Evaluation of Suction Cup Lysimeters for Obtaining Substrate Solution from a Pine Bark Substrate

Abstract

Abstract Protocols are needed for extracting the container substrate solution of plants in large containers [≥ 18.9 liter (#5)] since the container substrate solution is representative of the nutrients available to the plants. The objective of this study was to determine the effectiveness of suction cup lysimeters (SCLs) for this purpose. The lysimeter types tested were those with a 4.8 cm (1.9 in) diameter and a ½ bar or 1 bar air-entry value (AEV) and those with a 2.2 cm (0.87 in) diameter also with a ½ bar or 1 bar AEV. A sufficient volume of the substrate solution could be obtained after 5 min when a vacuum pressure of 30, 40 or 50 kPa was applied to 4.8 cm (1.9 in) ½ bar lysimeters. The 2.2 cm (0.87 in) lysimeters were suitable for extracting smaller sample volumes of solution or if installation space was limited. Electrical conductivity (EC) levels were unaffected by volume of substrate solution extracted by the SCL when volumes varied from 10 to 190 ml (0.34 to 6.4 oz). Overall, the 4.8 cm (1.9 in) diameter lysimeters are recommended for use with large nursery containers.