Submitted to: Encyclopedia of Soil Science
Publication Type: Literature Review
Publication Acceptance Date: June 4, 2001
Publication Date: N/A
Technical Abstract: In temperate regions, the average temperature of the soil profile warms from winter minimums to summer maximums as the growing season progresses. At the time of planting for most summer annual crops, a temperature gradient has developed in the soil profile with temperature decreasing with depth. As the soil surface absorbs thermal energy throughout the growing season, progressively deeper soil layers become warmer. Because temperature influences a wide variety of plant functions, it is not surprising that soil temperature affects root growth in many ways and that expansion of crop root systems in temperate regions is limited by cool soil temperatures. Root system expansion is a function of three temperature dependent processes: growth, development, and orientation. Temperature affects root growth through its influence on root weight, root length, and root diameter. Root development is affected by temperature's effect on root initiation and root turnover. Lastly, temperature controls root orientation through its impact on the direction of root growth and the gravitropic response.