**12. Soils and soilscapes**

withdrawal in southeastern Missouri. These alluvial materials were largely deposited by the ancestral Mississippi and Ohio River systems, coupled some prominent deposits by the Black, St. Francois, and Little River systems. Alluvial thickness is variable, with typical thicknesses west of Crowley's Ridge ranging from 15 to 45 m, whereas the alluvial thicknesses in Mississippi, Pemiscot, and Dunklin Counties average 76 m. These unconfined aquifers are baseflow recharged annually from the Mississippi River, other prominent rivers and land drainage

tions do occur between wet and dry seasons, no long-term depletions have been observed [18].

The study area is extensively irrigated, with many counties having center pivot, furrow and flood irrigation covering 60–70% of the landscape. Ten wells operated and continuously monitored by the United States Geological Survey (USGS) are located across the survey area [19], which sample groundwater associated in the unconfined surficial (alluvial) aquifers. The

For example, in the community of Delta, Missouri, the USGS water level monitoring well continuously documented well water levels centered around 5–7 m below the land surface (**Figure 2**). During very dry summers, the water levels subsided to approximately 8 m and then the water levels rebounded during the winter/spring season to approximately 4.6 m from the surface. In each year and for each of the test wells, the wetter winter/spring season permit-

**11. Observations of water levels in test wells in Southeastern** 

; however, although water level fluctua-

ditches. Water yield ranges from 3800 to 11,360 L min−<sup>1</sup>

160 Wetlands Management - Assessing Risk and Sustainable Solutions

depth to the mean water table ranges from 1 to 8 m.

ted aquifer recharge because of rainfall infiltration and baseflow.

**Figure 2.** Water depth levels for the Delta Missouri USGS monitoring well from 2000 to 2018 [19].

**Missouri**

In the study area, presentative soil orders (US Soil Taxonomy) include: Alfisols, Entisols, Histosols, Inceptisols, Mollisols, and Vertisols. Landforms include: alluvial fans, splays, flood plains and backswamp deposits, ox-bows and meander channels, Holocene and Pleistocene terraces of coarse to fine-silty textures, and modern to old natural levees and constructed levees. A great portion of the landscape has been recently land-graded for furrow and flood irrigation.

For example, the Cooter-Hayti-Portageville Soil Association rests on Holocene sediment having a transitional texture from sandy alluvium to silty-loamy alluvium to clayey alluvium (**Figure 3**). The poorly drained Portageville clay series (Vertic Endoaquolls: Ap/A–Bg–Cg) exhibits soil organic matter accumulation and soil profile depletion of Fe attributed to anaerobic conditions, whereas the Cooter (Fluvaquentic Hapludolls: Ap/A-2C1-2C2) is a bisequal soil (clayey over sandy) featuring few subsurface redoximorphic features because of the quartz parent material. The fine-silty, poorly drained, non-acid Hayti series (Mollic Fluvaquents: Ap-C) developed in recent silty alluvium lacks soil profile development because of the lack of time for soil profile horizonation.

The Memphis-Loring-Calhoun-Foley Association rests in the Advance Lowlands (also called the Western Morehouse Lowlands) with the fine-silty, deep, strongly acid, well-drained

**Figure 3.** The Cooter-Hayti-Portageville Association.

Memphis (Typic Hapludalfs: A-E-Bt-C) resting in thick loess on Crowley's Ridge (**Figure 4**). The fine-silty, strongly acid, moderately well-drained Loring series (Oxyaquic Fragiudalfs: A-Bt-Btx-C) possesses a well-developed fragipan whose surface represents a transition from Pleistocene silty alluvium to the overlying loess. The poorly drained, fine-silty Calhoun (Glossaqualfs (Ap-Ed-Btg-BCg) and Foley (Natraqualfs: Ap-Eg-Btng/E-Cg) series rest on Pleistocene terraces and may have thin loess mantles. The presence of argillic horizons in these soils indicate their relative more mature age when compared with the previous Holocene soils.

The Sharkey-Alligator Association is a commonly occurring association in the Morehouse lowlands (**Figure 5**). The soils of the Sharkey series consist of very deep, poorly and very poorly drained, very slowly permeable soils formed on level to nearly level backswamp positions along modern and former channels of the Mississippi River. The Alligator series consists of very deep, poorly drained, very slowly permeable soils formed in clayey alluvium in backswamps and sloughs.

