Gaseous Nitrogen Loss from Soybean Foliage¹

The loss of non‐elemental N from plant foliage was verified, and the significance of this loss was investigated. Soybean ( Glycine max (L.) Merr.) leaf vapors were condensed (–50 C) using a calibrated test tube tra in a closed system. Subsequent N analysis of this condensate revealed water soluble N forms. Since the pyrochemiluminescent technique that was used for N analysis does not detect elemental N, the N present must be in chemically bound forms; preliminary research indicates the N in both oxidized and reduced forms. Significant losses of N from the determinate cultivar ‘Davis’ were positively correlated to temperature and to transpiration rate under field conditions. These losses, which like transpiration followed a diurnal trend, were greater in early vegetative growth stages than during flowering and pod‐fill. The amount of N lost is significant under the high temperatures of field Conditions and may account for much of the reduction in potential seed yields under this stress condition.