Base cation saturation ratios, soil health, and yield in organic field crops

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Abstract
Base cation saturation ratio (BCSR) is a soil management philosophy that postulates having an ideal ratio of base cations for maximizing crop yields. This practice is widely used on organic farms, and BCSR practitioners commonly describe improvements in soil health and crop productivity. However, studies evaluating the efficacy of BCSR on soil biological and physical properties are lacking. This 6‐yr field study evaluated the effects of changing soil calcium/magnesium (Ca/Mg) ratios on organic corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields and comprehensive soil health properties at two sites in Ohio with contrasting soils. Three soil amendments—(a) control, (b) gypsum (calcium sulfate), and (c) epsom (magnesium sulfate)—were applied to drive soil Ca and Mg levels in opposite directions. Amendment application resulted in soil Ca/Mg ratios 1.6 and 2.5 times higher in gypsum soils relative to epsom soils. Soil biological health, measured by permanganate oxidizable carbon, mineralizable carbon, and soil protein, was not affected by either gypsum or epsom applications. Likewise, soil physical quality measured by aggregate stability, infiltration, and penetration resistance was not significantly affected by gypsum or epsom additions at either site. Amendment application did not affect crop yields and there was no significant relationship between crop yields and the range of soil Ca/Mg ratios. Results from this study do not provide any evidence that BCSR improves soil health and organic field crop productivity.

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