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

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.

Base cation saturation ratios vs. sufficiency level of nutrients: A false dichotomy in practice

“…Of particular importance to BCSR practitioners is the impact of using Ca to displace Mg from exchange sites to improve soil aggregation and physical structure (see Chaganti & Culman, 2017 for in-depth discussion). Using Ca to replace Mg on exchange sites is a fundamental tenet of BCSR practitioners (Brock, Jackson-Smith, Kumarappan, et al, 2021) and has scientific merit, but has not been robustly demonstrated in empirical field experiments to date (Chaganti & Culman, 2017;Chaganti et al, 2021). Future research is needed to better understand how soil type, clay mineralogy, and management practices influence crop and soil responses observed with increasing Ca saturation percentages and the relative roles specific cations (e.g., Ca vs. Mg) play in these responses.…”

“…The soil samples represented a diversity of organic farms, soils, and management practices. Complete details of the study and results are reported in Sprunger et al (2021). Of the 195 soil samples received and analyzed, 58% of these farms said they subscribe to and practice BCSR.…”

“…In this paper, we summarize key findings that we believe will provide agronomists and research scientists a more nuanced perspective of BCSR. Companion papers that follow report results of field studies that document the effects of BCSR on (a) soil health properties and crop productivity (Chaganti et al, 2021) and (b) soil health in organic corn fields across four eastern Corn Belt states (Sprunger et al, 2021).…”

“…We have independently verified that Mehlich-3 extracts proportionally more base cations than ammonium acetate (Culman, Mann, et al, 2020), which would slightly over-estimate CEC values without this correction. Soils were also analyzed for three measurements of active organic matter (permanganateoxidizable carbon (POXC), mineralizable carbon and autoclaved-citrate extractable (ACE) soil protein), with more details provided by Sprunger et al (2021). Soil test data from the organic farm survey were analyzed via ANOVA to determine differences in soil properties due to subscription to BCSR (Yes/No).…”

Soil fertility status and land suitability evaluation for rice crops on former shrimp ponds

“…Nevertheless, recent reports also recorded perceived positive impacts and long-term use of BCSR among many American farmers (Brock et al 2020;Culman et al 2021) as well as its continuing efficacy studies (Souza et al 2016;Bonomelli et al 2019;Chaganti et al 2021). Some researchers and soil scientists designated that the BCSR approach is also essential in terms of lime, gypsum, soil acidity, and cation competition study (Webster 1985;van Biljon et al 2007;Wood & Litterick, 2017;Culman et al 2021).…”