Effect of urea on lead absorption in corn (Zea mays l.), spinach (spinacia oleracea l.) and cabbage (brassica oleracea l.)

Agricultural intensification has led to an elevated use of pes-ticides and fertilizers such as urea, without considering the negative effects these products can cause, such as acidification of the soil and the entry of lead (Pb) into the trophic chain. The objective of this research was to determine the effect of urea on the absorption of lead (Pb) in the leaf structure of corn (Zea mays L.), spinach (Spinacia oleracea L.), and cabbage (Brassica oleracea L.). These three plant species were exposed to five different concentrations of urea and a constant concentration of Pb in the form of Pb acetate for 93 days. The effect of urea and Pb was determined through analysis of the leaf structure. The results showed an increase in the dry weight of corn, whereas in spinach (T₄) (1.5 g urea kg^-1 of soil plus 0.5 g Pb kg^-1 of soil) dry weight decreased as well as the fresh weight and foliar area. An increase in the chlorophyll index in corn, spinach, and cabbage was observed in the treatments with urea, and there was an influence on soil acidification. We also observed that spinach concentrated more Pb (T₄) in its foliage at higher rates of N application. The idiosyncratic nature of the crop responses to the combined effects of Pb and N highlights the need for more research on this subject.