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ABSTRACT
A nonporous wax surface crust technique was devised to study seedling emergence of wheat, grain sorghum, and guar. Emergence through crusts with wax penetration numbers ranging from 15 to 80 was evaluated using crust thicknesses of
,
, and 1 inch.
Seedling emergence of wheat, grain sorghum, and guar was affected by hardness and by thickness of crusts. A curvilinear relationship existed between seedling emergence and crust hardness. No emergence occurred in any of the 3 plant species when the wax penetration number was 27.0 or less. There was no difference between species in this critical wax penetration number. As crust thickness increased, higher wax penetration, i.e., softer waxes, were required before any seedling emergence occurred.
1 Contribution from the Soil and Water Conservation Research Division, ARS, USDA, in cooperation with the Texas Agr. Exp. Sta.
2 Research Soil Scientist (Physics), Southern Plains Branch, Soil and Water Conservation Research Division, ARS, USDA, Southwestern Great Plains Field Station, Bushland, Tex.
Received for publication December 19, 1961. Accepted for publication February 27, 1962.
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