تاثير تاريخ كاشت و تغييرات فصلي بر عملكرد و گره زايي سه رقم يونجه

Effects of sowing date and seasonal changes in growth and nodulation of three alfalfa cultivars

In a field experiment the influence the used of planting date and seasonal changes on growth and nodulation of three alfalfa cultivars was studied. cultivars Sacoeal, Hamadani and Ghara-youngeh inoculated by Rhizobium meliloti, were planted in April, May and June 2001 at experimental farm of Urmia University, and carried out for two subsequent years. A split plot in space and time design with four replications was used. Monthly samples were taken to determine individual shoot dry weight and nodule weight per plant. Plant dry weight and nodule weight was higher in the May sowing date. There were a significant differences between alfalfa cultivars in their shoot and nodule dry weight, Hamadany was higher than others. All species had marked seasonal peaks in shoot and nodule dry weight in end of the summer before flowering. There-after a rapid decline in the number and weight of nodules and in shoot weight were occurred once of flowering and cutting and subsequently by frost in the end of the growing season. Build-up of nodules in the second growing season which followed the vegetative growth, demonstrated that Rhizobia of the nodules was survived at low temperature in the region during winter.