Research Project: Stewardship of Upper Midwest Soil and Air Resources through Regionally Adapted Management Practices

Location: Soil Management Research

2021 Annual Report

Objectives
Objective 1: Evaluate conservation practices adapted for use in short-growing seasons to enhance soil quality, improve nutrient use efficiency and sustain agronomic productivity. Objective 2: Integrate soil and crop management practices that enable sustainable, climate-resilient agriculture for the Upper Midwest.

Approach
Two objectives are being addressed using a temporally-stratified and multi-faceted approach to select, evaluate and initiate integrated conservation practices for regional suitability. Data from seven long-term studies are providing the foundation for evaluating individual and integrated practices using statistical modeling and management assessment indices. These studies were designed with several types of conservation practices including tillage, conversion of perennials, including perennial in extended rotations, addition of cover crops and impacts of variable stover harvest rates. Each experiment study was set out as a randomized complete block or as a split plot – with randomized complete block within the spilt. All have four replications of each treatment. These long-term studies have SOC and corn grain yield data in common; so those variables will be used if conversion to 1) conservation tillage; 2) perennial grasses; or 3) including a winter rye cover crop increase SOC and if returning all crop biomass increases SOC compared harvesting stover. Soil quality assessment indices approach: Assessment one tests the hypothesis that soil quality assessment scores will be greater (indicting improved soil quality) following multiple years of deploying a conservation practice compared to business as usual. Assessment scores at two (or more) time points from existing datasets from the long term studies will be used to determine if soil quality appears to be aggrading, degrading or remaining the same over time. A second assessment will be made using data collected form a common future data set from studies that will have been in place at least 10 years compare treatments lacking conservation to treatments with one or more conservation practices deployed. Comparisons of management strategies will be made using a mixed model ANOVA procedure to assess soil scores among treatments. The ability of annual rye grass or forage radish to improve nutrient use efficiency in corn is being addressed. The null-hypotheses for this experiment are that yield, and N use of corn grown following cover crops (annual rye grass or forage radish) will not differ from corn grown without a preceding cover crop, and that the nitrogen fertilizer requirements will be similar for corn following wheat with or without a cover crop. Treatments were arranged in a replicated, randomized complete block design, which was blocked by field location and replicated four times. Cover crop shoot and root biomass, crop yield and N uptake, and soil N levels will be measured. Statistical analyses will analyze linear and quadratic effects of N treatments. Using a mixed-model ANOVA, cover crop will be treated as a fixed effect, N-rates as a continuous variable, and replication (within a site year) and site-year as random effects.

