EFFECT OF VARIED N RATES AND N TIMINGS ON YIELD, N UPTAKE AND FERTILIZER N USE EFFICIENCY OF A 6-ROW AND A 2-ROW WINTER BARLEY

The effects of N rates and N timings on yield formation, N uptake at f ive growth stages and fertilizer N use efficiency of six-row and two-r ow winter barley were evaluated in field trials conducted from 1990/91 to 1992/93 at the TU Munich's research station Roggenstein. On averag e over 3 years the six-row cultivar yielded most at a total rate of 11 0 kg ha(-1) N including an early application of 40 kg ha(-1) N up to E C 30 (Zadoks scale). The two-row cultivar achieved maximum yield at a total rate of 140 kg ha(-1) N including early applications of 70 kg ha (-1) N up to EC 30. The highest yielding N-treatments of six-row barle y regularly took up less nitrogen at EC 32 (95 kg ha(-1) N on average) than the non-optimally fertilized treatments, whereas full exploitati on of the yield potential of two-row barley was associated with higher rates of N-uptake at EC 32 (113 kg ha(-1) N on average). Lodging did not occur in the trials conducted in 1991 and 1992 and no difference w as detected between the two cultivars in fertilizer N use efficiency. With six-row barley the N treatment giving maximum yield also led to a n optimum fertilizer N use efficiency. Full exploitation of the two-ro w barley yield potential was associated with suboptimal fertilizer N u se efficiencies.