Nitrogen fertilization of new cultivars of lettuce

The present work aimed to study production and accumulation of nitrate by new cultivars of lettuce in response to nitrogen doses applied to the soil. Two field trials were carried out during 1999-2000and 2000-2001,the soil had received 30 and 64 kg'ha-l of N, respectively, for the two trials as a pre-transplanting fertilization. Our main objective was to com~are a control unfertilized treatment with two nitrogen doses (75 and 150 kg'ha- ) applied by fertigation to different cultivars of lettuce belonging to the folIowingtypes: Lollo Bionda, Canasta, Lollo Rossa, and, in the second trial, Oakleaf. The Lollo Rossa cuItivars produced 26 and 56% less than the Canasta type, respectively, in the first and the second year, probably due to the absence of a real head in the Lollo type. The application of nitrogen by fertigation increased yield compared with the unfertilized control, but with no difference between doses and rates of fertilization. On the other hand, nitrogen posttransplanting fertilization increased the nitrate content in leaves. The Lollo cuItivars accumulated more nitrate than the other ones. The nitrate levels were greatly below the limit of 4.000 mg kg-1fw imposed by EU Regulation No. 563/2002.