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. 2024 Oct 27;53(6):978–988. doi: 10.1002/jeq2.20646

The LTAR Cropland Common Experiment at Upper Mississippi River Basin–Ames

John L Kovar 1,✉, Athanasios N Papanicolaou 1, Dennis L Busch 2, Amitava Chatterjee 1, Kevin J Cole 1, Brent J Dalzell 3, Bryan D Emmett 1, Jane M F Johnson 4, Robert W Malone 1, Amy J Morrow 1, Laurie W Nowatzke 1, Peter L O'Brien 1, John H Prueger 1, Natalia Rogovska 1, Sabrina J Ruis 1, Dennis P Todey 1, Ken M Wacha 1
PMCID: PMC11650521  PMID: 39462687

Abstract

Agricultural systems evolve from the interactions of climate, crops, soils, management practices (e.g., tillage, cover crops, nutrient management), and economic risks and rewards. Alternatives to the corn (Zea mays L.)–soybean [Glycine max (L.) Merr.] (C–S) cropping systems that dominate in the US Midwest may provide more sustainable use of resources, reduce the documented environmental impacts of current C–S systems, and improve production efficiency and ecosystem services. Innovative management practices are needed to offer producers options to increase farm resilience to variable weather conditions and offset negative environmental impacts. In response to this need, the Upper Mississippi River Basin Long‐Term Agroecosystem Research network site at Ames, IA, established a cropland experiment in 2016 to investigate an alternative crop management system that includes reduced tillage, cover crops, and right source, right rate, right time, and right place (4R) nitrogen (N) management. The experimental site is located on the Iowa State University Kelley Research Farm in Boone County, IA. Crop, soil, air, and tile drainage water measurements are made throughout the year using published methods for each agronomic and environmental metric. Our goal is to provide quantitative information to farmers, consultants, agribusiness partners, and state and federal agencies to help guide decisions on the effective use of alternative management practices. Future changes in experimental treatments will adopt a knowledge co‐production approach whereby researchers and stakeholders will work collaboratively to identify problems, implement research protocols, and interpret results.

Core Ideas

  • The Upper Mississippi River Basin (UMRB) Long‐Term Agroecosystem Research site includes cooperating locations at Ames, Iowa, Morris and St. Paul, Minnesota, and Platteville, Wisconsin.

  • The UMRB–Ames cropland common experiment (CCE) is located on the Des Moines Lobe landform with soils that are considered prime farmland.

  • Research at the UMRB–Ames CCE is conducted at the plot scale.

  • Results are being used to determine how management practices can offset the impact of more variable climate on crop production.

Abbreviations

ASP

aspirational

BAU

business‐as‐usual

CCE

cropland common experiment

C–S

corn–soybean

GHG

greenhouse gas

LSNT

late spring soil nitrate test

LTAR

Long‐Term Agroecosystem Research

N2O

nitrous oxide

SAM

secondary alternative management

UMRB

Upper Mississippi River Basin

1. THE REGIONAL CONTEXT

1.1. Regional characteristics

Regional boundaries can describe areas of similarity in collective patterns of biophysical and socioeconomic factors, such as land use and landscape topographic features (e.g., Green, 2010; Omernik & Griffith, 2014). Regional boundaries for Long‐Term Agroecosystem Research (LTAR) sites are being used to map and compare indicators from each domain across the network (Bean et al., 2021). The Upper Mississippi River Basin (UMRB) LTAR site includes several cooperating locations (Ames, Iowa; Morris, Minnesota; Platteville, Wisconsin; St. Paul, Minnesota) within the UMRB watershed (Figure 1). The LTAR cooperating locations are described elsewhere in this special issue (see Johnson et al. for Morris, Busch et al. for Platteville, and Dalzell et al. for St. Paul). The Ames location is managed by the USDA‐Agricultural Research Service (ARS)‐National Laboratory of Agriculture and Environment (NLAE). In the future, the Morris and St. Paul locations will coordinate efforts within the newly established Northern Headwaters (NH) LTAR site.

FIGURE 1.

FIGURE 1

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Long‐Term Agroecosystem Research (LTAR) Croplands Common Experiment research is conducted at sites throughout the Upper Mississippi River Basin. Sites are located near Ames, Iowa (main site); Morris, Minnesota; St. Paul, Minnesota; and Platteville, Wisconsin as indicated by stars (L. to R.) on the map.

