If you remember, I did a 10-part “micronutrients in soybean” column series in the Fall of 2020 that you can still read online at croptechcafe.org/soybeans. I decided to address another soil fertility topic series. This series is on the basic cation saturation ratio (BCSR) concept. It will be a 5-part series including the development, field research after development, expanded details on field research in Nebraska, the most recent scientific consensus from two published literature reviews, and my current recommendations related to the BSCR concept. Please follow this series as I walk through the over 100-yr scientific journey on the BCSR concept from its initial conception to our current scientific consensus on the concept.
I earned a PhD in Agronomy from K-State in 2012 where my research focused on soil fertility and plant nutrition. I enjoy writing on soil fertility topics like this. Among my University of Nebraska colleagues, I am known for talking about research studies conducted in nearby states in addition to our own! One research study or finding does not represent a field of science, the field of science is the entire body of knowledge or collective consensus around a topic. We continue to conduct soil fertility research to validate and confirm our understanding across a range of genetics, environments, and management. In that process we also debunk or disprove old concepts as we expand our learning beyond past generations of soil fertility scientists. It is my goal to provide the best scientific information currently available on a topic to you to make an agronomic decision.
Who researched and created the foundational concept of basic cation saturation ratios? Preliminary work on this concept dates to the 1800s. However, Bear and his colleagues at the New Jersey Agricultural Experiment Station in the 1940s are considered the major originators of the BCSR concept. Research by Graham in the 1950s and Albrecht in the 1970s at University of Missouri are considered to have further supported and finalized the BCSR concept in soil fertility science at that time.
What is the basic cation saturation ratio concept? The authors suggested that an ideal ratio of basic cations (calcium, magnesium, and potassium) and balanced cation saturation of the soil’s cation exchange capacity are needed, or plant growth will be reduced. Bear and colleagues recommended basic cation ratios of Ca/Mg at 6.5/1, Ca/K at 13:1, and Mg/K at 2:1. Albrecht concluded in the 1970s that a balanced soil is needed to maximize yield. He determined this to be the following cation saturation percentage of the soil cation exchange sites: 60-75% calcium (Ca), 10-20% magnesium (Mg), 2-5% potassium (K), 10% H, 0.5 to 5% sodium (Na), and 5% other cations.
In two weeks, I will share and summarize field research conducted over the past 50 years. We have learned a lot about soil fertility and plant nutrition since then. Do you think the BSCR concept still holds up to the last 50 years of scientific rigor?
For inquiries about this and other agronomic resources and programs from Nebraska Extension, contact me at or 402-821-1722. Know your crop, know your tech, know your bottom line at croptechcafe.org
