Effect of date of seeding of winter wheat on plant development and its relationship to winterhardiness

1. The percentages of winterkilling of winter wheat plants determined on date of seeding test trials during three consecutive years, 1923 to 1925, inclusive, were found to vary, depending upon the date on which the seed was sown. For a series of seedings made on or close to August 15, August 31, September 21, October 6, and October 19, the percentage of winterhardiness followed in decreasing order the seedings of September 21, September 4, October 3, October 17, and August 5, respectively. 2. The root development of plants for the various dates of seeding is strikingly different. The plants from the first seeding, August 18, show the greatest development of fall root system, followed in order by plants of the second, third, fourth, and fifth seedings. New root development in the spring usually proceded from the crowns of the plant. The old fall roots as a rule do not continue active growth in the spring, but subsequent spring root development continues from the crown of the plant. 3. Winterkilling did not occur, as a rule, from the fracturing of the roots, but because of the fact that the plants were raised out of the soil. As a result of this raising of the plant, death resulted through desiccation. This is an important factor in the late dates of seeding. If the spring season is humid, the dislodged plants may form new roots and become reestablished in the soil and continue growth. 4. Plants grown in soil, with 10% moisture content lived through the winter better and recovered better in the spring than did plants grown in soil having 25 to 30% moisture content. 5. Grain yields for the three years, 1922 to 1924 inclusive, are directly correlated with the amount of winterkilling. A low percentage stand of plants in the spring and also grain yield are not always indicative of high percentage of winterkilling. Especially is this true for the late seedings, namely, October 5 and October 19. It is on these late seeding dates that the greatest "heaving" of plants results which leads to plant desiccation. Therefore, death of plants in many of these instances is due to spring desiccation and not to actual winterkilling.