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This article in SSSAJ

  1. Vol. 38 No. 3, p. 387-390
     
    Received: July 16, 1973
    Published: May, 1974


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doi:10.2136/sssaj1974.03615995003800030009x

Seedling Growth of Sorghum in Clay-Sand Mixtures at Various Compactions and Water Contents1

  1. Delroy L. Hemsath and
  2. Andrew P. Mazurak2

Abstract

Abstract

Mixtures of kaolinite clay and fine sand fraction from Tripp subsoil (Typic Haplustoll) were prepared with 1.0, 3.8, 7.5, 15, and 30% clay. The clay-sand mixtures were compacted into cylinders at bulk densities of 1.00, 1.25, 1.50, and 1.75 g · cm-3. The cores were then subjected to matric suctions of 0.15, 0.33, 1.7, and 8.6 bars.

Penetrometer resistance of the cores increased from 0.25 to 68 kg · cm-2 as the bulk density of clay-sand mixture increased from 1.00 to 1.75 g·cm-3. Matric suction of the clay-sand mixture contributed much to the increased penetrometer resistance with a correlation coefficient of 0.57.

The elongation of sorghum [Sorghum bicolor (L.) Moench] roots in the cores increased as the clay content increased from 1.0 to 7.5% at all bulk densities when the matric suction was <1.7 bar. Further increase in the clay content decreased the root elongation. The largest negative correlation coefficient (r = −0.65) between root elongation and variables studied was with matric suction. It was considered to be the major factor affecting root length. Penetrometer resistance of clay-sand mixture was critical in relating soil physical conditions to root growth. At a penetrometer resistance of 20 kg·cm-2 or greater, no root growth in the clay-sand mixtures was observed.

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