Performing Department
(N/A)
Non Technical Summary
An ecological nutrient management approach involves practices that increase agroecosystem diversity, build soil organic carbon, and reduce nitrogen losses that cause greenhouse gas emissions and water pollution. At regional scales, the development of circular economies can recycle nutrients from livestock manure and human waste into valuable fertilizers. Integrating circular nutrient economies with ecological practices on farms could optimize sustainable nutrient management, but their combined effects on ecosystem services are unknown. Our interdisciplinary project will advance foundational understanding of two novel systems that couple circular economies and ecological nutrient management through three objectives: (1) Determine how adaptive multi-paddock grazing of cover crops affects soil nitrogen supply, microbial communities, and soil carbon fractions that reflect potential soil carbon storage; (2) Identify how urine-derived fertilizer (UDF) impacts soil nitrogen cycling and retention, soil biodiversity, and potential for soil carbon accrual within the Kellogg Biological Station Long-Term Agroecosystem Research (KBS LTAR) experiment; and (3) Examine barriers to, and enablers of, widespread adoption of cover crop grazing and UDF among farmers and other stakeholders.Objectives 1 and 2 will be addressed through two field experiments at KBS in southwestern MI: one at the Kellogg Farm and one in the LTAR Croplands Common Experiment. We will use the integrated crop-livestock system at KBS, and partner with a rancher and two neighboring row crop farmers in central MI, to identify tradeoffs and synergies in ecosystem services relevant to soil carbon and nitrogen cycling with cover crop grazing in different soil and management conditions. We will leverage the LTAR site at KBS to establish subplots within the Croplands Common Experiment that test outcomes of a visionary management system integrating nutrient recovery from waste (UDF) with ecological practices. The UDF experiment will generate new knowledge of agroecosystem carbon and nitrogen cycling with different nitrogen sources and levels of crop rotation diversity. Objective 3 will be met through interviews and focus groups with farmers and diverse groups of key informants in MI, building on research and lessons learned from the Rich Earth Institute in Vermont and farmers and other agricultural professionals in Michigan. The social science analysis will produce critical knowledge about social processes that enable or constrain novel ecological nutrient management systems. We will apply a co-learning approach to share science-based knowledge through a field day, roundtable meeting, and other outreach activities.
Animal Health Component
0%
Research Effort Categories
Basic
15%
Applied
70%
Developmental
15%
Goals / Objectives
This research project will advance foundational and applied knowledge of two novel cropping systems that link regional-scale circular nutrient economies with ecological nutrient management practices at the field scale. The first is re-integrating crops and livestock through adaptive multi-paddock grazing of cover crops, and the second is use of urine-derived fertilizer in diversified grain rotations. Both management systems recycle nutrients (from manure and wastewater, respectively) to farm fields to reduce GHG emissions and the demand for purchased inputs. There are large social and economic barriers to re-integrating crop and livestock production. And, despite successful nutrient recovery projects globally, there are large social and regulatory barriers to scaling up the use of urine-derived fertilizer. Therefore, we will also use focus groups and interviews to identify pathways to implementation for these two novel systems in Michigan. Specifically, this research project will improve knowledge of circular nutrient economies through three overarching goals. The three goals, and specific research questions we will address under each goal, are listed below.Objective 1. Determine how adaptive multi-paddock grazing of cover crops affects soil N supply, microbial community composition and activity, and soil organic C fractions that reflect potential for long-term soil C storage.Question 1.1. How does cover crop grazing affect soil health and soil N supply?Question 1.2. How does cover crop grazing impact soil C sequestration potential through microbial processing of organic residues and changes in soil C fractions?Objective 2. Identify how urine-derived fertilizer (UDF) impacts multiple ecosystem services related to soil N cycling and retention, and soil C accrual, within distinct management systems in the Kellogg Biological Station Long-Term Agroecosystem Research site.Question 2.1. How does UDF affect crop yield and N use efficiency in an "aspirational" rotation with ecological nutrient management practices (i.e., high crop diversity and use of organic nutrient sources) compared to "business as usual" corn-soybean cropping systems?Question 2.2. How does UDF impact soil nematode community composition and N mineralization?Question 2.3. How does UDF affect nitrous oxide flux? In a diversified farming system, how does co-application of UDF with compost affect the partitioning of losses as nitrous oxide or nitrate leaching?Objective 3. Examine the barriers to and enablers of widespread adoption of cover crop grazing and UDF among farmers and other agricultural stakeholders.Question 3.1 How do social networks, institutional factors, or other key factors enable or prevent farmers from adopting cover crop grazing and UDF?Question 3.2 What types of strategic communication strategies are most effective for encouraging UDF and cover crop grazing adoption?