The current UMRB regional boundary is delineated by a combination of Major Land Resource Areas, including 173 (Rolling Till Prairie), 176 (Central Iowa and Minnesota Till Prairies), 177 (Eastern Iowa and Minnesota Till Prairies), 186 (Illinois and Iowa Deep Loess and Drift, West‐Central Part), and HUC 6 areas 070200 (Minnesota) in the north to 071300 (Lower Illinois) in the south (Bean et al., 2021).

Studies conducted across ecological research networks often attempt to scale results to larger areas to identify emergent findings that are valid throughout larger enclosing regions. Network representativeness and constituency can be utilized to help scale‐up results over larger regions, usually with the development of ecological indicators to facilitate cross‐site comparisons (Papanicolaou et al., 2018). Among cropland sites, the UMRB region has the largest constituency area of approximately 29.14 million ha, with mean representativeness (0, not representative; 1, most representative) of 0.82 (Kumar et al., 2023). In Iowa, agricultural production occurs on 12.1 million ha of the state total land area of 14.6 million ha. Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are grown on 9.3 million ha, representing 64% of the state land area (National Agricultural Statistics Service, 2022).

Before European settlement, land cover was prairie, savanna, or forest depending on the location within the basin (USGS, 2015; Figure S1). Settlement began in the 1830s (Whittaker, 2009). Early agricultural production in the region consisted of subsistence frontier farming. This was replaced by commodity farming after the construction of railroad networks in the 1850s and 1860s (Whittaker, 2009). Land use shifted in the 20th century from diversified rotations of annual and perennial crops to a system of corn and soybean row crops (Schilling et al., 2008). Soybean production expanded greatly in the middle of the century at the expense of oat (Avena sativa L.) and pasture crops, such as hay and alfalfa (Medicago sativa L.).

The UMRB was inhabited by a number of Native American tribes before European settlement began in the 1830s. The Sauk and Meskwaki constituted the largest and most powerful tribes (Whittaker, 2009). Most of the European immigrants who came to the region after settlement began were from surrounding states, such as Illinois and Missouri. The settlers soon discovered that the area was primarily a prairie/tall grass region, an environment different from the heavily timbered areas they had known.

As thousands of settlers entered the region in the mid‐19th century, all shared a common concern for the development of adequate transportation. The earliest settlers shipped their agricultural goods down the Mississippi River, as steamboats were in widespread use on the major rivers by the 1850s. With time, railroads were built and expanded to provide year‐round transportation for agricultural products, which could then be shipped through Chicago to markets in the United States and worldwide.

1.2. Regional climate

The UMRB region has a continental climate with variably wet summers, springs, and falls, and drier winters. The surrounding region mimics variations of this climate, primarily with respect to annual precipitation. Precipitation is lowest in January and February, averaging about 25 mm per month. Rainfall is highest in May, June, and July, averaging 100–130 mm per month (Hatfield et al., 2011; Iowa Environmental Mesonet, 2024).

Iowa, Minnesota, and Wisconsin have experienced warming temperatures, increasing precipitation, and extending growing seasons. Between 1979 and 2021, these states experienced average annual warming of 0.7, 0.6, and 0.9°C, respectively, driven by warming fall, summer, and winter seasons. Average annual precipitation has increased during this period by 71.9 mm in Minnesota, 102.9 mm in Iowa, and 124.7 mm in Wisconsin. Iowa and Wisconsin have also experienced a lengthened frost‐free period; Iowa's average growing season lengthened by 2.2 days between 1979 and 2021, while Wisconsin's lengthened by 8.3 days. Future projections suggest that by 2040–2059, under scenarios with moderate continued greenhouse gas (GHG) emissions, there will be approximately 30 fewer nights each year that dip below freezing and four to ten more days that exceed 35°C. Spring, fall, and winter precipitation will continue to increase; however, summers will experience a decrease in rainfall under most emissions scenarios (Kucharik et al., 2023; Roop et al., 2024).

