Rooting Density and Water Extraction Patterns for Corn (Zea mays L.)
1973
Taylor, H. M. | Klepper, Betty
Because they occur at greater distances from the plant stem, roots deep within the profile often are considered less effective than those near the soil surface. An experiment was conducted to compare water-absorbing efficiency, per centimeter of root, of corn (Zea mays L.) roots deep in the profile with that of roots near the soil surface. Plants were grown in a rhizotron compartment with rainfall excluded by a metal cover over the soil. Soil water content was determined with a neutron probe; rooting density, from measurements of roots on the glass viewing surface of the compartment. Leaf area was calculated by a length-width method and plant height was measured daily. Stomatal aperture was estimated with a pressure drop promoter twice daily. With few exceptions, soil water content decreased and rooting density increased during the experiment. For the first weeks, transpiration exceeded pan evaporation, but toward the end of the experiment it was about half as much as pan evaporation. Water uptake per centimeter of root was affected most by soil hydraulic, conductivity, and at a given conductivity, it was greater at lower root densities. This effect of root density probably occurred because the roots were younger and more permeable at low root densities than at high root densities. Thus, for the conditions of these experiments, roots deep in the profile were probably more effective per centimeter of root for water uptake than shallow roots because they were younger and were in wetter soil.
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