GROWTH, NODULATION AND NITROGEN-FIXATION IN SOYBEAN AS AFFECTED BY AIR HUMIDITY AND ROOT TEMPERATURE

Growth, nodulation and N-2 fixation in Glycine mar L. Merr., cv. Biiso n as affected by the relative humidity of air (RH) during the dark per iod (95 or 50 - 65 %) and day/night root temperature (T-r) (28/28, 25/ 25, 18/18, 22/28, 22/18 degrees C) were studied. The growth parameters (plant fresh and dry mass, yield), nodulation (nodule number and fres h mass) and N-2 fixation abilities (total nitrogen content, nitrogenas e activity) increased significantly with the increasing T-r. In additi on, at the same T-r during the day all studied parameters were increas ed at the higher T-r during the dark period. Growth, nodulation and N- 2 fixation were significantly enhanced at low RH. The findings indicat e that all studied parameters could be regulated by environmental fact ors during the dark period.