1.3. Landforms and soils of the region

Iowa features a diverse array of landforms shaped by the retreat of glaciers (Trimble, 2013). The UMRB–Ames site is located within the Des Moines lobe and Southern Iowa drift plain landforms. The Des Moines lobe landform, often called the prairie pothole region, is characterized by gently rolling terrain and ridges. The Southern Iowa drift plain landform characterizes the southern half of Iowa and consists of rolling hills of Wisconsin‐age loess or Illinoian till. This rolling landform is subject to runoff and erosion.

Core Ideas

  • The Upper Mississippi River Basin (UMRB) Long‐Term Agroecosystem Research site includes cooperating locations at Ames, Iowa, Morris and St. Paul, Minnesota, and Platteville, Wisconsin.

  • The UMRB–Ames cropland common experiment (CCE) is located on the Des Moines Lobe landform with soils that are considered prime farmland.

  • Research at the UMRB–Ames CCE is conducted at the plot scale.

  • Results are being used to determine how management practices can offset the impact of more variable climate on crop production.

Most of Minnesota consists of rolling plains that were also created by retreating glaciers. The Central Till Plain occupies a significant portion of the state's heartland and is characterized by its gently rolling hills formed by glacial deposits. The Eastern Till Plain, extending to the border with Wisconsin, features a landscape similar to the Central Till Plain but with more pronounced rolling hills and valleys. The soils in the region benefited from the glacial history (Bettis et al., 2003), which resulted in land prime for farming. Prairie‐derived mollisols are the most common soils in the UMRB, but forest‐derived alfisols become more prevalent in eastern parts of the region (Figure S1).

1.4. Major crop production challenges of the region

The most common agricultural management systems in Midwestern agriculture are based on the two‐crop rotation of corn and soybean because these systems maximize production and simplify field operations. However, these systems have active vegetative growth during less than half the year, making them vulnerable to soil degradation and reduced production potential, particularly under changing weather patterns and extreme weather events (Abaci & Papanicolaou, 2009; Allen et al., 2018; Wacha et al., 2018; Wuebbles et al., 2017). Nonpoint‐source pollution from agroecosystems is a major contributor to high nitrate loads in surface waters, as N is transported from agricultural fields via runoff and artificial subsurface drainage. This pollution threatens water quality not only within watersheds in the UMRB (Hatfield et al., 2009; Jones et al., 2018; van Meter et al., 2016), but also nationally, as nitrate loads from this region have been linked with the expansion of the hypoxic zone in the Gulf of Mexico (Alexander et al., 2008; Turner & Rabalais, 2003).

Common practices within these systems, such as single rate N application, fall tillage, and tile drainage, contribute to the deterioration of water quality, depletion of soil organic matter, soil erosion, and degradation of soil structure and health (Dinnes et al., 2002; Dold et al., 2017; Hatfield, 2014; Hou et al., 2020; Papanicolaou et al., 2015). Continuation of these practices will not only reduce crop production potential but also further exacerbate weather variability and extremes by increasing GHG emissions (Emmett et al., 2022). These concerns are leading producers to explore climate‐smart agricultural practices to improve productivity and resilience under changing weather conditions. These goals can be met by alternative management systems that are designed to be sustainable and resilient (Ding et al., 2015).

A sustainable, resilient agricultural system design must meet two critical criteria. To be sustainable, the system must be able to maintain function and provide economic, environmental, sociocultural, and production services now and into the future (Pope et al., 2004). To be resilient, the system must be able to respond to challenges to the system (Bennett et al., 2021). The challenges that U.S. agriculture faces include economic (e.g., commodity prices and incentives; Claassen et al., 2011), sociocultural (e.g., shifting community and legal perspectives on agriculture; Wang et al., 2017), ecological (e.g., pests and diseases; Rand et al., 2014), agrotechnological (e.g., smart technologies for climate change; Lybbert & Sumner, 2012), and environmental (e.g., global climate change; Reitsma et al., 2015). Given the range of challenges, one important pathway to designing sustainable, resilient farmlands is crop diversification (Meuwissen et al., 2019; Sanford et al., 2021). Cropping system diversification targets temporal heterogeneity, for example, cover crops, double‐crops, perennials, and spatial heterogeneity, that is, a mosaic of different species on the agricultural landscape (Cabell & Oelofse, 2012).

