Nitrogen (total and ¹⁵N) uptake by barley and wheat under two irrigation regimes’

Abstract

Nitrogen (total and ¹⁵N) uptake by barley (Hordeum vulgare L., cv. ‘Walfajr') and wheat (Triticum aestivum L., cv. ‘Karaj I') plants subjected to water stress were studied at the College of Agriculture, University of Tehran Experimental Farm located in the city of Karaj, Iran. The treatments consisted of two irrigation intervals, 7 days (control) and 14 days (stress). The plants were at the reproductive stage of growth at the start of the ¹⁵N treatment. Nitrogen (¹⁵N) was applied to 1m x 1m plots selected at the center of the 2.5m x 2.5m main plots. The ¹⁵N was provided to plants by adding 250 mg ¹³N as (NH₄)₂SO₄ (5.1 Atom % ¹⁵N) dissolved in water to each plot. The ¹⁵N treatment period continued for 48 hours. The plants were harvested at 6‐hour intervals during the ¹⁵N treatment period. After each harvest, the straw and the grains were separated, oven dried at 65°C and dry weights were recorded. Plant materials were ground in a Wiley Mill to pass through a 2mm sieve for chemical analysis. Total N was measured by an Auto‐Analyzer after Kjeldahl digestion, and ¹⁵N was measured using a mass spectrometer.

Nitrogen (total‐N and ¹⁵N) content of both plant species decreased under stress, with wheat appearing more severely affected than barley. However, nitrogen concentration was slightly higher for the stressed plants as compared with the controls. This pattern was essentially similar for both plants.

Notes

This project was financially supported by the United Nations Development Program, Transfer of Knowledge Through Expatriate National (TOKTEN); Phase II: Project No. IRA/93/004.

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