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Nitrogen Volatilization from Rice Leaves. II. Effects of Source of Applied Nitrogen in Nutrient Culture Solution¹

The objective of this study was to determine the effects of source of N applied in nutrient media on the rate of volatile N lost from leaves of two rice (Oryza saliva L) cultivars in conjunction with the transpirational water vapors. The water-soluble, non-elemental N in the condensate was analyzed by pyro-chemiluminescence.

The N source in the nutrient culture solution did not significantly affect the rate of volatile N loss from the ‘Y’ and third leaves at tillering and panicle initiation. However, at heading the Y leaf of ‘Labelle’ and the third leaf of ‘Lebonnet’ grown in nitrate medium lost N at a lower rate than the corresponding leaves of plants supplied with ammonia. The percentage of N lost in oxidized form(s) was not affected by source of N applied in the nutrient solution at any of the three stages examined. The relative amounts of reduced and oxidized forms of volatile N loss varied with the growth stage; at heading the percentage of N lost in oxidized form(s) was lower than that at tillering and panicle initiation regardless of cultivar, leaf position, and N source applied. The percentage of N lost in oxidized form(s) varied from 8 to 28% of the total loss. For both cultivars the transpiration rates were not statistically affected by N source, but transpiration rate of the Y leaf was higher than that of the third leaf from the top at panicle initiator! and heading.

Key Words: Oryza sativa L. • NO₃—N • NH₄—N • Leaf area • Transpiration

² Dep. of Agronomy, Altheimer Laboratory, Univ. of Arkansas, Fayetteville, AR 72701.

Received for publication July 21, 1980.