Submitted to: Intnl Conference On Geospatial Information In Agriculture And Forestry
Publication Type: Proceedings
Publication Acceptance Date: December 15, 2000
Publication Date: January 5, 2000
Citation: Raper, R.L., Schwab, E.B., Dabney, S.M. 2000. Spatial variation of the depth of root-restricting layers in southeastern soils. Second Intnl Conference On Geospatial Information In Agriculture And Forestry. Lake Buena Vista, FL. pp. I-249-256. Interpretive Summary: Hardpan layers found in most Southeastern U. S. soils restrict root growth and limit crop yields. The presence of these root-restricting layers require annual deep tillage to remove their effects and allow proper root growth. Site-specific measurements of the depth of the hardpan layer were made in an upland soil in northern Mississippi with a multiple-probe soil cone penetrometer developed at the USDA-ARS National Soil Dynamics Laboratory. Analysis of the results showed that field traffic moved the depth of the naturally occurring hardpan nearer to the soil surface by almost 2.5 inches. It was also found that due to the nature of the variation of the depth of the root-impeding layer found in this soil, the concept of site-specific tillage might be a feasible option.
Technical Abstract: The root-restricting layers present in most Southeastern soils prevent adequate root growth into the soil profile. Reduced root elongation contributes to temporal drought stress which annually limits yield potential in this region. Many farmers combat this layer of soil by annually subsoiling, usually to a depth of 25-40 cm. However, the depth of this root-restricting layer varies greatly from field to field and also within the field. Knowledge about the variation of the depth of this layer will help to determine if application of a uniform tillage depth is the most effective method of soil compaction amelioration. A tractor-mounted multiple-probe soil cone penetrometer was used to determine the depth of the root-impeding layer in several fields in Alabama and Mississippi. The root-restricting layer was found to vary greatly in most fields. For one field in northern Mississippi, measurements of hardpan depth were found to vary mainly due to traffic effects, but were also found to be sensitive to soil moisture. The depth of hardpan was also found to be somewhat spatially dependent, and the semivariogram was fitted reasonably well by a spherical model. This spatial dependence in the depth of hardpan in this Southeastern field potentially indicates that applying tillage to a uniform depth to an entire field in this region could result in excessive expenditures of tillage energy.