Effect of Leachate Fraction on Nitrate Loading to the Soil Profile Underlying a Greenhouse Crop

Abstract

Abstract Poinsettia stock plants were grown in a greenhouse and irrigated with a 20 mM (280 ppm) N solution to produce a low (10%) or high (50%) leaching fraction (LF). At two week intervals, core samples were removed from the soil underlying the crop at 15 cm (6 in) increments to a depth of 90 cm (36 in). Leachate was collected from pots following each irrigation, and plant tissue and potting medium samples were collected. All samples (soil, leachate, plant tissue and potting medium) were analyzed for nitrate-N (NO 3− N) content. The rate of NO 3− N accumulation and the depth to which nitrate accumulated in the soil profile were significantly affected by leaching fraction. Under high LF treated plants, nitrate moved deeper into the soil profile and accumulated at higher concentrations than under low LF treated plants. Each irrigation event in the high LF treatment resulted in an average deposition of 243 ml (8.2 fl. ounces) of effluent containing 100 mg (3.53 × 10 −3 oz) of NO 3− N. The average low LF irrigation event deposited an average of 65.7 ml (2.2 fl. ounces) of effluent containing 33.5 mg (1.18 × 10 −3 oz) NO 3− N. Poinsettia cutting production and tissue nitrogen levels did not significantly differ between treatment groups.