Progress Report
This project, which focused on improving stewardship of soil and air resources by utilizing regionally adapted management strategies, is scheduled to expire within two months of fiscal year 2022. This progress report provides a summary and annual update on its two closely related objectives. Objective 1. Several winter-terminating cover crops and winter oilseeds were assessed for their ability to reduce the loss of reactive Nitrogen (N) and improve nutrient use efficiency. The winter oilseed work is highly complementary to NP305 project at the unit. Furthermore, this work attracted additional external funding and collaboration. The research highlighted that cover crops capture N but did not reduce rate of N fertilizer needed for the subsequent corn crop. A second manuscript "Cover crop and nitrogen rate management practices influence corn health throughout the growing season in the northern Corn Belt" has been drafted. Novel over-wintering oilseed crops contributed to nutrient loads in late winter meltwater largely due to ability of cover crops to trap snow. But they also reduced runoff volume, nutrient and sediment loads during high impact spring and early soybean growing season rainfall events compared to fallow systems. Papers published on the N fertilizer needs of novel oilseed crops indicated that N needed to be balanced to avoid over application and reduce environmental risks. A multi-field/farm evaluation of two novel systems, a winter camelina following silage corn for winter cover, and Kura clover employed as a perennial mulch in a silage corn – soybean rotation was maintained. This project supports the aspirational systems research for the Long-term Agroecosystem Research (LTAR) Upper Mississippi River Basin project and has been augmented with external funding. This grant project and the water quality components also support the Soil Management unit’s 305 Project Plan in that it extends research on winter camelina with on-farm evaluations. Alternative Biomass Production study (ABP), a comparison of six management strategies for corn or forage-based biomass production under strip-till practice, reached completion of the second full-rotation cycle (12 years total) with a final soil sampling before incorporating these plots back to the full field Tillage Study. During the 2020 growing season, components of the ABP field study, eight field plots that were managed as soybean-sorghum/sudan biomass production system, were transitioned into new “aspirational” strategies, wheat/winter camelina – soybean relay system, developed for LTAR within the Upper Mississippi River Basin (UMRB) evaluation component (for the new Project Plan phase in the next year). Spring and fall soil samples for these eight plots were taken to establish a new baseline. Three Eddy Covariance (EC) towers located on two farm cooperator sites are operating as part of LTAR-UMRB. In 2021 all sites are in the soybean phase of their respective crop rotations. All locations are instrumented with phenocams. Additional data collected at the LTAR sites includes micrometeorological data, soil samples, apparent electrical conductivity, combine yield, and RGB multispectral sUAS (drone) images. The Swan Lake Weather Station located at the Swan Lake Research Farm is part of the LTAR project and includes a phenocam taking images of plot-scale research of the Tillage/System/LTAR on-station component. Phenocam data collected at Morris was included in a recently accepted paper (June 2021) Jacot et al. “Use of PhenoCam Measurements and Image Analysis to Inform the ALMANAC Process-based Simulation Model” in Journal of Experimental Agriculture International. Phenocam data transferred to the National Agricultural Library (NAL) are displayed graphically and available. The LTAR research is augmented with external funding to measure nitrous oxide emissions and additional soil parameters, which establishes new collaboration with university scientists in Nebraska and South Dakota, and private partners. Considerable progress was made in assessing the impacts of corn stover harvest management on soil health and quality, soil carbon sequestration, greenhouse gas emission and sustaining soil resilience. Data from these studies has or is scheduled to be uploaded in the related data repositories housed in USDA-ARS AgCros https://agcros-usdaars.opendata.arcgis.com. The bioenergy work attracted external funding supporting cross-location, multiple government, non-government and private partners (see objective 2). Impact of stover management on water stable and dry stable aggregates and hydrological impacts was published, thus advancing the understanding of balancing harvest rates to sustain soil health. In collaboration the with University of Minnesota the bioenergy research was expanded to include microalgae. This research explores the potential of using microalgae, including cyanobacteria, to enhance soil fertility and improve soil aggregation. The first paper was published and the second has been accepted. Nitrous oxide emission and soil organic carbon (SOC) storage were compared among switchgrass, big bluestem, and corn all managed as cellulosic bioenergy feedstock. The increase in SOC storage under the grasses was inadequate to offset the increase in nitrous oxide emission related to N application. More nitrous oxide per unit of N applied was measured in the grasses compared to the corn-soybean rotation. In another study, aggressive nor moderate stover harvest altered the amount of nitrous oxide emission compared to only harvesting grain. A long-term study established in 2000 to assess strategies to increase SOC storage, compares extended crop rotations with alfalfa, three-year rotations (corn-soybean-wheat), corn-soybean rotation with a cover crop, and perennial grasses managed as a cellulosic biofuel to a corn-soybean rotation without a cover crop. All agronomic samples were collected, and analysis completed each year and periodic soil sampling for long-term analyses pending. In a related collaborative project, changes in soil physical, chemical, and hydraulic properties were assessed on the conversion from perennial grassland vegetation into annual row crop production; the manuscript is being revised. Objective 2. Significant progress has been made to understand soil and crop management practices that enable sustainable, climate-resilient agriculture for the Upper Midwest. Comparisons were made among conventional tillage and strip-tillage systems with and without fertilizer amendments and with two-yr or four-year crop-rotations on soil organic carbon. The data indicated that strip-tillage, four-year crop rotations, and manure applications were important for the build-up and maintenance of soil microbial populations. These results suggest that conservation practices can mitigate SOC loss and benefit soil microbes without compromising crop production. Substantial progress is being made on data synthesis based on the Resilient Economic Agricultural Practices (REAP) cross location effort using soil carbon as an indicator of soil quality. These efforts contributed to a metanalyses paper on impacts of corn stover harvest impacts. For this effort additional manuscripts were drafted, an integrated data set was assembled, and comparisons made for individual site and across sites. A related project with external funding used a chronosequence with 0 to 40 years of CRP conversion history to evaluate soil quality under different land use intensities (CRP, pasture, row crop), which was evaluated using the Soil Management Assessment Framework (SMAF). Additional analyses and completion of publications will be merged into the next project plan to take advantage of the existing data from multi-year studies assessing soil properties imparting sustainability and climate resilience.

