Location: Agroecosystems Management Research
2024 Annual Report
Objectives
Objective 1: Develop climate-smart frameworks for providing actionable information on both conventional and aspirational corn- and soybean-based cropping systems, including organic systems, with foci on nutrient cycling, soil water dynamics, and indicators of soil health.
Sub-Objective 1.A: Determine effects of conventional and aspirational C-S based cropping systems, including organic systems, on soil nutrient dynamics, nutrient losses in subsurface drainage, crop nutrient uptake, and crop yield with a vision for developing climate resilient cropping systems for regional producers.
Sub-Objective 1.B: Determine effects of conventional and aspirational C-S based cropping systems, including organic systems, on indicators of soil health.
Objective 2: Provide actionable information on the influence of microclimates modified by conservation management practices (such as no-till, relay or double cropping, extended rotations) on production efficiency and resilience of corn-soybean, organic, agroforestry, and forage-based cropping systems.
Sub-Objective 2.A: Quantify differences in soil temperature, plant available water, and canopy microclimate between conventional and aspirational row-crop systems and forage-based systems that impact sustainability and productivity outcomes.
Sub-Objective 2.B: Utilize measurements of light interception and weather data to compare RUE and PUE between conventional and aspirational row-crop systems and forage-based systems.
Approach
A combination of controlled experiments in the field and laboratory, tile drainage monitoring, and a variety of modeling techniques and statistical analyses will quantify the effects of 4R management (Right source, Right rate, Right time, and Right place) of nitrogen on nutrient (nitrogen, phosphorus, potassium, and sulfur) cycling in a corn-soybean system (Objective 1). This same approach will be used to determine the ability of cover crops and double-cropping to reduce nitrate losses and maintain soil health in a corn-soybean system, and the efficacy of an organic cropping system with extended rotations to both reduce nitrate losses and enhance soil health. We will determine how fall-planted cover crops and no-tillage within prevailing and alternative corn-soybean rotations affect tile drainage water flow and nutrient concentrations, and how drainage water quality and soil profile water storage differ in organic systems compared with prevailing corn-soybean systems. We will also quantify how diversified systemwide management affects water- and light-use efficiency of row crops and pastures (Objective 2). The approaches we have used in corn-soybean systems will be applied to pasture systems to provide quantitative assessments of the value of silvopasture systems in the Midwest. We will use several indicators of soil health, such as aggregate stability and nitrogen mineralization potential, to compare and contrast prevailing corn-soybean based cropping systems, corn-soybean based systems that include cover crops and double crops, and organic systems that include extended rotations. These comparisons are being conducted via experimental plots with individual subsurface (tile) drains that allow robust measurements of hydrologic and nutrient balances. We are monitoring microclimate (e.g., wind speed and evaporation) in long-term plots to understand the effectiveness of silvopasture systems as a climate change adaptation strategy that may reduce either the severity of extreme events (e.g., drought) or the impact of annual or seasonal climate trends (e.g., increasing temperature). Through a well-designed series of experiments that support modeling and upscaling and by employing the LTAR infrastructure, this study will identify optimal combinations of climate-smart practices and aspirational cropping systems that increase production and offset detrimental impacts to the environment.
Progress Report
The Long-Term Agroecosystem Research (LTAR) Common Experiment at the Kelley Farm Drainage Plots (KFDP) located near Ames, Iowa, was continued in 2023 and 2024. Established treatments contrasted different nitrogen (N) management strategies, and included measurements of nutrient losses (N, phosphorus (P), potassium (K), and sulfur (S) in tile drainage (Objective 1). The experiment compares a prevailing (conventional) corn-soybean (C- S) cropping system with tillage and fixed N fertilizer applications to four alternative C-S systems: 1) no-till C-S; 2) no-till C-S with a cereal rye winter cover crop; 3) no-till C-S with a fertilized winter cereal rye biomass crop that is double cropped with the subsequent soybean crop; and 4) a system with a winter camelina crop following corn that is double cropped with the subsequent soybean crop. Each of these alternative systems uses the late-spring nitrate test to determine spring sidedress N application rates. In 2023, camelina and soybean crops were harvested, and above-ground biomass and nutrient content measurements were made, as were nutrient contents for oilseed and grain. Similar research efforts are ongoing for the 2024 corn crop. Key soil health metrics (Objective 1), including wet aggregate stability, organic carbon content, pH, extractable P and K, and potentially mineralizable N also were measured. Data from the Kelley Farm Drainage Plots have been deposited in an internal database at the National Laboratory for Agriculture and the Environment. As available, these data are being exported to the NutriNet and LTAR databases. Established treatments at the Organic Water Quality (OWQ) research site located near Ames, Iowa, contrasted a prevailing C-S system with an organic corn-soybean-oat- alfalfa-alfalfa-alfalfa system (Objective 1), using replicated tile-drained plots. In 2023, yield data were collected. Similarly, data on nitrate-N loss in tile drainage from these systems during 2023 are still being processed. Research efforts are ongoing for the 2024 crop. Each year, data from the OWQ research site have been stored in an internal database at the National Laboratory for Agriculture and the Environment. When summarized, these data will be exported to NutriNet and LTAR databases.
