Effects of amending a gravel based growing medium with calcined clay on medium physical properties and growth of Gymnocladus dioicus seedlings

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] The Missouri Gravel Bed (MGB) is a system that uses pea gravel with 10% sand (v/v) as a root growth medium, allowing bare root plants to be removed from the gravel and planted 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 (TerraGreen) on medium physical properties and on growth of Gymnocladus dioicus seedlings. Adding 10% sand (v/v) increased water holding capacity of medium slightly at soil water pressures lower than -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 the medium amended with 40% calcined clay and no sand were over twice as great as those of seedlings grown in the standard MGB medium.