THE EFFECT OF PLANTING DATE AND PLANT-DENSITY AN NITROGEN UPTAKE AND NITROGEN HARVEST BY BRUSSELS-SPROUTS

Single and combined effects of three planting dates and three plant de nsities on nitrogen uptake and nitrogen harvest by Brussels sprouts (B rassica oleracea var. gemmifera) were studied in field experiments. Th e total amount of nitrogen taken up by the crop at harvest ranged betw een 220 and 325 kg ha(-1). Although final crop dry matter decreased, t otal nitrogen uptake was not lower when planting was delayed. This res ulted in increased nitrogen concentrations both in the total crop and in the harvested product. Forty to fifty per cent of the nitrogen take n up by the harvest was removed from the field with the product. Withi n the range of 2.7 to 4.4 plants per m(2), plant density had no effect on final nitrogen uptake nor on the amount of nitrogen harvested with the product. The results indicate that nitrogen fertilizer recommenda tions should take planting date into account, because with delayed pla nting less dry matter will be accumulated with a corresponding lower n itrogen requirement. There was no interaction of effects of planting d ale and plant density on nitrogen uptake.