Cotton and Soybean Root System Growth in Three Soil Temperature Regimes
- William L. Bland
Exploration of the soil by roots has significant implication for both plant growth and soil water dynamics. The important environmental determinants of root growth are identified, but an integrated and quantitative understanding of their relative importance through a range of environments is not yet available. The role of seasonal patterns of soil temperature on root system development throughout a crop's life was studied in controlled-environment experiments. Cotton, then soybean, was grown in 1.8-m deep controlled-temperature rhizotrons. Three soil temperature regimes were replicated three times for each species. In all treatments of an experiment, the near-surface (0 to 15 cm) temperature were equal, to promote similar aboveground growth. This near-surface temperature was increased during the experiment so as to mimic field conditions typical for each species. One treatment was isothermal with depth, the entire soil column warming the same as the surface. A pattern of subsoil warming similar to that found in regions where the crop is grown was the second treatment, and the third set of columns warmed at roughly one-half the rate of the second treatment. Rate of downward growth of root systems of both crops increased with the rate at which the soil body warmed. Cotton roots grew downward at 1.7, 1.4, and 0.7 cm d−1 in the treatments used for that study; soybean rooting depth increased at 2.6, 1.2, and 0.9 cm d−1. Results supported the hypothesis that root system growth can be predicted from the local soil temperature of the deepest roots and the temperature-dependent extension rate of seedling roots.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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