2. THE COMMON EXPERIMENT AT THE UMRB–AMES SITE

2.1. Crop production challenges being addressed

Alternatives to the corn–soybean (C–S) cropping systems in the UMRB include innovative management practices that offer more sustainable use of resources, reduce the documented environmental impacts (Section 1.4) of C–S systems, and improve production efficiency and ecosystem services (Scherr et al., 2012; LTAR Strategic Plan, 2024).

2.2. Research at the UMRB–Ames site

Research at the UMRB–Ames site is conducted at the plot, field, and watershed scales. The most intensive research is conducted at the plot scale and is the focus of the UMRB–Ames cropland common experiment (CCE).

The LTAR CCE uses a simple experimental design to maximize comparability across sites. The core design compares a prevailing production system (business‐as‐usual [BAU]) with an aspirational (ASP) system thought to advance sustainable intensification in locally appropriate ways (Spiegal et al., 2018).

The CCE was established in 2016 and is located at the Iowa State University (ISU) Kelley Research Farm 8 km northwest of Ames in Boone County, Iowa (42.05° N, 93.71° W). Twenty‐four field plots (each 30.5 m wide by 42.7 m long) with a C–S rotation were originally established at this site in 1999 (Kaspar et al., 2007). Plots were laid out in a randomized complete block design with four replications (Figure 2, Figure S2), with electrical conductivity (proxy for drainage) as the blocking factor (Jaynes et al., 2008). The cropping system is C–S, with soybean grown in odd‐numbered years and corn grown in even‐numbered years. During the time after establishment, treatments at the site changed (see O'Brien et al., 2022, for plot history) until the LTAR CCE was initiated. The current CCE compares a prevailing management system with ASP management that considers the sustainable, resilient agricultural system design in terms of agronomic practices, including 4R N fertilizer management (right source, timing, placement, and rate), use of a cover crop, and no‐till tillage. The treatments are:

  1. Prevailing management (BAU): Fall chisel plow tillage without a cover crop and a spring, single‐rate N fertilizer application before corn planting; established 2011.

  2. ASP management: No‐till system with a cereal rye (Secale cereale L.) cover crop; N applied at corn planting and in‐season according to the late spring soil nitrate test (LSNT; Sawyer & Mallarino, 2017); established 2000.

FIGURE 2.

FIGURE 2

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Treatment design of the Upper Mississippi River Basin (UMRB)–Ames Croplands Common Experiment field plots located in Boone County, Iowa. An aerial view of the site is shown in Figure S2.

Nitrogen fertilizer is applied at 197 kg ha−1 as anhydrous ammonia in the BAU treatment. For the ASP treatment, N is applied as a 2 × 2 liquid starter at planting, followed by an in‐season band application of urea‐ammonium nitrate liquid based on the LSNT at the V6 growth stage of the corn.

In addition to these two treatments, three additional treatments intended to further inform the CCE outcomes are included at the site (Figure 2; Table S1). These treatments include (1) a secondary alternative management (SAM1) system with reduced tillage, a winter camelina (Camelina sativa L. Crantz)/soybean double crop, and N applied at corn planting and in‐season according to the LSNT (established 2016); (2) an SAM2 system with no‐till, no cover crop, and N applied at corn planting and in‐season according to the LSNT (established 2000); and (3) an SAM3 system with no‐till, N‐fertilized cereal rye/soybean double crop, and N applied at corn planting and in‐season according to the LSNT (established 2023). Both winter cereal rye and winter camelina are considered cover crops in the secondary treatments, with camelina being studied as an alternative oilseed crop. The SAM1 treatment includes double‐cropped camelina with soybean opposite corn years in the rotation. Previous research with a camelina relay‐cropping system (Emmett et al., 2022) led us to consider double cropping as a more agronomically sound system. A shorter season corn hybrid is utilized in this system. The SAM3 treatment focuses on double cropping cereal rye with soybean in the rotation. A modeling study (Malone et al., 2023) suggested that harvesting a fertilized rye cover crop before soybean planting can reduce N loads to the Gulf of Mexico by 27% relative to production without a cover crop and can provide significant amounts of feedstock for biogas production. Initially, a zero N treatment (2012–2022) was included in the study but was dropped in order to include the double‐crop rye system. The double‐cropped camelina and double‐cropped rye systems incorporate a faster maturing soybean variety due to the later planting date. Soybean residue is not tilled in any treatment. The cereal rye cover crop is overseeded into the standing corn and soybean crops at physiological maturity. Cover crops are terminated with glyphosate prior to corn or soybean planting in the spring. Additional agronomic details for the current and past management of corn and soybeans are reported by O'Brien et al. (2022).

