EFFECT OF NITROGEN FERTILIZER ON NITROGEN ACCUMULATION BY COMMON BEAN (Phaseolus vulgaris)

Abstract

Legume plants capable of fixing N2 in the presence of abundant N in the soil are desirable to better integrate legumes into crop rotations including high N-demanding cereals. It has been suggested that the exotic bean line 'Puebla 152' may be insensitive to nitrate levels that normally inhibit bean nodulation and/or rate of fixation. Four levels (0, 30, 60, 120 Kg N/ha) of N as 15N-depleted ammonium nitrate were partialized into five weekly applications and imposed on Puebla 152, snap bean `Eagle', and non-nodulating soybean `Clay', in field experiments conducted in 1991 and 1992 on a very low N soil. CIAT's non-nod bean line Nod 125 was included in 1992. Each increment of added N increased the total N accumulated by the plants, in all genotypes. No significant genotype × N fertilizer interactions were detected. In average, Puebla 152 accumulated 25 and 46% more N than Eagle and Clay, respectively, in 1991, and 53, 119 and 119% more N than Eagle, Clay and Nod 125, respectively, in 1992. The analysis of 15N to estimate the proportion of N derived from the atmosphere is underway and will be presented at the meeting.