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Ms. Katie Harrigan: Federal and State Level Soil Health Legislation

Ms. Katie Harrigan of Tufts University provided an update on both U.S. federal and state soil health legislation during the Policy session of the Soil Health Institute’s 2020 Annual Meeting in her talk “Federal and State Level Soil Health Legislation.”

The 2018 Farm Bill (Agriculture Improvement Act of 2018) includes approximately 60 federal-level provisions that include soil health. Almost every provision is active by 2020. Provisions to land stewardship programs such as the Environmental Quality Incentives Program (EQIP) and Conservation Stewardship Program (CSP) encourage soil health planning, resource-conserving crop rotation planning, soil tests and soil remediation through increased incentive payments. Other provisions for land retirement programs, like the Conservation Reserve Program (CRP), enhance end of contract considerations in favor of conservation efforts and form a new Soil Health and Income Protection Program (SHIPP). These and other policy and program provisions will help buffer some of the investment costs as farmers and ranchers change the landscape of soil health.

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Dr. Cristine Morgan: North American Project to Evaluate Soil Health Measurements

The Soil Health Institute is leading the North American Project to Evaluate Soil Health Measurements (NAPESHM) with the goal of identifying the most effective indicators of soil health by measuring more than 30 indicators across 124 long-term research sites in Mexico, the United States of America and Canada. The Soil Health Institute coordinated a panel of scientists to help select appropriate measurement methods, and long-term research sites were selected from a list volunteered by scientists across North America. More specific details regarding the indicators selected, the methods used, and the sites selected can be found on the Soil Health Institute’s website and in a paper published in Agronomy Journal, Norris et al. (2020).

All sites were successfully sampled in 2019, with more than 97% of sampling being completed in the spring before planting. Soil sample analyses and associated quality control checks of data were completed in spring 2020, except a few carbon samples that needed re-testing (delayed because of COVID-19 closures). All management data from the sites have been collected, catalogued and verified. The eight scientists working on the project are in the process of preparing peer-reviewed manuscripts and reports that analyze and synthesize results. Those manuscripts will be submitted for publication in fall of 2020, and the Soil Health Institute anticipates providing a recommendation of a soil health measurement framework in the fall of 2020.

The Soil Health Institute acknowledges the many Partnering Scientists that have contributed their research sites, helped in sampling and offered data analysis ideas to the project. The project is funded by the Foundation for Food and Agriculture Research, General Mills and The Samuel Roberts Noble Foundation.

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Dr. G. Mac Bean: Effects of Soil Health Practices on Soil Water Characteristics

Soil structure and aggregate stability regulate the capacity of the soil to capture, transmit, store and release water. Damaging these soil properties can result in greater soil water runoff and erosion. Therefore, determining how agricultural management practices such as tillage, cover crops, and organic amendments affect soil water cycling is important for regenerative agriculture.

There are several soil measurements related to soil water cycling, including bulk density, saturated hydraulic conductivity and available water holding capacity (AWHC). These measurements were included as part of the Soil Health Institute’s North American Project to Evaluate Soil Health Measurements and were collected at more than 120 long-term agricultural research sites. The measurements at each site represented a business-as-usual practice as well as comparison treatment with soil health management practices. The measurement differences between the treatments were compared to evaluate the sensitivity of each measurement to soil health practices such as reduced tillage, cover cropping, crop rotation, and organic amendments.

Preliminary results show that bulk density and saturated hydraulic conductivity were both responsive to changes in tillage intensity. However, AWHC, measured using intact soil cores, was responsive to changes in both tillage intensity and cover crops with increases in AWHC by 7% and 6%, respectively. No measurement was sensitive to the addition of organic amendments. Overall, AWHC was the most sensitive measurement for determining the effects of management on soil water cycling.

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Dr. Kelsey L. H. Greub: Aggregate Stability as an Indicator of Soil Health for North American Soils

Aggregate stability is defined as the ability of a soil to maintain its physical structure and withstand external forces. Aggregate stability is related to physical, chemical, and biological soil properties, and is sensitive to changes in soil management, which makes it a useful indicator of soil health.

