Effects of source, rate and timing of nirtogen applied to wheat on soil N levels in a vertisol in the central highlands of Ethiopia
1997
Tilahun Geleto (Sinana Research Center, Robe (Ethiopia)) | Tanner, D.G. | Tekalign Mamo
In-crop and post-harvest soil mineral levels were measured in a study of wheat (Triticum spp.) response to three fertilizer nitrogen (N) sources, three N rates and three application timings. Large granular urea (LGU) resulted in a lower in-crop soil ammonium level than standard prilled urea, but did not differ from ammonium levels exhibited the sequence ASLGU = urea. Post-harvest soil nitrate and ammonium levels were significantly lower with all N applied at sowing vs. N top-dressed at mid-tillering or split -applied between sowing and mid-tillering. Marked differences were observed in soil N levels between the two wheat species studied, bread wheat (T. aestivum L.) and durum (T. Durum Desf.), and interactions among wheat species with N source, rate and/or timing were significant for some of the measured soil N parameters. Differences in soil N tended to reflect the lower total productivity of and N uptake and recovery by the durum wheat cultivar used in this study. To minimize the risk of detrimental effects of fertilizer N on the quality of surface and ground water, the use of agronomically appropriate fertilizer N sources, rates and application timing should be encouraged on the most productive crop species and cultivars. specific crop management strategies such as maintenance of crop stubble and adoption of conservation tillage could enhance the retention of residual soil N by reducing soil run-off and leaching.
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