Since the 1950s there have been three philosophies driving soil fertility recommendations throughout the U.S. concerning certain base cations (Ca2+, Mg2+, K+). They include build and maintain, sufficiency level, and base cation saturation ratio (BCSR). The theory of an “ideal” BCSR in the soil has been extensively discussed and used to a limited extent throughout the Midwest by some soil testing labs to guide fertility recommendations. This “ideal” soil was first suggested by researchers from New Jersey in the 1940’s (Bear et al., 1945; Bear and Toth, 1948; Hunter, A.S., 1949; Prince et al., 1947) and further emphasized by William Albrecht, Professor from the University of Missouri. Their theory built upon work done by Loew and May (1901) which suggested that Ca and Mg should be in a 5:4 ratio for optimal plant growth. However, this theory has been a subject of great debate in terms of its utility for affecting crop yields and farmer profitability. Numerous studies have found flaws in the BCSR method and showed no proven yield increases, while a greater research base exists to support the sufficiency and build and maintain approaches (Eckert and McLean, 1981; McLean et al., 1983). Yet, some consultants and ag. retailers still use the BCSR method to guide fertility recommendations. All land-grant university fertility recommendations in the Midwest use a sufficiency or build and maintain approach. The University of Wisconsin recommendations employ a build and maintain approach, as do most surrounding states (IL, IA, IN, MI). This paper will discuss the theory behind the BCSR method, its applicability, if there is any value to it, and why state fertility recommendations do not endorse the BCSR method.
Soil Science Extension
University of Wisconsin Madison