demonstrated that variability was not due to individual lysimeters, but to the coarse nature of the pine bark substrate. Substrate EC levels were not affected when volume of substrate solution extracted by the SCL's varied from 10 to190 ml.â

To determine the effectiveness of SCL's to monitor nutrient status of container-grown shade trees, two-year-old container-grown willow oak trees were grown in a pine bark substrate and fertilized with 0, 50, 100, 150, 200, 250 or 300 grams Osmocote Plus Northern (15N – 3.9P – 9.8K). Plant height and trunk diameter increased with up to 200 grams of Osmocote per container. There was a good relationship between solution EC and plant growth