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Mechanical Impedance and corn Seedling Root Growth¹

ABSTRACT

Using needle penetration and bulk density as measures of mechanical impedance, the effects of mechanical impedance on corn seedling root growth were studied in the laboratory. The corn seedlings were grown in artificially compacted samples of a Colo clay where the moisture was at a tension of 10 cm. in some samples and 100 cm. in others. The rate of corn seedling root elongation decreased linearly as bulk ensity of Colo clay increased from 0.94 g. per cc. to 1.30 g. per cc., or as needle penetration into the Colo clay decreased. In ohter laboratory experiments, the depth of corn seedling root penetration into sand contained in glass tubes of differing diameters was found to be linearly related to the depth of penetrometer penetration.

¹ Journal Paper No. J-4142 of the Iowa Agr. and Home Econ. Exp. Sta., Ames, Project No. 1235. This investigation was supported in part by consolidated Hatch Act Regional Project NC-17.

² Formerly Research Associate in Soils, Iowa State University, Ames, now Assistant Prfessor of Agronomy, Univesity of ARkansas, Fayetteville; and Professor of Soils and Physics, Iowa State University, Ames, respectively.

Received for publication June 21, 1961. Accepted for publication January 9, 1962.