Submitted to: American Society for Horticultural Science Abstracts 2000
Publication Type: Abstract Only
Publication Acceptance Date: May 31, 2002
Publication Date: N/A
Technical Abstract: The purpose of this study was to determine the effect of Ca:NH4 ration in the rhizosphere of hydroponically-grown sour orange seedlings (SO) (Citrus aurantium L.) on the plants' vegetative growth and N uptake. The experiment was prompted by our observation that application of N in the form of NH4 in conjunction with CaCl2 was more efficient in eliminating N deficiency in field-grown grapefruit trees than the same rates of N applie in the form of NH4NO3 without Cacl2. About 40 cm tall SO were pruned back to the 4th leaf and grown for 6 weeks in nutrient solutions containing 5 mM NH4+ at CaCl2:NY4+ molar ratios of 1.0, 1.3, 1.6, 1.9, 2.2, or 2.5. In an additional treatment, NO3 was used as the sole source of N at CaCl2: NO3- ratio of 1:1. The level of Ca:NH4 ratio had no effect on new leaves number, shoot growth, total and average leaf area, specific leaf weight as well as leaf, stem, and tap root dry weight. However, lateral root dry weight decreased at Ca:NH4 ratio of 2.5. No growth differences were found when the plants were supplied with NH4+ vs. NO3- at Ca:N molar ratio of 1:1.