glasshouse experiment was conducted in order to evaluate,

using the A value method, the liming effect on the efficiency

of nitrogen symbiotic fixation (NSF) of the common bean

genotypes BAT 58, BAT 477, DOR 364 and CC 25-9 (N) in

a Rhodic Ferralsol soil. NN 125, a non nodulant common

bean, was used as the control crop. All common bean

genotypes increased the fraction of N in plant derived from

soil due to liming, mainly CC 25-9(N), that show a very low

capacity to fix N from air if the soil is not amended with lime.

Moreover, a beneficial effect of liming on the soil N pool was

found, because the increasing total N uptake by plants was

due to the N coming from the air, and the quantity of N in

plant coming from the soil diminished, mainly for DOR 364

and CC 25-9(N). In addition, the ratio %Ndff/%Ndfs, the N

percentage in plant derived from the fertilizer and derived

from the soil, respectively, vary due to the N percentage

liming. Therefore, it is necessary to use two treatments for the

control in order to evaluate accurately the NSF: with and

without the lime application. The Nitrogen Use Efficiency

parameter is disscused.