Nitrate Concentration in Leafy Vegetables from the Central Zone of Chile: Sources and Environmental Factors

Abstract

Leafy vegetables constitute an excellent source of fiber, vitamins, minerals, and phytochemicals, producing many benefits to human health. However, nitrate (NO 3 -N) accumulation constitutes a risk factor for environment and human health. The present study was focused on the evaluation of concentrations and sources of NO 3 -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 NO 3 -N for summer and winter lettuce, respectively. On the other hand, NO 3 -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 NO 3 -N content. In addition, there was no correlation between the accumulation of NO 3 -N in vegetable tissue and soil N availability (average of 75 mg kg −1 NO 3 -N) or NO 3 -N concentration in irrigation water (average of 8 mg L −1 of NO 3 -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 NO 3 -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 NO 3 -N levels found in their tissues.

Effects of Fertilization Mode on the Growth of Lactuca sativa L. and Soil Nutrients in Facilitated Cultivation

“…A diagram of the row spacing and plant spacing measurements is shown in Figure 1d. The measured N content of Lactuca sativa seed was 2.436% [24] and the ideal Lactuca sativa dry matter N content was 4.831% [25], with a biomass of 199.8 g for a 1 m 2 planting area [26]. The amount of fertilizer required for this trial was 21.61 g per square meter of seed sown, which was converted to a combination of 40% compound fertilizer and 60% urea at 49.7 g. The specific fertilizer application rates are shown in Table 2.…”

Effect of growth seasons and nitrogen fertilization on the growth, yield and nitrate accumulation of lettuce (Lactuca sativa L.) plants

“…Nitrate accumulation in vegetables could be immediately linked to N fertilization practices, excess nitrogen applied resulted in increased NO3 accumulation (Ortega-Blu et al, 2020). Various studies reported a significant positive correlation between NO3 content in leafy vegetables and the dose of nitrogen supply (Fu et al, 2017;Urlić et al, 2017).…”