Accomplishments
1. Microalgae function as biofertilizers and soil structural enhancers. Microalgae, including cyanobacteria, have potential as a source of soil fertility and can improve soil structure; however, less is understood regarding their implementation in agricultural systems. ARS researchers from Morris, Minnesota, in collaboration with the University of Minnesota and Montana State University, synthesized the literature to identify the gaps in research on use of various algae species, with particular emphasis on nitrogen-fixing cyanobacteria. This critical evaluation established that microalgal inoculations to agricultural soils will likely result in positive influences on soil structure, nutrient delivery, and soil microbes, but research on specific species, cropping systems and soil types is badly needed. This work supports the use of microalgae-based biofertilizers to provide benefits to agricultural production system. This evaluation can be used by other researchers and policy makers to further develop and promote microalgae use as a renewable biofertilizer.

2. Integrating annual forage into grazing systems improves organic milk production. Organic dairy production must meet 120-day pasture grazing and 30% daily mass intake guidelines to remain certified as organic. However, the decline in available forage biomass on typical pastures during summer months can disrupt certification. ARS researchers in Morris, Minnesota, in collaboration with the University of Minnesota, compared forage quality, herbage mass, and milk production of cows grazing on either strict cool season perennial pastures or grazing on cool season pastures as well as high forage quality and biomass producing warm season annuals such as sorghum-sudan and teff grasses. Forage quality of cool season forages was similar to warm season annuals. Biomass production was 39% greater in cool + warm-season annual systems and thus replaced more biomass in the dairy grazing diet. This alternative-biomass-system maintained milk productio n and milk quality. These findings indicate that warm season annual forages can be incorporated into organic dairy cattle grazing systems to supplement the lower biomass produced in cool season pastures. These results will help researchers, organic land and dairy managers and policy makers to develop, support and promote alternative grazing strategies to improve forage availability to maintain compliance with organic grazing regulations and improve crop diversity.

3. Novel winter hardy oilseed cover crops help reduce nutrient loss in surface runoff. The cold climate and short growing season of the Upper Midwest have hindered the use of cover crops. Although winter hardy cover crops have been developed to overcome these barriers, producers need to know if these novel winter cover crops offer the same economic and environmental benefits as other cover crops typically used in other regions. ARS researchers in Morris, Minnesota, evaluated the ability of winter camelina and pennycress (novel over-wintering oilseed cover crops) to reduce nutrient and sediment loads in runoff water from snowmelt, spring rains and during soybean production. Although these novel crops contributed to meltwater nutrient loads in late winter, they were effective at reducing runoff (450%), nutrient (48%) and sediment loads (16%) from soybean planting through oilseed harvest, compared to fallow systems. These novel winter cropping systems provide a mechanism to reduce potential nutrient loss to surface waters, but also can be harvested which provides an economic incentive for their adoption. These results will help researchers, land managers and policy makers to develop, support and promote cover cropping strategies that provide both environmental and economic benefits.