During 2023, the effects of diversified systemwide management on water-and light-use efficiency of row crops and pastures were evaluated (Objective 2). Differences in soil temperature, plant available water, and canopy microclimate between conventional and aspirational row-crop systems and forage-based systems were quantified. The approaches we have used in C-S systems were applied to pasture systems to provide quantitative assessments of the value of silvopasture systems in the Midwest. These efforts support the project goal of developing actionable data on the influence of microclimates modified by conservation management practices (such as no-till, relay or double cropping, extended rotations) on production efficiency and resilience of C-S, organic, agroforestry, and forage-based cropping systems (Objective 2).
Accomplishments
1. Organic farming practices improve soil physical properties. The impacts of organic farming (OF) on soil physical properties are not well understood across regions and management strategies. ARS scientists in Ames, Iowa, in collaboration with University of Nebraska, worked to develop an understanding of the differences in soil physical properties between conventional and organic farming. Results showed that OF can improve soil structural quality and increase water infiltration and storage in many cases, but it has variable effects on soil compaction. The improvement in these physical properties suggests that OF could enhance crop yields and resilience of agricultural systems to extreme weather events. On one hand, there can be reduced potential for soil erosion and increased water intake under rainfall events. On the other hand, the increased water holding capacity can potentially contribute to improved adaptation to drought conditions. Study sites that were under OF for more than 10 years, used animal manure as an amendment, and were on silt loam or loam soils were common. However, these characteristics and management selections are not true of all organic farms, suggesting that future research should include other soils, fertility management, and tillage practices. The positive impact of OF on soil physical properties highlights OF’s potential for improved sustainability and resilience to extreme weather events. This information will be valuable to scientists and natural resource managers to understand how and in what timeframe OF can impact soil physical properties.
2. Silvopasture management improves ecosystem service delivery. Silvopasture, the intentional integration of trees, forage, and grazing livestock, is a promising management practice to maintain sustainable, resilient livestock production systems. The trees protect the livestock and forages from extreme weather and have potential to provide valuable products such as fruit, nuts, or timber. However, the ecosystem services–benefits to humans provided by the environment–delivered by these systems have not been researched enough due to the length of time it takes for trees to mature. ARS researchers in Ames, Iowa, Fayetteville, Arkansas, and Booneville, Arkansas, measured a series of ecosystem services in a mature silvopasture to compare against a traditional pasture without trees. The silvopasture outperformed the traditional pasture in many ways, including a 51% increase in forage production and an 18% increase in soil organic matter. The silvopasture also improved animal welfare by reducing cattle temperature and did not affect cattle weight gains. Overall, this holistic approach to measuring the effects of silvopasture showed environmental, production, and economic benefits. The findings of this study can foster the development of policies for the adoption of silvopasture as a climate-smart, regenerative production practice.
3. Eight years of cover crops improve soil health in rainfed and irrigated corn. Cover crop (CC) effects on soil physical, chemical, and biological properties may be driven by a variety of factors including duration under CC management, CC biomass production, and site-specific factors. ARS scientists in Ames, Iowa, in collaboration with University of Nebraska, measured soil physical, chemical, and biological properties after 8 years of winter rye CC in corn-based systems under rainfed and irrigated conditions in the western U.S. Corn Belt. The cover crop was not irrigated in this study. Across the 8-year experiment, winter rye CC biomass yield was about 0.6 Mg ha-1 (megagram per hectare) at the rainfed site and about 1 Mg ha-1 at the irrigated site. After 8 years of CC, CC effects on soil properties were confined to the soil surface (0-5 cm). The CC increased easily decomposable organic matter and soil wet-aggregate stability at both sites relative to no CC. The CC increased soil C at the rainfed site only. The winter rye CC increased microbial biomass but had no effect on water infiltration or storage at either site. The CCs improved many soil properties after 8 years, in contrast to results reported after 4 years for the same sites where no CC-induced changes to soil properties occurred. These data indicate that when CC biomass is low (<1 Mg ha-1), CC impacts on soil properties may take time to accumulate. Thus, winter rye CC can enhance soil properties at the soil surface in the long-term. This information will be valuable to scientists, farmers and others to understand which soil properties may change with a winter rye CC and how long it may take those changes to occur in corn-based systems of the western U.S. Corn Belt.
