The advent of reliable, cost-efficient, and operationally simple zero-tillage planting systems in the 1980s incentivized Southern row crop producers to adopt soil- and water-protective conservation practices following 150 years of clean-cultivated intensive cropping. Sloping topography and erosion-prone, acidic soils developed in the residuum of schist, gneiss, and granite are common geomorphic features of the North Carolina Piedmont. Exhausted mineral soil, combined with seasonal rainfall arriving mainly as intermittent showers interrupted by dry periods lasting from 1 to 2 weeks, pose challenging situations for annual rain-fed row crops like corn and soybean. Never the less, productivity gains have been realized from conservation practices that reduce or eliminate tillage and preserve land cover via crop and cover crop residues. The principal reasons cited for this are more efficient capture, utilization, and profile storage of available moisture, along with tillage cost savings.

The objectives of this research funded by the Soybean Growers Association of North Carolina were to (1) characterize the distribution of soil water with respect to tillage, traffic pattern, and depth in the prime soybean (and corn) rooting zone in two Piedmont Ultisols; and (2) assess the long-term consequences of conservation and conventional planting systems on management-sensitive soil properties and their relationship to soybean productivity. We used relatively new technologies like the multi-depth capacitance probe for measuring profile soil moisture; the multiple-probe soil cone penetrometer; soil sampling equipment designed to extract a relatively undisturbed subsoil core; and proximate remote sensing (scanning lidar, ground penetrating radar, and electromagnetic induction measurement of soil apparent electrical conductivity [ECa]) to characterize profile soil properties.

Two, long-term tillage trials, both on Typic Kanhupludults, at the Upper Piedmont Research Station near Reidsville, North Carolina were the foundation for these investigations. Both trials are randomized complete block experiments in a corn-soybean rotation with controlled traffic, described here. Project leaders: Jeffrey G. White, Robert D. Walters, Alan D. Meijer, Joshua L. Heitman, Adam M. Howard, Robert Austin.

 

Special thanks to Wesley Tuttle, USDA-NRCS geophysicist, for assistance in conducting the geophysical surveys. We also thank Joe French, Superintendent, Upper Piedmont Research Station; and Larry Shough, Auman French, Darryl Ellington and the UPRS field crew who never let us down.