Vol. 75 No: 6

Title:
The effect of nitrogen application on nitrogen utilization by white cabbage (Brassica oleracea var. capitata) and on nitrogen in the soil at harvest

Authors:
A.P. EVERAARTS and R. BOOIJ

pp: 705-712

Abstract:
During two seasons and at four locations the effect of the rate of nitrogen application and the method of application on the nitrogen uptake by white cabbage (Brassica oleracea var. capitata) was studied. Maximum nitrogen uptake by white cabbage was around 400 kg ha^-1. Split application had no effect on nitrogen uptake. Band placement incidentally stimulated nitrogen uptake by the crop. The efficiency of nitrogen utilization for product dry-matter production decreased with increasing nitrogen rates. With increasing amounts of nitrogen applied the dry matter concentration of the heads decreased linearly with increasing nitrogen concentration. The nitrogen harvest index, the amount of nitrogen removed from the field with the product as a percentage of the total uptake by the crop at harvest, was not influenced by the rate or method of nitrogen application and varied between experiments from 54 to 60%. The amount of nitrogen in crop residues increased with increasing amounts of nitrogen applied and, in two experiments, was higher with band placement of nitrogen. At the optimum nitrogen application rate (= 330 - 1.5Nmin 0-60 cm kg ha^-1; Everaarts and De Moel, 1998) an average of 113 kg of nitrogen ha^-1 would have been left in the field in crop residues at harvest. The amount of nitrogen left in the soil at harvest was low and amounted to a maximum of around 40 kg ha^-1 for the soil layer 0-90 cm. Leaching of nitrogen during growth is probably limited. High amounts of nitrogen band placed resulted in a horizontally unequal distribution of soil nitrogen at harvest. The amount of nitrogen unaccounted for at harvest was proportional to the amount of nitrogen available and for all experiments could be described by one linear equation. The method of fertilizer application had no effect on this relationship. The amount of nitrogen in crop residues is the largest single source of potential loss of nitrogen with white cabbage cultivation.

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