New Article Highlights Variation in Soil Health Indicators Over Space and Time

Through collaboration between SHP and Utah State University, a new academic article was published in the June 2021 issue of Soil Security. This scholarly journal publishes original research in soil science and the article focuses on how SHP helps build soil security by supporting the adoption of soil health-promoting practices and monitoring and assessing soil health. Soil security is a multifaceted framework that considers soil as an integral part of addressing environmental challenges. The concept of soil security seeks to understand the human, economic and ecological aspects of securing soils in the same sense that food and water can be secured to ensure availability, quality and use for humanity. Measuring and monitoring soil health is a critical component of that goal. The researchers at Utah State University have been engaged in a series of data analysis projects in collaboration with SHP to investigate the relationships among soil health indicators, crop yield and variation over time and space to promote soil security.

Soil security is composed of five dimensions: capability, condition, capital, connectivity, and codification. Capability asks the question, “What can a soil do?”, while condition addresses, “Can this soil continue to do this?” Connectivity, capital and codification are related to how humans interact with and value soil resources and implement soil stewardship policy. Soil health assessments such as Cornell University’s Comprehensive Assessment of Soil Health (CASH), the USDA’s Soil Management Assessment Framework (SMAF), and the Haney Soil Health Tool utilize soil health indicators that represent soil processes relevant to a soil fulfilling its functional capability without constraint to its condition. Interpreting soil health indicators requires databases regionally calibrated to conditions on the ground.

Dimensions of Soil Security

The article published in the journal Soil Security is the product of an in-depth analysis of temporal and spatial variation within and across the SHP member sites. These variation measures are crucial to monitoring progress toward more secure soils and validating changes in soil condition from benchmark values following the adoption of soil health-promoting practices. This contrasts with other recent studies on soil health that have quantified soil health indicator values under differing agronomic systems; however, few have published descriptions of soil health indicator variation over time and space. These types of variation need to be accounted for because soils naturally differ across a field, from farm to farm, and over time. Many factors contribute to this variation. Some of those factors are field topography, crops and other vegetation, organisms living in the soil, climate, season, and management practices, such as tillage or equipment traffic patterns. Soil sampling and laboratory analysis methods are also sources of variation in soil health indicator values. To minimize these human sources of variation, SHP exercises diligent effort to standardize soil sampling and analysis procedures.

The researchers at Utah State University found that soil health indicators have different temporal and spatial variation magnitudes. Their study reported that not all soil health indicators have the same level of variation across a field or over time at the same sampling location. That in-depth understanding will allow growers and researchers to interpret soil health assessments better. For example, some soil health indicators of biological processes, such as soil microbial activity, have much higher temporal variation (inherent change over time) than soil organic matter content, which changes slowly. Physical soil health indicators, such as the components of available water holding capacity related to soil texture, do not readily change over time. In contrast, soil wet aggregate stability, a measure of how well soil aggregates remain intact when wetted, varies to a greater degree across a field and in time because of soil management, crop type, precipitation, and temperature. These examples are illustrative of patterns similarly observed in a dozen other soil health indicators.

Soil security graphs

Spatial (a) and temporal (b) variation calculated at each SHP member site for biological, chemical, and physical soil health indicators. Abbreviations: ACE, autoclaved citrate extractable soil protein; ActC, active carbon; AggStabl, aggregate stability; AWC, available water content; OM, organic matter; Resp, microbial respiration (4 d); WEOC, water-extractable organic carbon; WEON, water-extractable organic nitrogen.  

This inherent variation in soil health indicators complicates interpreting a soil health assessment when many indicators are sampled simultaneously. For growers and researchers, this means that these different levels of variation may need to be accounted for to validate whether a change is taking place following a management shift that adds cover crops, for example. This study’s preliminary conclusion was that monitoring soil health needs to be scheduled consistently to minimize seasonal variations. Additionally, some indicators known to have higher variation levels should be sampled more regularly, such as measuring aggregate stability every other year while measuring ones that slowly change, such as soil organic matter, every three to five years, following a management change. The Utah State University researchers will soon also publish a study investigating whether taking temporal variation into account supports identifying changes in soil health indicators following cover crop adoption.

