GROWTH OF POINSETTIAS, NUTRIENT LEACHING, AND WATER-USE EFFICIENCY RESPOND TO IRRIGATION METHODS

'Gutbier V-14 Glory' poinsettias (Euphorbia pulcherrima Willd. Ex. Klo tzsch) grown with ebb-and-flow irrigation used the least amount of wat er and produced the least runoff, and plants grown with capillary mats used the greatest amount of water and produced the most runoff, compa red to microtube and hand-watering systems. The maximum amount of wate r retained by the pots and media was greatest for the microtube and eb b-and-flow systems and became progressively lower for the hand-waterin g and capillary mat systems. The media and leachate electrical conduct ivity from plants grown with subirrigation systems was higher than tho se grown with top irrigation. For the two top-irrigation systems (micr otube and hand-watering), plants grown with 250 mg N/liter from a 20N- 4.4P-16.6K water-soluble fertilizer had greater leaf, stem, and total dry weights than those grown with 175 mg N/liter. The two subirrigatio n systems (ebb-and-flow and capillary mat) produced plants that were t aller and had greater leaf, stem, and total dry weights when grown wit h 175 than with 250 mg N/liter. The higher fertilizer concentration le d to increased N, P, Fe, and Mn concentration in the foliage. Nitrogen concentration was higher in top-irrigated plants than in subirrigated plants. The ebb-and-flow system produced the greatest total dry weigh t per liter of water applied and per liter of runoff; capillary mat wa tering was the least efficient in regard to water applied and runoff.