Soil Temperature, Water Content, Seeding Depth, and Simulated Rainfall Effect on Winter Wheat Emergence.
G.P. Lafond and D.B. Fowler

ABSTRACT

Winter wheat (Triticum aestivum L.) can be produced on the northern edge of the North American Great Plains provided it is protected from winterkill by an insulating blanket of snow. No-till seeding into standing stubble (stubbling-in) bas provided the most emdent means of maintaining this protective snow cover. Soil water at seeding is usually below optimum level for growth and development with this management system, and producers are often left with the dilemma of either seeding at the optimum date into a dry seed-bed or delaying seeding until after a rain. The objective of this study were to determine the effect of soil temperature, soil water, and seeding date and depth on median emergence time, development, and cold tolerance of winter wheat plants under controlled laboratory conditions. Median emergence time decreased by 1.3 d and emergence was more uniform for every degree increase in soil temperature in the 5 to 20°C range. Median emergence time increased as soil water potential decreased from -0.20 to -1.5 MPa. However, simulation studies demonstrated that 9.3 mm of precipitation on a dry soil was adequate to establish winter wheat seeded less than 25 mm deep. Increasing the depth of seeding from 19 to 76 increased median emergence time by 4.4 d for the optimum seeding date and 9.6 d if seeding was delayed 3 wk. Consequently, delayed deep seeding resulted in poorly developed plants with a reduced ability to withstand low temperatures. From a practical standpoint, this study demonstrates that in western Canada stubbled-in winter wheat should be seeded shallow (10 to 25 mm) at the optimum date even if it means seeding into a dry seedbed.

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