Managing Prior Converted Hydric Soils to Support Agriculture Production and Maintain Ecosystem Services: A Dedicated Outreach to the Agriculture Community

Abstract

Hydric soils and prior converted soils are frequently used for agricultural production. Agriculture production and their associated agribusinesses are the chief economic sector; thus, agriculture is critical for rural prosperity. However, the continuous production of grain crops increases the risk of disease and insect outbreaks, which may lead to soil nutrient exhaustion or substantial usage of annual fertilizer amendments, loss of soil carbon, and soil structure degradation attributed primarily to tillage, decrease in biodiversity, and increased soil compaction. At the David M. Barton Agriculture Research Center at Southeast Missouri State University, our focus has been to support profitable agriculture production and environmental stewardship. We have developed a decade-long research program specializing in subsurface controlled irrigation with the gradual development of edge-of-field technologies. We further developed a constructed wetland to address nutrient pollution concerns with confined feeding operations. Pastures associated with the confined feed facility and the constructed wetland have initiated a soil health program. Our evolution has now permitted the David M. Barton Agriculture Research Center to become a regional center to showcase the relationships that support both profitable agriculture and environmental stewardship.

1. Introduction

Knowledge of water and nutrient flux in wetlands is integral to land management across southeastern Missouri. The region has the largest completed land drainage project in the USA [1]. The Little River Drainage Project converted 1.6 million ha (4 million acres) of marshlands into productive croplands. The economic development of the region is primarily vested in agriculture; however, the realization that the restoration of ecosystem services is important for water quality, soil health, nutrient management, habitat preservation, and advancing biological diversity is emerging. This vast region currently produces corn (Zea mays), soybeans (Glycine max), wheat (Triticum aestivum), rice (Oryza sativa), cotton (Gossypium hirsutum), and specialty crops. Livestock includes beef (Bos taurus), swine (Sus domesticus), sheep (Ovis aries), and chicken (Gallus gallus domesticus).

Nitrogen migration from croplands supports eutrophication of freshwater resources and results in hypoxia across the Louisiana and Texas continental shelf [2, 3]. Additionally, the United States Environmental Protection Agency established 10 mg NO₃-N L⁻¹ as the nitrate drinking water standard; however, 1.5 mg NO₃-N L⁻¹ may support eutrophication [2]. A significant portion of the Mississippi River nitrate discharge into the Gulf of Mexico is derived from 15 million ha of artificial drainage within the Mississippi River watershed [1, 2]. Aide et al. [3] demonstrated that the nitrate concentrations from tile drainage effluents were a function of rainfall after nitrogen fertilization involving corn. Soil analysis demonstrated that nitrate was effectively leached to the tile-drainage technology.

The objective of this article is to demonstrate how to develop and install infrastructure that supports both production agriculture and environmental stewardship.

2. Research to limit Nitrogen transport from tile-drained agricultural lands

Tile drainage is common across the US corn belt, providing removal of excess water. Much of the drainage is uncontrolled, implying that the producer may not have the capacity to limit the tile drainage. Advantages of tile drainage include: (i) creating soil aeration permitting optimal root and seed respiration; (ii) promoting soil warming, especially in the spring; (iii) timely field operations; and (iv) minimizing nitrogen loss because of denitrification. A key disadvantage of tile drainage is the leaching losses of nitrate and sulfate, which require additional fertilization and threaten water quality [4, 5, 6, 7]. Faust et al. [7] evaluated management practices used in drainage ditches to reduce (i) total suspended solids and (ii) nitrogen and phosphorus concentrations, especially for moderate rainfall intensities.

Agronomic approaches to limiting nitrogen losses from tile-drainage fields include: (i) appropriate the timing and rates of nitrogen fertilizers, (ii) anticipate the nitrogen supply arising from mineralization, (iii) establish appropriate yield goals, (iv) utilize urease and nitrification inhibitors, (v) monitor crop nutrient status, (vi) employ diverse crop rotations and implement cover crops, (vii) manage plant residues, (viii) utilize precision fertilization practices, and (ix) install riparian buffers and other edge-of-field technologies [8].

