Effects of Subsurface Asphalt Layers on Corn and Tomato Root Systems1
- G. K. Saxena,
- L. C. Hammond and
- W. K. Robertson2
In recent years several reports have indicated an improved crop production on droughty sands treated with a subsurface asphalt layer at depths of about 60 cm. Root growth in these modified soil profiles has not been investigated. This study was initiated to determine the nature and reason of any influence of a subsurface asphalt layer on root growth and distribution in the soil profile.
Observations of root distributions of sweet corn (Zea mays L. var. ‘Rugosa’) and tomato (Lycopersicon esculentum Mill. var. ‘Commune’) were made in freshly dug pits. Root sections in and out of the asphalt layer were photographed and examined microscopically for morphological effects. The “line-intercept” method was used to obtain quantitative measurements of root concentration (cm root/cc soil) of field corn (Zea mays L).
Tomato roots in the asphalt layer were larger in diameter and showed damage to cells in the cortex. Rooting of all crops was less extensive in soil below the asphalt layer than in soil at the same depth without the asphalt. Concentration of corn roots in the top 60 cm of soil averaged 1.6, 1.7, 2.0, and 2.2 cm/cc for the following respective treatments: control, control with irrigation, asphalt layer, and asphalt layer with irrigation. This compensation effect would limit any reduction in value of the root-resistant asphalt layer to situations of low rainfall without irrigation.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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