Nitrate-N uptake from soil depends on root growth and uptake activity. However, under field conditions N-uptake activity is difficult to estimate from soil-N depletion due to different loss pathways. We modified the current mesh-bag method to estimate nitrate-N-uptake activity and root growth of two oilseed-rape cultivars differing in N-uptake efficiency. N-efficient cultivar (cv.) 'Apex' and N-inefficient cv. 'Capitol' were grown in a field experiment on a silty clayey gleyic fluvisol near Gottingen, northern Germany, and fertilized with 0 (N(0)) and 227 (N(227)) kg N ha(-1).