2.1 Edge-of-field technologies to limit Nitrate degradation of water resources

Aide et al. [2, 3, 8] discussed the installation and evaluation of edge-of-field technologies primarily engineered to eliminate nutrient transport from croplands. Aide et al. [3] demonstrated that a denitrification bioreactor effectively reduced nitrate-N concentrations from 69 mg NO₃-N L⁻¹ to 21 mg NO₃-N L⁻¹ from May through June (2015). For the 2018 corn harvest, Aide et al. [4] reported that the mean tile-drainage nitrate concentration ranged from 1.5 to 109 mg NO₃-N L⁻¹. The influent drainage into the denitrification bioreactor ranged from 0.4 to 103 mg NO₃-N L⁻¹, whereas the outlet drainage from the denitrification bioreactor ranged from 0.3 to 5.2 NO₃-N L⁻¹. The smaller tile-drainage nitrate concentrations in 2019 were approximately 1.6 to 4.5 mg NO₃-N L⁻¹ because of soybean cultivation and the lack of nitrogen fertilization. Data for subsequent years corroborates the presented findings.

2.2 Constructed wetlands to capture nutrient-laden overland flow

Constructed wetlands are engineered soil infrastructures designed to capture overland flow and subsequently facilitate soil-vegetation pathways to convert water-bearing nutrients into plant materials. Constructed wetlands enhance ecosystems by enhancing hydrological, biological, geochemical, and pedogenic processes that improve water quality and other ecosystem services. Perceived advantages of constructed wetlands include: (i) on-site nitrogen and phosphorus conversions into plant materials, (ii) reduced biological and chemical oxygen demands, (iii) odor reduction, (iv) wildlife habitat, (v) esthetics, and (vi) potential economic benefits [9, 10, 11, 12, 13, 14, 15, 16].

2.3 Cover crops

Cover crops are used primarily to (i) constrain wind and water erosion, (ii) enhance available water capacity, (iii) suppress weeds and reduce herbicide usage, (iv) become compatible with an integrative pest management system to limit the incidence of specific insect and pathogens, (v) augment soil porosity and maintain appropriate soil bulk densities, (vi) convert soil nitrate and phosphate to plant-based organic nitrogen and phosphate to reduce off-site nutrient migration, and (vii) increase soil organic matter contents. The choice of plant speciation of the cover crop annually is governed by crop rotation, soil nutrient concentrations, and economics concerning seed purchase. Wheat (T. aestivum) and rye (Secale cereale) are popular cover crop choices, frequently interseeded with forage legumes.

2.4 Soil health and pasture management

Proper rotational grazing is integral to maintaining a vibrant forage program. However, for most producers, forage production detractions occur because of weather, forage species competitiveness, weed and disease management, soil fertility programs, the intensity and oversight of the rotational grazing program, and other factors. The United Sates Department of Agriculture—Natural Resources and Conservation Service defines soil health as follows: “Soil health is defined as the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans” [17]. Soil health provides five key services: (i) regulating water, (ii) sustaining plant and animal life, (iii) filtering and buffering potential pollutants, (iv) cycling nutrients, and (v) providing physical stability and support. Landowner management may support soil health by (i) maximizing the presence of living roots, (ii) minimizing the disturbance because of tillage and animal traffic, (iii) maximizing soil cover with living plant material, and (iv) maximizing biodiversity [17].

Soil quality is assessed individually for each soil and is documented and measured using indicators [18, 19, 20, 21, 22, 23, 24, 25, 26]. The relevant indicators in pastures that we employ to document soil health improvements include: (i) physical attributes (rooting depth, bulk density, and infiltrate capacity), (ii) chemical attributes (total organic carbon, total organic nitrogen, labile (active) carbon, and pH), and (iii) biological attributes (microbial carbon biomass, microbial nitrogen biomass, potential N mineralization, phospholipid fatty acids, and soil respiration).

3. Existing infrastructure at the David M. Barton agriculture research center to support profitable production agriculture and environmental sustainability

Southeast Missouri State University is a regional comprehensive public university that provides student-centered education and experiential learning experiences across the curriculum. The David M. Barton Agriculture Research Center, located at Cape Girardeau County (Missouri, USA), is an experiential learning facility for the Department of Agriculture at Southeast Missouri State University. Figure 1 illustrates the spatial distribution of the environmental technologies and the material transport pathways.

Figure 1.

Map of the infrastructure layout.

