Rooting pattern and nitrogen uptake of three cauliflower (Brassica oleracea var. botrytis) F-1-hybrids

In a two-year field trial at the sites Ruthe (Germany, loess soil, Orthic L uvisol) and Schermer (The Netherlands, marine day soil, Eutric Fluvisol) th e cauliflower F-1-hybrids Marine, Lindurian and Linford were compared in th eir efficiency of N use from limiting and optimum supplies of N. Limiting N was N,. at planting. Optimum N was 250 kg ha(-1) as the sum of inorganic N content of the soil (N-min) at planting and fertilizer-N. Marine was the most efficient variety, producing the highest shoot dry-matt er and quality (% class 1 curds) at both limiting and optimum N supplies. T he N supply did not affect the horizontal and vertical distribution of root length density per soil volume (RLD, cm cm(-3)) irrespective of variety. T he RLD decreased exponentially with increasing soil depth. Varietal differe nces in RLD were not found at Ruthe, whereas at Schermer Marine had the hig hest RLD in all soil layers investigated (0 to 60 cm). No correlations were found between RLD and residual N-min at harvest, except at limiting N supp ly in Schermer where a strong negative correlation was found between RLD in the 45 to 60 cm layer and N-min at harvest. Thus, varietal differences in N efficiency are speculated to be rather due to different internal N-use ef ficiency than to differences tin N-uptake efficiency.