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

The effects of planting date, plant density and their interaction on p hosphorus (P) uptake during the season and on phosphorus harvest by Br ussels sprouts (Brassica oleracea var. gemmifera) were studied in fiel d experiments. Plant density in the range of 2.7 to 4.4 plants per m(2 ) had no or only a limited effect on crop phosphorus concentration and no effect on final crop phosphorus uptake. A delay in planting reduce d the final uptake of phosphorus, but increased phosphorus concentrati on in the crop and in the product at harvest. Mainly depending on plan ting dare, 33 to 50 kg of phosphorus was taken up by the crop at harve st. Forty to 60 per cent of this amount was removed from the field wit h the product. There were no interactions between the effects of plant ing date and plant density. The effect of planting date on phosphorus uptake has no consequences for phosphorus fertilizer recommendations. Currently recommended phosphorus fertilizer amounts are likely to be i n excess of the amount of phosphorus harvested with the product.