Farmers make multiple management decisions daily — decisions driven by questions and input. Helpful input can come from many sources, guiding what to choose or avoid. Most university-led research has placed soil balancing on the “avoid” list. Still, it’s practiced by many farmers who report improved soil tilth, better crop yields and quality, and greater ease in managing weeds as the ‘balance’ of their soils improves.
At least one team of university researchers remains curious, wanting another look at soil balancing. Their work is beginning to reveal that farmers and researchers think, talk about, experiment with, and understand soil balancing differently. If those differences could be bridged, what new questions and helpful input might researchers and farmers find by working together?
The Science Behind Soil Balancing: Basic Cation Saturation Ratio
Soils vary in their nutrient content, but also in their ability to hold nutrients. A soil’s ability to hold nutrients is measured by its cation exchange capacity (or CEC). Generally, a soil high in clay content will have a higher CEC, but organic matter also increases CEC. Soils with a high CEC hold more nutrients and thus, can release more than soils low in CEC.
Soil balancing focuses on managing the ratio of specific cations in a soil’s CEC. Based on the theory of Basic Cation Saturation Ratio (or BCSR), soil balancers strive to attain an optimal ratio of the cation nutrients calcium (Ca), magnesium (Mg) and potassium (K), in the soil. Although recommendations have varied by researcher, most call for 65% Ca, 10% Mg, and 5% K.
Soil balancing concepts were first proposed in the late 1800s by a German scientist, Oscar Loew, and then were built upon by others starting in the mid-1900s. However, the main concepts are commonly associated with William A. Albrecht, a Professor at the University of Missouri during the 1930s-1960s. Albrecht believed crops responded to limestone or gypsum primarily because of increased Ca levels, not changes in soil pH.
A Review of Past Research
The benefits of Ca have been supported by research. Ca helps form bridges between organic and clay surfaces, leading to better soil aggregate stability, while very high Mg levels can reduce pore space and lead to “tighter” soils. Improved soil structure facilitates better drainage, which can mean better seedling establishment, root growth, aeration, and nutrient availability. BCSR theorizes that adding Ca through large inputs of calcium-rich amendments like limestone or gypsum, will improve soil structure. But in controlled experiments, crops performed the same at a variety of Ca:Mg ratios, as long as sufficient supplies of Ca and Mg were available. Past research has also shown good soil structure to exist at a variety of Ca:Mg ratios.
With regard to soil fertility management, land grant universities have historically advocated for determining a sufficient level for each nutrient in the soil. This approach is sometimes called Sufficiency Level of Available Nutrients (SLAN) and differs from BCSR’s focus on Ca:Mg:K ratios. Agricultural researchers have evaluated SLAN-based approaches for decades, but BCSR approaches have been studied and reported on far less.
When comparing the two approaches, researchers have not seen increased yields with BCSR. For many soils, achieving balance requires relatively large inputs of soil amendments to raise Ca to the desired level. A balanced soil is rarely achieved quickly and often requires an investment of time and materials. Based on research to date, that investment is unlikely to be paid back with increased crop yields.
With few reproducible scientific studies to back up the positive experiences reported by farmers, soil fertility specialists like The Ohio State University’s Steve Culman are hesitant to include soil balancing in recommendations or classroom lectures.
“I will remain skeptical until I find out otherwise,” he says. “I am going to need very good evidence right now to suggest that spending all that money on material is worth it.”
However, there are limitations in the past research, as noted by a literature review done by Culman and postdoctoral researcher Vijayasatya Chaganti. Initial discussions with leading proponents of balancing revealed a general feeling that past research studies were too short, focused on too narrow a conception of soil balancing, or measured too few of the outcomes organic farmers consider as important.
Looking for New Direction
Despite the lack of support for BSCR in scientific literature, farmers and farm-advisers continue to report improvements in their soils and crops that they attribute to a soil balancing approach. These reports and the limitations of previous research were enough to pique the interest of several researchers at Ohio State.
Lead investigator Doug Doohan, a weed specialist at Ohio State, says he had encountered soil balancing in the ’90s, but had not taken it very seriously. Around 2011, a graduate student research project prompted Doohan to think soil balancing was more wide-spread among organic farmers than he had initially thought. He found colleagues at Ohio State with similar experiences. Vegetable production specialist Matt Kleinhenz also experienced farmers mentioning soil balancing as a way to improve crop quality. Incorporating input from farmer stakeholders affiliated with the university’s organic research program, several researchable questions began to crop up. Many of these questions crossed traditional discipline lines, allowing the Ohio State soil balancing project to include contributors from multiple research areas. Current primary investigators include Doohan and Kleinhenz, plus soil fertility specialist Steve Culman, economist Subbu Kumarappan, and social scientist Doug Jackson-Smith.
Team members were interested in the thought process behind organic farmers’ adherence to soil balancing. Did the farmers’ direct experience and unique vantage point reveal something researchers were missing?
To develop a better picture of practitioner views on balancing, researchers Doug Jackson-Smith and Caroline Brock conducted a series of semi-structured interviews with farmers and consultants. Starting with recommendations from the team’s advisory board and partner farmers, Jackson-Smith and Brock eventually interviewed a cross-section of 33 growers and crop consultants.