This multi‐factorial experimental design enables direct comparisons of a prevailing system with both an ASP system and a series of alternative systems, that is, reduced tillage, 4R N management, cover cropping, and double cropping (Table S1). As part of the original 1999 experimental design, four plots have woodchip denitrification walls (in situ bioreactors) installed in a no‐till system without a cover crop (Moorman et al., 2010; Rogovska et al., 2023). This treatment was established for research purposes and is not considered an LTAR management system.

Research conducted at the field and watershed scales is discussed in the Supporting Information. Gaging stations in the South Fork of the Iowa River in central Iowa (Figure S3) have been used since 1995 to monitor water quality in the watershed. Field‐scale experiments established within the South Fork watershed (Figure S4) complement both the LTAR CCE plot‐scale research and the watershed‐scale research. Eddy covariance measurement systems (Figure S5) provide estimates of evapotranspiration and carbon flux at the field sites.

2.2.1. Landform, soils, and climate

The two predominant soils at the CCE site and found throughout the Des Moines Lobe landform are Canisteo (fine‐loamy, mixed, super active, calcareous, mesic Typic Endoaquolls) silty clay loam and Nicollet (fine‐loamy, mixed, super active, mesic Aquic Hapludolls) loam. Both soils are poorly to somewhat poorly drained due to a low permeability till layer at 3‐m depth (Jaynes et al., 2008). The study site is relatively flat with an elevation ranging from 307.2 m asl on the north to 310.5 m asl on the south end of the field (Rogovska et al., 2023). The mean annual temperature is 9.8°C at this location. Approximately 1012 mm of rainfall occurs on a yearly basis.

2.2.2. Key measurements

Observations and measurements are made to provide a fundamental understanding of crop growth and soil physical, chemical, and biological processes under different management and seasonality, which allows us to develop indices representing cause and effect relations and to assess tradeoffs (Table S1). A weather station records precipitation, air temperature and humidity, wind speed and direction, and total solar irradiance. Method details are published at Protocols.io ltar.

Crop growth

Aboveground plant biomass and nutrient content are measured for each crop every year. For corn, whole‐plant samples are collected at the R6 growth stage. For soybean, samples are collected at the R6/R7 growth stage to minimize loss of tissue due to leaf drop that occurs before maturity (R8). Plants are both hand and machine harvested. Plant biomass and grain samples are analyzed for total C and N and content of macro‐ and micronutrients. Aboveground biomass of the rye cover crop is sampled immediately before termination in the spring. Nitrogen‐use efficiencies and fertilizer N, P, K, and sulfur (S) nutrient recovery efficiencies are calculated (Norton et al., 2015) and compared for each treatment receiving fertilizer. Of note, these metrics are based on inputs and outputs of the system, so they may not be effective for monitoring transformations or retention within organic and inorganic pools in the system.

In addition, treatment effects on early‐season nutrient uptake are determined in corn years by analysis of whole‐plant nutrient content at the V5 growth stage. At anthesis, ear‐leaf samples are collected and analyzed for nutrient content to evaluate mid‐season nutrient sufficiency. In soybean years, treatment effects on early‐season nutrient uptake are determined by analysis of trifoliate leaf tissue samples collected at the early bloom (R2) growth stage.

Soil properties

After harvest each year, soil samples are collected from each plot and analyzed for available P, exchangeable K, Mg, and Ca, pH, SOC, and inorganic N. Soil samples are collected from the 0‐ to 0.05‐m, 0.05‐ to 0.15‐m, and 0.15‐ to 0.30‐m depth increments to evaluate possible nutrient stratification in the no‐till systems. Soil test results are used to guide nutrient (P, K, and S) and lime applications for subsequent crops. To evaluate nutrient cycling in the prevailing and alternative plots, soil inorganic N and total C and N are measured by taking soil cores 1.20 m deep in the fall after harvest. Soil bulk density is also measured so that C and N stocks can be calculated.