Several methods for quantifying aggregate stability exist; however, the methods differ greatly in the amount and type of external force applied, size and weight of aggregates used, output unit and scale used to quantify aggregate stability, and cost of each analysis. These differences make comparing aggregate stability values for soil health management difficult and raise the need for a universal method for quantifying aggregate stability.

For the North American Project to Evaluate Soil Health Measurements (NAPESHM), scientists at the Soil Health Institute compared four aggregate stability methods, including the Cornell Rainfall Simulator, Wet Sieve Procedure, SLAKES smartphone application, and Soil Stability Index. Each method was evaluated for sensitivity to inherent soil properties, sensitivity to management, and overall utility for stakeholders.

Overall, the methods showed minimal sensitivity to soil organic carbon, as soil organic carbon was poorly correlated with aggregate stability. All methods were sensitive to changes in tillage, with significant increases in aggregate stability when tillage intensity decreased. The Cornell Rainfall Simulator and SLAKES methods also responded significantly to the implementation of cover crops, as well as the removal of crop residue. Based on the results from this study, the SLAKES method is recommended for evaluating aggregate stability due to its high sensitivity to changes in management, low cost, and fast turnaround time for results.

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Dr. Charlotte Norris: Evaluating a Biological Measurement of Soil Health in Agricultural Ecosystems Across North America

What is the phospholipid fatty acid (PLFA) procedure for soils? What do you want to think about when comparing PLFA lab reports? Dr. Charlotte Norris addressed these questions within an agricultural context.

Dr. Norris, Forest Soils Research Scientist with Natural Resources Canada, presented on “Evaluation a Biological Measurement of Soil Health in Agricultural Ecosystems.” In her presentation, Dr. Norris introduced the phospholipid fatty acid (PLFA) procedure and how soil scientists use it to identify the soil microbial community.

Dr. Norris suggested the measure needs some further work to be a universal tool in reporting microbial diversity, and she mentioned other things to consider when comparing across lab reports. She concluded with initial results showing how the tool could be used to assess local environmental conditions for soil microbial health.

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Dr. Elizabeth Rieke: Selecting for Microbial Life Strategies in Agricultural Soils Under Soil Health Promoting Practices

Soil microbes are largely responsible for degrading organic materials and cycling nutrients in soil, and are highly sensitive to physical and chemical changes in soil. Biological measurements currently used to assess soil health provide an understanding of available resource pools, metabolic byproducts, and overall community sizes of these microbes. While these measurements are sensitive to changes in agricultural management practices, less is known regarding which microbes are responsible for driving the changes due to management. Incorporating 16S rRNA amplicon sequencing in soil health studies allows for examination of bacterial and archaeal taxa at finer resolutions.

The Soil Health Institute, using data from the North American Project to Evaluate Soil Health Measurements, identified inherent soil properties and management practices which significantly affect bacterial and archaeal communities in soil using 16S rRNA amplicon sequencing. Preliminary results show between site variation in bacterial and archaeal community structures is highly dependent on soil pH and climate moisture regimes, while within site variation is dependent on management practices. Reducing tillage intensity from intense management to minimal disruption resulted on average in a 13% shift in bacterial and archaeal community structures. Additionally, relative abundances of three bacterial and archaeal orders directly related to nitrogen cycling were significantly greater in minimum tillage systems.

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Dr. Shannon Cappellazzi: Flexible Framework to Quantify the Functions of Soil: Examples with Nitrogen Cycling

The Soil Health Institute is working on building a flexible framework to quantify the functions of soil as a means of interpreting soil health measurements. This framework will be meaningful for farmers and ranchers, those interested in ecosystem services provided by soils, and a host of other stakeholders, according to Dr. Shannon Cappellazzi, Lead Scientist at SHI.

A healthy soil is a vital living ecosystem that functions to its capacity. Soil Health Institute soil scientists are using a suite of tests to develop formulas that assess how well a particular soil is storing carbon, cycling nitrogen and other nutrients, storing water, infiltrating water, purifying water, providing habitat, being a source of biological diversity, suppressing pests and disease, and regulating atmospheric gases such as carbon dioxide (CO2) and nitrous oxide (N2O).

