Fellow: Yangbo He
Advisor: Thomas DeSutter, Ph.D., Assistant Professor, Department of Soil Science, North Dakota State University.
Degree Progress: Ph.D. in Soil Science, expected graduation in Fall 2014.

Many soils in ND are being drained through the use of subsurface tiles. The purpose of subsurface drainage is to 1) decrease excess soil water, specifically at times of planting and harvesting and 2) remove soluble salts from the root zone (Chatterjee and DeSutter, 2012; Franzen, 2007). However, as noted by Cihacek et al. (2012), many soils may be negatively impacted because sodium is part of the exchange complex. Sodium is known a dispersant and this dispersion is accelerated when the concentration of soluble salts is reduced, which will likely occur in tile-drained soils (Cihacek et al., 2012; Curtin et al., 1994a). Dispersion can lead to decreased Ksat, water percolation, and increased runoff, and finally decrease drainage performance. Currently, there are no management strategies that have been developed for ND to help combat the effects of dispersion or to prevent dispersion from occurring within tile-drained soils.

Project Objectives:

The main objective of this study is to characterization sodic soils and produce management guidelines for sodic soils that have been tile drained. The specific objectives include:

• Determine physical and chemical properties (Ksat, dispersion, swelling, and pore volumes of water) of sodic soils from that have the potential to be subsurface drained
• Develop laboratory and simulation experiments (equations and computer-based models) to determine calcium requirements for remediation of sodic soils within tile drained soils.

Progress:

Investigation of how pure clay minerals react (disperse or flocculate) under different sodicity and salinity levels was finished this past summer. For the project for which I got funding, soil samples have been collected, air-dried, and ground, but laboratory assessment and computer modeling have yet to be completed.

Significance:

Excessive levels of salts occur in large areas around the world and profoundly affect land use. Usually, these problematic soils are defined into two major types, namely, saline and sodic soils. When saline soils are dominated by sodium salts, soils are termed “sodic.” Estimates of the globe that are covered by sodium-affected soils are about 581.0 million ha, which occupy a large proportion of a total 932.2 million ha of salt-affected soils (Szabolcs, 1989; Sumner and Naidu, 1998). Sodic soils occur in many areas of Northern Great Plains, and in North Dakota, about 4.7 million acres are negatively affected by sodium (Brennan, Personal communication, North Dakota USDA-NRCS, 2008). One of the main concerns that NDSU soil scientists have about the draining of these sodium-affected soils is the potential of decreased soil water hydraulic conductivity (Ksat) due to the factors that control soil swelling and dispersion: (1) sodium on the exchange sites and (2) decreased electrical conductivity (EC) of the soil solution due to drainage. This concern has resulted in the publication of a tile-drainage Extension bulletin by Cihacek et al. (2012) so that tile-drainage installers and landowners can become more aware of this concern and have a tool by which they can learn more about their soils. However, this publication only addresses the soils that might be affected and does not inform landowners of how to manage, in particular, sodium-affected soils.

Publications:

     He, Y., T.M. DeSutter, D. Hopkins, D. Wysocki, and D. E. Clay. 2014. The relationship between SAR1:5 and SARe of soil to water extract. Soil Sci. Soc. Am. J. (Submitted).

     He, Y., T. DeSutter, L. Cihacek, D. Clay, F. Casey, D. Franzen, S. Clay, and D. Steele. 2014. Behaviors of Na-affected soils: implications for subsurface drainage. Land Degradation & Development (In preparation).

Conference/Presentation:

     He, Y., T. DeSutter, L. Cihacek, D. Clay, F. Casey, D. Franzen, S. Clay, and D. Steele. Behaviors of Na-affected soils: implications for subsurface drainage. ASA, CSSA, &SSSA International Meeting, Nov. 2-5, 2014, Long Beach, CA. (Abstract submitted).

     He, Y., and T. DeSutter. Advances in our knowledge of dispersion and swelling with soil sodium and the interaction of sodium chemistry with soluble salts. Soil and Soil/Water Training, Jan. 22, 2014, Fargo, ND.

     DeSutter, T., and Y. He. Chemistry of sodium-affected soils. Presented at the What is Successful Reclamation? Second annual North Dakota Reclamation Conference. February 24 and 25, 2014, Dickinson, ND.