Wednesday, April 15, 2009

No Leach Irrigation Strategies for Easter Lily Production

This is a continuation from the previous post on No Leach Irrigation Strategies for Easter Lily Production. In addition to studying no leach irrigation on poinsettia production, Sean Moody also did a follow-up study using 'Nellie White' Easter lilies (provided by the Fred C. Gloeckner & Company, Inc.), which were subjected to three irrigation strategies: 10% leach, ebb-and-flood and no leach or pulse, at two constant liquid feed fertilizer rates, 100 and 200 ppm N from Technigro 17-5-24 plus; Fisons Horticulture Inc.

The study was conducted from week 1 (case-cooled bulbs were transplanted) and spaced at emergence week 4 in a FRP-glazed greenhouse. The plants were grown in 6-inch azalea pots using Premier Pro-Mix HP. The study was terminated week 13.

All plants on the ebb-and-flood benches were irrigated when approximately 2.5 cm of moist media remained at the bottom of the pot. The irrigation solution was pumped from the holding tank to the containers bench top, held for 10 min., and drained back to the tank for later recirculation. Fertilizer solution was added to the tanks when the level dropped below half to maintain enough solution to sufficiently flood the benches. Pulse and 10% leach strategies were calibrated to where the leachate was equal to zero and 10% of applied solution, respectively. Pulse irrigation was conducted once daily until week 40 and twice daily subsequently at 900 and 1300 MDT study. The 10% leach plants were irrigated daily.

Leaching of containers is a common practice to prevent high salt build-up in the medium of greenhouse crops. The salt levels are typically measured by determining the electrical conductivity (EC) of the root-zone medium. For this study, from three horizontal sections of the media, top, middle and bottom, a saturated paste extract for each irrigation treatment was collected. The EC was then determined from those sections.

Easter lily plant growth was not affected by fertilizer rate. Easter lily plants were tallest when grown with ebb-and-flood irrigation and pulse irrigation reduced dry weight, height width and growth indices slightly (Fig. 1). The irrigation practices 10% leach and ebb-and-flood irrigation resulted in the lowest EC values for Easter lilies compared to ebb-and-flood and pulse irrigation (Fig. 2). Higher EC values for all three irrigation strategies were evident in the top layer, which was expected due to the wicking of water to the medium surface as with poinsettias. The EC value of the top layer from the pulse irrigation treatment at 200 mg·L-1 N resulted in an EC value considered to be potentially dangerous to plant growth (4-8 mS·cm-1).

Easter lilies of acceptable quality may be successfully grown using ebb-and-flood or pulse irrigation strategies at constant liquid feed fertilizer rates of 100 mg·L-1 nitrogen (N). No leach irrigation practices in excess of 200 mg·L-1 N may result in excessively high EC values resulting in poor plant growth. These practices effectively reduce runoff as and can be adopted to reduce the non-point source pollution risk of a greenhouse.

To see Sean's thesis, click here.
Sean now works for Landscape Designs by Ellison

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