Final Report for GNC13-165
Project Information
The Conservation Reserve Program (CRP) was established in the 1985 to prevent further soil degradation by subsidizing landowners to set aside marginal lands for decades at a time. However, because historical fire and grazing inundations that maintained native plant cover are largely gone from the system, land placed under CRP can rapidly succeed towards dense, low diversity stands of perennial grasses, non native species, and woody plants. To combat this, CRP enrollees are obligated to implement management to restore the ecosystem to early secondary succession once per decadal contract. This so called “mid-contract management” can take the form of disking, herbicide application, interseeding high diversity seed mixes, or low intensity burns. The goal of my proposed SARE research was to assess whether alternative mid-contract management strategies are associated with different soil health and biodiversity outcomes, two of many concurrent land management goals of the CRP, state agency personnel, and private landowners.
Specifically, by assessing measures of soil health and plant biodiversity on replicated disked, herbicide, interseeded, and burned plots in a CRP field in the North Central Great Plains, this work provides information to support landowners as they work to meet both contractual requirements and their own current and post-CRP management goals, and to establish relevant, quantifiable methods to track soil health on CRP land once our investigation ends.
We addressed this by comparing these mid-contract management approaches as replicated treatments on an 800-acre CRP field in the North Central Great Plains in Holt County, Nebraska and tracking the response of multiple soil and plant variables. We also assessed land owner perceptions of both CRP and mid-contract management to gain a better understanding of why farmers and ranchers enroll in the program, what ecosystem services they value, and how scientists can better communicate our results to support land owners as they balance multiple objectives in their decision making. Outputs included peer reviewed manuscripts, outreach to elementary schools, blogposts for popular non profit and academic outlets, mentoring former and current technicians and a pamphlet for agency personnel and landowners.
Introduction:
The Conservation Reserve Program (CRP) was established in the 1985 to prevent further soil degradation by subsidizing landowners to set aside marginal lands for decades at a time. However, because historical fire and grazing inundations that maintained native plant cover are largely gone from the system, land placed under CRP can rapidly succeed towards dense, low diversity stands of perennial grasses, non native species, and woody plants. To combat this, CRP enrollees are obligated to implement management to restore the ecosystem to early secondary succession once per decadal contract. This so called “mid-contract management” can take the form of disking, herbicide application, interseeding high diversity seed mixes, or low intensity burns. The goal of my proposed SARE research was to assess whether alternative mid-contract management strategies are associated with different soil health and biodiversity outcomes, two of many concurrent land management goals of the CRP, state agency personnel, and private landowners.
Specifically, by assessing measures of soil health and plant biodiversity on replicated disked, herbicide, interseeded, and burned plots in a CRP field in the North Central Great Plains, this work provides information to support landowners as they work to meet both contractual requirements and their own current and post-CRP management goals, and to establish relevant, quantifiable methods to track soil health on CRP land once our investigation ends.
In spring 2014, the mid-contract management treatments were applied to the field, meeting the first major milestone of the project. Across the 800 acre CRP/Focus on Pheasants study area, we had nine replicates each of interseeded, disked, burned, and herbicided treatments, along with controls.
That summer, land owner surveys were written and submitted for IRB approval. These survey were aimed at understanding why landowners enroll in CRP, what mid contract management they choose and why, their perspective on soil health, and how they value various grassland ecosystem services. At the same time, I discovered that a colleague was using similar surveys across the entire state, so we combined forces and resubmitted a larger survey to IRB, which was approved the following winter. Surveys were sent out over the next year and a half, and continue to return.
In summers 2014 and 2015, intensive soil and vegetation sampling was conducted. Following each field season, laboratory analyses were conducted either at University of Nebraska-Lincoln or through Ward Laboratory in Kearney, NE.
An essential component of this study was to determine objective measures of soil health based on mixed methods approaches that combine surveys and informal interviews. Developing landowner driven, objective measures of soil health was not as straightforward as I initially speculated, but conversations with local landowners combined with early findings indicated that soil carbon quality was a next step. I am currently conducting these analyses.
The primary output of this work is an in-progress report for private landowners and state agency personnel describing the economic and ecological tradeoffs associated with different mid-contract management activities. While the rural, diffuse geographical area our project precludes any landowner-attended workshops, outreach to elementary schools in Lynch and Spencer, NE, both of which are located within 30 miles of the field site, are planned for winter 2017.
Another major objective included presentation at annual meetings. I shared results of this SARE funded research at the following conferences: American Association of Geographers Annual Meeting in April 2015, Gordon Research Seminars: Unifying Across Ecological Scales in July 2016, The Conference on Complex Systems in Amsterdam, Netherlands in September 2016, and at the Nebraska Fish and Wildlife Cooperators’ Annual Meetings in 2014, 2015 and 2016.