For further reading, see the published article at https://doi.org/10.1016/j.soisec.2021.100005

3 Ingredients for Success in Soil Health

Profitable conservation systems do not look the same on every farm. Growers must implement different strategies to address their specific needs, thanks to a wide range of variables including soil type, moisture availability, equipment and labor. However, just because every farmer takes a slightly different approach to soil health, that doesn’t mean there aren’t some consistent success factors that we should consider.

In our recent report, Conservation’s Impact on the Farm Bottom Line (developed in partnership with Environmental Defense Fund and the agricultural accounting firm K·Coe Isom) we discovered that farmers who felt their soil health practices were making a difference – both in the data and anecdotally – took some similar approaches. These three “ingredients for success” increased their chances for achieving profitable conservation systems.

Ingredient #1 – Set clear goals for your conservation system

When deciding which approach to take, how to tailor a practice and evaluating success, the farmers in our study benefited from having clearly defined goals. For many of them, these goals fell into two broad categories:

  • Improving soil structure to help with erosion control and water holding capacity
  • Reducing hours on the tractor to save time, machinery and overhead costs

Each farmer reached these goals in their own unique way and all saw positive outcomes as a result of clearly knowing the direction they wanted to head.

Ingredient #2 – Identify areas to go all-in and where to experiment

It is important to recognize that there are different financial dynamics at play when comparing conservation approaches. Those dynamics should be considered when deciding how to implement a practice, based on your financial goals and comfort levels. In our study, we found that most farmers:

  • Made a wholesale shift to conservation tillage with associated equipment updates, knowing they could achieve short-term cost savings
  • Took a stepwise approach to cover crops, experimenting with seed varieties and seeding methods, knowing that the cost savings and soil health benefits with cover crops can take longer to achieve

While it would be great to see a quicker shift to cover crops – in the same way that we see with tillage practices – we found that, as long as expectations are clearly set up front and in alignment with long-term goals, farmers are more comfortable taking the time to “get it right.”

Ingredient #3 – Determine your priorities

Since most farmers face time and practicality constraints in adopting conservation practices on all acres, farmers in our study were most successful when they targeted specific fields or prioritized the biggest challenges needing to be solved. Examples of this include:

  • Using cover crops in fields with swales to retain soil during heavy rain events
  • Changing conservation practices based on crop rotation
  • Choosing to cover crop owned or long-term contracted ground over land with higher rent

Although farmers differed in the tactics used for tailoring their conservation system, they all identified the highest-priority ways to test, adopt and scale their soil health approach.

Digging In

Success looks different for every grower, but by setting clear goals, identifying where it’s safe to go all-in versus where you might need to experiment and prioritizing your approaches, the likelihood that you will find value in your soil health strategy will increase exponentially. To learn more about our work in Conservation’s Impact on the Farm Bottom Line, visit soilhealthpartnership.org/farmfinance.

TNC and SHP Scientists Show Soil Health Indicators Increase Due to Cover Crops

In exciting new research published in the journal Nature Food, Soil Health Partnership – in collaboration with The Nature Conservancy – set out to answer the question: how do cover crops impact soil health indicators in SHP trials? Do we see evidence of changes in the soil, and how quickly do they show up in the data?

Although it might sound obvious that cover crops benefit soil health, much of the research on how soil health changes with adjustments in management practices is conducted in controlled, experimental settings—and many soil health indicators and processes respond slowly to management. That’s why it’s so exciting that we found evidence of soil health improving in the first few years of cover crop use on farms participating in SHP.

Changes seen in microbial activity, soil structure and soil carbon

Using data from 96 farms (see map to the right) over 3-5 years, we looked for changes in six key soil health indicators that are part of the Cornell Comprehensive Assessment of Soil Health that reflect the biological and physical properties of the soil: active carbon, soil organic matter, aggregate stability, available water capacity, respiration and soil protein. Four of these indicators showed evidence of change with cover crops, and the effect of the cover crop increased with the amount of time cover crops had been used on the field:

map of SHP trial sites

  • Active carbon and soil organic matter – different measures of carbon in the soil that are critical to how soil functions
  • Respiration – an indicator of microbial activity in the soil that can contribute to nutrient cycling and residue turnover on the field
  • Aggregate stability – an indicator of soil structure measured by how well soil withstands simulated rainfall in the lab; this can reflect how well water might infiltrate into soil (rather than running off the soil surface), and therefore soil’s erodibility

These indicators can translate into improvements in soil function around soil nutrient cycling and water management on the field, which can have benefits to farmers ranging from less erosion to fewer wet spots to longer planting/harvest windows thanks to improved field conditions.

