Infl uence of storage conditions on survival and sowing value of seed of tropical pasture grasses. 2. Sowing value and storage strategies

Evaluation of effects of storage conditions of seed of 5 tropical pasture grass seeds (Panicum maximum, Brachiaria decumbens, Brachiaria humidicola, Setaria sphacelata and Chloris gayana) was extended from laboratory tests (Part 1) to seedling emergence and establishment tests in greenhouse and fi eld in north Queensland. Seed cool-stored in woven bags at 10°C and 50% RH mostly had higher fi eld sowing value than comparable open-stored seed, because the superior preservation of viability and vigour tended to outweigh the disadvantages of dormancy retention. Exceptions occurred when dormancy persisted, as it did inconsistently across seed lots, even within a single cultivar. Reduction in storage moisture content of seed sealed in moisture-proof packs helped to preserve viability and vigour, particularly with seed stored at ambient temperature. However, very low moisture content (7.2%) prolonged dormancy, with adverse effects on sowing value. Dormancy delayed germination even when not wholly preventing it. The benefi ts of retained vigour and the restrictions of dormancy were displayed in the fi eld, but were masked in the more benign environment of the greenhouse. Cold storage at −12°C intensifi ed dormancy of Gatton panic, delaying germination of seed in the greenhouse until the second and third seasons after sowing. The shortcomings of conventional storage and means of mitigating them are discussed, with emphasis on the need to vary strategies depending on the duration of storage required.