Nitrogen balances during growth of Brussels sprouts and leeks

摘要

The nitrogen balance at different N-application rates was determined in 2 field experiments carried out during 1991-92 at Wageningen (Netherlands) on a sandy soil. The N-input (from fertilizer and mineralization) and the N-output (N in the above-ground crop parts and residual mineral N in the soil) were calculated. No deficit in the N-balance was observed in Brussels sprouts with N application up to a rate of 300 kg/ha. There was no imbalance in leeks up to a rate of 125 kg/ha. However, a deficit occurred from 90 days after transplanting when 250 kg/ha was applied at the time of transplanting, with N-output being lower than N-input. In one year, this deficit was 160 kg/ha N by early September. Based on a simulation of nitrate movement in the soil,this deficit was in good agreement with the amount of N leached from the soil (0-60 cm) at the final harvest in November. At the final harvest, the level of mineral N in the soil was less than 20 kg/ha for all N treatments on both crops. The uptake of Nduring the last part of the growing period in leeks played an important role in maintaining the intensity of the green colour of the leaves. The results are discussed with regard to the need for a mineral N buffer.