Abstract

The micronutrient interactions in the process of root and/or leaf uptake can lead to contradictory results in the interpretation of sufficiency concentrations in plants when using only the results of soil analysis, as observed with copper (Cu), which has a negative interaction with other cations, mainly calcium (Ca). To define the critical level of Cu for the two most representative biomes of soybean crops in Brazil, soybean leaves, and grains were collected, and grain yield was evaluated at 52 and 60 sites that were originally covered with forest vegetation ('Atlantic Forest' and 'Cerrado', respectively). In the average of the two biomes, the Cu concentrations in the leaves ranged from 6.7- to 14.4 mg kg(-1) for yields of 3,000 and 4,200 kg ha(-1), with an average concentration for the maximum estimated yield (MEY) of 10.3 mg kg(-1), while for grains Cu concentration ranged from 8.1- to 16.2 mg kg(-1) with an average of 12.2 mg kg(-1) for MEY. There was a significant correlation between Cu concentrations in leaves and grains, and both proved to be efficient for use in assessing the nutritional status of Cu in soybean crops.