Nitrogen fractions and nutritional efficiency in bean lineages (Phaseolus vulgaris L.)

Twelve bean lineages (Phaseolus vulgaris L.) in the presence and absence of nitrogen in three places in the south of Minas Gerais were evaluated aiming to study the relationship between nitrogen fractions in leaves and the efficiency of nitrogen usage in the bean crop. In each place, distinct experiments with and without nitrogen application were installed using randomized blocks design, with three replications. The parcels were constituted by three-meter-long lines. Grain productivity (kg ha(-1)), amounts of total N in leaves and grains, and total N in leaf fractions (soluble-N, NO3--N, insoluble-N, and soluble organic-N) were evaluated. The average of grain productivity with nitrogen application was 63.7% higher than the productivity without this nutrient. The ESAL 629 and MA-I-2.5 presented higher grain productivities in all places and in all N levels and they were also more efficient in relation to N usage. The nitrate levels had higher values without N application than with it, and, on the other hand, the other fractions of N and total-N in leaves and grains presented higher values when there was nitrogen addition instead of absence of it. There was no good relationship between amounts of total-N and N fractions in leaves, and efficiency of N usage among the studied lineages; however, in the case of ESAL 629 and MA-I-2.5 there were evidences that the N fractions and total-N in leaves could explain their higher efficiency of N usage.