Effect of tillage system and nitrogen fertilization on efficacy of applied nitrogen by maize in Western Ethiopia

Abstract

Nitrogen is the most limiting nutrient for maize production under conventional and minimum tillage systems in western Ethiopia. Thus application of N is essential to sustain production in the region. However, very little is known about the efficiency of the fertilizer N applied. Experiments were therefore conducted to determine the integrated effects of tillage systems and N fertilization on the usage of applied N by maize from 2000 to 2004 at five sites. Three tillage systems (MTRR = minimum tillage with residue retention, MTRV = minimum tillage with residue removal and CT = conventional tillage) and three N levels (the recommended rate, 25% less and more than this rate) were combined in factorial arrangement with three replications. A significantly higher grain N content was recorded with MTRR than with MTRV and CT. The stover N content was not significantly affected by the three tillage systems. However, grain, stover and total biomass N uptake were consistently superior with MTRR compared to MTRV and CT. The agronomic (NAE), recovery (NRE) and physiological (NPE) efficient use of applied N by maize for the same tillage system were consistently higher at the lower N level range of 69 − 92 kg ha⁻¹ than at the higher N level range of 92 − 115 kg ha⁻¹. At the lower N level range NAE and NRE were larger with CT than with the other two tillage systems. Both indices were higher with MTRR than with the other two tillage systems at the higher N level range. The NPE was not significantly affected by the tillage systems. However, the trend at both N level ranges was higher with MTRR than with MTRV and CT.