اثر زمان و شرايط محيطي بر كاهش سختي بذر در يونجه يكساله

The effects of time and environmental conditions on the pertcentage of hardseed breakdown in annual medic (Medicago scutellata) cv. Robinson

To study the trend of hardseed breakdown of annual medic (Medicago scutellata) cv. Robinson at different storage and natural systems, an experiment was conducted at climatic research station of Khoram-Abad during 2002 and 2003. The treatments consisted of 1. Pods kept at natural pasture conditions (pods left in medic residues), 2. Pods separated from residues and exposed directly to climatic conditions and 3. Pods kept in storage room at constant temperature. Seed germination tests were carried out at harvest time (early July), September, October, November and December of each year and the percentage of hardseed breakdown was measured for each month separately. The data were arranged as split plot in time and were analyzed and compared using a complete block design with three replications. The percentage of hardseed breakdown increased with time from harvest and the highest percentage was observed in December across all storage systems. Exposing the pods directly to climatic conditions caused the highest hardseed breakdown compared to other storage systems while the lowest was seen in pods kept at store room with constant temperature. The interaction of time and storage conditions revealed that the highest rate of hardseed breakdown happened when seeds were directly exposed to climatic conditions up to December each year.