Hare (1993) demonstrated in frost chambers that a -2°C air frost for 6 h reduced seed yield by 45% and a -5°C frost by 96% (Fig. 23-6). The -2°C frost reduced germination by 13% (Table 23-13), while the seed from the -5°C frost had zero germination. A -2°C air frost is equivalent to a -4°C ground frost. Frost at ear emergence resulted in a larger seed yield decline than frosts at anthesis to 4 d after anthesis. Frosts at 6 and 8 d after anthesis had less damage, but yields were still lower than for the control (Fig. 23-7). The copper-containing protectant Kocide (cupric hydroxide; DuPont, Wilmington, DE) did reduce the impact of frost slightly, with relative yields (no frost control = 100) of 61 and 47 for Kocide and no protectant, respectively (Hare, 1993).


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Table 23-13. Effect of frost on seed yield, 1000-seed weight (TSW), and germination (Hare, 1993). 

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Fig. 23-6. Frost (-2 and -5°C) damage to tall fescue seed production in New Zealand (Hare, 1993).



Fig. 23-7. Effect of time of -2°C air frost on relative seed yield of tall fescue (Hare, 1993) (DAA = days after anthesis).




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Paddock (Field) Selection: Soil Type and Site Characteristics (This Chapter)