Water quality

Tile drainage water from each individual plot is collected, flow volumes measured, and recorded with a data logger. Area‐based drainage rate is calculated as daily flow volume divided by the plot area (Kaspar et al., 2012). Proportions of composite water samples are collected on a weekly basis and stored/refrigerated at 4°C until analysis.

Nutrient concentrations in drainage water samples are determined via flow injection analysis. Nitrate (NO3) is reduced to nitrite through cadmium reduction, followed by colorimetric determination, meaning NO3‐N and nitrite are analyzed together. Ammonium (NH4) is determined separately. Dissolved P is determined on a 0.45‐µm field‐filtered sample. Digestion for total P is conducted on a whole sample using an acid persulfate method followed by colorimetric determination.

Air quality

Soil nitrous oxide (N2O) emissions are measured in all plots during both the growing and non‐growing season (Emmett et al., 2022; Parkin et al., 2016). Plot‐level measurements are complemented with an automatic chamber system to provide high temporal resolution data.

2.3. What have we learned?

Data recorded and analyzed from previous research at the UMRB CCE site and new information obtained during the period after 2016 when the CCE site was established are being used to adjust management practices as research at the site progresses. Two examples of what we have learned are discussed below.

With legacy data (2011–2015) from the CCE site, O'Brien et al. (2022) compared NO3 losses, N2O emissions, and crop production under systems with fall chisel plow tillage, fall chisel plow tillage with an oat cover crop (CP‐oat), no‐till (NT), no‐till with a winter rye cover crop (NT‐rye), and NT with zero N fertilizer. Importantly, pathways for NO3 losses and N2O emissions were not linked. Nitrate losses were dictated by drainage volumes and NO3 concentrations. No‐till with a rye cover crop reduced NO3 losses by 59% compared with CP‐oat and 67% compared with NT. N2O emissions were closely tied with fertilizer N application and seasonal weather patterns. In contrast to NO3 losses, neither cover crop nor tillage consistently affected N2O emissions or crop yield. These results suggested that NO3 leaching and N2O emissions are regulated by separate mechanisms, some of which may be interactive, so conservation management may require stacking multiple practices to be effective.

Emmett et al. (2022) compared crop yields, NO3 losses in drainage, and N2O emissions from soil in the C–S rotation under prevailing management BAU with the corn‐winter camelina‐soybean relay cropping system (SAM1). Despite filling a niche as an overwintering crop with the potential to assimilate soil N, NO3 loads in drainage were not reduced in SAM1. Management changes to support the camelina crop tripled cumulative N2O emissions from 3.57 kg N2O‐N ha−1 in the prevailing C–S rotation to 12.2 kg N2O‐N ha−1 in the camelina relay system. Most of the increased emissions in the camelina system were associated with emissions events following tillage and fertilizer application in the fall. Relative to BAU, corn and soybean yields were decreased in SAM1 by 9.8% and 23.3%, respectively, due to management changes to the system and interspecific competition. However, combined grain dry weight of soybean and the camelina oilseed crop were similar to the soybean yield in the basic C–S rotation. These findings highlight the need for careful evaluation and optimization of sustainable intensification systems to ensure environmental and production goals are met.

3. STAKEHOLDER ENGAGEMENT

The UMRB–Ames LTAR site includes collaborations with the USDA‐ARS at the North Central Soil Conservation Research Laboratory in Morris, MN, the Soil and Water Management Research Unit in St. Paul, MN, and the Pioneer Farm at the University of Wisconsin, Platteville, WI. Several other ARS and non‐ARS collaborators and stakeholders partner with UMRB–Ames including ISU, the Iowa Nutrient Research Center, the USDA Natural Resources Conservation Service, the Soil Health Institute, Nutrien, the Environmental Defense Fund, the National Agroforestry Center, the South Fork Watershed Alliance, the Practical Farmers of Iowa, The Nature Conservancy, The Fertilizer Institute, the Foundation for Food and Agriculture, and a number of local Certified Crop Advisors and farmers.

Stakeholders are engaged via biennial meetings with NLAE scientists and staff, professional society meetings (e.g., American Society of Agronomy, Soil Science Society of America, Soil & Water Conservation Society), workshops, seminars, and field days.

