Polyurethane plant growth medium

Abstract

A plant growth medium is disclosed having a polyurethane matrix with at least 40% and preferably 50 to 55% open cells, and from about 36% to about 50% (and more for example 60%) by weight of a granular filler dispersed throughout the polyurethane matrix, which filler comprises about 69% to about 78% by weight of clay of relatively high cation-exchange capacity, such as a calcium-hydrogen montmorillonite clay, and from about 22% to about 31% by weight plant nutrients and their carriers. The medium is self-contained and suitable for mechanized and automated plant propagation, growth, and outplanting; it has unique nutrient retention and release mechanisms coacting with the polyurethane matrix, including integrated anion retention sites which, together with the cation retention sites of the clay and at least part encapsulation of the nutrients by the matrix cell membranes, result in a plant propagation and plant growth medium having properties and characteristics similar to and beyond those occurring in natural soils and which are especially valuable for performance. The growth medium may be used as a self-contained soil in various physical shapes and it may be ground and used by itself or in potting mixes. A number of examples is set forth.