NITRATE, NITRITE, CALCIUM, POTASSIUM AND SODIUM IN ORGANIC, HYDROPONIC AND CONVENTIONAL VEGETABLES

Lettuce and arugula are vegetables that provide several health benefits and represent the most produced and consumed leaf vegetables in Brazil. The present study aimed to assess the levels of nitrate, nitrite, potassium, sodium and calcium in lettuce and arugula grown using organic, hydroponic and conventional systems. Nine samples of each vegetable grown using the three systems were used. The vegetables were harvested from properties in the municipalities of Vale do Taquari, Rio Grande do Sul, Brazil. The data were analyzed using the Kruskal-Wallis non-parametric test with a significance threshold set at 5% (p≤0.05). Vegetables obtained from the hydroponic system showed higher mean levels of nitrate (p≤0.05) compared with organic and conventional vegetables; organic arugula was the only one that presented nitrite in its composition (3.52±4.92 mg/kg). Arugula and lettuce showed the highest mean levels of potassium when grown using the organic system (270.86±61.92 mg/100 g and 207.45±46.53 mg/100 g, respectively). Organic and hydroponic arugula exhibited the highest mean levels of calcium, whereas samples of conventional lettuce presented the highest mean level of calcium (28.53±7.20 mg/100 g). Organic lettuce and arugula were the ones with the highest concentrations of sodium (4.67±2.65 mg/100 g and 3.02±1.26 mg/100 g, respectively). It is concluded that the hydroponic vegetables exhibited significantly higher mean levels of nitrate. Except for calcium in lettuce samples and sodium in arugula samples, we found greater amount of minerals in organic vegetables