THE EFFECT OF TILLAGE AND WHEAT RESIDUE MANAGEMENT ON NITROGEN UPTAKE EFFICIENCY AND NITROGEN HARVEST INDEX IN WHEAT

In order to evaluate the effects of tillage and wheat residue management on nitrogen uptake and distribution,nitrogen uptake efficiency, nitrogen use efficiency and nitrogen harvest index in wheat, a two-year fieldexperiment was implemented as a split block experiment in a randomized complete block design with twentytreatments and three replicates at experimental site of Ferdowsi University of Mashhad, Iran in 2013 and 2014growing seasons. Four different tillage practices namely, conventional tillage applied by mouldboard plough +disk, reduced tillage practices applied by sweep plough + disk and chisel plough + disk and conserved tillageapplied by disk as vertical factor and five different crop residue applications (0, 25, 50, 75 and 100% wheatresidue) as horizontal factor. According to the results, the lowest (2.58 %) and highest (2.77%) grain nitrogenpercentage were observed when disk and chisel plough + disk were used, respectively. Employing chisel plough+ disk led to the maximum nitrogen uptake efficiency and nitrogen use efficiency. Grain nitrogen percentage,nitrogen uptake efficiency and nitrogen use efficiency significantly increased with increasing wheat residue level.For instance, when wheat residue was applied at 75% ratio, nitrogen uptake efficiency increased by 61.2%compared with control treatment. According to the results it appears that application of wheat residue alongwith reduced tillage could improve nitrogen utilization efficiency, especially in arid and semi-arid regions.