Most Delta soils are derived from alluvium of the present Mississippi River and tributaries and ancient rivers. Delta soils in SE Missouri, NW Tennessee, and NE Arkansas are generally high in phosphous and low in potassium. Without proper liming, they tend to become strongly acid. Soil organic matter content is usually below 2 percent. Climate is normally favorable for crop production with 3 to 4 inches of precipitation monthly during the growing season. However, summer droughts are common. With proper surface drainage, corn and soybean can be planted on most soils in the region. Because rice is flooded, it is usually planted on poorly-drained soils which will retain water with clay either in the surface or subsoil horizons. On the west side of Crowley's Ridge rice is often grown on soils with silt loam top soil and clay subsoil. On the east side of Crowley's Ridge, rice is often planted on Sharkey clay soil. The highest cotton yields are usually produced on well-drained silt loam and sandy loam soils.

Compaction. Many Delta fields have a compacted layer called a traffic or plow pan located 6 to 18 inches below the surface. Sometimes deep tillage is used to penetrate the pan and allow roots to grow into the subsoil horizons. Typically, the greatest yield response occurs on sandy soils. A soybean field experiment was conducted from 1999 through 2001 to evaluate the effects of compaction on soil physical properties and evaluate tillage equipment on Malden fine sand, Tiptonville silt loam and Sharkey clay soils.  Experiments were conducted at Portageville and Clarkton, Missouri. In a test comparing types of tillage equipment, treatments included no-till, paraplow, chisel, and parabolic sub-soiling systems.  On the Malden fine sand soil, soybean yields were increased by deep tillage on average 8 bushels per acre by parabolic sub-soiling followed by disking and do-alling. When sub-soiling was done without disking afterwards, the seedbed was often very rough and caused problems getting a good stand of soybeans.

Cone pentrometer used to measure subsurface compaction.

In 2000 and 2001, a corn deep tillage experiment was conducted at Portageville on a Reelfoot fine sandy loam. Artificial compaction was applied with a heavy roller when the field was wet to simulate the effects of large farm equipment. A parabolic sub-soiler was used with and without chicken manure to remediate the effects of compaction. On average subsoiling increased corn yields 30 bushels in 2000 and 52 bushels in 2001.  This research was publish in Soil and Tillage Research 71:121-131  REQUEST REPRINT

Soil Variability. The effects of the 1811-12 earthquakes along the New Madrid Fault can still be observed in crop fields today. The most significant soil features for farmers are sand vents shown in the photo on the right. These occurred as downward pressure from shaking caused the wet sand deep in the soil to spew up in small sand volcanoes. Furrow irrigation is inhibited because water flows into a vent and does not continue down the row middles. For rice and catfish farmers the sand vents make it difficult to flood because the fields often leak water through the vents. Variable rate nitrogen was evaluated in 1999 through 2001 on a cotton field with numerous sand vents. Cotton yields were significantly reduced in sandy zones. These areas also had lower optimum nitrogen rates.  READ MORE.

Three-year cotton yields at Portageville in variable rate cotton test.

Light colored areas in aerial photo are sandy zones resulting from earthquake vents. Narrow horizontal lines were alleys mowed through the cotton before harvesting to divide the field into a matrix of cells. Yellow curvey lines are soil type bonderies.

Soil and Water

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