Time and experience make a difference for soil health indicators

Similar to other research conducted by SHP, this study found that the benefits of soil health management are amplified with time and experience. With cover crops, we found that all of the soil health indicators mentioned earlier improve the longer this practice is in place (see below). This reinforces our recommendation that cover crops should be approached as a long-term investment and strategy, both to give growers a chance to optimize their system and to recognize the greatest benefits to soil health.

graph showing changes in soil health indicators on cover crop fields

Changes in the soil are one of the many benefits of cover crops

Although our work did show that soil health indicators are responding to cover crops, it’s also important to remember that, in many cases, these changes are small and still happen relatively slowly. For example, in our dataset, aggregate stability increased by 1.02% per year more on cover crop strips than control strips—and soil organic matter by 0.01% more per year. This is a big reason why farmers should not expect to see huge changes in indicators like soil organic matter in the first 3-5 years of cover crop use, or else they might run the risk of being disappointed.

“This isn’t to say that soils aren’t undergoing real changes early on, but just that it is hard to detect small changes with existing methods,” says Stephen Wood, Senior Scientist for Agriculture and Food Systems at The Nature Conservancy and a co-author of the study. “For instance, with organic matter and carbon, there’s a lot of carbon already in the soil, so what we’re trying to detect can be like finding a needle in a haystack early on.”

Laboratory indicators are also somewhat limited in their ability to reflect soil function in the field—so it’s important that farmers pay attention to how indicators like infiltration, soil structure, and compaction are changing over time. Just like taking a child’s temperature doesn’t tell us if they have a cough when they are sick, we can’t expect that laboratory indicators will give us a complete picture of soil health.

There is also need for more science that translates how these soil health indicators are related to agronomic and environmental benefits that farmers and society care about. “It’s great to be able to show that soil health indicators increase,” says Maria Bowman, lead scientist at SHP and the other co-author on the study. “But we need to be able to go the next step and say how much yields, yield resilience, and even profitability are likely to be impacted when you see a certain change in a soil health indicator.”

Finally, although observable changes in the soil can be an important benefit of cover crops, we know that some of the other benefits cover crops can provide might show up more quickly than changes in the soil—and be just as valuable. For example, cover crops can scavenge excess nitrogen and keep a living root in the soil during winter months when soil is most vulnerable to nutrient loss and erosion—which has proven benefits for water quality. Cover crop residue can also play a role in suppressing weeds that affect cash crop production and controlling the incidence in herbicide resistant weeds.

“When combined with longer-term changes in soil health, these short-term benefits add up – and can contribute to making cover crops part of a resilient and profitable soil health management system,” Bowman said. “With partners like TNC, we look forward to continuing to evaluate the impacts of soil health practices on agronomic, environmental, and soil health outcomes.”

Visit Nature Food’s website to read the complete article.

Soil Health Indicators

The USDA’s Natural Resources Conservation Service defines soil health as the “continued capacity of soil to function as a vital living ecosystem that sustains plants, animals, and humans.” Soil health is complex and dynamic, which means that a healthy soil can look different in different regions and cropping systems. A number of different soil health indicators can be useful for tracking how the soil responds to management, and measuring soil health in the field and in the laboratory.

Indicator types

Chemical Indicators

pH

Soil pH impacts availability of key nutrients, which means that an optimal pH (between 6 and 7 for corn, soybeans, and wheat) is critical for crop growth.

Primary Macronutrients

N, P, and K are all essential macronutrients that are vital to plant growth. Crops need sufficient quantities of these nutrients in order to grow and thrive.

Secondary and Micronutrients

Nutrients such as Ca, Mg, and S and micronutrients such as Mg, Fe, Mn, and Zn are also critical for crop growth, but in smaller quantities. Typically, soils provide plants with enough of these nutrients, but consider regional recommendations for sufficient levels of these nutrients when reviewing soil test results.

Biological Indicators

Soil Organic Matter

Organic matter influences water holding capacity and contains nutrients that can be broken down by bacteria or fungi to make them available for growing plants. The ability to increase soil organic matter through management varies with climate and soil type and texture. However, decreasing soil disturbance by reducing tillage and keeping living roots in the soil (e.g. by using cover crops) may contribute to building soil organic matter.

