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ABSTRACT
The level of CO2 and of subsoil density were varied in a growth chamber study of the interaction of these two factors on root growth of cotton seedlings at constant O2 concentration. At very low density root elongation rate decreased progressively with increasing CO2, although moderate to good growth occurred even at 24% CO2, the highest concentration used. At higher subsoil level densities, CO2 had little effect on root penetration. Retardation by CO2 was somewhat more severe for roots growing into solution culture than for those growing into loose subsoil, indicating that application of results of aeration experiments in nutrient solution to soils should be made with caution. Results suggest that in well-drained, medium-to-coarse-textured soils such as the Norfolk, CO2 will seldom be a limiting factor for root growth even in compacted zones near the surface. The mechanical impedance of such zones, will definitely restrict root penetration and proliferation in subsoils.
1 Contribution from the Department of Agronomy and Soils, Auburn University, and the Soil and Water Conservation Research Division, ARS, USDA. Part of a dissertation submitted by the senior author in partial fulfillment of requirements for the Ph.D. degree. Presented before Div. S-1, Soil Sci. Soc. Am., Nov. 18–21, 1963, Denver, Colo.
2 Research Soil Scientists, USDA, Temple, Texas and Auburn, Alabama, respectively. Senior author was formerly National Defense Fellow, School of Agriculture, Auburn University.
Received for publication January 3, 1964. Accepted for publication July 8, 1964.
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