Influência de diferentes fontes e doses de adubos nitrogenados nos teores de n-nitrato e na produtividade de alface

Abstract

Heavy fertilization with nitrogen may cause accumulation of nitrate and nitrite in foods causes health problems, the aim of this study was to compare the use of organic and mineral fertilization on the accumulation of nitrate in lettuce. A field experiment was conducted at the Embrapa Agrobiology Research Center, was laid out in a randomized block design, in a factorial 4x3, with 4 doses of manure (control, 1, 2 e 3 kg/m2) and 3 types of foliar fertilizer (control, biofertilizer and urea) and 4 replicates. Foliar spraying was performed every 7 days. Plants were harvested after 60 days. Leaves were separated into exteriors leaves (lower one third of the plant), medium leaves (medium one third) and interiors leaves (upper one third of the plant). The leaves were extracted with alcohol and the extracts were analysed for nitrate-N. Nitrate concentration was highest in plants treated with urea, being that the foliar application with biofertilizer did not differ significantly from the control. The exterior leaves had presented greaters nitrate concentrations. The better nutritious value of plants treated with cattle manure and biofertilizer, with lower levels of nitrate in their tissues. The weight of the fresh matter/head of lettuce did not differ between doses of manure. The leaf fertilization did not interfere in this parameter except control, with lower productivity.