The very-fine textured Sharkey soils (very-fine, smectitic, thermic Chromic Epiaquerts) have an Ap - Bssg - Bssyg - Bssg soil horizon sequence. The soil colors range from dark and very dark grayish brown in the silty clay to clayey Ap soil horizon to dark gray and gray in the clayey cambic horizon. The near surface horizons are slightly acid to neutral and deeper soil

horizons are neutral to moderately alkaline. The cation exchange capacity (CEC) is generally high, attributed to the abundance of smectic clay. The soils of the very-fine Alligator series (very-fine, smectitic, superactive, thermic Chromic Dystraquerts) present an A - Bg - Bssg - Bssycg soil horizon sequence, with all horizons having a clayey texture. These soil horizons are commonly very strongly acid. The grayish brown Bssg and Bssycg horizons have coarse wedge-shaped structures with grooved slickensides on their surfaces. The CEC is generally

A Large-Scale Wetland Conversion Project in Southeastern Missouri: Sustainability of Water and Soil

http://dx.doi.org/10.5772/intechopen.81254

163

With the advent and continued maintenance of the Little River Drainage Project the region's hydrologic conditions have been irreversibly altered towards achieving agricultural productivity [20]. Because the Little River Drainage System and its extensions are relatively new and given that soil changes are a function of time and no previous soil baseline data exists prior to land drainage, it is difficult to quantify soil changes because of regional land drainage. Yet soil evolution has been altered and the expected macro-soil changes likely include: (i) loss of accumulated soil organic matter because of oxic soil conditions, (ii) soil acidification coupled with nutrient leaching, (iii) deeper soil water tables resulting in fewer near-surface alternating episodes of soil oxidation-reduction, (iv) loss of soil structure attributed to tillage, land grading, and loss of soil organic matter, (v) changes in the microbial communities, (vi) changes in the invertebrate and vertebrate populations, and (vii) acceleration of mineral weathering intensities, particularly alteration of smectites to kaolinite and apatite dissolution. Because of agriculture, fertilization practices have increased the phosphorus and potas-

high, attributed to the abundance of smectite clay.

**Figure 5.** The Sharkey-Alligator Association.

sium soil test values.

**Figure 4.** The Memphis-Loring-Calhoun-Foley Association.

**Figure 5.** The Sharkey-Alligator Association.

**Figure 4.** The Memphis-Loring-Calhoun-Foley Association.

swamps and sloughs.

162 Wetlands Management - Assessing Risk and Sustainable Solutions

Memphis (Typic Hapludalfs: A-E-Bt-C) resting in thick loess on Crowley's Ridge (**Figure 4**). The fine-silty, strongly acid, moderately well-drained Loring series (Oxyaquic Fragiudalfs: A-Bt-Btx-C) possesses a well-developed fragipan whose surface represents a transition from Pleistocene silty alluvium to the overlying loess. The poorly drained, fine-silty Calhoun (Glossaqualfs (Ap-Ed-Btg-BCg) and Foley (Natraqualfs: Ap-Eg-Btng/E-Cg) series rest on Pleistocene terraces and may have thin loess mantles. The presence of argillic horizons in these soils indicate their relative more mature age when compared with the previous Holocene soils. The Sharkey-Alligator Association is a commonly occurring association in the Morehouse lowlands (**Figure 5**). The soils of the Sharkey series consist of very deep, poorly and very poorly drained, very slowly permeable soils formed on level to nearly level backswamp positions along modern and former channels of the Mississippi River. The Alligator series consists of very deep, poorly drained, very slowly permeable soils formed in clayey alluvium in back-

The very-fine textured Sharkey soils (very-fine, smectitic, thermic Chromic Epiaquerts) have an Ap - Bssg - Bssyg - Bssg soil horizon sequence. The soil colors range from dark and very dark grayish brown in the silty clay to clayey Ap soil horizon to dark gray and gray in the clayey cambic horizon. The near surface horizons are slightly acid to neutral and deeper soil

> horizons are neutral to moderately alkaline. The cation exchange capacity (CEC) is generally high, attributed to the abundance of smectic clay. The soils of the very-fine Alligator series (very-fine, smectitic, superactive, thermic Chromic Dystraquerts) present an A - Bg - Bssg - Bssycg soil horizon sequence, with all horizons having a clayey texture. These soil horizons are commonly very strongly acid. The grayish brown Bssg and Bssycg horizons have coarse wedge-shaped structures with grooved slickensides on their surfaces. The CEC is generally high, attributed to the abundance of smectite clay.

> With the advent and continued maintenance of the Little River Drainage Project the region's hydrologic conditions have been irreversibly altered towards achieving agricultural productivity [20]. Because the Little River Drainage System and its extensions are relatively new and given that soil changes are a function of time and no previous soil baseline data exists prior to land drainage, it is difficult to quantify soil changes because of regional land drainage. Yet soil evolution has been altered and the expected macro-soil changes likely include: (i) loss of accumulated soil organic matter because of oxic soil conditions, (ii) soil acidification coupled with nutrient leaching, (iii) deeper soil water tables resulting in fewer near-surface alternating episodes of soil oxidation-reduction, (iv) loss of soil structure attributed to tillage, land grading, and loss of soil organic matter, (v) changes in the microbial communities, (vi) changes in the invertebrate and vertebrate populations, and (vii) acceleration of mineral weathering intensities, particularly alteration of smectites to kaolinite and apatite dissolution. Because of agriculture, fertilization practices have increased the phosphorus and potassium soil test values.