4. Increasing rye cover crop biomass production after corn residue removal to balance economics and soil health. Cover crops are often killed weeks before planting main crops, leading to low cover crop biomass yield and few soil benefits. The effects of cover crop kill date combined with different rates of corn residue removal on soil properties, crops, and farm income are not well-understood under no-till rainfed and irrigated continuous corn. ARS scientists in Ames, Iowa, in collaboration with University of Nebraska-Lincoln, found that a winter rye cover crop killed 2-3 weeks before corn planting (early-killed) yielded <0.45 ton/ac/yr of biomass. A winter rye cover crop killed at corn planting (late-killed) yielded 0.7 ton/ac/yr at the rainfed site and 1.3 ton/ac/yr at the irrigated site. After 6 years, early-killed cover crop did not affect soil properties. The late-killed cover crop with 1.3 ton/ac/yr of biomass improved soil structure and increased soil organic matter content. Across sites, highrates of residue removal had negative impacts on most soil properties. The negative impacts of corn residue removal on soils generally were larger than the positive impacts of the late-killed cover crop. A high-yield (>1 ton/ac/yr) cover crop could partially maintain soil properties only at some sites. Overall, if a winter rye cover crop produces at least 1.3 ton/ac/yr of biomass, it may partially maintain soil properties when corn residue is removed, but the risks of only a partial offset in soil properties must be balanced with farm income. This study provides valuable insights regarding how cover crop management affects cover crop biomass yield, soils, crop yields, and income in corn systems with residue removal.
5. Streambank erosion due to channel migration is an important contributor to phosphorus losses. Losses of phosphorus (P) from agricultural lands represent a major cause of water quality impairment within Iowa and elsewhere. Producers and land managers have made progress in reducing P losses via soil erosion from agricultural lands, but there is a growing body of evidence that much of the sediment and P delivered to the surface waters from agricultural landscapes originates from streambanks. Working in the Nishnabotna River watershed in southwestern Iowa, ARS scientists in Ames, University of Iowa, and Iowa State University collaborators used a multi-step process that included a new remote sensing tool (Aerial Imagery Migration Model (AIMM)) along with physical sampling of river bank sediments to first map channel migration patterns and then to estimate the net contribution of bank erosion to sediment budgets and P losses. During the period between 2009 and 2018, they found that roughly 43% of the P that entered the Nishnabotna River resulted from bank erosion due to river channel migration. They also found that the larger streams and tributaries in the watershed contributed relatively more to sediment and P losses than the smaller streams. The results demonstrated that future attempts to decrease losses of sediment and P should focus on controlling bank erosion in the larger streams and tributaries in the watershed. An improved understanding of streambank P contributions will help natural resource managers make improved recommendations for effective soil and water conservation practices that best reduce P loading to rivers.
Review Publications
Ruis, S.J., Blanco-Canqui, H., Jasa, P.J., Slater, G., Ferguson, R.B. 2023. Increasing rye cover crop biomass production after corn residue removal to balance economics and soil health. Field Crops Research. 302. Article 109076. https://doi.org/10.1016/j.fcr.2023.109076.
Blanco-Canqui, H., Ruis, S.J., Koehler-Cole, K., Elmore, R.W., Francis, C.A., Shapiro, C.A., Proctor, C.A., Ferguson, R.B. 2023. Cover crops and soil health in rainfed and irrigated corn: what did we learn after 8 years? Soil Science Society of America Journal. 87(5):1174-1190. https://doi.org/10.1002/saj2.20566.
O'Brien, P.L., DeSutter, T.M., Casey, F.X., Wick, A.F., Bartsch, Z.J., Croat, S.J., Struffert, S. 2024. Oil spill soil remediation using thermal desorption: project synthesis and outcomes. Agrosystems, Geosciences & Environment. 7(1). https://doi.org/10.1002/agg2.20463.
Amorim, H., Ashworth, A.J., O'Brien, P.L., Thomas, A.L., Runkle, B., Philipp, D. 2023. Temperate silvopastures have greater ecosystem services than conventional pasture systems. Scientific Reports. 13. Article 18658. https://doi.org/10.1038/s41598-023-45960-0.
Williams, F.F., Moore, P.L., Allen, J.V., Isenhart, T.M., Thomas, J.T., Kovar, J.L., Schilling, K.E. 2023. Sediment and phosphorus contributions from eroding banks in a large intensively managed watershed in western Iowa, United States. Journal of the American Water Resources Association. 60(1):148-162. https://doi.org/10.1111/1752-1688.13164.
Margenot, A.J., Zhou, S., McDowell, R., Hebert, T., Fox, G., Schilling, K.E., Richmond, S., Kovar, J.L., Wickramarathne, N., Lemke, D., Boomer, K. 2023. Streambank erosion and phosphorus loading to surface waters: knowns, unknowns, and implications for nutrient loss reduction research and policy. Journal of Environmental Quality. 52(6):1063-1079. https://doi.org/10.1002/jeq2.20514.
Blanco-Canqui, H., Ruis, S.J., Francis, C.A. 2023. Do organic farming practices improve soil physical properties? Soil Use and Management. 40. https://doi.org/10.1111/sum.12999.