Rather than expensive testing that measures each of these outcomes specifically, we are evaluating more than 31 soil health indicators to draw relationships between simple measurements and these functions. In doing so, we will determine a minimum suite of measurements that provide scientifically rigorous data while maintaining economic feasibility for a wide variety of potential stakeholders, Dr. Cappellazzi said.

Preliminary results show that grouping soils for inherent climate and soil features and then measuring soil organic carbon, microbial respiration through a 24 hour CO2 test, and testing aggregate stability using a smartphone application called SLAKES, can tell us nearly as much about the soil’s ability to function to its potential as a more extensive suite of tests. Additional tests will be analyzed and potentially added to this base suite for quantification of each specific function.

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Dr. Daniel Liptzin: Effects of Soil Health Management Practices on Soil Carbon Dynamics

Carbon has long been considered central to soil health because it plays many roles in soil function. Measuring total soil carbon has been possible for decades, but many other soil carbon measurements have been proposed recently to quantify soil health. These alternative indicators measure some type of biological activity or chemical fraction of carbon and are thought to be more sensitive to management decisions. The Soil Health Institute, through the North American Project to Evaluate Soil Health Measurements (NAPESHM), compared soil organic carbon (SOC) measurements with permanganate oxidizable carbon (POx-C), respiration, microbial biomass, water-extractable organic carbon, and beta-glucosidase enzyme activity.

Preliminary results show that correlations of indicators with climate and soil texture were weak. The correlations among the indicators were moderate, except for microbial biomass which was weak. All of the indicators (except microbial biomass) had a similar capability to detect changes in management. While the cost of most of these tests is similar, the POx-C and 24 hour respiration assays have advantages of being widely available at commercial labs and offer the option of a “field” test. These tests are suggested to respond quickly to changes in management.

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Dr. Michael Cope: Management Indices that Reflect Foundational Soil Health Practices

Soil health management systems are comprised of many specific management decisions such as crop rotation, tillage and cover cropping practices. Categorical (i.e. text- or label-based) characterizations of soil health management (e.g. “no-till” or “conservation till”) overgeneralize important details about soil health management and can be regionally specific. As a result, the categorical descriptions limit our ability to synthesize soil health data across different sectors of agricultural production.

The Soil Health Institute, through the North American Project to Evaluate Soil Health Measurements (NAPESHM), is developing a numerical indexing system to represent core components of soil health management systems. The management indices, based on the principles of soil health, are being used to evaluate soil health measurements along continuous gradients of soil health management practices within and across different sectors of agricultural production.

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Dr. Wayne Honeycutt: Comprehensive Strategy for Advancing Soil Health

Dr. Wayne Honeycutt, President and CEO of the Soil Health Institute, discussed a comprehensive strategy for advancing soil health, a strategy that the Soil Health Institute employs to increase adoption of soil health systems in order to achieve on-farm and environmental benefits at scale.

By 2050, our agricultural systems will need to support another 2 billion people. Yet, in the last century, many agricultural soils have lost 40%-60% of the basic building block that makes them productive (organic matter). The societal and environmental costs of soil loss and degradation in the United States alone are estimated to be as high as $85 billion every single year. Greenhouse gas emissions have reached the highest level ever recorded and are continuing to increase. Drought is expected to increase from impacting 1% of the world’s arable land to over 30% by the end of the century due to climate change. Approximately 80% of our nation’s rivers and streams are currently impaired due to nutrient runoff and other contaminants.

We are at a critical juncture in human history where we must address these challenges by transforming agriculture, and soil health is the framework to do just that, Dr. Honeycutt said.

An abundance of research shows that practices designed to improve soil health also reduce nutrient loss to waterways, reduce greenhouse gas emissions, increase carbon sequestration, increase drought resilience, enhance yield stability, increase biodiversity, enhance pollinator/wildlife habitat, and provide many other benefits. In short, soil health is the foundation for regenerative and sustainable agriculture. However, achieving these benefits at scale requires providing the information our land managers need when deciding whether to adopt new management practices/systems.

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