Abstract: A support rail for use in supporting a planting tray during its initial growing period in a greenhouse. The support rail is especially suited for use with trays having a high-density matrix of small-sized soil plugs, and comprises a horizontally extending, vertically disposed web member and a pair of support members projecting from opposite sides of the web member at its lower extremity. The support members are angled downward from the horizontal so that a tray resting on support member will be supported along the tray's lower edges and not along the bottom surface. The rails are arranged in a uniformly spaced, parallel configuration, which provides stable support for a plurality of trays without providing a preferential growing environment for those soil plugs closest to the edges of the trays.

Abstract: Apparatus for continuously and rapidly forming trays of highly uniform elastomeric soil plugs comprises means for continuously mixing a water-containing soil slurry with a water-reactive pre-polymer compound, means for supplying the soil slurry and the pre-polymer compound to the mixing means at respective controlled rates, and means for delivering the mixed soil slurry and pre-polymer compound to a dispensing station for dispensing into mold receptacles; the receptacles are disposed in a closed path and carried by transport means seriatim past the dispensing station. Releasable bias means biases a tray mold member against a base mold member within each receptacle so as to extrude soil-pre-polymer mixture into plug-molding cavities of the tray mold member. The bias means is released after the plugs within the tray mold member have cured.