Mr. David Lamm: Healthy Soils for Sustainable Cotton Program

Today’s consumers want to know their food and fiber products are sustainably grown and the cotton industry is listening. Cotton farmers, manufacturers and retailers are collaborating to deliver cotton in a way that increases soil organic carbon as well as reduces greenhouse gas emissions, soil loss, and water use.

In partnership with the Walmart Foundation, Wrangler® Jeans and the VF Foundation, the Soil Health Institute is working with cotton producers to increase soil health management system adoption. The Healthy Soils for Sustainable Cotton project offers farmer-focused education and training events delivered by Soil Health Institute scientists, partnering soil health technical specialists and farmer mentors who produce cotton using soil health-promoting practices. Healthy Soils for Sustainable Cotton farmer mentors and soil health technical specialists provide producer guidance and technical assistance throughout the term of the project as part of a farmer-to-farmer network.

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Dr. Dianna Bagnall: A New Tool for Farmers to Build Drought Resilience through Soil Health

Farmers know that soil health-promoting practices increase soil organic carbon, drought resilience, and farm profitability. Despite this, equations provided in soil science literature have not shown this relationship. As a result, farmers have not had a tool that estimates how a management practice will change their farm’s drought resilience.

New data from the North American Project to Evaluate Soil Health has allowed scientists at the Soil Health Institute to create new equations. These equations capture the link between soil organic carbon and plant-available water. The newly collected data include the effects of soil health-promoting practices and soil structure.

Using the new equations, Colorado State University, the U.S. Department of Agriculture, Natural Resources Conservation Service, and the Soil Health Institute have developed a decision support tool that will be freely available as a part of the online CarbOn Management and Emissions Tool (COMET-Farm). The decision support tool, currently in beta version, will allow farmers to explore how to build soil carbon and improve drought resilience. Farmers and their advisers can calculate changes in plant-available water that are driven by soil health management practices, such as no-till or cover crops. This significant advancement provides a powerful incentive to drive the adoption of soil health management practices and enhance on-farm profitability.

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Dr. Archie Flanders: Identifying Costs and Benefits of Soil Health Management Systems

Research indicates that soil health management systems (SHMS), which include reduced tillage and incorporating cover crops with production of cash crops, decreases soil erosion, improves water infiltration, increases soil carbon, and reduces inputs that can have potentially adverse environmental impact. Encouraging production practices that improve soil health includes demonstrating that individual farm profitability is increased by adoption of SHMS.

Partial budget analysis is a farm management analytical method in which comparative financial returns are determined by quantifying the net effect of only specific proposed changes in production.

For example, converting from conventional tillage without cover crops to no-till production with cover crops will eliminate field activities that impact associated costs. A partial budget analysis will account for the cost of cover crop seeds and costs associated with planting and terminating the cover crop, all of which are specific to the change of adding cover crops to the management system.

The partial budget methodology presented demonstrates procedures for quantifying changes in production costs associated with adoption of SHMS. The Soil Health Institute has ongoing projects applying partial budget analysis to research plot trial data as well as case study farm data, Dr. Flanders said.

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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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