"Solid-Phase P Buffer for Sustained, Low-Leaching P

Fertilization of Container Plants"

Inventors: J. P. Lynch et al.

PSU Invention Disclosure No. 1269

U.S. Issued Patent No. 5,693,119

A major problem associated with container plant production is the relatively large amount of fertilizer that must be applied and leached from the pot to insure adequate plant nutrition without excessive salt buildup. The leached fertilizer, especially N and P, is an environmental contaminant that causes water pollution. At recommended rates of fertilization and leaching, greenhouse production adds an estimated one (1) Billion kg of P contamination to U. S. water resources each year. State and federal regulatory agencies are contemplating restrictions on fertilizer effluent that will increase demand for more efficient fertilization technologies. An associated problem with fertilization of container plants is the difficulty of adjusting nutrient availability to plant needs as the plants grow and are subjected to diverse environmental conditions, especially in the hands of homeowners with little horticultural expertise.

Researchers at The Pennsylvania State University have developed a novel solution to this problem through the use of solid-phase chemical buffers that provide a stable supply of P to plant roots over time in amounts that are dependent on actual plant need. This technology uses commercially available materials. When loaded with P through special processing, the product becomes a solid-phase P buffer that establishes an equilibrium with solution-phase P at the desired set point (determined by the loading conditions). As plant roots acquire P from the solution, the buffer will replace the absorbed P to maintain equilibrium, thereby providing a buffered supply of P to the roots that is regulated by actual plant requirement and uptake. The regulation of P release into solution by plant P uptake reduces P leaching from the pot by more closely matching P supply and demand. This system also assures the plant a continual supply of P without the need for supplemental P fertilization over extended periods. Any added P from fertilizer or irrigation solution would bind to the input material and enter into the exchange equilibrium established. We envision that potting media could be sold with the P-loaded solid already mixed in, so that the media would essentially come with its own P fertilization system incorporated.

Penn State researchers have already conducted experiments with Marigold (Tagetes spp.) in which they compared the growth and health of plants supplied with conventional fertilizer, complete nutrient solutions, or their own solid-phase system at various percentages of the dry media. They observed that the solid-phase system is entirely adequate for production of this annual flower in standard pots, and indeed promoted better growth and crop quality than commercial fertilizer. Research is ongoing to establish the loading conditions and other parameters needed for employing this technique in pot plant production.