I also met the objective of submitting a manuscript to a peer reviewed journal; in this case The Journal of Environmental Management. The paper was entitled “Adaptive Management for Soil Ecosystem Services” and drew directly from experiential learning I gained while on this grant. Other manuscripts are pending directly based on this research, and I expect to publish at least two more based on drafts currently underway.
Cooperators
Research
In spring 2014, the mid-contract management treatments were applied to a 800-acre CRP/Focus on Pheasants field. In total, we had nine replicates each of interseeded, disked, burned, and herbicide treatments, along with controls.
Soil sampling included taking physical soil cores for bulk density, composite cores for total carbon, nitrogen, pH, phospholipid fatty acid (microbial biomass and community composition markers), and in field soil infiltration and erosion pin measurements. Vegetation sampling was conducted according to the nested quadrat approach, with two pseudo replicates taken in each of the 45 treatment plots.
Landowner surveys were written and submitted for IRB approval. These survey were aimed at understanding why landowners enroll in CRP, what mid contract management they choose and why, their perspective on soil health, and how they value various grassland ecosystem services. Informal conversations comprised the other part of my mixed methods approach and allowed me to elucidate a better understanding of landowner attitudes towards soil health.
There is no unified, measurable definition of soil health. Soil health for many is a “you know it when you see it”, subjective measure. For others it means greater returns (yields minus inputs). In sandy, highly drained soils of the North Central Great Plains, soil carbon might be a strong indicator of soil health. Soil carbon originates from aboveground plant litter inputs and belowground root turnover.
As litter and roots are decomposed and mixed through the soil, they decreasingly resemble the original plant material, and instead become a heterogeneous mixture of microbial biomass and humus bound to minerals. Soil carbon quality exists along a continuum of biochemical complexity (simple sugars to multi-ring structures) and physico-chemical protection (free in the soil to adsorbed on mineral surfaces or shielded within aggregates) that together determine its ecological properties, resistance to microbial decomposition, and mean residence time in the soil. Soil carbon imparts structure, water holding capacity, fertility, microbial activity, nutrient retention, cation exchange capacity, and erosion prevention. As a result, soil carbon is central to both “you know it when you see it” returns-driven definitions of soil health.
SARE funds allowed me to assess the effect of these treatments on soil carbon quantity, as I originally proposed. However, because I ended up doing more of the analyses myself and because I was given a university discount I was able to follow some interesting results down a path not initially proposed. In the control plots, soil carbon was roughly 0.5% (± 0.4). To provide some reference, organic soils are defined as >18% carbon, and most mineral soils under rowcrop or grazing agricultural cover contain 8-14% carbon. In marginal CRP lands of the arid Great Plains, it is not uncommon to have soil carbon fall in the range of 1-5%. So the very small soil carbon percentages in the study area were surprising, and perhaps indicative of why this land was removed from irrigated, rowcrop agriculture and placed under CRP twenty years ago. Also unsurprising was the lack of % soil carbon response to the treatments I applied. Physically disrupting soil exposes soil carbon to oxygen and bacteria. These conditions accelerate soil carbon respiration to CO2. The lack of soil carbon decline in response to intensive disking treatments could be attributable to a pool of carbon that is very old and resistant to respiration, even when oxygen is available. This lack of response could be attributable to a restrictively small microbial biomass, so I was able to use SARE funds to examine this otherwise un-probed mechanism (results currently being analyzed).
I also had enough funding to analyses ~30% more samples for soil carbon. Instead of taking a single pool approach (total C), I am fractionating soil into multiple pools using aggregate separation to see whether mid-contract management treatments have any effects on the internal carbon quality dynamics. Different soil carbon pools are different functionally from an ecological standpoint, and also respond to external variations and disturbance differently, so there is strong incentive to measure multiple pools. By measuring something as inherently complex as soil carbon quality, this work can provide an additional index of soil health for farmers that would otherwise be out of reach due to the resource intensive nature of soil carbon quality investigations.
While survey data is partly in, much of the data is stored on a server accessible only by university collaborators, so I have intermittent access to results. I have begun to synthesize some of the soil health and ecosystem services components from parts of the survey that I wrote. Unsurprisingly, economics is a major driver of CRP enrollment although soil health concerns and interest in hunting, biodiversity and other ecosystem services matter to landowners for enrollment and re-enrollment. Mid-contract management choices are trickier to elucidate, but cost and convenience are immediate driving factors of management choices, even if they do not align with longer-term CRP objectives.