Soil Protein

The nitrogen contained in soil organic matter is primarily found in soil proteins. Soil protein indices such as the Autoclaved Citrate Extractable (ACE) protein index indicate how much nitrogen can potentially be mineralized by the soil microbial community and made available to plants.

Active Carbon

This measures the portion of soil organic matter that is readily broken down by microbes as food. Active carbon is essentially a measure of the food stock available for microbes, which promotes nutrient availability and cycling.

Respiration

This measures the amount of CO2 produced by microbes, which is an indicator of soil microbial activity.

Physical Indicators

Soil Texture

Inherent soil properties such as soil texture cannot be changed through management practices. Soil texture impacts what management practices might be a good fit for an operation, and also mediates responses of other soil health indicators to changes in management.

Available Water Capacity

Available water capacity depends on innate soil texture but can be impacted by the amount of soil organic matter and soil aggregation, both of which can increase water holding capacity.

Aggregate Stability

Soil aggregates are held together tightly via root exudates, soil fungi, and inherent soil properties. They can be improved upon by creating environments for “biological glues” to be produced by plants and microbes by reducing tillage that physically breaks soil aggregates.

Bulk Density

The proportion of dry solid material in a cubic volume indicates the amount of pore space in a soil. Soils with a high bulk density have less pore space, which leaves less room for air and water critical for root growth and nutrient cycling. This can also be an indicator of how compacted the soil is.

Inherent soil properties such as soil texture cannot be changed through management practices.

Soil health indicators in the field

water-infiltration-icon-sm

Water Infiltration

Root-health-icon-sm

Root Health and Rooting Depth

smell-icon-sm

Smell

Slump-slake-test-icon-sm

Slump Test or Slake Test

Erodibility-icon-sm

Erodibility

Soil-fauna-icon-sm

Soil Micro and Megafauna

You can find a print version of this informational resource by clicking the button below.

Find Out More

Learn more about the soil health indicators SHP uses when working with farmers.

Get to Know What Lives in Your Soil

Healthy soil is the foundation for productive crops and a resilient farming system. When it comes to building soil health, we often talk about the physical and chemical properties of soil – things like soil texture, aggregate stability and soil organic matter. There is a third component of soil health, though, that is highlighted less frequently: the biological component.

At its most basic level, soil is made up of weathered rock material, water, air, and the remains of decomposed plants and animals. Beyond that, the soil is an entire functioning ecosystem full of life! In just one handful of soil, there can be billions of microorganisms, including some you’re probably already aware of, like bacteria and fungi. 

Other living organisms in the soil can be classified as invertebrates. An invertebrate is simply an organism that does not have a backbone. Some common soil invertebrates include mollusks, earthworms, arthropods (i.e., insects, spiders and crustaceans), and nematodes. Soil invertebrates living beneath the soil surface may be harder to detect, but by familiarizing yourself with the most common invertebrate groups, you can be sure you won’t underestimate their impact on soil health and agriculture.

Arthropods and Earthworms

The role of arthropods and earthworms in agriculture is well-established. Arthropods, at the soil surface and beneath, are great decomposers and nutrient cyclers. Arthropods that feed on plant residue help to build soil organic matter and can impact soil fertility. Soil-dwelling arthropods can be pests (e.g., cutworms or white grubs), but they can also help to control pest populations. For example, ground beetles and spiders are arthropod predators that are often encountered in fields. 

When earthworms move through the soil, they create channels that can help improve soil drainage. Earthworms also enhance soil structure and nutrient cycling through their movement and feeding habits. Scouting for earthworms is fairly simple and can be done by counting the number of earthworm middens on the soil surface. An earthworm midden is a small pile of plant material and worm castings (worm poop!) that can be found at the entrance of a worm burrow. The photo below shows five earthworm middens in a no-till field. Click on the link below the photo for more information. 

Earthworm Middens

Credit: Sjoerd Duiker via No-Till Farmer

Nematodes

Nematodes – or microscopic roundworms – are lesser-known organisms in the soil. Plant-parasitic nematodes can be agricultural pests that impact plant health and yield by sucking out the contents of plant cells using piercing, needle-like mouthparts. This type of nematode can also vector plant diseases, such as tomato mosaic virus. There are also beneficial nematode groups that are present in healthy soils, such as bacteria feeding, fungal feeding, and predatory nematodes. 

