A Charlatans Soil Amendments

A Look at Soil Balancing

A Fringe Idea

Proper fertilizer recommendations are an essential component of scientific agriculture. Testing the amounts of nutrients in a soil and adding amendments to bring those nutrient levels to a precise optimal quantity is one of the often unsung marvels of modern farming.

However, to properly interpret these tests, we need to have a solid method that guides how recommendations are made. The standard method is SLAN or Sufficiency Level of Available Nutrients. This method assumes that plants need a specific amount of nutrients, be it nitrogen, potassium, molybdenum, etc., and once that level is reached, more of those nutrients will not aid in improving growth outcomes for the plant. So, when interpreting soil tests, agronomists will determine what this sufficiency level is for that soil and crop combination and recommend fertilizer amendments to bring those levels up to where they need to be.

Visualization of SLAN (courtesy of Cornell Extension

Soil balancing is a competing method that dispels this notion of individual sufficiency levels in favor of ratios of nutrients. Specifically, calcium, magnesium, and potassium are zeroed in under this procedure. Different ratios are recommended by different sources, but broadly, having 65% calcium to 15% magnesium is considered an “ideal” soil.

Die-hard soil balancers make some extravagant claims about the practice. They say that, by applying these principles, both the productivity of cropping systems and the quality of crops are improved. Crop quality refers to the nutritional properties of the grain, which is an unusual metric to find in a discussion on soil fertility. Balancers also believe that soil structure and microbial diversity are improved under this practice.

None of these claims hold much water. Several trials have been conducted comparing soil balancing to standard fertilization regimes. Crop yields are never better under any of these trials. Similarly, nutritional contents are similar to crops grown under both systems. This claim is particularly bizarre to me, as plant nutritional contents are determined genetically, so again, the level of nutrients available would be more important than the ratio in which they are available. Soil microbial activity is also similar between both systems, with carbon compounds indicative of microbial life being similar. Some improvement in soil structure can be observed, but it is not tied to a specific ratio and is more generally a result of calcium improving the aggregation of soil particles. Overall, soil balancing seems to fail any rigorous scientific test of its effectiveness.

By themselves, utilizing calcium and other amendments is not a bad thing. There are calcium-deficient soils, and adding more calcium and other compounds can improve aspects of fertility and soil structure, improving productivity. The problem with this method, rather, is the chasing after these magic ratios. Reaching a line of sufficiency for each nutrient individually is much easier than trying to balance a ratio of multiple nutrients tied together. Say you have a field that is only deficient in magnesium. Under the SLAN method, you would add magnesium until you reached that line again. But under soil balancing, you need to amend all of the nutrients to achieve that ratio again. This can get incredibly costly. In a 1982 study at the University of Nebraska-Lincoln, researchers found that utilizing the ratio method can as much as double a farmer’s fertilizer bill to no discernable benefit.

The Lack of a Mechanism

There are soil properties that impact the availability and uptake of nutrients, namely soil pH and cation exchange capacity. While the amendments utilized in soil balancing can be used to improve soil pH, with calcium and magnesium being used to turn basic soils more acidic, focusing on ratios is ludicrous. Across biology, there are situations where synergistic effects are seen when two nutrients or compounds meet that can increase nutrient uptake or effectiveness. For example, vitamins such as A or K are more available to our bodies when eaten with fatty foods. This is why you should eat dressing with your salad, as it improves nutrient absorption. While there is certainly precedent for these sorts of things, you need to be able to identify a mechanism as to how such a ratio corresponds to improved nutrient uptake in crops.

As far as I can tell from the literature, soil balancers don’t have a proposed mechanism. There are hints at synergies between calcium and magnesium that are said to improve nutrient availability when in their goldilocks ratios or the promotion of microbial diversity that somehow helps to boost availability. But again, how those molecules are interacting to actually drive this is not identified. Because they are not there. It’s similar to the ‘vaccine causes autism’ crowd who endlessly speculate on what is in vaccines that actually causes autism. It’s just endless speculation because it’s impossible to study a process that is not occurring.

Despite these issues of evidence, some farmers still believe that, when employing these practices, they are seeing improvements in their productivity. I believe that because their amending practices in a roundabout way improve soil pH and structure, they take it as a validation of the practice, despite the fact that the same outcomes could be achieved much more cheaply using the SLAN method.

Academia vs. Consultants

What I find interesting within the soil balancing story is the interplay, or lack thereof, between academia, consultants, and farmers. Given the scarcity of any meaningful evidence that soil balancing does any good, it’s of no surprise that agronomists from universities, extension services, and other institutions of scientific agriculture consider the whole practice pseudo-science. One of my favorite quotes from a researcher describing the industry is, “[soil balancing] is the province of charlatans who wish to sell unneeded soil amendments.” Therefore, the major proponents of this practice are fringe consultants and publishers, mostly in sustainable and organic spaces. Because of this, most of the farmers utilizing this practice are organic producers.

