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The effect of four nitrogen fertilizers on N use efficiency (NUE) of a high yielding barley (var. Triumph)

K.A. Jayatilake, N.J. Mendham and J.A. Beattie

Department of Agricultural Science, University of Tasmania, Hobart, 7001.

Recent studies using a barley cultivar, (Triumph), have shown a high yield potential under local conditions (1). We have investigated the effect of four different N sources on NUE of this variety grown in a solodic, with a sandy loam A horizon (pH 5.3-5.5). NUE is expressed in terms of % grain N recovery efficiency (RE), physiological efficiency (PE), and yield efficiency (YE), on incremental basis, with respect to increases in the fertilizer rate (2).

Materials and Method

Four forms of N fertilizers - urea (ur), Ca(NO1)2 (CN), NH4NO3 (AN), (NH4) SO4(AS), at two different rates (1- 50 and 2- p0 kg N/ha), were broadcast after sowing in June 1986. Quadrat samples (0.25 m ) were used to determine total content of grain (NG) and yields were taken from final harvest of 15 m plots. Total N analysis was carried out using the Kjeldahl digestion method (3).

Results and Discussion

The effect of increased rate of fertilizer application on yield was significant only for AS (p=0.05).At both rates of fertilizer application, NH4-N supplying fertilizers always gave poor yields in comparison with similar rates of NO -N fertilizers. This could be attributed to possible loss of N as NH3 volatilisation or to "fixation" of NH4 on the exchange complex. In contrast, the loss of nitrate N due to leaching would have been minimal since the relatively impermeable clay horizon may have prevented extensive drainage.

When rates were increased from 0 to 50 kg N/ha, the increases in the RE, PE, and YE were greater than those from 50 to 120 kg N/ha with all fertilizers except for AS. The low NG of the AS-1 treatment resulted in significantly low efficiencies when compared to Ur-1, CN-1, AN-1 treatments. Since NH4 fertilizers are used extensively in agricultural production further studies on the effects of such fertilizers on NUE are required.

1. Mendham, N.J. and Russell, J. 1985. Proc. 3rd Agronomy Conf. p. 271.2.

2. 2Bock, B.R. 1984. Efficient use of nitrogen in cropping systems. In "Nitrogen in Crop production" (ed. R.D. Hauck). ASA Publ. pp. 273-294.3.

3. Bremner, J.M. 1965. Total nitrogen. In "Methods of Soil Analysis, Part II" (ed. C.A. Black). ASA publ. pp. 1149-1176.

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