Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/30/1995
Publication Date: N/A
Technical Abstract: Corn (Zea mays L.) grown on a fine sand soil under irrigated ridge tillage has a shallow root system. Approximately 80 percent of the roots occur within the top 0.3 m of soil while less than 10 percent of the roots extend below 0.6 m. The objective of this study was to determine which physical factors limited root growth. It is proposed that this shallow rooting pattern is a result of a tillage pan. A zone of compaction occurs within the 0.15 to 0.45 m depths. High bulk densities (1.55 Mg/m**3) and slower saturated hydraulic conductivities (12.5 cm/h) characterize the compacted layer. Cone penetration resistance within the compacted zone, whether wet (17 percent v/v) or moderately dry (13 percent v/v), exceeded 3 MPa, which is suggested as the threshold for impedance of corn root elongation. Mechanical impedance was more important in limiting root growth in this soil than water content.