Project Methods
Goal 1Experimental design: At the KBS research site we will use two fields, one lower and one higher fertility. At the working farm site we will also select two neighboring row crop fields in row crop rotations with contrasts in soil fertility. Each field will be divided into 4 replicate blocks with 3 treatments: i) a cover crop mixture with adaptive multi-paddock (AMP) grazing in the fall and spring over two years; ii) the cover crop mixture without grazing; iii) a control with no cover crop and no grazing (i.e., typical management for the region). The experiment will begin in summer 2024, spanning two overwintering cover crops, and one cash crop season (2025). Following an AMP grazing approach, we will use animal units to determine the stocking rate and desired density, aiming to defoliate the cover crop to 80-90%. The cover crop will be grazed 1-2 times in fall before frost and again in spring prior to cash crop planting in both years.Soil sampling and analysis: Before planting the experiment, a composite soil sample to 25 cm depth will be collected by plot to subdivide for baseline analysis of soil health indicators with a focus on measures of biological soil health. On subsamples of dried, sieved soil, we will isolate POM and MAOM fractions of soil organic matter using a sized-based fractionation method. To assess relationships between cover crop grazing and microbial community function, we will measure soil microbial biomass using chloroform fumigation-extraction. Taxonomic diversity of soil bacterial and fungal communities will be characterized by extracting DNA from fresh (immediately frozen) soil samples and amplicon sequencing of the 16S rRNA gene and the ITS region at the UM Microbiome Core with Illumina MiSeq sequencing. Microbial community function will be quantified by measuring extracellular enzyme activity for enzymes that reflect microbial decomposition of organic C compounds and release of organic N.Biomass and yield samples: Cover crop shoot biomass will be sampled in fall and spring before grazing and analyzed for total C and N. After grazing, mean sward height will be measured in 1 m2 quadrats to estimate the amount of biomass grazed. We will estimate the amount of manure deposited during grazing using quadrats and will analyze manure C and N content. At KBS we will measure corn yield from the middle 4-5 m of plots with a field scale combine and weigh wagon. A subsample of grain and stover will be analyzed for %N. At the farm sites, we will estimate yield by sampling grain and stover from two quadrats per plot. These samples will be dried, ground, and analyzed for N content.Goal 2Experimental design: The KBS LTAR Croplands Common Experiment has four replicates in a randomized complete block design. In year 1, we will apply our fertility treatments to the corn phase of the rotation, in subsections of the main plots designated for manipulation. The business-as-usual (BAU) system will have two treatments: 1) UDF and 2) current synthetic N fertilizer (NH4SO4) as a control, both applied at 224 kg N ha-1. The aspirational system will have four treatments: 1) UDF plus compost, 2) UDF, no compost, 3) synthetic N plus compost, 4) synthetic N, no compost (control), applied on an equivalent N basis at 125 kg N ha-1 (i.e., a lower synthetic N rate than BAU following the cropping systems design). In year 2, we will repeat the experiment in four new plots entering the corn phase of the rotation. In years 1 and 2, we will also set up four additional plots in another phase of the aspirational rotation - winter wheat in year 1, and winter canola in year 2 - with the same four fertility treatments. These plots will allow us to determine the effects of UDF applied to the same plots over two years, and to include small grain crops that may foster a different rhizosphere community and outcomes for soil C and N cycling processes.Soil analyses: Baseline soil test data are available for the KBS LTAR plots. Prior to fertilization and planting, we will take a composite soil sample in all experimental plots (n=40) to 25 cm depth, which we will subdivide for additional biological and physcial soil health analyses and analysis of soil organic matter fractions.Crop yield, N uptake, and N use efficiency (NUE): Corn yield will be measured and a subsample of grain from the combine bin will be analyzed for % C and N. We will measure wheat and canola yield using two 1 m2 quadrats per plot. In the aspirational system we will sample cover crops at peak biomass from quadrats during the entire study period. All biomass samples will be separated by species (or cash crops threshed to separate plant components), dried and ground for chemical analysis. NUE will be measured as total N harvested/total N applied.Nematode analysis: We will extract nematodes from ~200 g of fresh soil from each plot using a modified Cobb's decanting and sieving method. Nematodes will be identified to taxonomic genus using a compound microscope. Genera will be assigned to taxonomic families and trophic groups, followed by calculations of indices of food web complexity, genus diversity, and successional maturity. We will also determine whether there are any differences in the presence or abundance of pollution-sensitive nematode taxa by treatment.N mineralization, nitrate loss, and GHG emissions: N mineralization rates will be measured for ~60-80 days following fertilization of the corn, wheat, and canola crops using buried bags. As a measure of potential nitrate leaching (i.e., nitrate lost below the root zone), we will measure nitrate in deep soil cores (to 1 m) twice per season in both years in the corn phase of the rotation. GHGe will be monitored over several weeks: once before, and up to 14 times after applying fertility amendments. Sampling of nitrous oxide, methane, and CO2 will be conducted in situ using the static chamber methodGoal 3We will use document review, interviews, focus groups, and feedback from the field day and roundtable events to examine the messaging that influences farmer perceptions and the network of supportive actors, institutions, and policy that builds wider knowledge, capacity, legitimacy, markets, and financing needed to enable UDF and cover crop grazing adoption. We will start with an analysis of regulatory pathways that may support or impede UDF use and the scaling of cover crop grazing, particularly grazing across farms. Our methods will include document review of water quality and environmental regulations and other permitting associated with nutrient management alongside interviews with groups who influence nutrient management. We will carry out semi-structured interviews with approximately 30 farmers of varying farm types and scales, plus 20 key informants (e.g., fertilizer suppliers, septic haulers, Cooperative Extension, nutrient management advisors, conservation agencies) from MI counties with different political orientations and varying levels of pressure to reduce nutrient loads. Interviews will also allow us to apply a risk/strategic communication methodology using a one-page hand out to determine how knowledge about risks, benefits and uncertainties affects willingness to use or recommend the ecological nutrient management practices. Comment cards will be collected after the field day and roundtable to determine if our findings influence participant receptivity to trialing UDF and cover crop grazing. Finally, four focus groups will be conducted to share, discuss, and collectively interpret the findings of the field trials and interviews; to workshop ideas for regulatory changes, supply chain interventions, and messaging (e.g., "semantic trips" to avoid); and, to define the type of technical support producers need to adopt cover crop grazing and UDF.