4. Corn stover retention reduces soil water erosion. Corn stover is the material remaining after harvesting corn grain. Harvesting stover for bioenergy or for use as animal bedding reduces the mass returned to the soil, which may alter the soil’s ability to form water-stable aggregates, aggregates are groups of soil particles sticking together. Water-stable aggregates are less susceptible to being eroded by water so when the number or size of stable aggregates increase it means more resistance to water erosive forces. ARS researchers in Morris, Minnesota, used a unique opportunity to compare repeated four rates of stover returned in a side-by-side fields with different tillage. Furthermore, the multiple rates allowed these researchers quantified the relationship between the mass of stover retained and the fraction of water stable aggregates. They found that on tilled and untilled soils water-stable aggregates increase proportionally as the mass of stover increased. Therefore, leaving stover on the field makes the soil less vulnerable to erosion and less likely to cause undesirable downstream negative impacts on water quality. This information is valuable to producers who want to protect their soil resource but are considering harvesting stover for bioenergy or other uses such as animal bedding.

5. Refining nitrogen management following cover crops to provide economic and environmental benefits. Nitrogen fertilizer is applied to crops to support crop yield, but if the nitrogen is not used by the crop it can escape into the environment becoming an environmental liability. Cover crops are proposed to prevent nitrogen escaping between cropping seasons so it can be used by the next crop. ARS researchers in Morris, Minnesota, tested diakon radish and annual ryegrass at different nitrogen rates to determine how well these cover crops prevented nitrogen from escaping and whether the nitrogen remained to be used by the following corn crop. Both cover crops scavenged residual N, but neither cover crop treatment maintained subsequent corn yields with less nitrogen-fertilizer compared to no cover crop. Corn yield response to nitrogen fertilizer was similar with or without cover crops. The full nitrogen rate resulted in increased potential for nitrogen loss after corn, highlighting the need to refine fertilizer rate recommendations and identify the most effective cover crops to meet agronomic and environmental needs. These results will help researchers, land managers and policy makers to develop, support and promote cover cropping strategies that provide both environmental and economic benefits.

Review Publications
Alvarez, A.L., Weyers, S.L., Goemann, H.M., Peyton, B.M., Gardner, R.D. 2021. Microalgae, soil and plants: A critical review of microalgae as renewable resources for agriculture. Algal Research. 54. Article 102200. https://doi.org/10.1016/j.algal.2021.102200.
Brockamp, R.L., Weyers, S.L. 2021. Biochar amendments show potential for restoration of degraded, contaminated, and infertile soils in agricultural and forested landscapes. In: Stanturf, J; Callaham, M., editors. Soils and Landscape Restoration. Cambridge, MA: Academic Press. p. 209-236. https://doi.org/10.1016/B978-0-12-813193-0.00008-4.
Ojekanmi, A., Johnson, J.M. 2021. Quantifying improvements in water-stable aggregation caused by corn stover retention. Soil Science Society of America Journal. 85(3):776-788. https://doi.org/10.1002/saj2.20198.
Ritz, K.E., Heins, B.J., Moon, R.D., Sheaffer, C.C., Weyers, S.L. 2021. Milk production, body weight, body condition score, activity, and rumination of organic dairy cattle grazing two different pasture systems incorporating cool- and warm-season forages. Animals. 11(2). Article 264. https://doi.org/10.3390/ani11020264.
Ritz, K.E., Heins, B.J., Moon, R., Sheaffer, C., Weyers, S.L. 2020. Forage yield and nutritive value of cool-season and warm-season forages for grazing organic dairy cattle. Agronomy. 10(12). Article 1963. https://doi.org/10.3390/agronomy10121963.
Weyers, S.L., Gesch, R.W., Forella, F., Eberle, C.A., Thom, M.D., Matthees, H.L., Ott, M., Feyereisen, G.W., Strock, J.S. 2021. Surface runoff and nutrient dynamics in cover crop-soybean systems in the Upper Midwest. Journal of Environmental Quality. 50(1):158-171. https://doi.org/10.1002/jeq2.20135.