“The interview method is a very effective way to get into depth and detail about the nuances of what people do and why they do it,” says Jackson-Smith.
Very little work has been done to document the experiences and practices of the soil balancing community, according to Brock, who is also studying the history of soil balance theory. What exactly were practitioners observing on their farms? How did they carry out soil balancing techniques in real field conditions? How widespread is the practice?
By asking open-ended questions about management practices and decision-making, Brock and Jackson-Smith began to see a “complexity” of ideas out there.
“Farmers and consultants have a broad approach to soil balancing, which includes multiple factors: chemistry, biology, and physics, along with key management practices,” noted Brock.
According to Brock, this broader view included a ‘balanced soil biology,’ which may involve the applications of micro-nutrient blends and microbial formulations thought to facilitate the balancing process and contribute to overall soil health. Farmers either included these additional practices in their definitions of soil balancing or considered them as crucial in making balancing work.
Jackson-Smith said several interviewees actually warned against thinking that “altering your Ca-Mg balance was going to be a magic bullet.” Rather, balancing was “part of a suite of things they were doing.”
Many farmers are even using balancing in conjunction with conventional SLAN fertility programs. Perhaps past research studies that tested these two practices as competing theories have missed the mark. Alternatively, the working definition of soil balancing may have shifted over time and no longer hinge on BCSR alone.
Another important find in the interviews related to the goals of soil balancing. While most research trials on BCSR have focused on increasing crop yields, this was not the most frequently mentioned benefit of balancing during the interviews. Improved soil structure was cited most often. One farmer referred to balancing as a way of “feeding the soil rather than the crop.”
Ohio State’s Soil Balancing team also used a more traditional survey. While interviews are good at finding in-depth information on decision making processes, a survey can collect enough data to reveal characteristics about a larger group of people. In a survey of organic corn growers in the Midwest, respondents were given a definition of soil balancing that focused on BCSR and asked if they were soil balancers by that definition. A little more than half of the 850 respondents indicated they were soil balancers. However, in an open-ended question respondents were asked what management practices they used for soil balancing. Only 20% mentioned BCSR-related concepts, indicating there is more to balancing for many of these growers.
“I think there are two definitions we’re becoming aware of,” summarizes Culman. “One is the more academic take which is really focused on calcium-magnesium ratios. The second is a more holistic approach that nearly every grower or person that we’ve talked to about this thinks, which is certainly more than just Ca:Mg, but more of a whole nutrient profile type.”
Lead project investigator and weed specialist Doug Doohan says this difference of definitions plays into a longstanding issue with research in organic agriculture. While scientists often focus on testing single variables, organic farming is more focused on systems and long-term results. Thinking about systems requires a different approach than most researchers are used to and involves some “stepping outside the comfort zone,” according to Doohan.
Asking New Research Questions
To ensure their research matches more closely with real farmer situations and practices, the research team established a stakeholder committee of growers and consultants very early in the process. This group provides feedback on research approaches and future directions the work might take. By partnering with organic grower associations, the team has also been able to include on-farm research plots, which brings a variety of conditions and soil types into the mix.
According to team researcher and vegetable production specialist Matt Kleinhenz, lengthening the study and evaluating variables other than yield alone were major changes the team planned to implement from day one. The team is also looking at a larger variety of crops, including both agronomic and vegetable production systems.
The ongoing experiments at Ohio State research stations and partner farms are examining a range of variables: yield, but also input costs, crop nutrient content and quality, weed and pest populations, drainage, and other soil health indicators. In addition, they are studying the effectiveness of different Ca-rich amendments next to amendments that simply raise the pH without adding Ca. And field experiments vary from short-term, one growing season studies to five-year studies – hopefully longer.
Moving the Conversation Forward
As data from surveys and field studies are analyzed, new questions are already arising. Does soil type change the effectiveness of balancing? Can soil balancing cause or prevent nutrient interactions and deficiencies? What additional variables should be examined?
The Ohio State team is of course looking to document any significant effects traditional soil balancing has on the physical and biological properties of soils, fields, or crops grown on them. But an equally important goal is to foster a better exchange of ideas between researchers and those in the field. The team seeks to establish a commonly accepted knowledge base on soil balancing that will help move the conversation forward.
So far researchers have found common ground among soil balancers, many of whom are using balancing not as a replacement for recommended methods, as some researchers once thought, but as a supplement, also relying on more agreed-upon techniques such as increasing organic matter and conducting soil tests. In time, the research team hopes their work will result in practical and relevant guidelines for those using or considering soil balancing as part of their management techniques.
Doohan says the team has caught a few glimmers of light in their field research data. He feels confident the group will find theoretical explanations for the observations farmers are reporting.
Meanwhile, the open communications between researchers and growers has been a positive learning experience.
“They’ve learned that we actually are interested in their experiences. And that we are interested in working with them,” says Doohan. “And I think they’ve learned that we respect them; that we respect their knowledge, their experience, as special, unique, and different from ours, and that we can learn from them.”
Interested in joining the conversation? Ohio State will host a series of three Call-in Conversations in the fall of 2018. October 17, November14, and December 12 from 1:30-3 p.m. EST. For more information, visit their website, go.osu.edu/SB-call-in.
Ohio State hopes to share additional research findings in future articles. Stay tuned for results of survey and field data so far.