Synopsis
A highly significant negative correlation existed between Cl in nutrient solution and the uptake of SO4 in the tops of potato plants. Uptake of SO4 by roots was significantly increased by additions of P32 but not by S35 or no radioisotope. Intermediate levels of Cl reduced the uptake of P31 as compared with low and high levels of Cl. Chloride also affected maturity and dry weight relations of potato plants.
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 (NO3−N) content. The rate of NO3−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 NO3−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) NO3−N. Poinsettia cutting production and tissue nitrogen levels did not significantly differ between treatment groups.
Cornus amomum and Rhododendron ‘Cary's Red’ were grown in #3 (10 1) containers outdoors and supplied with a controlled release fertilizer (CRF). At two week intervals, core samples were removed from the soil underlying the crop at 30 cm (12 in) increments to a depth of 90 cm (36 in). Soil samples and foliar samples were analyzed for nitrate nitrogen (NO3-N) concentration. NO3-N accumulated rapidly in the upper 30 cm (12 in) of soil underlying containerized crops. Accumulation in the 30–60 cm (12–24 in) layer occurred later in the growing season and NO3-N buildup in the 60–90 cm (24–36 in) layer lagged behind both upper soil layers. Maximum NO3-N concentrations exceeded 40 mg/kg (6.36 × 10−4 oz lb−1) of soil and levels above 20 mg/kg (3.18 × 10−4 oz/lb) of soil were sustained throughout the 90 cm (36 in) soil profile for much of the growing season. Patterns of soil NO3-N concentration suggest that, by the middle of the growing season, rapid-growing Cornus may better utilize released N fertilizer than slower growing Rhododendron. Foliar samples confirm significantly higher NO3-N uptake by Cornus than by Rhododendron.
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