Influence of harvest time and storage location on the longevity of timothy (Phleum pratense L.) seed

Abstract

Norwegian agriculture relies heavily on a safe supply of seed of winter-hardy timothy cultivars. To buffer variations in seed consumption and seed yields, seed companies keep stocks corresponding to 50–100% of average annual seed consumption. Such large stocks are risky to maintain as seeds lose germination over time. Our objective was to elucidate the effect of seed harvest time and seed storage location on the longevity of timothy seed. In 2003, the Norwegian timothy cultivars, ‘Grindstad’, ‘Vega’ and ‘Noreng’, were combined directly at three different seed harvest times corresponding to a seed moisture content (SMC) of 33–35% (H1), 26–28% (H2) and 16–20% (H3), respectively. Germination analyses were conducted before storage and after 12, 24, 36, 48 and 60 months of storage in a conditioned seed store at Landvik (4°C, 30% RH) or in unconditioned warehouses at three climatically different locations (Tynset, Holstad and Vaksdal). Seed harvest time became increasingly significant as time went by. After 60 months seed harvested at 16–20% SMC (H3) germinated, on average for storage locations and cultivars, 24% units better than seed harvested at 33–35% SMC (H1). Seed stored in the conditioned store at Landvik germinated, on average for harvest times and cultivars, 4, 15 and 47 units better than seed stored at Tynset (continental), Holstad (intermediate) and Vaksdal (coastal), respectively. A significant interaction emphasised the importance of storing seed combined at a high SMC under optimal conditions in order to avoid germination loss. This linkage between harvest time and storage conditions for timothy seed longevity has not earlier been reported. Probably due to larger seeds that were more susceptible to mechanical damage, seed of ‘Grindstad’ usually had the lowest germination. These new results suggest that appropriate adjustment of drum speed and concave clearance is especially important when harvesting ‘Grindstad’.