|Laboski, C.A.M. - UNIVERSITY OF MINNESOTA|
|Lamb, J. - UNIVERSITY OF MINNESOTA|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 10, 1998
Publication Date: N/A
Interpretive Summary: Protection of ground water quality in production agriculture depends upon the effectiveness of the plant root system to intercept applied plant nutrients. To address this problem, we must know how root distributions are affected by soil density and strength. Corn root distributions, soil penetration resistance, and soil bulk density were measured in the field at tour large Management Systems Evaluation Area (MSEA), water quality researc site. It was discovered that high soil strength below six (6) inches was restricting root growth greatly, with 85 percent of all roots occuring in the surface, 6 inches of soil. Chiseling to a 12-inch depth under the row enhance root penetration into deeper soil layers. This knowledge will be used by consultants, farmers, and farm planners developing tillage recommendations for sustained crop production with adequate protection of ground water quality.
Technical Abstract: Initial observations of corn (Zea mays L.) rooting at the Minnesota Management Systems Evaluation Area on a fine sand soil suggested a shallow rooting pattern. Since root distribution influences where and how much water and nutrients the plant will absorb, it is essential to know why root growth was limited. The objective of this study was to determine the factor(s) limiting rooting depth of corn grown on an irrigated fine sand soil. Chisel, non-chisel, deep chisel, and non-irrigated (disked) treatments were used to assess the effects of chiseling and irrigation. Soil resistance to cone penetration was measured to determine soil strength. Roots were sampled at the tasseling to examine the greatest extent of the root system. Undisturbed soil cores were used to determine saturated hydraulic conductivity, water release characteristic, and bulk density. Cone penetrometer readings greater than 3 MPa indicated a high strength layer in the 15- to 40-cm layer, which coincided with a high bulk density up to 1.58 Mg m-3 in the 15 to 60 cm layer. Approximately 85 percent of all roots in the non-chisel treatment occurred within the upper 30 cm of soil; while only 62 percent of all roots were in the 0- to 30-cm layer of the deep chisel (30 cm) treatment. Deep chiseling significantly decreased soil strength for at least 6 weeks and allowed roots to grow within the former high strength region. Root distributions in both irrigated and non-irrigated areas were controlled by the high strength/bulk density layer in this soil. Soil water was ample throughout the growing season to support crop growth. It was concluded that high soil strength (> 3 MPa) and bulk density were the main factors limiting corn root growth in this soil.