Abstract

The Missouri Gravel Bed (MGB) is a system that uses pea gravel with 10% sand (v/v) as a root growth medium, allowing plants to be removed from the gravel and planted, bare root, during the growing season. However, the low water holding capacity of the medium necessitates frequent irrigation. This study was conducted to determine the effects of amending pea gravel with calcined clay (Terra-Green^®) on the physical properties of the medium and on growth of Gymnocladus dioicus (L.) K. Koch seedlings. Adding 10% sand (v/v) increased water holding capacity of the medium slightly at water tensions above 1 kPa. Gravel amended with 40% calcined clay had 16% air-filled porosity and had 3.5 times more plant available water than gravel with sand only. Dry weights of seedlings grown in gravel amended with 40% calcined clay and no sand were over twice as great as those of seedlings grown in the standard MGB medium.