The edible vegetables have a high capacity to accumulate nitrate in the leaves and stem. The excessive consumption of nitrate can be harmful to human health. The best combination of doses and sources of N and supply time were determined in the nutritious solution to reduce the nitrate concentration in cv. Vera leaves of lettuce. The treatments were (T1) 210 mg L-1 of N as nitrate (N-NO3-) from transplantation to harvest; (T2) 189 mg L-1 (90%) of N as nitrate (N-NO3-) associated with 21 mg L-1 (10%) of N as ammonium (N-NH4+); (T3) 210 mg L-1 of nitrate until the 24th day and substitution for 189 mg L-1 of nitrate and 21 mg L-1 N-NH4+ until the end of the cycle; (T4) 210 mg L-1 of N-NO3- until the 24th day of the transplant and reduction to 105 mg L-1 of N-NO3- until the end of the cycle; (T5) 210 mg L-1 of N-NO3- until the 24th day of the transplant and reduction to 52,5 mg L-1 of N-NO3- until the end of the cycle. The best results were obtained with the treatments T2 and T3, with levels of nitrate in the edible part varying from 1,756 to 1,920 mg kg-1 in the fresh matter and equivalent yield to the treatment 1. The reduction of nitrate in nutritious solution in the end of the cycle did not reduce the quantity of nitrate in leaves.
Lactuca sativa; hydroponic cultivation; nitrogen sources