The paper that inspired this piece, “Soil balancing within organic farming” by Brock et al. (see below for references), dived into the disconnect between farmers and agricultural science utilizing a framework called Communities of Practice. This framework assesses professional communities by the specific practices or guiding philosophies they use to perform the same or similar goals. For example, in medicine, you could say there are separate Communities of Practice among MDs and DOs. They both do the same job but have different doctrines of medicine.

The Community of Practice among soil balancers is very insular, with little input from agricultural scientists, and the information flows are dominated by these consultants and publishers. They focus heavily on the ratios, which are linked to the consumption of amendments. They also hone in more on crop quality, making it a major selling point of the practice. Another major focus of these consultants, in response to the scientific research showing soil balancing’s lack of outcomes, is that these trials are not ‘on farm’ and thus cannot be applicable to the context of actual working lands. This is a bizarre counterpoint to me. As long as the soils and cropping systems are relatively similar, there should be no difference in how these methods play out on a research farm vs. a production farm. The purpose of on-farm trials is either to see how a practice integrates into an enterprise or as a way to demonstrate the science to producers. The consultants are analogizing research farms to lab mice and production farms to human bodies, which is just ridiculous since there are no meaningful differences in the actual systems under investigation.

Farmers, of course, have their own perspectives independent of the consultants. They were much more focused on issues of soil biology and chemistry, valuing the perceived microbial diversity and activity much more highly than consultants seem to. Farmers also consider soil balancing only as a part of a wider series of management strategies they use to improve their soils and yields. Again, many of the farmers come from an organic background and value biodiversity, ecosystem services, and quality food very highly. These values are part of why soil balancing attracts them in the first place, as it purports to support these values.

Learning that most of the farmers who utilize soil balancing are organic, I wasn’t particularly surprised. The scientific establishment has not been great at working with farmers who have sustainability-oriented goals. Land grant universities and extension agents are optimized to work with conventional growers over those who wish to color outside the lines. However, sustainable farmers are still hungry for information on how to realize their goals. And when the institutions don’t meet the supply, the demand goes elsewhere. Unfortunately, this has led countless farmers to waste money on consulting services and useless inputs.

What I’m Reading, Watching, and Listening to

Bubblegrunge for Beginners: Found myself diving back into this dichotomous music genre.

On Cats: Article showing some adorable cat illustrations in medieval manuscripts, accompanied by a nice rant.

Quantified Breakup: An old blog written by a data scientist who was at the time going through a divorce. To help cope, she analyzed her behaviors during the breakup and of her life after. It was a fascinating trip. I learned about this blog from this interview with its creator.

References

Battle, B. 2018. Soil cation ratios versus sufficiency levels. MSU Extension. https://www.canr.msu.edu/news/soil_cation_ratios_versus_sufficiency_levels (accessed 15 October 2023).

Brock, C., D. Jackson-Smith, S. Culman, D. Doohan, and C. Herms. 2021. Soil balancing within organic farming: negotiating meanings and boundaries in an alternative agricultural community of practice. Agric Hum Values 38(2): 449–465. doi: 10.1007/s10460-020-10165-y.

Chaganti, V.N., and S.W. Culman. 2017. Historical Perspective of Soil Balancing Theory and Identifying Knowledge Gaps: A Review. Crop Forage & Turfgrass Mgmt 3(1): 1–7. doi: 10.2134/cftm2016.10.0072.

Chaganti, V.N., S.W. Culman, C. Herms, C.D. Sprunger, C. Brock, et al. 2021. Base cation saturation ratios, soil health, and yield in organic field crops. Agronomy Journal 113(5): 4190–4200. doi: 10.1002/agj2.20785.

Culman, S.W., C. Brock, D. Doohan, D. Jackson‐Smith, C. Herms, et al. 2021. Base cation saturation ratios vs. sufficiency level of nutrients: A false dichotomy in practice. Agronomy Journal 113(6): 5623–5634. doi: 10.1002/agj2.20787.

Kopittke, P.M., and N.W. Menzies. 2007. A Review of the Use of the Basic Cation Saturation Ratio and the “Ideal” Soil. Soil Science Soc of Amer J 71(2): 259–265. doi: 10.2136/sssaj2006.0186.

Leiva Soto, A., S.W. Culman, C. Herms, C. Sprunger, and D. Doohan. 2023. Managing soil acidity vs. soil Ca:Mg ratio: What is more important for crop productivity? Crop, Forage & Turfgrass Management 9(1): e20210. doi: 10.1002/cft2.20210.

Saha, U. 2022. Cation Exchange Capacity and Base Saturation. University of Georgia Extension Circular 1040. https://secure.caes.uga.edu/extension/publications/files/pdf/C%201040_3.PDF (accessed 15 October 2023).

Sever, M. 2023. Managing Soil Acidity, Not Soil Balancing, Affects Yield. Crops & Soils 56(4): 18–20. doi: 10.1002/crso.20279.