4. FUTURE DIRECTION

4.1. Near‐term challenges

The intended outcome of the UMRB–Ames research is to provide stakeholders with science‐based management information to enhance Midwestern C–S production systems by (1) improving nutrient‐use efficiency and soil health, (2) improving water quality, and (3) sustaining or increasing yields without increasing inputs. Results obtained from these studies will determine the potential of alternative management practices to offset the impact of increasingly variable weather, leading to greater resilience and increased sustainability of agricultural production systems.

4.2. Evolution of practices

Our assessment of climate resilient systems includes long‐term analysis of crop yield, subsurface NO3 losses, and soil N2O emissions with the understanding that more resilient systems will be less affected by annual weather variability than will prevailing BAU systems. The focus on long‐term system performance makes it difficult to ascertain when the current prevailing and alternative practices should be changed. Clearly, this decision will require stakeholder input, perhaps a knowledge co‐production approach for the next generation of management practices (LTAR Strategic Plan, 2024). Currently, stakeholder interest exists in a variety of production practices, including the use of biostimulants in C–S cropping systems, “short corn” versus conventional hybrids, organic production, agroforestry, and integrated crop–livestock systems. To identify optimal combinations of climate‐smart practices and ASP cropping systems that increase production and offset detrimental impacts to the environment, a well‐designed series of experiments that support modeling and upscaling will be required.

AUTHOR CONTRIBUTIONS

John L. Kovar: Conceptualization; data curation; methodology; project administration; writing—original draft; writing—review and editing. Athanasios N. Papanicolaou: Conceptualization; funding acquisition; investigation; project administration; writing—original draft; writing—review and editing. Dennis L. Busch: Conceptualization; investigation; project administration; writing—review and editing. Amitava Chatterjee: Investigation; writing—review and editing. Kevin J. Cole: Data curation; investigation; methodology. Brent J. Dalzell: Conceptualization; project administration; writing—review and editing. Bryan D. Emmett: Conceptualization; data curation; investigation; methodology; writing—review and editing. Jane M. F. Johnson: Conceptualization; funding acquisition; investigation; project administration; writing—review and editing. Robert W. Malone: Conceptualization; investigation; methodology; writing—review and editing. Amy J. Morrow: Data curation; investigation; methodology; writing—review and editing. Laurie W. Nowatzke: Investigation; writing—original draft. Peter L. O'Brien: Conceptualization; data curation; investigation; methodology; writing—review and editing. John H. Prueger: Data curation; investigation; methodology. Natalia Rogovska: Conceptualization; data curation; investigation; methodology; writing—review and editing. Sabrina J. Ruis: Conceptualization; data curation; investigation; writing—review and editing. Dennis P. Todey: Data curation; project administration. Ken M. Wacha: Conceptualization; methodology; writing—review and editing.

CONFLICT OF INTEREST STATEMENT

The authors declare no conflicts of interest.

Supporting information

Supplemental Material

JEQ2-53-978-s001.docx (4.4MB, docx)

ACKNOWLEDGMENTS

We would like to acknowledge the contributions of Jay Berkey, Derek Carney, Michelle Cryder, Kent Heikens, Ross Isley, Ben Knutson, Keith Kohler, Samantha Purdy, Anna Radke, Gavin Simmons, and Walter Woolfolk in field management operations and data collection, processing, and analysis. This research is a contribution from the Long‐Term Agroecosystem Research network and was supported by the USDA Agricultural Research Service. The USDA is an equal opportunity provider and employer. Additional support for this research was provided by the Foundation for Food and Agriculture Research (Grant Number 534655) and the 4R Research Fund (IPNI‐2017‐USA‐4RF01).

Kovar, J. L. , Papanicolaou, A. N. , Busch, D. L. , Chatterjee, A. , Cole, K. J. , Dalzell, B. J. , Emmett, B. D. , Johnson, J. M. F. , Malone, R. W. , Morrow, A. J. , Nowatzke, L. W. , O'Brien, P. L. , Prueger, J. H. , Rogovska, N. , Ruis, S. J. , Todey, D. P. , & Wacha, K. M. (2024). The LTAR Cropland Common Experiment at Upper Mississippi River Basin–Ames. Journal of Environmental Quality, 53, 978–988. 10.1002/jeq2.20646

Assigned to Associate Editor G Philip Robertson.

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