Abstract

Leafy vegetables constitute an excellent source of fiber, vitamins, minerals, and phytochemicals, producing many benefits to human health. However, nitrate (NO3-N) accumulation constitutes a risk factor for environment and human health. The present study was focused on the evaluation of concentrations and sources of NO3-N in lettuce and spinach under different production systems, located in the Metropolitan region (Chile). Nitrate concentration was determined in vegetable tissue, soil, water, and organic fertilizers, and compared to Chilean and international standards. Results indicated average, dry matter basis, concentrations of 3065 and 4766 mg kg−1 of NO3-N for summer and winter lettuce, respectively. On the other hand, NO3-N concentration for spinach reached 1686 and 1244 mg kg−1, respectively, for the same seasons. The studied species did not show significant differences in NO3-N content. In addition, there was no correlation between the accumulation of NO3-N in vegetable tissue and soil N availability (average of 75 mg kg−1 NO3-N) or NO3-N concentration in irrigation water (average of 8 mg L−1 of NO3-N). Finally, a nitrogen balance determined that in lettuce production systems 240–430% excess N was applied. On the other hand, organic fertilizers used did not comply with the maturity parameters established by the NCh 2880/04, 2016. There were some lettuce samples with high NO3-N contents, without surpassing the maximum allowable concentration. The nitrogen balance for lettuce determined a large excess N application as organic and/or inorganic fertilizers, which was related to larger NO3-N levels found in their tissues.