Educational & Outreach Activities
Participation Summary:
I continued to volunteer at McPhee Elementary School in Lincoln, NE for the first year of the grant. I’ve been in contact with rural schools near my field site for the past year to come give a presentation. Unfortunately, in Nebraska, rural schools need a threshold of 20 continually enrolled students to stay open, so the principals have been focused on census the past few years. We have tentatively agreed to my coming up this winter to speak.
Along with other publications, this work inspired a soil management paper:
Birge, HE, Bevans, RA, Allen, CR, Angeler, DR, Baer, SG, Wall, DH (2016) Adaptive management for soil ecosystem services. Journal of Environmental Management 183: 371-378, doi: 10.1016/j.jenvman.2016.06.024
This publication was noticed by the “Beneath Our Feet Blog”, and they invited me to write a guest blog to communicate our paper to a broad audience. I invited the master’s student co-author on the paper to help me write the blog, and our post had the most Facebook shares of 2016 dates:
Birge, HE & Bevans, RA Preserving ecosystem services through adaptive soil management, Blog Entry, Beneath Our Feet Blog – Global Soil Biodiversity Initiative, Summer 2016.
My soil work led me to collaborations with The Nature Conservancy (TNC) in Nebraska, where I interviewed their science director on the work he does with state, federal and private entities to come up with innovative land management strategies. The result was a blog post (below).
Birge, HE Combining private, state, and federal forces to protect Nebraska’s natural resources, Press Release, The Nature Conservancy of Nebraska, Spring 2016.
I also interviewed a fellow UNL graduate student doing work to study aboveground and belowground ecological response post severe fire on TNC land in the Sandhills ecosystem for TNC’s quarterly print newsletter.
Project Outcomes
Economic Analysis
A few valuation estimates of soil health exist, but there are no real ways to capture all of the ecosystem services derived from the soil. Soils and sediments comprise the literal and functional foundation of all terrestrial and aquatic ecosystems. Soil provides a medium for medicinal, food, fuel, fiber, production, regulates nutrient cycling, purifies water, sequesters carbon, remediates disease, pests, and pollutants; serves as a reservoir for biodiversity; and provides building materials for inhabitants of developing nations. By 2050, the United Nations projects that agricultural output must increase by 70% to meet human population growth. To meet these demands, soil structure and function must be altered without concurrently impacting other valuable soil ecosystem services. Soil health is emerging as an answer to this possible conundrum. By promoting healthy soils, farmers can use fewer inputs (i.e., fertilizers, tillage, pesticides) to get higher yields. By using fewer inputs, soil structure and function is preserved, and soil health is promoted. Yet this potential positive feedback among the economic, social, and ecological aspects of the system is not well studied, and requires a careful, scientific appraisal to avoid hidden feedbacks that could lead to unwanted surprises down the road. The SARE funded work I did addressed this very issue, by examining the effects of grassland management on a former rowcrop CRP field that could be under agricultural cover in the future as crop prices fluctuate.Farmer Adoption
I hope that my pamphlet will improve farmer and rancher adoption of practices that best meet their economic, social, and ecological goals across multiple time scales. However, I have also learned that bridging the gap between science and landowner perspective is not as simple as collecting and presenting scientific results. Science literacy of farmers and ranchers, and farming/ranching literacy of scientists is an essential component of farmer adoption of science based management strategies. Based on this learning, I have put forth a postdoctoral research proposal that partly addresses this literacy gap. Specially, I propose to assess farmers’ perceptions of soil health, measurable components of soil health on their fields, and how their farming practices influence these components. Using these data I can identify the degree of coupling between farmer’s perceptions of soil health and objective measures of soil health, and which ecological and social factors, if any, contribute to variation in the tightness of this coupling. This will provide a social context for understanding how the adoption of alternative farming practices can be scaled beyond the farm scale to improve soil health and agricultural returns at regional and greater scales so that scientists can improve how they contribute information to farmer adoption of sustainable agriculture.Areas needing additional study
During this investigation, I identified two additional areas of study. The first was the lack of whole soil C response to treatments. The second was a lack of understanding of how farmers’ perceptions of soil health influence decision-making. While the surveys addressed how farmers value CRP lands and ecosystem services, ongoing research should target soil health specifically. Fortunately, I am beginning to address these areas. For the first, I am using the freedom given to me by the SARE grant to look at multiple pool response (i.e., soil carbon quality) to management treatments. To examine the latter, I am writing a NatureNet postdoctoral research proposal to work with The Nature Conservancy, The University of Minnesota’s Institute on the Environment, and The Soil Health Partnership to assess soil health measures and land owner perception of soil health across a handful of demonstration farms in Illinois, Iowa, and Nebraska.