sustainable and profitable agriculture, while identifying farming practices that are wetland suitable, even when the wetland has been altered by previous land drainage projects. A corollary is attempting to identify wetland benefits and reinstitute practices to return or augment wetland benefits to these altered landscapes while preserving agriculture productivity. One key initiative includes "soil health". Soil health (soil quality) is defined as the continued capacity of soil to function as a vital living ecosystem that sustains plants, vertebrate and invertebrate animals, microorganisms, and humans [22]. This definition speaks to the importance of managing soils to optimize living organisms that contribute to maintaining soil structure, soil organic matter, and functioning nutrient soil and plant connectivity. Considering soil as a living ecosystem reflects a fundamental thinking shift towards nutrient management for plant growth, supporting the soils ability to absorb and hold rainwater for use during dryer periods, filter and buffer potential pollutants from leaving fields, and provide habitat for soil microbes to flourish and diversify. This website [22] provides an annotated bibliography with citations of current literature on soil health initiatives that support water availability, soil structure improvement, soil organic matter optimization (including promotion of active carbon contents), nutrient availability, and limited nutrient transport of nutrients from farm fields to fresh water resources.

A Large-Scale Wetland Conversion Project in Southeastern Missouri: Sustainability of Water and Soil

http://dx.doi.org/10.5772/intechopen.81254

165

A key land practice associated with soil health is the establishment of cover crops. We define cover crops as grasses and legumes cultivated to provide cropland vegetative cover during the off-season to support soil carbon accumulation, improved soil structure (including reduced soil compaction), improved water availability, and substantial reduction is both water and wind induced soil erosion. Our cover crop programs frequently rely on establishment cereal rye (*Secale cereale* L.), crimson clover (*Trifolium incarnatum* L.), and canola (*Brassica napus* L); however, many producers and extension services support other plant compositions. In early spring, the cover crops will receive chemical burndown with the new crop established with a

USA has established the Mississippi River Basin Healthy Watersheds initiative across 13 USA states [21] to limit the Mississippi River's nutrient and sediment loads. The initiative supports direct payments to agriculture producers to establish erosion and nutrient migration mitigation, primarily through the Environmental Quality Incentives Program (EQIP) and the Agriculture Conservation Easement Program (ACEP). Nutrient reduction strategies are tailored to individual states. Wetland restoration is a key and central provision wherein mar-

Southeast Missouri State University and the United States Department of Agriculture—Natural Resources Conservation Service have partnered to address nutrient transport from production agriculture. The development of Edge of Field Technologies is gaining producer acceptance and has witnessed the establishment of denitrification bioreactors to intercept tile drainage

trification bioreactor at the David M. Barton Agriculture Research Center effectively reduced

[23]. Currently, Southeast Missouri State University and the United States Department of Agriculture—Agriculture Research Service has been active in pumping nitrate and phosphate bearing tile drainage effluent into off season water retention basins to reapply the water as an irrigated source during the growing season. The goal is to reduce aquifer depletion. This

NO<sup>3</sup>



 NO<sup>3</sup> -N

no-till grain drill/planter into the existing cover crop residue.

ginal land is returned to a wetland status.

effluent to render the effluent comparatively free of NO3

nitrate-N concentrations from between 10 and 100 mg L−<sup>1</sup>

CEC is cation exchange capacity (cmol kg−<sup>1</sup> ); SOM is soil organic matter (%).

Btg – argillic horizon (Bt) that is gleied (g or low chroma colors).

Btgn – Btg horizpon that has natric characteristics (high exchange sodium percentage (ESP).

**Table 1.** The essential properties of the Overcup soil series in an old growth natural forest.

All soil evolution is a complex interplay between horizonation (development of diagnostic soil horizons) and haploidization (the phenomena of organisms and vegetation altering the soil profile to reduce the expression of soil horizons). Land drainage should support the intensity of soil processes to create and maintain soil horizons, particularly albic and argillic horizons. Conversely, loss of soil organic matter will alter mollic (high base saturation and high soil organic matter) and umbric (low base saturation and high soil organic matter) epipedons to orchric (low organic matter) epipedons. Wetlands are commonly acknowledged to purify surface waters and facilitate surface water transfer to shallow aquifers. There is growing concern that land drainage and the associated agriculture will promote nutrient migration and support fresh water eutrophication. Installed levees prevent river flooding in selected areas, leading to greater flooding elsewhere on lands not levee protected. Irrigation may lead to aquifer overdraft; however, this issue is not apparent in this study area.

For example, the Overcup soil series from the Advance Lowlands (fine, smectitic, thermic Vertic Albaqualfs) are very deep, poorly drained, very slowly permeable soils that formed in alluvium. Soil analysis by the authors of the Overcup soil series in both long-term deciduous forest settings and modern rice production fields (unpublished) demonstrate that considerable soil organic matter contents are evident in the forest settings (**Table 1**), whereas the production fields have diminished near-surface soil organic matter contents. The Overcup soil series shows considerable gray color patterns because of seasonal or fluctuating soil water tables within the solum. Soil acidification is evident in the upper argillic horizon, a feature attributed to base removal by leaching. The lower argillic horizon shows a neutral to alkaline pH with a considerable exchangeable sodium presence because restricted drainage has not permitted base leaching, especially including exchangeable sodium. Thus, the placement of cover crops in rice production fields should re-establish soil organic matter contents in the near-surface soil horizons.