3.1 Study area climate

The mean annual temperature is approximately 13°C (56°F), and the mean annual precipitation is approximately 1.12 mm (44 inches) [27]. The mean monthly temperature for January is 3°C, and the mean monthly temperature for July is 25°C. Peak temperatures typically occur in July, with some days having a maximum near 40°C (104°F). Rainfall is typically greater from March to May; however, Gulf of Mexico weather events may provide heavy rain events from June to October. The mean October rainfall is 7 cm, whereas the mean May rainfall is 13 cm. The growing season is approximately 210 days [27].

3.2 The soil resource

The Wilbur series (coarse silty, mixed, superactive, mesic Fluvaquentic Eutrudepts) is the dominant soil series in the Crop Science Unit (Bottomlands). The pedons are very deep, moderately well-drained, permeable soils formed in silt loam alluvium that display an Ap–Bw–Cg horizon sequence. Saturated hydraulic conductivity is 4.2 to 14.1 micrometer sec⁻¹, and the permeability is moderate. The soil pH ranges from slightly acidic to neutral in the ochric epipedon and strongly acidic (pH 5.1 to 5.5) and very strongly acidic (pH 4.5 to 5.0) in the cambic and deeper soil horizons, respectively.

Upland landscapes contain soils formed in thick loess and exhibit 2 to 6 percent slopes. The Menfro series (fine silty, mixed, superactive, mesic Typic Hapludalfs) consists of very deep, well-drained, moderately permeable soils exhibiting A–E–BE–Bt horizon sequences. The Winfield series (fine silty, mixed, superactive, mesic Oxyaquic Hapludalfs) consists of very deep, moderately well-drained soils exhibiting A–E–BE–Bt–Btg horizon sequences. Both soil series have argillic horizons, exhibiting moderately acidic to strongly acidic pH levels.

3.3 Crop science infrastructure overview

The David M. Barton Agriculture Research Center has a 40 ha (100 acre) crop science unit featuring a controlled subsurface drainage and irrigation technology. The subsurface controlled drainage system design involves parallel tiles having 10-meter spacing. Irrigation and drainage are monitored and regulated by using stop-log boxes fitted with adjustable baffles to permit irrigation/drainage water to be added/removed by gravity flow. Submersible pumps support the irrigation.

A 12 × 10³ meter³ (3.3 × 10⁶ gallon) tile-drainage water capture basin was constructed to store excess tile-drainage water collected during the off-season to be reapplied as subsurface irrigation water during the cropping season, thus reapplying nitrogen to support plant growth and development.

A denitrification bioreactor is connected to the controlled-subsurface irrigation and drainage technology to receive drainage effluent. The denitrification bioreactor was designed and installed to transform nitrate to inert nitrogen gas (N₂), nitric oxide (NO), or nitrous oxide (N₂O). The relative speciation of nitrate-N into the three nitrogen gaseous species is pH dependent. Notably, in spring and summer rainfall events, the denitrification bioreactor consistently receives tile-drainage influents having nitrate-N concentrations between 20 and 40 mg NO₃-N L⁻¹ and having effluent discharges from 3 to 10 mg NO₃-N L⁻¹ [2, 3].

A riparian buffer is an edge-of-field technology designed to limit nutrient-laden runoff from entering freshwater resources. The riparian buffer is designed as 22.9 meters (75 ft) of trees and understory, with 7.6 meters (25 ft) of warm-season grasses. The riparian buffer is along an order III stream, and all trees, shrubs, and grasses/forbs are native. Collectively, the riparian buffer and the denitrification bioreactors are designed to limit nutrient migration from the crop production area to freshwater resources.

3.4 Animal science infrastructure overview

The animal science unit primarily focuses on cow-calf production with dedicated infrastructures including: (i) a pavilion for animal care and breeding, (ii) a semiconfined feed facility, and (iii) a confined feed facility. A grazing paddock system consists of 56 ha (140 acres) primarily having cool-season hay/pastures (tall fescue or Schedonorus arundinaceus) and warm-season grass pastures (bermudagrass or Cynodon spp). Water is provided through underground conduit that is fitted with freeze-preventive hydrants.

4. Research involving agriculture production and environmental Stewardship

4.1 Crop production

The Crop Science Unit maintains a corn (Z. mays) and soybean (G. max) rotation. Research involving the corn–soybean rotation is conducted annually to better estimate the influence of agronomic practices on the concentrations of tile drainage nitrate. Research involving nitrate tile drain concentration variations were attributed to: (i) nitrogen fertilization timing and rates; (ii) nutrient uptake patterns over crop growth stages, harvest removal, and residue return; and (iii) crop yields and their contribution to farm profitability.

