Abstract

Direct seeding into standing stubble from a previous crop (stubbling-in) has allowed successful production of winter wheat (Triticum aestivum L.) on the northern edge of the North American Great Plains. Soil at seeding is usually very dry with this production system, and the producer is often left with the dilemma of either seeding at the optimum date into a dry seedbed or delaying seeding until after a rain. The objectives of this study were to determine the importance of soil temperature and moisture potential on kernel water uptake and germination, so that the minimum requirements for successful crop establishment could be identified. Controlled environment studies demonstrated that germination could occur at moisture contents as low as 512 g water kg⁻¹ kernel dry weight. Therefore, differences in rate of water uptake observed for kernels placed in a Typic Haploboroll soil at −0.2, −1.0, and −1.5 MPa did not result in differences in speed of germination. Temperature differences in the 5 to 30°C range had a large influence on rate of kernel water uptake and speed of germination. As temperature increased, rate of water uptake increased and median germination time decreased from 6.9 d at 5°C to 0.9 d at 25 and 30°C. This study demonstrated that the effects of temperature on speed of germination are much larger than those of moisture, indicating that seeding of stubbled-in winter wheat should proceed at the optimum date regardless of seedbed moisture conditions.

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