THE EFFECT OF PLANTING DATE AND PLANT-DENSITY ON POTASSIUM AND MAGNESIUM UPTAKE AND HARVEST BY BRUSSELS-SPROUTS

The effects of planting date and plant density on potassium (K) and ma gnesium (Mg) uptake and harvest by Brussels sprouts (Brassica oleracea var. gemmifera) were studied in field experiments. Crop potassium con centration generally decreased towards harvest, but the pattern in pot assium concentration during crop growth differed between planting date s. Plant density in the range of 2.7-4.4 plants m(-2) had no effect on crop potassium concentration. The amount of potassium in the crop at harvest decreased with a delay in planting, but was not influenced by plant density. Mainly depending on the planting date, around 100-200 k g potassium ha(-1), or approximately 40-50 % of the potassium in the c rop at harvest, is removed from the field with the product. Averaged o ver treatments and years, potassium concentration in the (fresh) produ ct was 5.2 kg ton(-1). The amount of magnesium in the crop at harvest decreased with a delay in planting. Depending on the planting date, up take at harvest was 10-17 kg magnesium ha(-1). Plant density had no ef fect on this amount. On average per ton (fresh) product, 0.20 kg of ma gnesium was removed from the field.