For the 2022 harvest season, soybean yields were spatially variable but averaged from 4036 kg ha⁻¹ (60 bushels acre⁻¹) when planted after wheat and 4372 kg ha⁻¹ (65 bushels acre⁻¹) for full season (planted after cover crop). For the 2021 and 2022 growing seasons, we estimated harvest loss and residue return for nitrogen, phosphorus, potassium, sulfur, magnesium, and calcium (Table 1).

	Nitrogen	Phosphorus	Potassium	Sulfur
Harvest removal	225	25	73	14
Residue return	40	7	17	5

Table 1.

Harvest removal and residue return (kg ha⁻¹) for key nutrients for 2021 soybean.

The data simply illustrates quantitative assessment of nutrient cycle components that are integral to assessing land management influences. Note that harvest removal and residue return concentrations influence soil fertility, the potential for nutrient leaching and water quality, soil microbial activity, and wildlife habitat.

4.2 Manure nutrient capture zones and a constructed wetland to inhibit Nitrogen and Phosphorus flux

In 2022, we installed a land-graded constructed wetland to provide discrete zones having different water saturation intensities and durations. Nutrient bearing inflow into the constructed wetland occurs from the winter sacrifice pasture. Water overland flow is channeled by a terrace system. In spring 2023 we will seed native aquatic plants to document which plant species are most suited to the constructed wetland and its difference water saturation zones.

The research objectives for the constructed wetland must be visioned with the manure-laden winter sacrifice pasture and the associated confined feed facility. Our objectives are: (i) to evaluate a constructed wetland to reduce nitrogen and phosphorus transport and impact to freshwater resources, (ii) to assess the aquatic plant composition for augmenting ecosystem services and compatibility across different water saturation regimes, and (iii) to determine if selected aquatic plants may be harvested for resale. Associated with the constructed wetland is a series of grazing pastures. Our soil health program is designed to merge the benefits of soil health with advanced grazing practices [28].

4.3 Connectivity of environmental Stewardship and farm profitability to support producer acceptance

Wetlands provide benefits, including: (i) critical habitat and breeding grounds, (ii) feeding and resting grounds for migratory birds and habitat corridors, (iii) recreational and esthetic benefits, (iv) reduction of erosion and flooding, (v) moderation of groundwater levels and base flow, (vi) assimilation of nutrients, and (vii) protection of drinking water sources [29]. Expertly managed upland pastures also provide benefits, including: (i) forage for livestock, (ii) supporting rainfall infiltration and reducing overland flow to nearby streams, (iii) with vigorous vegetation growth encouraging nutrient cycling, (iv) reducing the quantity of fertilizer amendments, (v) distributing manure across a greater area, (vi) increasing carbon sequestration levels, and (vii) augmenting farm profitability.

Our outreach goal is to provide meaningful and informative learning activities to a diverse audience, wherein we concentrate on farm profitability and environmental sustainability. The outreach programing focuses on aligning agricultural production with viable and environmental-based cultural practices and incorporating applicable soil engineering structures (Figure 2). The topics that the faculty address to the agricultural community include: (i) controlled subsurface drainage/irrigation, (ii) edge-of-field technologies, (iii) modern pasture management, (iv) soil health, and (v) agronomic practices to augment economic and sustainable crop yields. Audiences include a single producer to producer workshops, agriculture educators and their students, and state and federal personnel. Social media is being developed for more distant interested individuals.

Figure 2.

Illustration for modeling information flow.

5. Conclusion

The purpose of this article is to demonstrate how to develop and install infrastructure that supports both production agriculture and environmental stewardship. At the David M. Barton Agriculture Research Center, the infrastructure development and installation include: (i) a controlled subsurface drainage and irrigation technology, (ii) a denitrification bioreactor to limit tile-drainage nitrate concentrations, (iii) riparian corridors, (iv) a drainage water capture basin to reuse drainage water for irrigation, and (v) a constructed wetland and a confined beef feeding facility. Collectively, these infrastructures permit the teaching and outreach capabilities to link production agriculture and environmental stewardship.