Another wet spring, and many farmers postpone field work awaiting drier conditions. Could improved drainage be obtained through the application of common gypsum? This is one of the claims made by many consultants and farmers who use a practice called soil balancing.
Ohio State’s five-year study on soil balancing has been mentioned in previous VegNet articles. The project involved multiple long-term field tests, as well as interviews and surveys to better document practices and beliefs surrounding soil balancing. Despite a lack of past research proving soil balancing’s effectiveness, we found that the practice is used heavily by organic and conventional farmers in our region to reduce weeds, and improve soil quality, crop quality, and yields. While we were unable to demonstrate improvements in crop yields or quality, we did see limited effects on soil quality and weed populations in some of our test sites during the final year of the study.
Defining Soil Balancing
Traditionally, soil balancing strives to keep base cations calcium (Ca), magnesium (Mg), and potassium (K) at a recommended ideal ratio (typically 64:10:5). Although long practiced by farmers, soil balancing is not recommended by most researchers and Extension educators. Our study indicated around half of organic corn growers in the Midwest used a soil balancing approach, but more than 75% of the Extension researchers we surveyed felt soil balancing had no scientific merit.
It’s true that most soil balancing studies done in the past 20 years have reported the practice had no effect on production. However, our research reveals several potential gaps in these studies. Consultants and farmers we interviewed commonly reported that soil balancing improved overall soil quality and structure, which led to improved drainage and reduced weeds. While farmers also reported improved yields and profit, it was generally not the first improvement they mentioned. Interviewees noted that these improvement often happened gradually over several years. In short, past research may not have captured long range positive effects. Most recent studies were short-term, lasting one or two years; were conducted in a greenhouse rather than field; focused only on improved yields; and were conducted on limited types of soils. (Chaganti and Culman, 2017)
We also found that many farmers pair cation balancing with other soil improvement practices such as cover crops and biostimulants. The goal, according to the “balancers” we spoke with, is to improve the physical and biological properties of the soil.
Using both on-farm and Ohio State research station sites, we collected data on soils, weeds, and crops, while applying a variety of soil amendments to change Ca:Mg ratios. We measured crop quality using Brix, color, size, and other characteristics specific to individual crops. Vegetable crops included tomato, butternut squash, cabbage, popcorn, and edamame. Agronomic field crop trials were conducted as well.
We were unable to document any treatment effect on yield or crop quality. In the last year of testing, we did see effects on weed populations (either lower weed populations overall or lower populations of foxtail on “balanced” soils) and on soil root resistance (indicating improved soil structure with higher Ca saturation). These effects appeared only on some fields, but they do support our hypothesis that the positive results of soil balancing are related to improvements in soil structure and drainage. We hope to continue monitoring these fields to see if results become more consistent over time.
For now, we are unable to officially encourage or discourage the use of soil balancing. The following recommendations are based on field trials and on the experience and advice of our stakeholder advisory committee.
- Soil test data is critical to making informed decisions about what to apply. Some Ohio soils may already have large concentrations of Ca due to Ohio’s limestone bedrock.
- Watch your pH if using lime. Gypsum is a better choice to change the Ca level without affecting pH and it also provides sulfur.
- Soils with a CEC below 10 may develop deficiencies. In soils with a low holding capacity for cations, excess Ca can lead quickly to deficiency levels of K, and possibly Mg. We did work in fields with Ca saturations well above 80% and observed K deficiencies in the soil and vegetables in these situations.
- Consider economic factors. The higher your CEC, the more time and amendments will be needed to increase the Ca:Mg ratio. At some point—depending on the amount of change needed and the value of your crop—using soil balancing becomes an expensive practice.
- Any time you try a new practice, monitor the results. If possible, try using the new practice on only part of your farm and compare it with a similarly managed area to see if the new technique is making a positive contribution over time.
With widespread use of the practice, soil balancing is a pertinent area for research and cooperative education. Our team hopes to continue studying the practices and long-term effects of soil balancing on a larger variety of soils. Drawing on experiment data and the experience of farmers and consultants, we will work toward guidelines and toward a mutual understanding of soil balancing.
Read more about this study at the Soil Balancing Project Site or the Vegetable Production Systems Laboratory. This work is supported by Organic Agriculture Research & Extension funding grant no. 2014-51300-22331/project accession no. 1003905 from the USDA National Institute of Food and Agriculture.