Nematode feeding damage is often misidentified as a nutrient deficiency in crops; plant symptoms – such as chlorosis, stunting, and wilting – are common examples. While some nematodes, like Soybean Cyst Nematode, can be visible on plant roots, most nematodes will require positive identification through a soil sample. When soil sampling for nematodes during the growing season, use a soil probe to sample 6-8 inches deep and sample at the base of the plant in the root zone. If sampling outside of the growing season, fall is the best time for detecting nematodes because populations will be at their highest.

Some plant-parasitic nematodes are very common and can be found in nearly every soil type or cropping system (root lesion and stunt nematodes [see picture below], for example). Generally, these nematodes will rarely cause economic harm to crops. Some nematodes, however, are more specific to a soil type or to the crop they are attracted to. Two examples of harmful plant-parasitic nematodes are Soybean Cyst and Corn Needle (see picture below) Nematodes.

The head of a Corn Needle Nematode. This nematode feeds almost exclusively on corn roots and the economic threshold is just 1 or 2 individuals in 100 CC of soil (about a handful of soil). 

Stunt nematodes are plant-parasitic nematodes that feed on field and vegetable crops. The economic threshold for stunt nematodes varies by crop and soil type, but is 100-200 individuals in 100 CC of soil (about a handful of soil) in corn.

Digging In

The soil is a living, functioning ecosystem full of organisms you can and can’t see. Microscopic or not, these organisms can have a big impact on your productivity. The next time you’re out in the field, keep an eye out for signs of earthworms and other invertebrates that can be seen with the naked eye. And, if you are interested in learning more about soil invertebrates on your farm, reach out to your SHP field manager or your local agronomist to explore scouting and soil sampling options.

Why No Change in Yield Can be a Good Thing

The success of a growing season is typically measured by yield, bushels per acre, actual production history (APH) and farm average. It’s commonplace to hear comparisons of these measurements in conversations at the local coffee shop this time of year. The higher the increase in a season, we tell ourselves, the more successful we were. However, I’m going to argue that not seeing a change in those measurements can actually be a good thing. 

When it comes to agriculture, business decisions are made more methodically and emotionally then in most business sectors. The way your farm operates goes back generations – my father did things this way, my grandfather did things this way – and those family ties make operational changes difficult. 

However, in 2020, consumers are demanding more from their products. They want sustainable, renewable, green, organic products that are not only perceived to be good for them, but also good for the environment. At the same time, farmers have begun to realize the importance of resilient soil and that soil health practices are a tool to manage the function of soil and crop productivity.  The bright side here is that, at the Soil Health Partnership, we are seeing positives in these shifts

Since SHP began in 2014, questions from farmers have been, “How have cover crops and no-till trials compared to the normal practices?” And when they talk about comparison to “normal,” they mean one thing: yield. 

Do cover crops pay? Can I afford to no-till? 

After six years of research and studies on more than 200 farms, we are seeing many farms able to maintain their yields when implementing soil health building approaches and, to us, that’s a good thing. Here’s why:

Maintaining yield from the get-go is important because a farmer can confidently make the switch to sustainable practices and know their production will still be there. They can market, plan ahead, and sleep at night knowing their APHs will stay put. Even though our trials show no significant yield loss or change, they are showing big differences when it comes to soil health management factors like soil quality, soil resilience, weed suppression and organic matter…just to name a few.

When we look at these factors, it’s easy to see that yield isn’t the only factor in these decisions anymore. I, for one, have growers who have eradicated herbicide resistant marestail by simply putting down a basic cereal rye cover crop. They’ve eliminated a fall burndown pass and, depending on establishment, a spring burndown when they plant soybeans green, as well. 

I have other growers who experience a more timely harvest and planting time frame on no-till fields – where the soil structure is better than on tilled fields, allowing them to get into the fields sooner and with less ruts and damage during wet harvests. The combination of cover crops and no-till are also helping growers prevent gullying and erosion, especially when weather patterns lately are bringing large quantities of rain at a single time frame compared to 1-2” rains in a timely manner. 

