Soil Moisture Studies in the Mississippi Delta Kristofor R. Brye University of Arkansas Edgar Mersiovsky USDA-NRCS

Background Initial Problem Some soils in MLRA 131A (Southern Mississippi River Alluvium) had interpretations of seasonal water tables, as inferred by depth to RMFs, between 0.4 and 1.1 m from the soil surface during wet seasons Assumed to be the result of Alluvial Aquifer fluctuations  Alluvial Aquifer level confirmed to be decreasing due to extensive agricultural irrigation withdrawals  Many soils have also been artificially drained by constructed ditches  Regional hydrology has likely changed

Previous Work Cooperative Agreement “Seasonal Saturation in the Dundee Soils in the Lower Mississippi Valley” by E. Mersiovsky, P. Owens, E. Rutledge, and L. West 2004 to 2008 Phase I Dundee soils Many have been drained as well Typic Endoaqualfs  Very deep, somewhat poorly drained soils that formed in loamy alluvium  Level to gently sloping soils on natural levees and low terraces

Previous Work Dundee Water Table Study 16 sites from NE AR to S LA 24 to 58 months Pedons described Piezometers installed Above Bt (~30 cm depth) Within Bt (~75 cm depth) Below Bt (~190 cm depth)  Outfitted with electronic water-level sensors IRIS tubes installed at select sites Evaluate degree of Fe reduction

Previous Work Dundee Water Table Study (Phase I) Results No water table within < 2 m at 6 of 16 sites Seasonal water table observed within < 2 m at 9 of 16 sites  Minimum depth was typically > 1 m Water table observed within < 1 m at 2 of 16 sites  Only temporary At only 1 of 16 sites, water table rose from > 2 m to the soil surface each wet season monitored Conclusion Seasonal water tables are likely deeper than present interpretations indicate Recommendation Establish a drained phase for Dundee soils in MLRA 131A to recognize deeper water tables  Conversion should made on a site-by-site basis Implication Will loosen current soil-use limitations due to high water tables

Current Work Phase II Cooperative Agreement “Evaluation of Contemporary Water Tables in Select Soils of MLRA 131A in the Lower Mississippi River Valley” by K.R. Brye October 1, 2011 to September 30, 2014 (extended to Sept. 30, 2015) Objective To monitor contemporary seasonal water table fluctuations in select loamy soils on a similar geomorphic surface throughout MLRA 131A in the LMRV Difference from Phase I study Target a slightly lower, younger surface Commerce soils targeted  Fluvaquentic Endoaquepts  Deep, somewhat poorly drained, moderately slowly permeable soils that formed in loamy sediments on level to undulating alluvial plains  No argillic

Current Work Phase II Water Table Study 10 sites from NW TN to S LA 24 + mo monitoring planned  Lauderdale County, TN (2)  Phillips County, AR (2)  Washington County, MS (1)  Sharkey County, MS (1)  Madison Parrish, LA (1)  Pointe Coupee Parrish, LA (2)  W. Baton Rouge Parrish, LA (1) Pedons described PSA analysis conducted on profile samples from 7 of 10 sites Piezometers installed ~40 cm depth ~230 cm depth  Outfitted with electronic water-level sensors * Phase II sites * * * * * * *

Current Work Sites Lauderdale County, TN Two (2) sites Mixed, deciduous hardwoods adjacent to cultivated cropland Shallow (1) and deep (1) Phillips County, AR Two (2) sites Bottomland hardwood forest Shallow (1) and deep (1) Washington County, MS One (1) site Pecan grove Shallow (1), intermediate (1), and deep (1)

Current Work Sites Sharkey County, MS One (1) site Pecan grove Shallow (1), intermediate (1), and deep (1) Madison Parrish, LA One (1) site Mixed, deciduous hardwoods Shallow (1) and deep (1) West Baton Rouge Parrish, LA One (1) site Periodically mowed grassland Shallow (1) and deep (1)

Current Work Sites Pointe Coupee Parrish, LA Two (2) sites Hayed grassland  Shallow (1), intermediate (1), and deep (1) Periodically grazed pasture  Shallow (1) and deep (1)

Cooperators Questions? NRCS scientists and staff from TN, AR, MS, and LA