The time has come to reframe our measurement of success. It’s not always about more yield anymore. It can be about less – less weeds, herbicides, fuel, compaction…all while maintaining yield. It can be about more of other things, like lengthening the planting window, better water infiltration, and improved aggregate stability. This fall at the coffee shop, I challenge you to talk about less – as in, what you didn’t do while still maintaining your yields. Not only for our generation of farmers today, but for the generations to come in our ever-changing industry.

The Importance of Data Collection

After the harvest issues in 2018, planting issues of 2019, and the heavy rains in mid-May of 2020, data software and collection might be on the back burner of important things on your operation. Farmers have been so focused on getting a crop in or out of the field that, when the monitor beeps or acts up, the reaction for most is to ignore it and keep on going. Not to mention prices have been volatile, making breakevens tight and preventing farmers from upgrading their systems.

Why, then, is data collection still something to focus on?

At Soil Health Partnership (SHP), we believe quality information is critical to farmer success. For example, in order to truly understand the yield potential and fertilizer efficiency for every grower in our program, we look at planting dates, fertilizer rates, and population counts (among many other things), and tie that information to harvest data – which gives us a more complete picture of farming practices for the year in that SHP trial.

Data collection allows us to report back to the grower the best information possible. In return, that information helps the farmer decide what to do or not do in the years to come. Our data and reports are only as good as the data we receive – proving that good data collection is pivotal for you and SHP.

Here’s another example of just one of the many reasons information gathering can be useful:

Let’s say your crop was planted in a timely manner, was open and growing – and then heavy rains came through and washed out 5-10% of the field. If you were collecting good data, this would show up on a harvest map come that fall. Because you’re able to take this map to your landlord and show them the problem spots in the field, you can help the landowner understand the value of tile drainage, and how the return on investment (ROI) of tiling could quickly increase both their income and the value of that piece of ground.

Another interesting takeaway from good data is the ability to look more closely at areas that struggle to be profitable. Wet holes, fence rows and tree lines are places that drainage and conservation farming practices will not help. These areas might be prime candidates for NRCS programs, which ensure an income while setting back acres that are costing you money year-in and year-out. When you use this data and look at it from an ROI point-of-view, it can help you make decisions that can increase your bottom line and decrease your workload.

I encourage you to research and look into ways to track and collect data on your operation. There are many different companies out there; I recommend finding a local company with great service to work with. With so many products available, service and reliability are my top two priorities. From there, learn the software and find ways to utilize the data received, both on and off the farm. As with any software, keep up-to-date with everything, as companies are constantly upgrading systems to help justify and simplify things annually for their growers.

10. Wayne Honeycutt – Farmer Adoption of Best Soil Health Practices is Key

Wayne Honeycutt is the CEO of the Soil Health Institute – not to be confused with the Soil Health Partnership. The Soil Health Institute is focused on the science of soil health and how different practices impact different elements of the soil.

Honeycutt’s interest in the soil stems from a big “A-ha!” moment as he conducted research on the soil in Maine. In one study, he was able to double the yield of potatoes in one cropping system by either irrigating or by improving soil health. After soil health improved, he discovered irrigating no longer boosted yield. Soil health was the answer on that Maine farm – and Honeycutt remains convinced the same can be said for many farmers in many regions of the country.

“The whole concept of soil health is holistic. There are chemical, physical and biological properties. It’s like human health. For human health, we don’t just go in and ask for our blood pressure to be checked and feel like we have a complete picture. We have many other things that we want to be analyzed, including what’s in our blood. It’s a similar way with soil health. There are not just one or two things. There’s a whole suite of things that need to be analyzed,” Honeycutt said.

For now, the Soil Health Institute is focused on analyzing each aspect of soil health and figuring out how to increase farmer adoption. They are working on programs to quantify the business case for farmers and identify the best measurements and tools for farmers to select management practices that improve soil health.

Farmer adoption is key.

According to Honeycutt, the models indicate that if farmers will adopt soil health practices on at least three-fourths of land, then all greenhouse gas emissions for the entire U.S. agriculture sector are reduced. Also significantly reduced, by millions of pounds, would be the amount of nutrients that are lost to U.S. waterways.

“And, of course, these losses are not just environmental issues and impact. They also directly impact the pocketbook of farmers, too,” said Honeycutt.

Listen in below to learn more about this innovative and exciting new area where scientific discovery will eventually make prescriptive soil health a reality.